Quantitative wear assessments for composite restorations in primary molars

Studies to date have assessed wear of composite restorations in primary molars using the United States Public Health Service (USPHS) evaluation criteria. Direct clinical evaluations of 148 Ful-Fil® restorations using the USPHS wear criteria were made at baseline, 6, 12, and 24 months. Quantitative assessments were made by comparing calibrated standard casts with the die stone casts obtained at the same recall intervals. Results for the USPHS evaluation revealed almost no wear after 24 months. Quantitative results, reported in average micrometers of wear, were: baseline -O; 6 months -40; 12 months -72; 24 months -93. Although wear was minimal, it was apparent that the USPHS criteria did not identify early wear as critically as the quantitative method. After 24 months, wear was within the guidelines for the ADA" s acceptance program in primary molars. Research on composite restorations in primary molars has proliferated in the past few years and several clinical trials have been reported. 1-4 Better understanding about the properties that influence the clinical performance of composites has led to significant improvements in those used for posterior restorations. These advances are underscored by the fact that recently the ADA granted provisional acceptance to a composite material (Ful-Fil") for use in primary molars, s A major factor limiting the suitability of composite restorative materials in posterior teeth has been inadequate wear resistance. 6,7 To date, no in vitro wear tests have been found that will predict composite wear performance accurately. Thus, clinical trials remain the only definite evaluation technique for posterior composite formulations. 8 Most primary tooth studies of posterior composites have addressed wear in clinical trials using the United States Public Health service (USPHS) criteria developed by Cvar and Ryge9 (Table 1). Recently, several investigators have concluded that wear measurements based on these criteria may not be precise enough for predicting in vivo performance. 6-8,1° To complement these criteria, a number of methods have been described to make physical measurements of material loss using impressions and study casts. Santucci and Racz~ have described a method of measuring the ledge which forms between the enamel occlusal surface and the composite restoration at several points. Dennison et al. ~2 have described a volumetric measurement technique using a wafer of silicone impression material between a template of baseline and recall casts. Lutz et al. 6 have described a method using computer mapping of a restoration cast. While these methods are appealing, all are time consuming and some involve expensive equipment and supplies. In 1981 Goldberg et al. ~3 presented a technique that TABrE 1. USPHS Criteria for Rating Restorations for Anatomical Form (Wear) Alfa