DEVELOPMENT OF NEW DENTAL COMPOSITE FORMULATIONS

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The long range goal of this study is the development of dental composites which are less technique sensitive, wet tooth structure more readily, and have reduced curing shrinkage and water sorption. Composites have several advantages over available alternative materials: direct technique, esthetic appearance, and adhesion to tooth structure. Even so, remaining problems limit their increased use in posterior applications, where dental amalgams are still used in three-fourths of all restorations. Two major problems are stresses in the tooth created by uncompensated curing shrinkage, and the necessity of isolating current materials from moisture during placement, which requires the use of demanding and unpopular clinical procedures. The urgency of solving these problems is increased by the possibility that dental amalgam, (the only alternative direct material), may be banned because of mercury hazards. This study proposes to prepare and evaluate the series of composite materials based upon newly synthesized matrix monomers. The work is based upon the hypothesis that the problems with current materials are largely due to the quantity of diluent monomers required to control matrix viscosity, and therefore that the use of matrix monomers of lower viscosity would lead to improved properties. Recent pilot work in this laboratory has confirmed this hypothesis. Modifications of the traditional BIS-GMA monomer will be prepared, as well as two series of monomers in which the central -C(CH3)2- is replaced by groups containing phosphorous or fluorine. In each series three monomers will be prepared. One with pendant -OH group characteristic of BIS-GMA, and others with the -OH replaced by -H and -CH3. Synthesis schemes and conditions will be adjusted to avoid hydrogen bonding and oligomerization, thus minimizing viscosity. Where the viscosity of the pure monomer exceeds the viscosity characteristic of present uncured matrix materials, it will be diluted with TEGDM as needed to produce a standard viscosity. Each material will be evaluated as a monomer, as the unfilled polymer and as the matrix of a hybrid composite. The monomers will be tested for viscosity, wetting ability, water sorption and curing shrinkage. The polymers and composites will be tested for water sorption, we ability by water and saliva, and a series of physical and mechanical properties.