Novel coatings to minimize surface degradation and fracture susceptibility of dental ceramics

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PROJECT SUMMARY/ABSTRACT This proposal is focused on establishing the efficacy of protective coatings in minimizing surface degradation of glass-ceramic veneers as well as minimizing chipping of ceramic-ceramic prostheses. This R01 proposal is designed to analyze the chemical durability and fracture resistance of three glass-ceramic veneering materials with different microstructures through in vitro simulation tests and to determine whether a novel pH cycling methodology will reliably simulate the chemical degradation that is controlled by pH fluctuations in the oral environment. The long-term goal of this research program is to develop fracture-resistant and chemically stable (durable), dental ceramic coatings for veneered dental ceramic prostheses. The central hypothesis of this project is that dental ceramic veneers will sustain minimal surface degradation and maintain or increase their apparent strength when coated with an optimized protective, adherent surface layer. This unique, translational research project will apply corrosion testing and damage analysis of ceramic veneering materials through in vitro simulation. We will employ a novel pH cycling methodology, which will apply three sequences of alternating pH buffer solutions from acidic to alkali, alongside intermittent abrasion. This cycling mechanism effectively simulates the fluctuating pH levels of oral fluids and can more accurately test chemical durability of ceramic materials. More importantly, we will establish the effectiveness of optimized protective coatings deposited using plasma enhanced coating vapor deposition technology in minimizing ceramic corrosion and improving fracture resistance. We will analyze the surface composition and topographical changes using x-ray photoelectron spectroscopy (XPS), environmental scanning electron microscopy (ESEM), energy dispersive x-ray analysis (EDAX), digital microscopy, and 3D laserscanning for wear analysis. We propose the following aims to test our central hypothesis: Aim 1: Test the hypothesis that glass-ceramic veneers undergo an alternating dissolution process (selective leaching and total dissolution) as a function of cycling pH environments resulting in compositional changes and rapid surface degradation of the glass phase; Aim 2: Test the hypothesis that a significant decrease in the biaxial flexural strength of glass- ceramic veneers will occur as a result of a simulated oral environment of alternating low and high pH or simulated occlusal forces with intermittent abrasion or a combination of both; Aim 3: Test the hypothesis that a protective coating can be optimized to achieve good resistance to low pH and high pH environments, ideal bonding to the ceramic substrate, good abrasion and fracture resistance and proper esthetics; Aim 4: Test the hypothesis that the optimal protective coating will significantly decrease the in vitro corrosive rate of glass- ceramic veneers as evidenced by a reduction in surface compositional changes caused by fluctuations in pH and abrasion factors, and maintain or significantly increase their “apparent” biaxial flexural strength.