BIOPSY AND ANALYSIS OF 5 TO 10 YEAR OLD COMPOSITES

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The Operative Dentistry Clinical Research Program at the University of North Carolina maintains the largest database of information on dental composite research patients. During the past 10 years, 15 projects have been conducted. Many of the restorations are now in the 5 to 10 year old category and will require replacement shortly. This provides a unique opportunity to remove, recover, and analyze restorations that are fully characterized and have a long history of clinical evaluation data. The objective of this proposal is to use (a) clinical evaluation wear data, (b) microstructural and microchemical data from biopsies, and (c) published property values to test the validity of current composite wear theories. Biopsies will be collected from pre-selected patients to (1) explain differences between patients with high wear rates vs low wear rates, (2) evaluate specific intraoral location factors such as anterior vs posterior, molar vs premolar, class 1 vs class 2, and occlusal contact areas vs non-contact areas, and (3) evaluate differences in wear rates between early periods of service at 1 to 3 years and wear rates after long periods of service from 5 to 10 years. Biopsies will then be sectioned in half and polished to provide samples for both SEM microstructural analyses and FTIR microchemical analyses. SEM measurements of microfractures, pores, and cracks will be used to assess current mechanical wear theories. FTIR analyses of chemical composition and degree of conversion will be used to evaluate current chemical degradation theories. Information in both cases will be collected on both superficial and interior zones for comparison. Information from clinical evaluations, laboratory analyses, and published properties will be statistically examined for correlations of wear with causal relationships.