Restorative material

Technology Assessment Conference Statement on Effects and Side Effects of Dental Restorative Materials, National Institute of Dental Research, NIH, Bethesda, Md., Aug. 26-29,1991. 

Resin-modified glass—ionomer lining and restorative materials add a multifunctional acidic monomer to the poly(acryhc acid) [9003-01 Hquid component of the system. Once the glass powder and Hquid are mixed, setting can proceed by the acid—glass—ionomer reaction or the added monomer can be polymerized by a free-radical mechanism to rapidly fix the material in place (74,75). The cured material stiH retains the fluoride releasing capabiHties of a glass—ionomer. 

Restoratives. Polymer reskis were iatroduced as tooth restorative materials ki the early 1940s. These materials can be classified as unfiUed tooth-restorative reskis, composite or fiUed restorative reskis, and pit and fissure sealants. 

Composite or Filled Tooth Restorative Resins. Improvements in the properties of resin-based restoratives, brought about by the addition of silane-treated inorganic fillers to unfilled resins, has made these the primary anterior restorative material used today. 

Once a metal surface has been conditioned by one of the above methods, a coupling agent composed of a bifimctional acid—methacrylate similar to a dentin adhesive is appHed. This coupling material is usually suppHed as a solvent solution that is painted over the conditioned metal surface. The acidic functional group of the coupling molecule interacts with the metal oxide surface while the methacrylate functional group of the molecule copolymerizes with the resin cement or restorative material placed over it (266,267). 

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. 

In the late 1940s a reaction against this idea of a dental material took place. Increasing attention was paid to problems of compatibility between the restoration and the tooth. We now believe that a restorative should be at one with the tooth material in all respects. It should possess identical properties. Its thermal characteristics should be the same as those of the tooth and its appearance should match that of the enamel. It should provide some therapeutic action. In fact, a restorative material should no longer be regarded as a filling but as an enamel or dentine substitute . 

To achieve such compatibility the primary requisite is that the restorative adheres to tooth material. This concept of adhesion is hardly to be foimd in the literature of the 1920s and 1930s. For that reason we find no attempt at developing tooth adhesives in that period. Adhesion was, apparently, only recognized as a desirable property in the 1950s. It seems for some reason to be associated with the introduction of simple resins as dental restorative materials. Although they were not a great success, attempts were made to bond them to tooth material. 

A restorative material can be used for the aesthetic restoration of the front (anterior) teeth only if it is as translucent as tooth enamel. This is because colour matching depends on translucency as well as hue and chroma. 

Goldman, M. (1985). Fracture properties of composite and glass ionomer dental restorative materials. Journal of Biomedical Materials Research, 19, 771-83. 

Hembree, J. H. Andrews, J. T. (1978). Microleakage of several class V anterior restorative materials a laboratory study. Journal of the American Dental Association, 97, 179-83. 

Hunt, P. R. (1984). A modified class II cavity preparation for glass ionomer restorative materials. Quintessence International, 15, 1011-18. 

Leirskar, J. Helgeland, K. (1987). Mechanism of an in vitro toxicity of restorative materials pH, fluoride and zinc. International Endodontic Journal, 20, 246-7. 

Lloyd, C. H. Adamson, M. (1987). The development of fracture toughness and fracture strength in posterior restorative materials. Dental Materials, 3, 225-31. 

Lloyd, C. H. Mitchell, L. (1984). The fracture toughness of tooth coloured restorative materials. Journal of Oral Rehabilitation, 11, 257-72. 

Tobias, R. S., Browne, R. M. Wilson, C. A. (1985). Antibacterial activity of dental restorative materials. International Dental Research, 18, 161-71. 

Tyas, M. J. (1977). A method for the in vitro toxicity testing of dentine restorative materials. Journal of Dental Research, 56, 1285. 

Tyas, M. J. Beech, D. R. (1985). Clinical performance of three restorative materials for cervical abrasion lesions. Australian Dental Journal, 30, 260-4. 

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. 

Williams, J. Billington, R. W. (1991). Changes in compressive strength of glass ionomer restorative materials with respect to time periods of 24 h to 4 months. Journal of Oral Rehabilitation, 18, 163-8. 

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

McComb, D. (1982). Tissue reactions to silicate, silicophosphate, glass ionomer cements and restorative materials. In Smith, D. C. Williams, D. F. (eds.) Biocompatibility of Dental Materials. Volume III. Biocompatibility of Dental Restorative Materials, Chapter 4. Boca Raton CRC Press Inc. 

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. 

Spangberg, L., Rodrigues, H., Langeland, L. Langeland, K. (1973). Biological effects of dental materials. 2. Toxicity of anterior tooth restorative materials on HeLa cells in vitro. Oral Surgery, Oral Medicine, Oral Pathology, 36, 713-24. 

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

Updegraff, D. M., Change, R. W. H. Joos, R. W. (1971). Antibacterial activity of dental restorative materials. Journal of Dental Research, 50, 382-7. 

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. 

Roydhouse, R. H. Weiss, M. E. (1964). Tissue reactions in restorative materials. Journal of Dental Research, 43, 807. 

Evaluating the P/S ratio requires particular care first, because of the presence of mixtures of more than one binder, such as egg and oil in tempera grassa secondly, due to the presence of waxes, and in particular beeswax, which has been widely used as a coating and restoration material and thirdly, due to the contribution of FAs from other sources such as fouling or micro-organisms, which can considerably alter the P/S values from those expected for reference materials. For instance, because the ratio for walnut oil falls between the value of linseed oil, poppy oil and egg lipids, using the P/S ratio it is not possible to differentiate between pure walnut oil, and mixtures of linseed and poppy oil or egg. 

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