This revised proposal complements a K23 grant, which is focused on analyzing in vivo variables that control the survival of three-unit, implant-supported, all-ceramic bridges. Dr. Anusavice is the primary mentor for Dr. Josephine Esquivel-Upshaw, the PI of the K23 award who is currently recruiting 128 human subjects for the five-year clinical study. The overall objective of this R01 proposal is to design and validate a systematic process for accurately predicting, through cyclic and dynamic fatigue tests of the same trilayer ceramic system, the survival probabilities of the ceramic bridges to be monitored in the K23 study. This study will test the hypothesis that fracture survival probabilities predicted from dynamic fatigue test data of the same ceramic component materials, processing variables, and thermal treatments, will not be significantly different than those estimated from cyclic fatigue data. The experimental phase will characterize the potential effects of surface processing damage, thermal treatment effects, microstructural changes, and environmental effects that control the chipping and fracture susceptibility of the three-unit prostheses of either the zirconia core ceramic, the ceramic liner, or the fluorapatite glass-ceramic veneer. The analytical phase will employ finite element stress analysis to determine the stress distributions in the simulated K23 grant implant-supported prostheses and the Cares/Life software to calculate the time-dependent probability of fracture. The following five aims are proposed:
Aim 1. Characterize the type and depth of localized microstructural phase changes in the yttria- stabilized zirconia core ceramic (Y-TZP) produced by same surface grinding procedures that will be used in the K23-supported clinical study and by the thermal regeneration process used to convert transformed zirconia phases in the core ceramic surface back to the tetragonal zirconia phase.
Aim 2. Identify the effects of surface damage in the zirconia core ceramic on the interfacial toughness of the trilayer zirconia/liner/veneer ceramic system.
Aim 3. Analyze the effect of the water exposure on the dynamic fatigue fracture resistance and stress corrosion susceptibility of the zirconia core and glass-ceramic veneer.
Aim 4. Characterize the effect of thermal processing on microstructural changes, the estimated time-dependent fracture probability, and the probable mode of failure.
Aim 5. Test the hypothesis that dynamic fatigue tests will provide slow crack growth and Weibull parameters comparable to those from cyclic fatigue. Thus, dynamic fatigue parameters will yield comparable time-dependent fracture probabilities that are indicators of potential clinical performance in the clinical study supported by the K23 grant.
This basic-clinical translational study represents a unique opportunity to integrate bench-top research on the fracture resistance of a dental ceramic system and survival predictions for simulated all-ceramic prostheses with on-going clinical research on the performance of implant-supported three-unit ceramic bridges made from the same materials and processes. The comparative evaluation of results from the two studies will provide critically important validation of a cost-effective in vitro model for systematically evaluating new ceramic materials.
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