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Guidelines for fiber reinforced resin composite

Posted on 18 August, 2019 at 6:30 Comments comments (0)

Guidelines for fiber reinforced resin composite

Grossly destructed posterior vital teeth can be restored with resin composite reinforced with fiber. The following guidelines can be kept in mind while doing such restorations.

 

 

Resin composite restorations reinforced with fiber are indicated for grossly destructed posterior vital tooth. This restorative technique is very useful to preserve the vitality of the grossly destructed tooth structure and to act as holding restorations. However there are no protocols or guidelines present in the existing literature for doing such restoration. It is assumed that the reader is already aware of the technique and guidelines to do such technique are discussed in this article.

 

The operator can either use glass fiber (Splint-it : Jeneric-pentron co.,/Interlig: angelus co.,/Vectris: ivoclor co.,) or polyethylene (Ribbond: ribbond co.,). The fibers are available in unidirectional or braided or woven. Fibers are included in the restorations to increase the resistance form which will allow the restorations to withstand high occlusal forces. The retention for these restorations is achieved by the bonding agents only. If additional retention is required then additional pins can be used.

 

The following brief guidelines will help the clinician to do such restorations in their day to day practice.

 

Type of fiber:

Literature states that reinforcement with glass fiber provides better improvement in physical properties than polyethylene. But the manipulation of glass fiber is very difficult and it cannot be adapted well to the different contours of the cavity preparations. On the other hand, ribbond can adapt easily and save considerable chair time. It also leads to predictable restorations. While ribbond is preferable overall, glass fibers can be effectively used in small pieces for discontinuous reinforcement.

 

Fiber architecture:

Fibers are available in unidirectional, braided or woven. The direction of the fiber dictates the direction of reinforcement. Maximum reinforcement is obtained in the direction parallel to the fiber direction. Since restorations are subjected to occlusal stress from different directions, unidirectional fiber will not be suitable. Braided or woven fibers which can resist multi directional forces will be a good choice for chair side reinforcement -restorative technique.

 

Resin impregnation:

Pre-impregnation of fibers with resin is very useful for laboratory reinforcement. For restorative procedure, which requires chair side manipulation, impregnation of fiber with unfilled resin (older generation bonding agent) gives the best results.

 

Layer of reinforcement:

Fiber can be reinforced on tension side or compression side or on neutral zone. In cavity preparations, the area near the gingival third forms the tension and the area near the occlusal surface forms the compression side. The middle zone in between is the neutral zone. Placing the fiber in neutral zone does not seem to increase the physical properties of the restorations. Earlier studies indicated that tension zone reinforcement gives the maximum strength; while the present evidence states that the compression zone reinforcement is more effective that the tension zone. Reinforcement of restorations can be done with one layer of fiber or two layers of fiber. More than two layers will compromise the biological form.

 

Uni-layer reinforcement with one layer of fiber can be done for cavity of depth within 3mm. Since there has to be at least 1-1.5mm of composite restorative material over the fiber, the uni- layer reinforcement can be best placed on the tension zone only.

 

Bi-layer reinforcement with two layers of fiber is done for cavity depth of 4-5mm. one fiber can be placed on the tension zone and one can be placed on the compression zone.

 

Width of the fiber:

Fibers are usually available in 2mm, 3mm and 4mm. For most of the restorative reinforcement 2mm of fiber should be ideal for all cavities. Reinforcement of pulp chamber in endodontic treated tooth for post endodontic restoration will require 3-4mm width fiber.

 

Direction of reinforcement:

Fibers can be placed horizontally, obliquely or circumferentially. Vertical placement is not done as oblique placement is more advantages than vertical placement. The reinforcement can be made in small pieces of fiber in specific area and can be called as “discontinuous reinforcement” or can be placed continuously along the lost structure and can be termed as “continuous reinforcement”.

 

1. Horizontal placement (mesio-distally/bucco-lingually)

• Usually placed as part of the bi-layer reinforcement.

•Discontinuous reinforcement in different directions across the lost cusps or marginal ridge.

•Wide proximal box reinforcement.

•Along the direction of oblique ridge (maxillary) for reinforcement of lost oblique ridge.

 

2. Oblique placement (cervico-occlusally)

• Reinforcement of cusps.

•Reinforcement of wide proximal box.

•Reinforcement of wide buccal or palatal extention.

 

3. Circumferential placement (cervico-occlusally)

• Ideal for reinforcement of pulp chamber.

•Continuous reinforcement along the lost cusp and marginal ridge in deep dentinal cavities.

 

The suggested guidelines can be improvised and incorporated during the restorative procedure of fiber reinforced restorations. The reader is encouraged for further reading for mastering the technique.

 

 

Bibliography

1.Belli S, Erdemir A, Ozcopur M, Eskitascioglu G. The effect of fiber insertion on fracture resistance of root filled molar teeth with MOD preparations restored with composite. International Endodontic Journal 2005;38:73-80.

2.Bender A. J, "Single Appointment Crown and Bridge, An Innovative Technique," Dentistry Today 2002; 84-87.

3.Deliperi S , Bardwell D, Colana C, "Reconstruction of Devital Teeth Using Direct Fiber-reinforced Composite Resins: A Case Report" Journal Adhesive Dentistry 2005 7, 1-7.

4.Dickerson W.G, "A Conservative Alternate to Single Tooth Replacement: A Three Year Follow-Up," Practical Periodontics and Aesthetic Dentistry 1993, 43-49.

5.Dyer SR, Lassila LVJ, Jokinen M, Vallittu PK. Effect of cross-sectional design on the modulus of elasticity and toughness of fiber reinforced composite materials. J Prosthet Dent 2005;94:219-26.

6.Dyer SR, Lassila LVJ, Jokinen M, Vallittu PK. Effect of fiber position and orientation of fracture load of fiber reinforce composite. Dent Mat 2004;20:947-955.

7.Frelich MA, Meiers JC, Duncan JP, Goldberg AJ. Composition, architecture and mechanical properties of fiber reinforced composite. Berlin: Quintessence publishing Co., Inc.;1999.

8.Frelich MA. Karmaker AC, Burstone CJ et al .Developement and clinical applications of a light polymerized fiber reinforced composite. J Prosth Dent 1998;80:311-8.

9.Gouroshi SK, Lassila LVJ, Vallitu PK. Fiber reinforced composite substructure: Load bearing capacity of an onlay restoration. Acta Odontol Scand 2006;64:281-5.

10.Karbhari VM, Wang Q. Influence of triaxial braid denier on ribbon based fiber reinforced dental composites. Dent Mat 2007;23:969-976.

11.Karbhari VM, Strassler H. Effect of fiber architecture on flexural characteristics and fracture of fiber reinforced dental composites. Dent Mat 2007;23:960-68.

12.Peirera CL, Demarco FF, Cenci MS et al. Influence of polyethylene fiber reinforcement and type of composite. Clin Oral Investig 2003;7:116-9.

13.Vallitu PK. Flexural Properties of acrylic resin polymers reinforced with unidirectional and woven glass fibers. J Prosthet Dent 1999;81:318-26.

14.Vallitu PK. Use of woven glass fibers to reinforce a composite veneers.A fracture resistance and acoustic emission study. J Oral Rehab 2002;29:423-9).

15.Van Dijken JWV, Grönberg KS. Fiber-reinforced packable resin composites in Class II cavities. J Dent 2006;34: 763-769

Silver Amalgam restoration

Posted on 13 April, 2019 at 8:55 Comments comments (4)

Silver Amalgam restoration

Carving Silver amalgam Restoration is a challenge in clinical Practice and it becomes a nightmare during the undergraduate learning period. Establishing proper contacts and contours in the restoration is important for the longevity of the resoration .

Dental Amalgam

 

An amalgam is an alloy of mercury and other metal(s). Dental Alloy is a powdered alloy of silver, tin, and other metals, which can be mixed (triturated) with mercury to form dental amalgam.

 

Old fashioned low copper Dental Amalgam Alloy

 

70% Silver gives strength and corrosion resistance.

25% Tin slows the setting time when the alloy is amalgamated, allowing the material to be placed and carved.

4% Copper increases the strength

1% Zinc (if present) improves the wettability of the alloy particles with the mercury.

 

Percentages are approximate

 

When Dental Alloy reacts with mercury, some of the alloy remains unchanged (especially at the centre of the powder particles). The part that reacts forms a matrix in which the un-reacted particles are suspended.

 

 

The unreacted phase is called the gamma phase. The matrix consists of a mixture of gamma-1 and gamma-2 phases.

Gamma phase : Ag3Sn - Silver/Tin, very strong & corrosion resistant.

Gamma-1 phase : Ag2Hg3 - Silver/Mercury, quite strong & corrosion resistant.

Gamma-2 phase : Sn7Hg - Tin/Mercury, weak & easily corroded, results in marginal breakdown of filling.


Glossary OF COMMONLY USED DENTAL TERMS

Posted on 14 March, 2019 at 7:35 Comments comments (0)

GLOSSARY OF COMMONLY USED DENTAL TERMS

 

A

 

• Abutment : A tooth or implant used to support a prosthesis. A crown unit used as part of a fixed bridge.

• Abcess : A localized inflammation due to a collection of pus in the bone or soft tissue, usually caused by an infection.

• Amalgam : A dental filling material, composed of mercury and other minerals, used to fill decayed teeth.

• Alveoloplasty : A surgical procedure used to recontour the supporting bone structures in preparation of a complete or partial denture.

• Anesthetic : A class of drugs that eliminated of reduces pain. See local anesthetic.

• Anterior : Refers to the teeth and tissues located towards the front of the mouth ( upper or lower incisors and canines).

• Apex : The tip end of a root.

• Apexification : A method of inducing apical closure, or the continual apical development of the root of an incompletely formed tooth, in which the pulp is no longer vital.

B

• Bicuspid : A two-cuspid tooth found between the molar and the cuspid also known as an eye tooth or canine tooth.

• Biopsy : A process of removing tissue to determine the existence of pathology.

• Bitewing x-ray : X-rays taken of the crowns of teeth to check for decay.

• Bleaching : The technique of applying a chemical agent, usually hydrogen peroxide, to the teeth to whiten them.

• Bonding : A process to chemically etch the tooths enamel to better attach ( bond ) composite filling material, veneers, or plastic/acrylic.

• Bone loss : The breakdown and loss of the bone that supports the teeth, usually caused by infection or long-term occlusal ( chewing areas of the teeth ) stress.

• Bridge : A fixed prosthetic replacement of one or more missing teeth teeth cemented or attached to the abutment teeth or implant abutments adjacent to the space.

• Bruxism : The involuntary clenching or grinding of the teeth.

C

• Calculus : The hard deposit of mineralized plaque that forms on the crown and /or root of the tooth. Also referred to as tartar.

• Canine tooth : The second tooth from the big front tooth, commonly called the eye tooth.

• Cantilever Extension : Part of a fixed prosthesis that is supported at one end only.

• Cap : Another term for crown; usually referring to a crown for a front tooth.

• Caries : The correct technical term for decay which is the progressive breaking down or dissolving of tooth structure, caused by the acid produced when bacteria digest sugars.

• Cavity : A layman’s term for decay. Also, the dental term for the hale that is left after the decay has been removed.

• Cement : A special type of glue used to hold a crown in it’s place. It also acts as an insulator to protect the tooth’s nerve.

• Cementum : The very thin, bonelike structure that covers the root of the tooth.

• Clenching : The forceful holding together of the upper and lower teeth, which places stress on the ligaments that hold the teeth to the jawbone and the lower jaw to the skull.

• Complex rehabilitation : The extensive dental restoration involving 6 or more units of crown and/or bridge in the same treatment plan. Using full crowns and/or fixed bridges which are cemented in place, that your dentist will rebuild natural teeth, fill in spaces where teeth are missing and establish conditions which allow each tooth to function in harmony with the occlusion ( bite ).

• Composite : A tooth-colored filling made of plastic resin or porcelain.

• Consultation : A diagnostic service provided by a dentist other than the treating dentist.

• Cosmetic dentistry : Any dental treatment or repair that is solely rendered to improve the appearance of the teeth or mouth.

• Crown : The portion of a tooth that is covered by enamel. Also a dental restoration that covers the entire tooth and restores it to its original shape.

• Crown lengthening : A surgical procedure exposing more of the tooth for restorative purposes.

• Curettage : A deep scaling of that portion of the tooth below the gum line. Purpose is to remove calculus and infected gum tissue.

• Cuspid : See canine tooth.

• Cusp(s) : The protruding portion(s) of a tooth’s chewing surface.

D

• Decay : see caries

• Deciduous : See primary teeth

• Dental Floss : A thin, nylon string, waxed or unwaxed, that is inserted between the teeth to remove food and plaque.

• Dental hygienist : A dental professional specializing in cleaning the teeth by removing plaque, calculus, and diseased gum tissue. He/She acts as the patients guide in establishing a proper oral hygiene program.

• Dentin : The part of the tooth that is under both the enamel which covers the crown and the cementum which covers the root.

• Dentition : The teeth in the dental arch.

• Denture : A removable appliance used to replace teeth. A complete denture replaces all of the upper teeth and/or all the lower teeth.

• DDS : Doctor of Dental Surgery or DDS, Doctor of Dental Medicine. Degrees given to dental school graduates. Both degrees are the same particular dental schools identify at their discretion their graduates as DMD or DDS.

• Diastema : A space, such as one between two adjacent teeth in the same dental arch.

• Distal : Farther from any part of reference.

• Direct pulp cap : The procedure in which the exposed pulp is covered with a dressing or cement that protects the pulp and promotes healing and repair.

• Dry socket (osteitis) : A localized inflammation of the tooth socket following an extraction due to infection of a blood clot.

E

• Enamel : The hard, calcified (mineralized) portion of the tooth which covers the crown. Enamel is the hardest substance in the body.

• Endodontics : The dental specialty that deals with injuries to or diseases of the pulp, or nerve, of the tooth.

• Endodontist : A dentist who deals with the cause, prevention, diagnosis, and treatment or injuries and diseases that affect the dental pulp , tooth root, and periapical tissue.

• Equilibration : (occlusal adjustment) The achievement of a balance between opposing teeth or forces by adjustive grinding of an interfering tooth structure during the functional stroke.

• Extraction : The removal of a tooth.

• Excision : Surgical removal of bone or tissue.

• Extosis : The overgrowth of normal bone.

• Extracoronal : The outside crown of the tooth.

• Extraoral : The outside of the mouth.

F

• Facial : Pertaining to or toward the face ( Buccal, Labial ).

• Filling : Material used to fill cavity or replace part of a tooth.

• Fissure : A deep ditch or cleft in the surface of the teeth.

• Floss : see dental floss.

• Fluoride : A chemical compound used to prevent dental decay, utilized in fluoridated water systems and/or applied directly to the teeth.

• Frenum : Muscle fibers covered by a mucus membrane that attaches the check, lips and or tounge to associated dental mucous.

• Frenectomy : The removal of a frenum.

G

• Gingiva : The soft tissue that covers the jawbone. Also referred to as the gums.

• Gingivectomy : An inflammation or infection of the gingiva (gum tissue); the initial stage of gum disease.

• Gingivitis : An inflammation or infection of the gingiva; the initial stage of gum disease.

• Gingivoplasty : A surgical procedure to reshape or repair the gingiva (gum).

• Graft : A piece of tissue or synthetic material placed in contact with tissue to repair a defect or supplement a deficiency.

• Gum : see gingiva.

• Gum Disease : see gingiva.

H

• Hemisection : The surgical separation of a multirooted tooth through the furcation area in such a way that the blocked, defective, or periodontally affected root or roots may be removed along with the associated portion of the crown.

• High noble metal : See metal, classification of.

I

• Immediate denture : A denture constructed for immediate placement after removal of the remaining teeth.

• Impacted tooth : An unerupted or partially erupted tooth that is positioned against another bone or soft tissue so that total eruption is unlikely.

• Implant : An artificial device, usually make of a metal alloy or ceramic material, that is implanted within the jawbone as a means to attach an artificial crown, denture , or bridge.

• Incipient : Dental carries in an early stage of development, usually not requiring immediate restorations.

• Incisal : Pertaining to the cutting edges of incisor and cuspid teeth.

• Incision and Drain : (I and D) A sweeping incision made through the core of a lesion to allow draining of infection, and removal of any abnormal or unhealthy tissue.

• Indirect pulp cap : A procedure in which the nearly exposed pulp as covered with a protective dressing to protect the pulp from additional injury and to promote healing and repair via formation of secondary dentin.

• Inlay : A cast gold filling that is used replace part of the tooth.

• Interproximal : The area between two adjacent teeth.

• Intracoronal : The area within a crown of a tooth.

• Intraoral : The inside of a mouth.

L

• Labial : The area pertaining to or around the lip.

• Lingual : The area pertaining to or around the tongue.

• Local Anesthetic : The injection given in the mouth to numb the areas where a tooth or area needs a dental procedure. Often referred to as Novocain.

M

• Malocclusion : The improper alignment of biting or chewing surfaces of upper and lower teeth.

• Mandible : The lower jaw.

• Maryland bridge : The trade name that becomes synonymous with any resin bonded fixed partial denture (bridge).

• Mastication : The act of chewing.

• Maxilla : The upper jaw.

• Mesial : Toward or situated in the middle.

• Metals, classification of : The noble metal classification system has been adopted as a more precise method of reporting various alloys in dentistry commonly used in crowns, bridges, and dentures. These alloys contain varying percentages of Gold, Palladium, and/or Platinum. High noble contains more than 60% of Gold, Palladium and/or Platinum (with at least 40% Gold); noble contains more than 25% Gold, Palladium and/or Platinum; predominately base less than 25% Gold, Palladium and/or Platinum.

• Molars : The broad, multicusped back teeth, used for grinding food are considered the largest teeth in the mouth. In adults there are a total of twelve molars (including the four wisdom teeth, or third molars), three on each side of the upper and lower jaws.

N

• Nitrous oxide : A controlled mixture of nitrogen and oxygen gases (N2O) that is inhaled by the patient in order to decrease sensitivity to pain. Also referred to as laughing gas.

• Novocain : A generic name for the many kinds of anesthetics used in the dental injection, such as Xylocaine, Lidocaine, or Novocaine. See local anesthetic.

O

• Occlusal x-ray : An intraoral x-ray taken with the film held between the teeth in biting position.

• Occlusal surface : The chewing surface of the back teeth.

• Occlusion : Any contact between biting or chewing surfaces of upper and lower teeth.

• Onlay : A cast gold or porcelain filling that covers one or all of the tooth’s cusps.

• Oral surgery : The removal of teeth and the repair and treatment of other oral problems, such as tumors and fractures.

• Orthodontics : A specialized branch of dentistry that corrects malocclusion and restores the teeth to proper alignment and function. There are several different types of appliances used in orthodontics, one of which is commonly referred to as braces.

• Overbite : A condition in which the upper teeth excessively overlap the lower teeth when the jaw is closed. This condition can be corrected with orthodontics.

P

• Palate : The hard and soft tissues forming the roof of the mouth.

• Palliative : Treatment that relieves pain but is NOT curative.

• Panorex : An extraoral full-mouth X-ray that records the teeth and the upper and lower jaws on one film.

• Partial denture : A removable appliance used to replace one or more lost teeth.

• Periodontist : The area of dentistry concerned with the prevention, diagnostic, and treatment of periodontal disease.

• Pediatric dentistry : The specialized branch of dentistry that deals solely with treating the children’s dental disease. Also referred to as Pediodontics.

• Periapical : The area that surrounds the tip of a tooth.

• Pericorontis : An inflammation of the gum tissue around the crown of a tooth, usually the third molar.

• Periodontal : Relating to the tissue and bone that supports the tooth (from peri, meaning “around”, and dont , “tooth”).

• Periodontal disease : The inflammation and infection of the gums, ligaments, bone, and other tissues surrounding the teeth. Gingivitis and periodontis are the two main forms of periodontal disease.

• Periodontal pocket : An abnormal deepening of the gingival crevice. It is caused when disease and infection destroy the ligament that attaches the gum to the tooth and the underlying bone.

• Periodontal surgery : A surgical procedure involving the gums and jawbone.

• Periodontics : Te dental specialty that deals with and treats the gum tissue and bone that supports the teeth.

• Periodontitis : Inflammation of the supporting structures of the tooth, including the gum, the periodontal ligament, and the jawbone.

• Periradicular : The area which surrounds a portion of the root of the tooth.

• Permanent teeth : The thirty-two adult teeth that replace the baby , or primary teeth. Also known as secondary teeth.

• Pit : A recessed area found on the surface of a tooth, usually where e the grooves of the tooth meet.

• Plaque : A film of sticky material containing saliva, food particles, and bacteria that attaches to the tooth surface both above and below the gum line. When left on the tooth it can promote gum disease and decay.

• Pontic : An artificial tooth used in a bridge to replace a missing tooth.

• Post and core : An elongated metallic projection fitted and cemented within the prepared root canal, serving to strengthen and retain restorative material and/or a crown restoration.

• Premolar : Another name for bicuspid.

• Preventative dentistry : Education and treatment devoted to and concerned with preventing the developement of dental disease.

• Preventative treatment : Any action taken by the patient, assisted by the dentist, hygienist, and the office staff that serves to prevent dental or other disease. Sealants, cleanings and space maintainers are examples of preventative treatment.

• Primary teeth : The first set of teeth that humans get, lasting until the permanent teeth come in. Also referred to as baby teeth.

• Prophylactic odontonomy : A procedure done to a tooth to remove decalcified areas that are susceptible to decay, exposing healthy tooth structure.

• Prophylaxis : The scaling and polishing procedure performed to remove calculus, plaque, and stains from the crowns of the teeth.

• Prosthesis : (DENTAL) Any device or appliance replacing one or more missing teeth.

• Prosthodontics : The dental specialty dealing with the replacement of missing teeth and other oral structures.

• Pulp : The hollow chamber inside the crown of the tooth that contains its nerves and blood vessels.

• Pulpotomy : The removal of a portion of the tooth’s pulp.

Q

• Quadrant : The dental term for the division of the jaws onto four parts, begging at the midline of the arch and extending towards the last tooth in the back of the mouth. There are four quadrants in the mouth; each quadrant generally contains five to eight teeth.

R

• Rebase : The process of refitting a denture by replacing the base material.

• Receded gums : A condition characterized by the abnormal loss of gum tissue due to infection or bone loss.

• Referral : When a dental patient is sent to another dentist, usually a specialist, for treatment or consultation.

• Reline : The process of resurfacing the tissue side of a denture with a base material.

• Replantation : The return of a tooth to its socket.

• Resorption : The breakdown and assimilation of the bone that supports the tooth, i.e., bone loss.

• Restoration : Any material or devise used to replace lost tooth structure (filling, crown) or to replace a lost tooth or teeth (bridge, dentures, complete or partial).

• Retainer : A removable dental appliance, usually used in orthodontics, that maintains space between teeth or holds teeth in a fixed position until the bone solidifies around them.

• Retrograde filling : A method of sealing the root canal by preparing and filling it from the root tip, generally done at the completion of an apiocoectomy.

• Ridge enhancement : (bone replacement) The placement of a synthetic bone material, or freeze dried bone, inserted immediately after an extraction into the socket of the tooth. This is done to prevent collapsing of the surrounding bone.

• Root : The part of the tooth below the crown , normally encased in the jawbone. It is made up of dentin, includes the root canal, and is covered by cementum.

• Root Canal : The hollow part of the tooth’s root. It runs from the tip of the root into the pulp.

• Root canal therapy : The process of treating disease or inflammation of the pulp or root canal. This involves removing the pulp and root’s nerve(s) and filling the canal(s) with and appropriate material to permanently seal it.

• Root planning : The process of scaling and planing exposed root surfaces to remove all calculus, plaque, and infected tissue.

S

• Scaling : A procedure used to remove plaque, calculus, and stains from the teeth.

• Sealant : A composite material used to seal the decay-prone pits, fissures, and grooves of teeth to prevent decay.

• Six-year molar : The first permanent tooth to erupt, usually between the ages of five and six.

• Socket : The hole in the jawbone which to tooth fits.

• Space maintainer : A dental appliance that fills the space of a lost tooth or teeth and prevents the other teeth from moving into the space. Used especially in orthodontic and pediodontic treatment.

• Stainless steel crown : A pre-made metal crown, shaped like a tooth, that is used to temporarily cover a seriously decayed or broken down tooth. Used most often on children’s teeth.

• Subgingival scaling : The removal of calculus and plaque found on the tooth below the gum line.

• Supra gingival scaling : The removal of calculus and plaque found on the tooth below the gum line.

• Systemic : Relating to the whole body.

T

• Tartar : see calculus.

• Temporomandiblar joint (TMJ) : The connecting hinge mechanism between the upper jaw and the base of the skull.

• Third molar : The last of the three molar teeth, also called wisdom teeth. There are four third molars, two in the lower jaw two in the upper jaw, on each side.

• Torus : A bony elevation of normal bone. Usually seen on the upper palate behind the front teeth or under the tongue inside the lower jaw.

• Treatment plan : A list of work that the dentist proposes to perform on a dental patient based on the result s of the x-rays, exam, and diagnosis. Often more than one treatment plan is presented.

V

• Veneer : An artificial filling material, usually plastic, composite, or porcelain, that is used to provide an anesthetic covering over the visible surface of a tooth. Most often used on front teeth.

W

• Wisdom teeth : See third molar.

 

 

 

CLASSIFICATIONS OF DENTAL CARIES

CLASS I - occlusal decay

CLASS II - interproximal decay

CLASS III - on anterior teeth, interproximal surfaces, but not involving the incisal surface.

CLASS IV - lesion on the interproximal surface and involving the incisal surface of the incisor or cuspid

CLASS V - caries on the gingival 1/3 of the tooth, and below the height of contour on the labial, facial, and lingual surfaces of the teeth.

CLASS VI - cavities in the incisal edges and smooth surfaces of teeth above the height of contour.

 

Electronic data base and evidence based decision making

Posted on 1 March, 2019 at 10:10 Comments comments (0)

Electronic data base and evidence based decision making

Information explosion is the agony and ecstasy of the present day science. The internet revolution has opened up the flood gates of data made up of bits and bytes to anyone accessing from anywhere. Thus information has become omnipresent, just in the air, waiting to be accessed. One may assume that this exponential growth in internet and information will provide the best opportunity for data mining. But on the contrary, a chaotic, unorganized tsunami of data that is crashing on to the beaches of scientific civilization just lets us have either “something” or“everything”, seldom the “right thing”. Hitting the bull’s eye in a massive swirl of data depends on how well it is organized and also how methodically it is accessed. The best proof for this is our good old dictionary and encyclopedia. However, as the information architecture in the cyber world is not that conventional, a new skill has to be acquired by one and all.

 

“Knowledge is of two kinds. We know a subject ourselves, or we know where we can find information on it.” Information that exists outside us has to be processed by a knowledge within us, called as information processing skill. Without this new found ability all of us are sure to catch up with an ailment called as “Information Fatigue Syndrome” – a frustration that arises by staring at a barage of data that makes no sense.In our dental curriculum this information processing skill begins with and alas! ends with the post graduation program – precisely with the submission of the thesis! But we are now at the cross roads of a new philosophy in practice, called as “Evidence Based Decision Making,” (EBDM) in all the health sciences, where we are urged to continue this literature hunt even as clinical practitioners in quest for the appropriate scientific evidence for the treatments offered to the patients.Tracking down information, in order to keep abreast with the latest in the field is not anything new for clinical practice. But the rapid transformation of all the hard copy information into the “Electronic Data Base” and the opinionated informations into well “Researched Evidence” and the submissive patients into wise “decision making partners”, gives novelty to this concept of Evidence Based Decision Making.The evidence based approach educates the clinician to convert the patient’s problems into well framed questions, to search for the right evidence in a methodical fashion, to critically appraise those evidences and categorise them as good, bad and ugly and finally to effectively translate those evidences into clinical solutions that becomes the best care for the patients. In essence, Evidence based approach weds the long separated clinical practice and research. Finally the time has come for research to achieve its prime objective of reaching out to the patients. Though principally evidence based approach is designed for the clinical practice and the patient care, this concept also gives a refreshing insight into different aspects and current status of scientific research to the academic bodies. Through this philosophy we are being educated about various sources of evidence, levels of evidence, quality of evidence, various search engines and also about a pristine method of surfing through this wild electronic database. This can enhance our information processing skills and help us reach the evidence early and effectively. Through this we also stand to gain information about the areas where there is an acute lack of evidence. Thus we may be motivated to do the appropriate research in those areas of lacunae and enrich the repository of evidence, for , after all we are the evidence providers, as well as the end users!

 

This section will help one

 

to learn the step by step approach of searching the Electronic Database in the Evidence Based Decision Making way

throw light on the critical areas of Conservative Dentistry and Endodontia that are lacking in evidence

underscore the emphasis on more clinical reasearches to fill in these voids.

Electronic Data Bases – The sources of evidence:

 

There are two types of evidence based sources – Primary and Secondary. Primary sources are original research publications. Secondary sources, developed by evidence based groups, are systematic analysis of many primary research studies in a particular topic and provide a summarised evidence. Such publications are very useful for the busy practitoners.

 

Primary sources:

 

Out of many data bases, the MEDLINE is the most reliable and easily accessible multi purpose database for the primary scientific literatures. Created and maintained by the United States National Library of Medicine (NLM) of the National Institutes of Health since 1966, it covers medicine, dentistry, nursing, veterinary medicine, health care services and the preclinical sciences.

 

The NLM allows free access to the full MEDLINE through three websites called, Pubmed (http://www.ncbi.nlm.nih.gov/ ), Internet Grateful Med (IGM) and the NLM Gateway. Pubmed and Gateway also provide access to pre 1966 journal citations (OLDMEDLINE) and books, serial titles and audio visual resources (LOCATORplus).

 

A very useful site is MedFetch. MedFetch enables you to repetitively perform a Medline search and receive the results via e-mail. The search is performed weekly or monthly until you delete the search. MedFetch is a web-based software program. With an Automated Medline Query (AMQ), every week you will be e-mailed the 20 most recent citations that match your query from the 11 million citations in MEDLINE and Pre-MEDLINE.

 

Embase is yet another data base like Medline, which claims more coverage of journals and countries. However this allows access with registration.

 

Secondary sources:

 

Secondary sources are best accessed in the sites maintained by government organizations, academic institutions, evidence based groups and the sites of medical search engines. The following is a long list of sites available in the net.

 

* Centre for Evidence Based Dentistry This is a very exhaustive site on Evidence Based Dentistry. Most recommended site for learning every aspect of EBD. This site also provides evidence based summary of numerous topics categorised topic wise, as well as speciality wise. It also links to other evidence based sites and journals.

 

* Evidence based dentistry is in an extensive form in this site which enables learning EBD as well as searching for evidence

 

* The School of Health and Related Research ScHARR at the University of Sheffield, UK features “Netting the Evidence: A ScHARR introduction to evidence based practice” on the internet, which is an alphabetical compilation of links to numerous evidence based resources.

 

* The Health information Research Unit at McMaster University, in Hamilton, Ontario conducts research in the field of health information science and is dedicated to the generation of new knowledge about the nature of health and clinical information problems, the development of new information resources to support evidence-based health care, and the evaluation of various innovations in overcoming health care information problems.

 

* The library of Ottawa General Hospital provides links to many aspects of evidence based approach.

 

* NIH Clinical Trials and the Current Controlled Trials gives idea about the clinical trials in progress in the topic of interest.

 

* Medical Matrix is a medical search engine, a paid site requiring registration.

 

*Mediaformatics - Evidents is a dental PICO based search engine for real-time searches of PubMed . Searching for answers to clinical question is made very easy here.

 

*TRIP – Turning Research into Practice- another meta search engine, that is UK-based . Click and see the way the results were displayed on typing a search term. On clicking on each category we shall land up in gold mine of information

 

*SUMsearch is a medical meta-search engine which searches a range of databases andinternet site

 

*Organized Medical Networked Information OMNI is a free catalogue of hand-selected and evaluated Internet resources in Health and Medicine

 

*Critical Appraisal Skills Program CASP is a site that gives all the informations on evidence base that includes the following sections: CASP critical appraisal tools , Open learning resource, E-learning. Sources of evidence , Search filters.

 

*ADEPT This is a workshop and distance learning based programme, about different filters for retrieving the evidence. This comprises of 6 distance learning packages such as Introduction to Research Design, Therapy , Diagnosis, Reviews , Prognosis , Etiology, Economic Evaluations and Guidelines.

 

* The Cochrane Collaboration is an international non-profit and independent organization, dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. The Cochrane Collaboration was founded in 1993 and named after the British epidemiologist, Archie Cochrane. The major product of the Collaboration is the Cochrane Database of Systematic Reviews which is published quarterly as part of the Cochrane Library, where you can browse and search abstracts of reviews free of charge. Abstracts of Cochrane Review and Abstracts of Cochrane Oral Health and Group Reviews are a must – visit aspects of Cochrane database.

 

* Attract In this site when aclinician contacts this site, the evidence is rapidly searched by the answerers in Attract, appraised and summarized onto a side of A4 and then faxed back to the clinician - within 6 hours if necessary.

 

* Database of Abstracts of Reviews of Effectiveness DARE contains summaries of systematic reviews which have met strict quality criteria. Each summary also provides a critical commentary on the quality of the review. The database covers a broad range of health and social care topics and can be used for answering questions about the effects of interventions, as well as for developing guidelines and policy making.

 

* National Library of Health UK and Oral Health Specialist Library UK summarize some of the recent studies.The following are evidence-based publications are available on subscription.

 

* Evidence-Based Dentistry Published by the British Dental Association

 

* Evidence-Based Dental Practice an American journal

 

* The bandolier journal is an independent journal about evidence-based healthcare, Oxford scientists.

 

Searching EDB the EBDM way:

 

The invasion of the human mind by the machines, the cyber world gadgets, is amazing. We have a tendency to hold on to the flimsy threads of the web, woven by the information networking, as our life line, in getting informations right from recipes to research. So handling the net may not be a brand new experience for anyone in any age group. Similarly as students, academicians and researchers, we all have had a free hand on the Electronic Data Bases. Whenever in doubt, we type the raw words in the search box and accept whatever spews out of the system happily, even if it takes too much of time or paper. But now,Evidence Based Decision Making brings to the lime light the separate vocabulary and language that is used to communicate effectively with the Electronic Data Bases and also a separate set of protocols in getting what we want out of the congested mass of information. Evidence Based Decision Making encourages the clinician to ask the right question, to get the right answer.A right question is the one that explains precisely the clinical problem that needs to be solved, the methods which are going to be used to solve that problem and the solution that is desired. In EBDM language this is called as the “PICO process”, were P stands for Patient or Problem, I for Intervention, C for Comparison and O for the Outcome. Therefore, a right question will consist of all these four components to convey the query, very specifically. The question can be therapy related, diagnosis related, prognosis related and causation related. The following examples enable a better understanding.

 

* Therapy related question:

 

P – For an adult patient, with extensive tetracycline stain in the anterior teeth.

I – will an indirect composite veneering

C – compared to a ceramic veneering

O – mask the discoloration effectively?

* Diagnosis related question

 

P –For estimating the working length of a root canal in an adult permanent tooth

I – will an apex locator

C – compared to the radiographic method

O – be able to provide reliable and accurate results?

* Prognosis related question

 

P –In an indirect pulpcapping procedure

I – will intentionally retaining the carious dentin

C – as compared to complete removal of carious dentin

O – affect the vitality of the pulp in the long run?

* Causation related

 

P –In root canal treatment of a permanent tooth, with an episode of acute apical periodontitis during treatment

I – will use of endomethasone sealer

C – as compared to grossmans sealer

O – result in a peri apical rarefaction later?

Once the right question is ready, in order to get the right answer, it is imperative to know, which type of research study will best answer a certain type of question.Therefore a brief recapitulation of the types of researches and their ranking in the evidence based hierarchy, will make the reading ahead more comprehensible.

 

A research Recap

 

Clinical research can be either experimental or observational. Experimental can be controlled and uncontrolled. The controlled experimental studies (where there is a comparison group) are stronger designs in the research family, than the uncontrolled research.

 

Randomized controlled trial is considered to be the strongest design for the clinical researches. Randomization. blinding, sample size justification, appropriate outcome measures and statistical analysis together reduce the bias in this design.

 

Observational studies observe a patient at a point of time (Cross sectional) or over a period of time (longitudinal). It can be either prospective (Cohort) or retrospective (Trohoc). In a cohort study, it is known at the outset, whether samples have been exposed or not, to a treatment or possible causal agent and are divided into groups or cohorts (treated or exposed versus non treated or non exposed) on this basis. They are then followed forward in time (prospectively) for years or even decades to see how many in each group develop a particular disease or other outcome. In Case control studies , samples with a particular condition are matched with a group of samples who do not have the disorder and the researchers look back in time to determine the proportion of samples in each group that were exposed to the suspected causal factor. Cross-sectional Studies attempt to establish an association between a possible causal factor and a condition, by determining an exposure to the factor and the condition at the same time. Case reports and case series are often used to describe a condition (usually a rare disorder or a novel aspect of a less rare condition), a new treatment or innovation, or adverse effects of an intervention. This brief knowledge on research designs will be useful in the further sections of the article.

 

The Research Hierarchy

 

In simple words, this specifies the ranking order from good design to bad design, in terms of valid and reliable results, with bias control. The highest level of evidence or “gold standard” is the Systematic review and Meta-analysis. These are followed by Randomized controlled studies, cohort studies, case-control studies, and studies not involving human subjects, in this order. The expert opinions rank the lowest in the evidence ladder.

 

Systematic Reviews provide a summary of individual research studies that have investigated the same phenomenon or question. This scientific technique uses explicit criteria for retrieval, assessment, and synthesis of evidence from individual RCTs and other well-controlled methods.

 

Meta-analysis is a statistical process commonly used with systematic reviews. It involves combining the statistical analysis and summarizing the results of several individual studies into one analysis. When data from multiple studies are pooled, the sample size and power usually increase.

 

Research and PICO relationship

 

Though the randomized control trials and clinical trials enjoy the high pedestal in Evidence Based Decision Making, for some clinical problems they may not be feasible or may not be required at all. Sometimes they may not have been done yet. For example, to assess the success rate of root canal treatment, treatment should be followed up over a period of time (Prospective Cohort study) to observe the prognosis. Here a randomized control trial is not required. Evidence Based Decision Making gives a guideline regarding the best research match for various typology of questions.

 

Diagnosis questions : Prospective cohort study

Prognosis questions : Prospective cohort study

Therapy questions: RCT

Causation questions :RCT, cohort or case-control study

Data Search with Pubmed

 

The following section will concentrate on a systematic and effective way of searching the MEDLINE Electronic Data Base through the PUBMED, the most commonly used primary source for information. What we have in hand now, to clarify our question, is the structured form of the question, the knowledge about the nature of the question and also the knowledge about which type of research papers we have to look for.PUBMED features all its inner space details in a tutorial It would be a satisfying experience to venture into this site. However the tour that we are going to take you through with a sample PICO question will highlight the importance of certain features in PUBMED that will help us in focusing our search.

 

Sample PICO structured clinical query:

 

The problem is therapy related

 

P – For treatment of caries in an adult patient with high caries risk,

I – will ozone therapy,

C – compared to conventional preventive treatment,

O – effectively cessate the progression of lesion?

The type of research to look out for are Meta analysis, Systematic Review, Randomized Controlled trials and Clinical trials in this order of preference. As was mentioned before, the MEDLINE database understands a different vocabulary than that is used in the above PICO question. It is called as the MeSH (Medical Subject Headings) term. This vocabulary contains main headings or index terms, each of which represents a single concept in the biomedical literature. New terms are continuously added and outdated ones are removed by subject specialists as new concepts emerge in the scientific literature. So the first step in the pubmed search is to find out the mesh term for the key topics in the question. Searching the MeSH term is an art by itself. PUBMED provides a MeSH database and MeSH search. Typing the important terms of the question in search box of MeSH database, will suggest relevant MeSH terminologies.Most of the journal articles now provide the key words and the MeSH terms, to make things less complicated.

 

As the first step in the data search for our clinical query, in the MeSH database of the PUBMED we typed the term ‘Dental Caries’ as in (Fig 3-click to view). The detailed subheadings under ‘Dental caries’ is shown in (Fig 4-click to view). Our question is related to dental caries therapy, we ticked the term ‘therapy’. In the ‘Send to’ pull-down menu we selected ‘Search Box with AND’. On clicking the ‘Send to’ button, the term with specifications appeared in the Search Box ( Fig 5-cllick to view). We did not attempt to search for the Mesh term for ‘ozone therapy’ (Fig 6-click to view). We decided to use the search by the Text word. Text word searches the database by the presence of this term in the title or the article.Thus the search terms [“dental caries/ therapy” AND ozone therapy] were framed. The ‘AND’ here is not simply English. This is called BOOLEAN OPERATOR in the data base search jargon.Boolean logic symbolically represents relationships between entities. There are three Boolean operators. The AND operator is used to retrieve a set in which each article contains all the search terms.The OR operator is used to retrieve documents that contain at least one of the specified search terms. The OR operator is used when you want to pull together articles on similar subjects. Use the NOT operator to exclude the retrieval of terms from your search. All Boolean operators should be typed in upper case.The PUBMED search with this assembly (Fig 7-click to view) yielded 10 articles out of which 3 articles were reviews. Two articles were in French, one was a congress report and two were personal views and letters. Only two RCT studies were obtained. To get the studies that are in the top of the evidence ladder, we can use the LIMIT feature to zoom-in more. LIMITlimits the searches to specific fields, age groups, gender, type of study, Entrez or publication date, a specific language, types of articles, or subsets. We limited the search by selecting Meta analyses (Fig 8-click to view) in the Publication type, English language and Human studies. This search yielded no results (Fig 9-click to view). Then the publication type was changed to Randomized clinical controland we ended up with two articles (Fig 10-click to view). The abstract of both the articles seemed to offer the answer to our question. The answers were promising for the use of the ozone therapy. We decided to obtain the full articles either by tracking down the journals or writing to the authors for reprint. We also have a feature for obtaining the articles in PUBMED which is called as the ‘Loansome DOC service’. As RCT is a recently popularized study design and clinical trials were frequently performed in the earlier times, we limited the search to Clinical trials (Fig 11-click to view) and ended up with the same two articles. However, a very interesting thing was observed. Among the 3 review articles one was a systematic review (Fig 12-click to view) by then Cochrane data base – real evidence! The important message here was, that there is no enough evidence to prove the superior efficacy of the ozone therapy over the other treatment modality! In fact a Meta analysis was not possible as there were no enough RCT in this area! What do we infer from this as a clinician? ..that we cannot promise or expect a cessation of the progression of the carious lesion on using a latest gadget of Ozone therapy, inspite of solitary claims by some studies and the manufacturer. What do we infer as an evidence provider? ..that this is one interesting area of Dental caries management that requires more clinical research. If proven effective, this concept can add to the ultraconservative revolution of Dental caries management. A potential area for a thesis!

 

More useful features of PUBMED

 

A very useful operation, called truncation, can be employed when doing text word searches. A truncated term is the first part of a word followed by an asterisk. This feature allows all terms beginning with that part of the word to be searched. For example, “dent*” will find all terms that begin with the letters d-e-n-t, including “dental,” “dentistry,” “dentist” and so on.

 

One can also access the results for our example PICO very quickly through Clinical Queries link on PUBMED sidebar. This is a search interface to find citations in the areas of Clinical Study Categories, where one can find citations corresponding to a specific clinical study category and Systematic Reviews where one can find citations for systematic reviews, meta-analyses, reviews of clinical trials, evidence-based medicine, consensus development conferences, and guidelines. Four study categories or filters are provided within Clinical Queries: therapy (default), diagnosis, etiology and prognosis. Two emphasis categories or filters are also provided: sensitive search (broad) and specific search (narrow).

 

Research lacunae and EDB

 

Now we approached the Electronic Data Base in the similar way, to search for lacunae in evidence for few vital topics, in Conservative Dentistry and Endodontia. The questions were formed on various topics in which we had our own doubts regarding the clinical efficacy or utility. Please note that this list is not a complete one of lacunae in our field. This is only the tip of the iceberg. This section is included in this article mainly to motivate the student and academic community to conduct more refined and relevant clinical studies. It was an awesome experience to find that Meta analyses and Systematic reviews are very few in the secondary evidence based dentistry sources. Searching the primary source in the PUBMED retrieved equally sparse RCTs and clinical trials. Even the prospective and retrospective observational studies relevant to prognosis and diagnosis related questions were very few. We repeated our search in one or more search engines to exclude the possibility of error in our search strategy. Apart from a routine search through the PUBMED, we had also used Clinical query service of PUBMED, Trip Database search engine and the Evident search engine.

 

The following are the topics where questions were raised and database was searched for answers, but found voids that are potential for research. The interested Post graduates can even consider them for their thesis/ dissertation.

 

* Diagnodent: The search term included the term sensitivity and specificity, a useful MESH term while looking for data related to diagnosis. No evidence based articles were found, but only one Randomized control trial study was found. 22 articles under the category of diagnosis articles were found. Browsing through them we found them to be more of evaluation studies and narrative reviews, which do not stand at the top of evidence hierarchy. A weak information architecture and clinical usefulness of this technology,makes this a potential research subject.

 

* Diagnostic aids used for proximal caries detection: A broad search of the database revealed just one clinical trial and nine other valuation studies. No systematic review or Meta analyses were found. A clinical challenge where we are dependent on just a radiographic image, in all fairness, should have more studies than that is just present now.

 

* Caries risk assessment tests : First rank evidence is severely lacking in the caries risk assessment methods. A simple search for microbial analysis weeded out only two clinical trial articles and about ten diagnostic articles and one causation related and one prognosis related article. However the conclusions of these studies did not singularly and strongly support the relationship of microbial count in saliva as a diagnostic tool for the disease.

 

* Casein (bovine milk phosphor protein): As an anti cariogenic material this material is already prevalent in the clinical practice. But the naked truth is, at this point of time of this search, only one RCT emerged that was done in 2002. Most of the other meager 8 articles found were animal studies and reviews only!

 

* Mineral trioxide aggregate: A material in vogue in clinical practice enjoys popularity in research in terms of 186 articles, but all of them were articles tracked without applying limits for better evidence. On applying evidence limits to human Rct in English language, we found only 13 results. Among these 13, only one evaluated MTA as a pulp capping agent. The others were evaluating MTA as a root end filling material. That is one golden area for research.

 

* Dentin bonding agents: This material as a pulp capping agent is always a subject of controversy between the eastern and western literature. On searching the PUBMED data base using relevant mesh terms, it was interesting to note that only 4 RCT in humans in English were present. More evidence in the form of clinical trials might definitely diffuse this controversy.In spite of all the attention on dentin bonding agents and their fast growing generations, the PUBMED database search for RCT study on humans, in English for the last 5 years, yielded just one study comparing single bottle and two bottle adhesive. This an in vivo study with a good criteria for evaluation. Such studies are welcome in this topic, instead of experimental in vitro studies, the results of which may not correlate well with complex in vivo situations.

 

* Veneer restorations: In the subject of Composite resin restorations, the most happening thing in clinical practice is the indirect composite resin restorations.. With gadgets made available for an in-office set up, it is time to see if there is any strong evidence to support their use. This is what we found searching for information on veneers. Wakiaga J, Brunton P, Silikas N, Glenny AM. Direct versus indirect veneer restorations for intrinsic dental stains. The Cochrane Database of Systematic Reviews 2004, Issue 1. Art. No.: CD004347.pub2. DOI: 10.1002/14651858.CD004347.pub2. This review concludes that “There is no reliable evidence to show a benefit of one type of veneer restoration (direct or indirect) over the other with regard to the longevity of the restoration.

 

* Apex locators: WL estimation with apex locators has been in use both in institutes and clinical practice since very many years. However a search for a good RCT revealed just one study in the year 2000. The reason for this lacuna definitely needs to be explored.

 

*Electric Pulp testers: In an era where lasers are being used for vitality testing in Endodontia, dilemma is still present in the use and interpretation of results with electric pulp testers. The data was mined for information on the diagnostic accuracy of these gadgets over the thermal tests and we landed up with only one article in the year 1999.

 

* Automated Endodontics: Rotary endodontics has taken a permanent place in a clinical set up. A search was made to find its efficacy in all clinical parameters compared to manual instrumentation. However clinical trial search limited to English language and human subjects, resulted in 14 studies. In the past 5 years, studies specifically comparing it with the manual instrumentation resulted in only 4 papers.

 

* Single visit endodontics: This is a debatable concept for too many years, but unfortunately has not initiated quality researches. Trip database revealed only 5 therapy articles and 1 good prognosis article.

 

Concluding remarks

 

Are the ways of Evidence Based Decision Making, the ultimate scale to measure the research status in our fraternity? The answer may not be strongly affirmative. Evidence tracking in evidence based approach, places articles published in English at the top of evidence ladder. Therefore studies in any other language, however good they may be, as per the norms of Evidence Based Decision Making, may get eclipsed. In addition, if a particular article does not mention the type of study design it has utilized (Clinical trial, or RCT, or evaluation study etc), again it gets lost in the search strategy. When searching through the PUBMED database, only journals that are indexed in this will be searched. Those that are not indexed, whatever quality or dedication they may possess, will not contribute to the database. For instance, Indian studies were too conspicuous, simply by their absence in the small search that we had done for this article. This in no way can mean that Indian dentistry has not contributed to the global dental research. The reason may be just that most of our journals are not indexed in the global databases. Is Evidence Based Decision Making going to be the future way of Indian dental practice? Again the answer may not be boldly affirmative. The evidence based practice is in the international scenario, primarily because of the consumer litigation against the dental professionals. That is why the nomenclature information has transformed to evidence, that smells legal! Even though India is shining here and there, most of the dental practices in rural areas are still not sophisticated enough to latch on to a computer system, to update on dentistry and most of our patients still do not have consumer awareness. Therefore Evidence Based Decision Making in India may not be pandemic, at least in the near future. However one off shoot advantage of Evidence Based Decision Making, as we had seen throughout this article is the awareness of research and its influence in clinical practice. In addition, as the dental education in our country is rapidly accelerating, it is time to think of a repository of information for Indian, by Indian. Every academic body in our country can become e- alert and disseminate their researches, electronically through their websites, for national and international benefit. More importantly, the dental post graduate curriculum has to change its outlook towards thesis/ dissertation and treat them as potential database providers than a mere formality to be completed for the partial fulfillment to obtain the Masters degree. If the details of the thesis/ dissertation right from the study objectives to study designs are taken care of, meticulously and scrupulously, the results that emerge are sure to be strong evidences. The curriculum should emphasize on more of clinical trials than in vitro experimental analysis. The data obtained by the experimental in vitro studies do contribute to information congestion that already exists, with at least 700 journals and at least 25,000 publications per year, but, never contribute to qualitative, clinically useful data.Unless and until these lacunae in our professional existence are not eliminated with a refreshed and revolutionary thinking, then the so called lacunae in the research will persist forever.

 

SUGGESTED READING:

 

1. Carounanidy Usha. Getting cornered or Getting ahead? – Evidence Based Dentistry: A view point. JIDA Vol. 72 July 2001.

 

2. David L Sackett, William M C Rosenberg, J A Muir Gray, R Brian Haynes, and W Scott Richardson. Evidence based medicine: what it is and what it isn't. BMJ 1996; 312: 71-72

 

3. Forrest JL, Miller SA.Evidence-Based Decision Making in Action:Part 1 - Finding the Best Clinical Evidence. J Contemp Dent Pract 2002 August (3)3: 010-026.

 

4. Forrest JL, Miller SA. Evidence-Based Decision Making in Action: Part 2 – Evaluating and Applying the Clinical Evidence. J Contemp Dent Pract 2003 February;(4)1:042-052.

 

5. Richards D, Lawrence A. Evidence based dentistry. Br Dent J 1995; 179(7):270-3.

 

6. Richard M. Beyers, DDS. Evidence-Based Dentistry:A General Practitioner’s Perspective. J Can Dent Assoc 1999; 65:620-2.

 

7. Sackett DL, Straus SE, Richardson WS, Rosenberg W, Haynes RB. Evidence-based Medicine: How to Practice and Teach EBM. Second Edition.Churchill Livingstone: Edinburgh, 2000.

 

8. Sackett DL, Wennberg JE. Choosing the best research design for each question.BMJ. 1997;315:1636.

 

9. Susan E. Sutherland, DDS .Evidence-based Dentistry: Part I. Getting Started .J Can Dent Assoc 2001; 67:204-6

 

10. Susan E. Sutherland, DDS. Evidence-based Dentistry: Part II. Searching for Answers to Clinical Questions: How to Use MEDLINE . J Can Dent Assoc 2001; 67:277-80

 

11. Susan E. Sutherland, DDS and Stephanie Walker, MA, MLS. Evidence-based Dentistry: Part III. Searching for Answers to Clinical Questions: Finding E-vidence on the Internet . J Can Dent Assoc 2001; 67:320-3

 

12. Susan E. Sutherland, DDS. Evidence-based Dentistry: Part IV. Research Design and Levels of Evidence .J Can Dent Assoc 2001; 67:375-8

 

13. Sutherland SE. The building blocks of evidence-based dentistry. J Can Dent Assoc 2000; 66(5):241-4.

 

Gold foil restoration --Is Old Still Gold ?

Posted on 1 March, 2019 at 9:30 Comments comments (0)

Gold foil restoration

The quest to search the ideal restorative material has been a challenge for the researchers and academicians in the fraternity of restorative dentistry. With the rapid advancement in the bio material science and bio technology, most of the material properties have drastically improved in the recent years. Among the available restorative materials, direct filling gold is the oldest filling material that is still used in restorative dentistry.

 

Is Old Still Gold ?

 

The concept of using metal as restorative material has arisen from the identification of mechanical demands of the oral apparatus. The vision to utilize the noble metals for the replacement of lost tooth structure stemmed from perfect harmony of its biological and mechanical properties excluding esthetics. While most of metals can be welded and alloyed at a temperature above the room temperature, the pure gold can be cold welded and made to adhere to each other at room temperature. This property coupled with strain hardening by which the strength and hardness of the material is increased as it is cold worked or welded makes direct filling gold unique. Since it is very ductile and malleable, the gold can be worked well against the walls of the cavity, creating excellent marginal adaptation of the restoration. However placing a gold foil restoration requires highly demanding and skilled operator. A well done direct gold restoration can last ones lifetime (1), in the properly selected cases.

Introduction:

 

Current status of gold foil: In spite of many favorable properties, the placement of gold foil restorations is at decline, both in the university based practice and in private practice globally. In India, it is almost none. In an excellent review by Gerald.D.Stibbs(1987)(2), he critically evaluated the reasons for this decline. The reasons stated by Gerald.D.Stibbs in universities/dental schools are: 1. Lack of emphasis of direct gold restoration in dental curriculum. 2. Lack of trained staff in direct gold restorations. 3. Change in overall attitude to settle for less than the best restoration. He further states that the same decline in private practice is because of the change in the current philosophy of practice. The olden days practice was based on more value based treatment with the concept of “need based practice” as the pivotal point. The need of the patient was given maximum importance and the same was delivered by the dentist and was equally accepted by the patients. But the present day private practitioner is more with a philosophy of “want based practice”. This change in demand by the patients, propelled by legal and insurance coverage factor has led the dental operators to deliver the treatment of what the patient wants than what is actually needed.

 

In the minimally invasive era…

 

Tooth colored material with both optical and physical properties similar to that of tooth structure is the current emphasis of research. The metallic restorations including direct filling gold definitely can not satisfy the esthetic demands. However there is no cost effective esthetic material that can last functionally and durably as direct filling gold for small lesions. Hence, when indicated for selected posterior teeth where the esthetic demand has been created iotrogenically, direct filling gold will be the prudent choice of material.

 

In the esthetic era…

 

Is there sufficient evidence to support and use direct filling gold as restorative material? The concept of evidence based dentistry has surfaced the past decade and most of the evidence based studies regarding longevity and holistic analysis of restorative material is from 1990. the material science researches is at snail pace for the direct filling gold. Even then, it has recent improvement with EZ gold and various types of precipitated gold. Most of the research regarding gold foil was done from 1900 till 1985. Where the direct filling gold restoration has stood the test of time , as G.V.Black pointed out in 1908,there is no restorative material as good as gold foil to take the full advantage of the modulus of elasticity of the dentine. The research in the arena of gold foil and other metallic restoration are not very aggressive because most of present researches are supported and funded by the manufacturers.(3) university based researches, other non profit funding agencies are very minimal and in the current scenario. Research based by manufacturers will definitely eclipse around the demand and the want of the patients. In the light of evidence based dentistry, the direct filling gold does not have any evidence to support; even then it has proclaimed itself to be one of the most durable materials from 1900 -1980!!

 

In the era of repair and replacement…

 

With the current evidence and in depth knowledge and understanding of restoration cycle, the concept of repair has gained acceptance than replacement. The ignored fact is that it may not be required to replace or repair a restoration if its durable with good marginal integrity.(4). Gold foil stands best with its marginal integrity and with current advancement, of mat and precipitated gold, it is possible to carry out an exact replica of both cast gold and direct filling gold restoration with the gold foil.

 

In this evidence based era…

 

One of the foremost thought of the restorative dentistry is that “now are we justified by doing gold foil restoration in this era, where conservation of tooth structure is the mantra? “Conservation of tooth structure in the context of minimally invasive technique is a very much misunderstood concept. Any modality to conserve the tooth structure should be viewed in association with the longevity of the restoration. The hidden factor often overlooked in the longevity of the restoration is the “restoration cycle”. Restoration cycle means that how regularly it is required to replace the restoration during ones lifetime. It has been proved that every time a restoration is replaced ,there is always an inadvertent removal of tooth structure. Also, this is more to do for the tooth colored restoration. Hence, if a restoration which is more durable because of the material per se, is likely to be the most conservative treatment plan than a restoration which can be restored with minimal cavity preparation but will last only for few years. In this ranking, direct filling gold is the most durable material that is available in the restorative material sciences. In fact, the cavity preparation is very minimal and can last long for small pits and fissures and proximal lesions.

 

References:

 

1. Gregory.E.Smith: Students art and science of operative dentistry, 4th edition. Pg:873.2. Gerald.D.Stibbs:direct gold in dental practice DMD1980. 3. Medina JE:Direct gold restoration in dental education. Oper Dent1987 winter12 (1).20-3.

 

4. Lamber.R.H, Gold fogelMH.Repair of defective restorations of direct gold oper dent 1985.summer 10(3):98-99.

 

With the current evidence and in depth knowledge and understanding of restoration cycle, the concept of repair has gained acceptance than replacement. The ignored fact is that it may not be required to replace or repair a restoration if its durable with good marginal integrity.(4). Gold foil stands best with its marginal integrity and with current advancement, of mat and precipitated gold, it is possible to carry out an exact replica of both cast gold and direct filling gold restoration with the gold foil.

 

Conclusion:

 

Even though gold foil restoration and the materials are very much favorable, the evidence to recommended its use is not available since the research has been stand still for the past 2 decades on one of the best restorative material. Also, unlike other restorative techniques, the gold foil restoration which has not been done to the highest degree of perfection, the same very best material can be the very worst restoration! The option to utilize gold foil as the best restoration or worst restoration totally rests on the shoulder of the operator!! Unless a conservative dentist takes a conscious attempt to tame and master this wonderful material and technique for many indicated lesions, the patient will be deprived of the very best treatment because of the fallacy of the conservative dentist.

Light Emitting Diode The unsung heroes

Posted on 2 February, 2019 at 3:45 Comments comments (0)

Light Emitting Diode

The unsung heroes

This article deals with the details of LED, Light Emitting Diode, covering all the topics from the evolution of LEDs to their future directions in relation to conservative dentistry and endodontics.

 

 

1. Evolution of LED

 

A Story of success

Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. Were we able to look into the future, we would see LEDs everywhere around us. In the past, LEDs were mainly used for advertisement signs and as background light, but LEDs are being used for an increasing number of applications, ranging from architecture and lighting design to traffic signals and even medicine. The full potential of this young and promising technology has not been realized yet. Given their superior technical properties, LEDs offer an immense potential for innovation and growth. LED lights are not only much more energy efficient than conventional halogen lamps, but they also offer an unmatched service life.

 

Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.

 

Russian Oleg Vladimirovich Losev independently created the first LED in the mid 1920s; his research was distributed in Russian, German and British scientific journals. But no practical use was made of the discovery for several decades. The first practical visible-spectrum (red) LED was developed in 1962 by Nick Holonyak Jr., while working at General Electric Company. Holonyak is seen as the "father of the light-emitting diode". M. George Craford, a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972. In 1976, T.P. Pearsall created the first high-brightness; high efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths. In February 2008, Bilkent university in Turkey reported 300 lumens of visible light per watt luminous efficacy (not per electrical watt) and warm light by using nanocrystals.

 

In January 2009, researchers from Cambridge University reported a process for growing gallium nitride (GaN) LEDs on silicon. Production costs could be reduced by 90% using six-inch silicon wafers instead of two-inch sapphire wafers. The team was led by Colin Humphreys.

 

 

2.Influence of evolution of material science on LED

UV light activation was first introduced to the dental community. This concept served as a major advance over conventional chemically cured composites by providing premixed, shelf-stable materials with infinite working time and cure-on-demand ability. For the first time, curing restorative materials required no mixing, provided adequate time for placement and preparation of anatomy, and delivered instantaneous results. This gave more control to the dentist and reduced the stress involved with restorative dentistry. UV photocuring dramatically changed the direction of dentistry; however, it still had several limitations including limited depth-of-cure due to light absorption of the resins, pigments and fillers in the composites, and also significant safety considerations due to the nature of higher energy UV light. The early 1980s led to further advances in the photocuring of dental materials. The key advance was in the area of visible light curing and the identification of CPQ as an ideal photoinitiator (Figure 1-Click to view). The advent of visible light curing and photoinitiator use in composite materials began changing the world of restorative dentistry. Blue light in the form of quartz-tungsten halogen curing lights became the standard for light curing, offering better depth of cure and a safer means of curing versus UV light. Restorative materials and curing light technologies continued to advance. Manufacturers continued to improve upon the physical and esthetic properties of composites while curing lights increased in intensity in an attempt to direct more light toward the restoratives to cure them faster and deeper. Plasma Arc and Laser curing lights entered the market, promising faster cures by producing more light. Light emitting diode (LED) curing lights are the latest advancement, coming to market with numerous benefits to traditional curing lights, including low energy consumption with the light output fine tuned to CPQ (Figure 2-Click to view).2,3,4.

 

 

3. Impact of changing clinical trends on LED

 

Sufficient curing is the prime concern of polymerization…

A restoration made of light-curing materials will only be a long-term success if discoloration and the formation of marginal gaps and increased abrasion. As the surface of light-curing composites appears hard after only short curing, it is impossible to determine the polymerization quality in practice by tactile means,using a probe or using other instruments. The physical values of the entire cured material are what matters. This includes the achieved hardness – in particular on the bottom side of the restoration, the flexural strength and elasticity as well as the abrasive values (Figure 3-Click to view). The specifications of the manufacturers regarding the gentle curing of the various materials are important guidelines. At least well-known suppliers base such recommendations regarding curing time and program on clinical tests with various materials and various layer thicknesses. Sufficient curing depends on many factors. The most important ones are, however, high light intensity and the activation of the photoinitiators used, i.e. the suitability of the curing light for the materials used. Light-curing materials, such as composites, are mainly composed of organic monomers and inorganic fillers.

 

 

The various photoinitiators

In order to transform a monomer into a polymer, photoinitiators, which break down into radicals when irradiated with light and thus cause a polymerization reaction of the monomers, are required. The most commonly used initiator is camphorquinone. Camphorquinone absorbs light in the wavelength range between approx. 390 and 510 nm and displays a yellow color, which unfortunately also affects the shade of the cured restoration. White photointiator which absorb light in the wavelength range between 380 and 430 nm (Figure 4-Click to view) such as phenylpropanedion (PPD) or Lucirin TPO are also used. These white photointiatiors are used in bleach shades of resin composite material. The ability of a curing light to cure all materials, therefore, decisively depends on the wavelength range that is emitted by the light. Given their broadband emission spectrum, halogen lights activated the various initiators without any problems. Because they typically have a narrow emission spectrum, conventional LED lights are not automatically suitable to universally cure all materials. Today, however, there are LED curing lights which generate blue light in the range between 380 and 515 nm and which are thus suitable for all light-curing materials (Figure 5-Click to view).2, 5

 

 

Wavelength range

LEDs in general have a more limited light spectrum than halogen lights. Therefore, the polymerization of materials which do not exclusively contain camphorquinone as photoinitiator might be problematic even when modern LED lights are used. Depending on the polymerization light used, this may be the case with very light composites (Bleach shades) and special adhesives. In such situations, lights with a spectrum which is not designed to match only the absorption maximum of camphorquinone, offer significant advantages. In order to safely use the materials in the own practice, a negative list of the incompatible materials is required from the manufacturer of conventional LED lights.

 

 

4. Physics behind LED

In contrast to halogen and plasma arc lamps, LEDs produce visible light by quantum-mechanic effects. LEDs comprise a combination of two different semiconductors, the ‘n-doped’ and the ‘p-doped’ type. N-doped semiconductors have an excess of electrons while p-doped semiconductors require electrons, resulting in creation of electron ‘holes’ (Figure 6-Click to view). When these two types of semiconductors are combined and a voltage is applied, electrons from the n-doped type connect with holes from the p-doped type. A characteristic light with a specific wavelength range is then emitted from the LED (Figure 7-Click to view). The color of an LED light, its most important characteristic, is determined by the chemical composition of the semiconductor combination. Semiconductors are in turn characterized by their band gap. In LEDs, this gap is directly utilized for light production. When electrons in the semiconductor combination move from higher to lower energy levels, the energy difference of the band gap is released in the form of a photon of light, In contrast to halogen and plasma arc lamps, LEDs produce light with a narrow spectral distribution. This is the main difference between light produced by LEDs and other light sources, as light of selected wavelengths can be preferentially produced using LEDs with appropriate band gap energies. This innovative method of light production therefore creates a more efficient way of converting an electric current into light.6,7

 

 

1,000 mW/cm2: the ideal value

Normal light is not enough to polymerize materials in the dental practice. For this process, energy-rich blue light is necessary. Already for direct restorations, an irradiance (commonly referred to as “light intensity”) of at least 400 mW/cm2 is required. The ideal value, however, is thought to be 1,000 mW/cm2, in order to ensure that indirect restorations are also sufficiently cured when the irradiation takes place through the ceramic restoration or tooth substance. According to the Total Energy Concept, light intensities of more than 1,000 mW/cm2 are necessary to provide adequate curing of composites in all suboptimal but routine conditions in only ten seconds. If the light intensity is lower, the curing time is accordingly longer. If the above prerequisites are not met, the composite or adhesive may be cured only insufficiently in deeper areas. Therefore, it is advisable to check the light intensity, which decreases in time, regularly. For that purpose, built-in or separately supplied radiometers or the integrating spheres are helpful tools.5

 

 

Total Energy Concept …

… Or: “What curing time is required for successful curing?” The Total Energy Concept states that the light-curing process depends on the energy and is basically determined by the multiplication of light intensity and time (for example: 20 seconds at a light intensity of 800 mW/cm2 = 20 s x 800 mW/cm2 = 16,000 mWs/cm2). The required dose depends on the type, shade and translucency of the composite. As a general rule, a dose of maximum 16,000 mWs/cm2 is required to adequately cure an increment of 2 mm – in some cases, the value might be lower. Based on this maximum value, various curing times can be calculated depending on the light intensity of the polymerization light used.5,8.

 

Total Energy Concept:8

Maximum curing time = Dose / Intensity

 

 

Interesting facts about the light probe

If a polymerization light is designed without a light probe and instead is equipped with an LED mounted at the front of the light-emission window, much of the intensity is lost due to scattering at a certain distance from the object to be cured. Fibreglass rods have proven themselves very adequate to reduce this loss due to scattering. These fibreglass rods consist of many individual glass fibreswhich are embedded in a protective glass case with a precisely defined light transmission. This, however, does not eliminate the need to increase the curing times with increasing distance from the object to be cured. In the case of the popular turbo light probes, the effective energy decreases by up to 50% at a distance of 5 mm, which means that the curing time must be doubled according to the Total Energy Concept. Given their outstanding light-scattering characteristics, parallel-walled (standard) light probes offer an advantage in this regard. The available energy is reduced by 50 % only at a distance of 9 mm (Figure 8-Click to view) (Figure 9-Click to view)

 

 

To summarize

Determining the required curing time in three steps

 

1.Check material compatibility

Not every conventional LED polymerization light is suitable to cure all light curing materials. Ask the manufacturer of your LED curing light whether it is compatible with the materials camphorquinone, Lucirin TPO and phenylpropanedion (PPD) – or ask the manufacturer of the composite which photoinitiators are contained in the composite.

 

 

2.Calculate curing time

With the help of a simple equation you can easily calculate the curing time for composite restorations.

 

 

3.Take the distance from the object into account

The curing time must be doubled if only 50% of the original intensity is available to cure the composite.

 

 

5. Current concepts in LED

Table 2 -Click to view. Product features according to the manufacturer.

 

POWER DENSITY (commonly referred to as “Light Intensity”):

 

Results: The highest light intensities were achieved with blue phase and the L.E.Demetron II, which were both over 1000 mW/cm2. FLASH-lite 1401 with a power density of 439 mW/cm2 was the lowest.

 

 

Depth of cure

Results: The depth of cure achieved with Herculite (Kerr Dental), a microhybrid composite, using the L.E.Demetron II light was the highest of all the LEDs. The depths of cure achieved with Heliomolar (Ivoclar Vivadent), a microfilled composite, were highest using the Coltolux, FLASH-lite’s 1401,Freelight, L.E.Demetron II and Radii Plus lights.

 

Comments: Depths of cure are dependent on the characteristics of the curing light (intensity and spectral distribution), the composite (type, shade, opacity and photoinitiator) and clinical variables such as distance of the light tip from the composite surface. In our study we measured the depths of cure of two types of composites (microhybrid and microfilled) and one shade (A2) with the light tip placed close to the composite surface.

 

 

Temperature rise

Results: Ultra-Lume LED 5, blue phase and L.E.Demetron II lights caused the largest temperature rise (over 12°C) over the 40 second curing time. SmartLite iQ caused the smallest rise in temperature (7.4°C).

 

Comments: The experimental setup may tend to overestimate the temperature rise. This is because the clinical situation allows more efficient heat dissipation. Also, dentin has a low thermal conductivity, which protects the pulp tissue.

 

 

Spectral distribution

Measures the distribution of light across the spectral range

 

Results: Ultra-Lume LED 5 exhibited two spectral peaks, one at 404 nm and one at 460 nm. All the other LEDs had a single peak between 444 nm and 468 nm.

 

Comments: The spectral emissions of all the LEDs allow curing of composites that contain camphorquinone, the most popular photo-initiator, which has an absorption peak around 470 nm. The bimodal spectral emission of Ultra-Lume LED 5 purportedly allows it to cure every photo-initiated product on the market, although this claim was not. As noted above, blue phase and L.E.Demetron II had the highest intensities compared to the other lights. However, while use of L.E.Demetron II also resulted in higher depths of cure this was not the case for blue phase, which has a spectral peak around 444 nm – well below the absorption peak of camphorquinone (the photoinitiator in the composites used). This demonstrates the point that intensity alone does not dictate the effectiveness of a curing light.

 

 

Corded or Cordless?

The advantages of a cordless light are obvious, but the disadvantages are not so apparent. When selecting a light, there are a few things to consider with respect to the type of battery and maintaining cordless operation. Consider how often and for how long you use your curing light. More frequent, light intensive procedures will require a battery that has a higher energy capacity. The lights tested used the Nickel Metal-Hydride (Ni-MH) or Lithium-Ion (Li-ion) batteries. These batteries cost about $100 to replace when they can no longer hold a charge. Two of the lights used a non-removable rechargeable battery. When they can no longer hold a charge, the light has to be replaced. To get the longest life out of a new Li-ion battery (the newest battery type), perform an initial conditioning of the battery. For the first three charge cycles, fully charge the battery overnight and allow it to fully discharge before recharging. Ni-MH batteries must also be conditioned before use and then again every 3-5 charge cycles. Li-ion batteries have a higher power density than Ni-based batteries. This allows longer battery life in a lighter weight battery. You can also recharge a Li-ion battery whenever convenient, without the full charge or discharge cycle required to keep Ni-MH batteries operating at peak performance. Lithium-ion batteries need to be used for maximum performance. If you don’t use your light very often, make sure you complete a charge cycle at least once per month.

 

L.E.Demetron II had a significantly higher average depth of cure associated with its use at 20 seconds; however, in the clinical forum, the dentists consistently rated this light lowest because of its bulky size. Dentists participating in the forum gave the highest scores to blue phase and FLASH-lite 1401.

 

Ultra-Lume LED 5 offers the advantage of a broader spectral range, which allows more efficient curing of materials containing photoinitiators with absorption peaks below 400 nm. Although camphorquinone is the most popular photoinitiator in dental materials, some materials contain other compounds like monoacylphosphine oxide (MAPO), bisacylphosphine oxide (BAPO) or phenylpropanedione (PPD)

 

.Table 3. Buyer's Summary for LEDs. .

 

Table 4. Summary of Led attachments available. .

 

6. Consideration for use

 

Power sources

The current/voltage characteristics of an LED are similar to other diodes, in that the current is dependent exponentially on the voltage. This means that a small change in voltage can lead to a large change in current. If the maximum voltage rating is exceeded by a small amount, the current rating may be exceeded by a large amount, potentially damaging or destroying the LED. The typical solution is therefore to use constant current power supplies, or driving the LED at a voltage much below the maximum rating. Since most household power sources (batteries, mains) are not constant current sources, most LED fixtures must include a power converter.

 

 

Electrical polarity

As with all diodes, current flows easily from p-type to n-type material. However, when a small voltage is applied in reverse direction, there will be no flow of current and hence no light production. If the reverse voltage becomes large enough to exceed the breakdown voltage, a large current flows and the LED may be damaged.

 

While all diodes release light, most don't do it very effectively. In an ordinary diode, the semiconductor material itself ends up absorbing a lot of the light energy. LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction.

 

 

Merits

Efficiency: LEDs produce more light per watt than incandescent bulbs.

 

Color: LEDs can emit light of an intended color without the use of color filters that traditional lighting methods require. This is more efficient and can lower initial costs.

 

Size: LEDs can be very small (smaller than 2 mm2)

 

On/Off time: LEDs light up very quickly. A typical red indicator LED will achieve full brightness in microseconds. LEDs used in communications devices can have even faster response times.

 

Cycling: LEDs are ideal for use in applications that are subject to frequent on-off cycling, unlike fluorescent lamps that burn out more quickly when cycled frequently, or HID lamps that require a long time before restarting.

 

Dimming: LEDs can very easily be dimmed either by Pulse-width modulation or lowering the forward current.

 

Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.

 

Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs.

 

Lifetime: LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer.

 

Shock resistance: LEDs, being solid state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.

 

Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner.

 

Toxicity: LEDs do not contain mercury, unlike fluorescent lamps.

 

 

Demerits

High initial price: LEDs are currently more expensive, price per lumen, on an initial capital cost basis, than most conventional lighting technologies. The additional expense partially stems from the relatively low lumen output and the drive circuitry and power supplies needed. However, when considering the total cost of ownership (including energy and maintenance costs), LEDs far surpass incandescent or halogen sources and begin to threaten compact fluorescent lamps.

 

Temperature dependence: LED performance largely depends on the ambient temperature of the operating environment. Over-driving the LED in high ambient temperatures may result in overheating of the LED package, eventually leading to device failure. Adequate heat-sinking is required to maintain long life.

 

Voltage sensitivity: LEDs must be supplied with the voltage above the threshold and a current below the rating. This can involve series resistors or current-regulated power supplies.

 

Light quality: the color rendering properties of common halogen lamps are often inferior to what is now available in state-of-art white LEDs.

 

Area light source: LEDs do not approximate a “point source” of light, but rather a lambertian distribution. So LEDs are difficult to use in applications requiring a spherical light field. LEDs are not capable of providing divergence below a few degrees. This is contrasted with lasers, which can produce beams with divergences of 0.2 degrees or less.

 

Blue Hazard: There is increasing concern that blue LEDs and cool-white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems.

 

Blue pollution: LEDs can cause more light pollution than other light sources.

 

7. Curing Techniques

Two categories of technique are commonly used in curing polymers: continuous and discontinuous. The continuous cure refers to a light cure sequence in which the light is on continuously. There are four types of continuous curing: uniform continuous cure, step cure, ramp cure, and high-energy pulse. Continuous curing is conducted with halogen, arc, and laser lamps. The discontinuous cure is also called soft cure, which commonly uses a pulse delay.

 

 

A. Continuous curing techniques

Uniform continuous cure

 

In the uniform continuous cure technique, a light of constant intensity is applied to a composite for a specific period of time. This is the most familiar method of curing currently used.

 

 

Step cure

In the step cure technique, the composite is first cured at low energy, and then stepped up to high energy, each for a set duration. The purpose is to reduce polymerization stress by inducing the composite to flow in the gel state during the first application. Theoretically, this practice reduces the overall polymerization shrinkage at the margin of the final restoration. The reduction in shrinkage, however, is small and results in less composite polymerization because the lower intensity light yields lower energy levels. In addition, this technique results in an uneven cure, since the top layer is more saturated with light and thus more highly cured. Step curing is possible only with halogen lamps; arc lamps and lasers cannot be used because they work by applying large amounts of energy over short periods of time.

 

 

Ramp cure

In the ramp cure, light is initially applied at low intensity and gradually increased over time to high intensity. This allows the composite to cure slowly, thereby reducing initial stress, because the composite can flow during polymerization. Ramp curing is an attempt to pass through all of the different intensities in hopes of optimizing a composite’s polymerization. Some studies indicate ramp curing causes polymerization with longer chains, resulting in a more stable composite. In theory, very high energy applied over a short period tends to cause dimethacrylate monomers to attach to themselves, resulting in shorter polymer chains and a more brittle material with higher polymerization shrinkage and more marginal gaps. Ramp curing, with its dependence on low intensity, is possible only with halogen lamps; arc and laser lamps can generate only large, nonvariable amounts of energy. It is possible to ramp cure manually by holding a conventional curing lamp at a distance from a tooth and slowly bringing it closer to increase intensity.

 

 

High-energy pulse cure

The high-energy pulse cure technique uses a brief (10 second) pulse of extremely high energy (1000–2800 mW per cm2), which is three to six times the normal power density. This type of polymerization has not yet been adequately examined, and there are three areas of potential concern: (1) the rapid application of energy might result in a weaker resin restoration owing to the formation of shorter polymers; (2) it is possible that rapid applications of energy could reduce diametrical tensile strength; and (3) there may be a threshold level at which a resin has good properties, and thus, higher energies would result in more brittle resin.

 

 

B. Discontinuous curing techniques

In the discontinuous or soft-cure technique, a low intensity or soft light is used to initiate a slow polymerization that allows a composite resin to flow from the free (unbound) restoration surface toward the (bound) tooth structure. This reduces polymerization stress at the margins and could reduce “white line” or other marginal openings or defects. To complete the polymerization process, the intensity of the next curing cycle is greatly increased, to produce the needed energy for optimal polymerization.

 

 

Pulse-delay cure

In pulse-delay curing, a single pulse of light is applied to a restoration, followed by a pause and then by a second pulse cure of greater intensity and longer duration. It is best thought of as an interrupted step increase. The lower-intensity light slows the rate of polymerization, which allows shrinkage to occur until the material becomes rigid, and is purported to result in fewer problems at the margins. The second, more intense pulse brings the composite to the final state of polymerization. Pulse curing is usuallydone with halogen lamps.

 

8. Clinical considerations of LED

 

LEDs hot stuff!

Apart from sufficient curing, preventing damage to the tissue and the pulp is also a factor that needs to be considered. The blue light that is emitted is primarily energy. However, a part of the light energy directed at the tooth and gingiva is converted to heat. This holds true for any curing light, regardless of the type of light source. Whether laser, plasma or LED lights are in use, they should always be used carefully and with the clinical common sense and knowledge. Under unfavorable circumstances, the irradiated tissue can be damaged if the light intensity is too high or if the tissue has been cured for too long.

 

 

Some like it hot – some DON’T

Heat is generated by the exothermic reaction and the irradiation energy during every polymerization; as a general rule, it can be stated that the higher the light intensity, the higher is the released energy and the perceived heat (and the shorter the required curing time). In order to prevent possible damage to the pulp or the soft tissue, polymerization lights should therefore always be used cautiously. The consensus in the scientific community is that the temperature of the pulp should not increase by more than 5.5°C (approx. 9°F). Manufacturers should be able to present the corresponding data regarding their product. More sophisticated LED lights additionally offer a choice between the full performance and a program with reduced intensity for sensitive areas.

 

 

The required equipment for routine use

In the routine application, many other factors also play an important role for dentists. The polymerization light is the most-used product in the dental practice. Given this background, ergonomic factors are also relevant. Low weight and a balanced handpiece that allows a good grip are equally important. A cordless light offers maximum freedom of movement, and both dentist and patient are no longer bothered by the power cord. This, however, raises questions regarding the capacity and reliability of the battery. One of the main factors is the duration of continuous operation of the light. Nothing is more annoying than interrupting the treatment of a patient and therefore the procedure of the entire practice just because the battery is empty or the curing light needs to cool down for several minutes. In addition, special programs to reduce the shrinkage stress or heat development in areas near the pulp offer convincing advantages.

 

 

Design should suit your needs

LED lights are generally available in two versions: the pistol shape that is well-known from the halogen lights and the pen or bar shape. It is your choice which one you prefer. The pistol shape is not as futuristic and is often more comfortable to handle due to the balanced weight distribution as compared with pen-shaped lights. Generally, the weight and the angle of the light probe including the handpiece should suit the individual needs of the user. All of this has an influence on an ergonomic and comfortable use. If there are any selection keys, they should be easy to reach and easily readable.

 

 

Can Modern batteries live longer?

Due to their design, many LED lights are smaller and lighter than their halogen counterparts. As the power consumption is lower, LED polymerization lights can be efficiently supplied with power by a battery. The current standard is the lithium technology, which is very widely applied and used in billions of mobile telephones. Lithium-ion batteries are small and light, they have a long service life while the self-discharge rate is low, and they can be recharged in a short time. More than 500 charging cycles are possible – even many more if the battery is only partially discharged. Moreover, special protective circuits provide a high level of security. The charger technology of lithium-ion batteries makes sure that there is no lazy battery or memory effect. This phenomenon causes older nickel metal hydride and nickel cadmium batteries to lose part of their capacity prematurely and irreversibly. In other words: The lights still available today that use nickel-metal hydride batteries should be completely discharged before they are (completely) charged again. To prevent that time and capacity is lost, it is therefore recommended to completely discharge nickel-metal hydride batteries daily, if possible, and to recharge it overnight. Due to the comparably long charging times of several hours, the main switch must not be turned off. This requires a certain amount of discipline and entails regular monitoring – otherwise, it may be that the treatment of a patient may be delayed. It is only a matter of time until all manufacturers will change over to the newest state of battery technology. We therefore recommend that you pay attention to the type of battery used.

 

 

Battery

The lithium-ion or lithium-polymer batteries that are used in high-quality LED lights do not need to be entirely discharged. Frequent charging even increases the battery life considerably. As a general rule it is therefore advisable to place the light back in the charging base after every use. Modern lights display the currently available capacity, ideally using symbols on a display or at least with a light-emitting diode. A warning signal is sounded before the light switches off.

 

 

Safety net for emergency operation

Nothing is more unpleasant than having to interrupt the treatment of a patient and therefore the entire work of the practice because the battery is empty. This raises the question of an “emergency mode” for situations when the practice team does not have time to recharge the battery and would like to carry out the treatment immediately. In such situations, there are generally two possibilities: First, an additional battery is supplied. Such an additional battery costs, and you must be sure that it is always charged and that it can be retrieved at any time. Secondly, there are innovative polymerization lights which offer the possibility to attach the handpiece to the power cord of the charging base. This allows the clinician to carry out treatments independently from the battery and at any time according to his/her requirements.

 

 

Proper maintenance of the battery

Rechargeable batteries, being small power plants, require careful handling. In order to use a battery for possibly several years, the following tips might be helpful: To prevent an irreversible deep discharge, nickel-metal hydride batteries must be recharged after three months at the latest and lithium-polymer or lithium-ion batteries after six months, if they have not been used in a long time.

 

Nickel-metal hydride batteries must be completely discharged before they are completely recharged. Lithium-ion batteries, however, can be discharged and recharged at any time. In order to prolong the battery life of lithium-ion and lithium-polymer batteries, it is even recommended to place the light in the charging base after every use. Clean battery contacts free of dust and composite residue ensure good conductivity and therefore charging capacity at any time. The electric contacts should therefore be cleaned regularly – for example using a wipe dipped in alcohol or a cotton swab. Ageing occurs in every type of battery, so that a decrease in performance is to be expected. Typically, lithium-polymer and lithium-ion batteries have lost about 30% of their original capacity after three years. This means that, instead of the 60-minute capacity, for instance, the battery can be used only for approximately 40 minutes.

 

 

Always with a fan

LED lights use up little space; they are energy-saving and have a long life span. These properties make them highly interesting also for use in dentistry. Like all electric parts, however, LEDs generate heat, which must be discharged, in order to prevent damage due to high temperatures or to prevent that the light prematurely fails to operate. The developing heat depends mainly on the light intensity of the LED light used. Modern lights offer an intensity of 1,000 mW/cm2 and more. Given this high performance, the best solution is to discharge the heat by means of a fan. If the light is not equipped with a fan, the housing or a special cooling unit must absorb this heat. During extended operation – when luting composites are polymerized for several minutes in the case of indirect restorations – the housing develops a perceivable heat. If a certain temperature is exceeded, it may happen that the light may be automatically switched off to prevent damage. If this happens, it takes several minutes until the light can be used again. If a fan is integrated, however, even high performance lights can be operated without restrictions.

 

 

Programs

If areas with only little residual dentin or areas close to the pulp are cured, polymerization should be carried out very cautiously, i.e., a reduced light intensity should be applied in order to prevent an excessive heat accumulation in the pulp or the soft tissue. If high-performance lights featuring intensities of 1,000 mW/cm2 are used, it is advisable to cure restorations in the cervical area, adhesives and liners using a so-called “Low Power” program. High performance also means increased polymerization stress in the composite. In this case, it is helpful to use a light which offers a special program including various levels of intensity or a “Soft Start” program which increases the intensity during curing.

 

9. Future directions of LED

By lowering the initial investment required and the operating costs associated with the use of light cure technology, these systems are allowing more manufacturers to take advantage of visible light cure adhesives.

 

The economic advantages of LED technology will continue to drive innovation in this area as light curing equipment suppliers find ways to satisfy clinical needs. On the horizon are LED systems that can cure larger areas, expanding the number of appropriate bonding processes. Increased irradiance may also allow LED systems to cure a broader range of resins.

 

10. References

1. Light-emitting diode - Wikipedia, the free encyclopedia.htm, accessed on 9-09-09.

2. Albers HF. Tooth colored restorations, Principles and technique, 9th ed., 2002, B.C. Decker.

3. Sturdevant R. Art and science of operative dentistry,5th ed., Mosby.

4. LED technology-Here to stay. Curing lights at a glance, 3M ESPE, accessed on 9-09-09.

5. User’s Guide-to the clinically relevant criteria for selecting a polymerization light, ivoclar vivadent,accessed on 9-09-09.

6. Elipar Free Light 2. Technical product profile, accessed on 03-10-2009.

7. HowStuffWorks Diodes.htm, accessed on 9-09-09.

8. Koran P, Kürschner R. Effect of sequential versus continuous irradiation of a light cured resin composite on shrinkage, viscosity, adhesion, and degree of polymerization; Am J Dent 1998:10,17–22.

9. L.E.Demetron II, technical product profile, accessed on 9-09-09.

10. ADA, American Dental Association: Professional Product Review, Vol. 1, Issue 2, Fall 2006.

11. Radii plus, technical product profile, accessed on 03-10-2009.

12. Oberholpez G, Botha CT, du Preez IC. Advances in light curing units and curing techniques: a literature review. SADJ. 2005 Nov;60(10):451-4.

13. Althoff O, Hartung M. Advances in light curing. Am J Dent. 2000 Nov;13(Spec No):77D-81D.

14. Davidson CL, de Gee AJ. Light-curing units, polymerization, and clinical implications. J Adhes Dent. 2000 Autumn;2(3):167-73.

 

 

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