Wear prediction for dental composites (an in vivo and in vitro correlative approach)

Abstract

During the last couple of decades, most of the information about dental restorative materials is embedded in a collection of huge numbers of lab oratory tests. A large share of the laboratory research done with dental materials has been concerned with the wear of the materials. Over the y ears, only about 5-10% of all the in-vitro information h as been associated with clinical data retrieved from clinical trials tha t are often short term and limited in terms of products tested. Establis hing the relationship between laboratory testing and clinical outcomes f or a collection of restorative materials is needed not only for the futu re predictions of their long- term in-vivo performance b ut also to drive evidence-based clinical decision making of the right restorative materials in dentistry. Focussing on the intraoral wear phenomenon, the objective of this PhD dissertation was to examine t he correlation of laboratory test results with the clinical wear events of a collection of commercial dental composites tested in randomized cli nical trials and explain the wear behavior of the investigated composite s relative to clinical decision making. Since RCTs provide ulti mate proof of performance of any restorative material, it was decided to first conduct two individual RCTs to investigate the overall clinical p erformance of a collection of commercial dental composites and to record the clinical wear events (wear magnitude and worn surface topography). Pooled analysis of the clinical wear data retrieved from both the RCTs e nabled a) establishing the CFOA and OCA wear rates of the investigated c omposites and that of human enamel; b) investigating a wide range of fac tors such as operator factors, material factors, intraoral location fact ors and patient factors suspected to be involved in the wear performance of any restoration. Subsequently, it was decided to identify l aboratory tests that correlate with observations of clinical wear events by examining if the laboratory tests rank the materials similar to that produced by clinical trials. Further attempt was made to understand the effect of mechanical stresses occuring cyclically during intercuspation , swallowing, or chewing on the clinical wear performance of the restora tives that might reflect as a change in the initial rank order. Very pro mising was the fact that the rank order produced by in-vitro scratch tests correlated well with the in-vivo CFOA wear rank order and a similar good correlation was observed between t he rank orders of simulated wear in a chewing simulator and in-v ivo contact wear. This indicated the suitability of the applied testing and simulating devices to reliably predict the in-vivo wear of new resin composite materials and the usefulness of the c orrelative rank order approach as a fast, simple method for estimating a nd/or predicting the relative clinical wear characteristics. Preservation of a similar rank order in-vitro and in-vivo by the investigated composites suggested that composites per forming superior in-vitro, also exhibit superior wear resista nce clinically, which is a useful evidence for clinical decision making.nrpages: 148status: publishe