Dental composite is being used extensively as an esthetic restorative for both anterior and posterior applications. However, current formulations often fail prematurely due to their inadequate ability to resist the forces of physical and chemical degradation over prolonged periods in vivo. The goal of this research proposal is to systematically study the effects of several variables on the wear and fracture mechanisms of different formulations of composites. These variables, which appear to contribute to in vivo degradation, include: the finishing procedure, mechanical and thermal fatigue, and chemical attack by solvents and UV radiation. This information should help to delineate the extend to which each environmental variable contributes to failure of specific composite formulations in vivo, and aid in the development of future composites. Composites will be formulated with various sizes and distributions of silanated and un-silanated quartz and barium glass in a single resin matrix, in order to test three hypotheses concerning the degradation of composites. Specimens will be finished with carbide and diamond burs and aluminum oxide disks, and then evaluated for subsurface damage (silver nitrate staining), fracture toughness (single-edge notched bars in bending), UV/water erosion (accelerated weathering tester), abrasion resistance (3-body) and degree of cure (micro-FTIR), to test the hypothesis that wear and fracture of composite is enhanced by subsurface damage created by finishing. The SEM will be used to compare failure mechanisms. The different formulations will also be subjected to fatigue loading (i.e. simulated chewing), UV/water erosion, storage in solvents, and thermocycling, all independently, before being analyzed for subsurface damage, fracture toughness, abrasion resistance and degree of cure, to test the hypothesis that wear occurs by a process of fatigue/fracture and chemical attack. The final hypothesis to be tested is that chip fracturing in microfills can be reduced by improving the adhesion between the matrix and filled resin blocks. Microfilled composites will be made filled resin blocks having three different degrees of cure to alter the potential for chemical bonding with the matrix. Fracture toughness, abrasion resistance, degree of cure and UV/water erosion will be evaluated, and the SEM will be used to assess adhesion and evaluate modes of failure.
| Ferracane, Jack L (2013) Resin-based composite performance: are there some things we can't predict? Dent Mater 29:51-8 |
| Musanje, L; Ferracane, J L; Sakaguchi, R L (2009) Determination of the optimal photoinitiator concentration in dental composites based on essential material properties. Dent Mater 25:994-1000 |
| Park, J W; Ferracane, J L (2006) Residual stress in composites with the thin-ring-slitting approach. J Dent Res 85:945-9 |
