Correlation of clinical performance with 'in vitro tests' of restorative dental materials that use polymer-based matrices.

OBJECTIVE: Review correlations of in vivo clinical performance with in vitro laboratory tests of restorative dental materials involving polymer-based matrices. Identify those factors interfering with the process.
MATERIALS AND METHODS: An evidence-based dentistry approach was used to identify clinical trials, critical reviews, and meta-analyses involving correlations. Factors impacting meaningful correlations were reviewed. The limited bona fide correlations were reviewed.
RESULTS: In vitro tests include physical, chemical, mechanical, and biological properties. Clinical research measurements routinely include 10-15 categories of clinical observations of performance such as color match, caries resistance, marginal integrity, surface texture, and others, but do not correspond well with laboratory properties. Clinical trials of restorative dental materials represent a small fraction of the total research in this arena (typically <10% of dental materials research over many years). Trials are generally short-term (2-5 years) and are designed primarily to test product "safety and efficacy." A large number of risk factors (operator, design, material, intraoral location, patient) affect clinical outcomes and are not simulated well in laboratories. Little long-term information exists for clinical performance other than on composite wear. Very few meaningful correlations of laboratory tests and clinical results are demonstrated. CONCLUSIONS/RECOMMENDATIONS: New studies should be focused on recovering restorations from service and characterizing them with the same tests as normally conducted in the laboratory. Many more long-term clinical trials that involve 10-20 years of observations are needed. Those trials should include planned restoration recovery to assess changes in laboratory properties of interest.