Restorative dentistry

In the realm of dentistry, restoration and protection of tooth enamel are of great importance in operative and conservative dentistry. Yamamoto et al. (2013) used PLD to create a freestanding flexible double-layered sheet composed of a 4 pm thin hydroxyapatite (HAp) layer coated with a 0.5 pm thin TCP layer. The adhesive strength between the HAp/TCP sheet and enamel was 5.7 MPa, decidedly higher than that between the monolayered HAp sheet and enamel (1.9 MPa). Electron microscopical observation revealed that the HAp/TCP sheet was largely fused with the enamel. Therefore, the double-layered HAp/TCP sheet can be used as a material to promote the repair of tooth eruption and to maintain healthy dentine. 

The predominant bonding mechanism is mechanical retention and the most common bonding systems are either a composite, generally light-cured, or polyalkenoate cements similar to those used in restorative dentistry (see Adhesion in dentistry restorative materiais). In a recent development to minimize operator errors, the bracket base is pre-coated with the adhesive so that there is no mixing, no contamination and there is a controlled amount of adhesive. The adhesive is typically a lightly filled combination of bisphenol A diglycidyl dimethacrylate and bisphenol A bis(2-hydroxyethyl ether)... 

The largest application of radiation-cured adhesives is for dental procedures (see Adhesion in dentistry restorative materials). Originally UV curable, these have given way to... 

Adhesion in dentistry restorative materials M SHERRIFF Polymers as filling materials... 

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

Elastomer Impression Materials. Dentistry requires impression materials that are easily handled and accurately register or reproduce the dimensions, surface details, and interrelationship of hard and soft oral tissues. Elexible, elastomeric materials are especially needed to register intraoral tooth stmctures that have undercuts. The flexibility of these elastomers allows their facile removal from undercut areas while their elasticity restores them to their original shape and size. 

Dental abrasives can be classified either according to their use or according to the degree of their abiUty to abrade (see Dentifrices). The use classification, adopted for the ADA specification no. 37 for powdered dental abrasive materials, is based on removal of stain from natural teeth or on restorations of all types. Several abrasives are used in dentistry in a variety of grit sizes and shapes. 

There have been numerous reports of possible allergic reactions to mercury and mercury salts and to the mercury, silver and copper in dental amalgam as well as to amalgam corrosion products Studies of the release of mercury by amalgams into distilled water, saline and artificial saliva tend to be conflicting and contradictory but, overall, the data indicate that mercury release drops with time due to film formation and is less than the acceptable daily intake for mercury in food . Further, while metallic mercury can sensitise, sensitisation of patients to mercury by dental amalgam appears to be a rare occurrence. Nevertheless, there is a growing trend to develop polymer-based posterior restorative materials in order to eliminate the use of mercury in dentistry. 

Thus, thought became directed towards developing adhesive dental materials, an approach that has led to considerable successes and has revolutionized restorative dentistry. 

The glass polyalkenoate cement uniquely combines translucency with the ability to bond to untreated tooth material and bone. Indeed, the only other cement to possess translucency is the dental silicate cement, while the zinc polycarboxylate cement is the only other adhesive cement. It is also an agent for the sustained release of fluoride. For these reasons the glass polyalkenoate cement has many applications in dentistry as well as being a candidate bone cement. Its translucency makes it a favoured material both for the restoration of front teeth and to cement translucent porcelain teeth and veneers. Its adhesive quality reduces and sometimes eliminates the need for the use of the dental drill. The release of fluoride from this cement protects neighbouring tooth material from the ravages of dental decay. New clinical techniques have been devised to exploit the unique characteristics of the material (McLean Wilson, 1977a,b,c Wilson McLean, 1988 Mount, 1990). 

Bitter, N. C. (1986). Glass ionomer-microfil technique for restoring cervical lesions. Journal of Prosthetic Dentistry, 56, 661-2. 

Knibbs, P. J., Plant, C. G. Pearson, G. J. (1986a). The use of a glass-ionomer cement to restore class III cavities. Restorative Dentistry, 2, 42-8. 

McLean, J. W. (1980). Aesthetics in restorative dentistry the challenge for the future. British Dental Journal, 149, 368-72. 

Welsh, E. L. Hembree, J. H. (1985). Microleakage of the gingival wall with four class V anterior restorative materials. Journal of Prosthetic Dentistry, 54, 370-2. 

Hannah, C. M. Smith, D. C. (1971). Tensile strengths of selected dental restorative materials. Journal of Prosthetic Dentistry, 26, 314-23. 

Matsui, A., Buonocore, M. G., Sayegh, F. Yamaki, M. (1967). Reactions to implants of conventional and new dental restorative materials. Journal of Dentistry for Children, 34, 316-22. 

Trivedi, S. C. Talim, S. T. (1973). The response of human gingiva to restorative materials. Journal of Prosthetic Dentistry, 19, 73-80. 

Jendresen, M. D. Phillips, R. W. (1969). A comparative study of four zinc oxide eugenol formulations as restorative materials. Part II. Journal of Prosthetic Dentistry, 21, 300-9. 

---