[The marginal adaptation of mechanically produced onlays in vitro]

In this study, 24 extracted human molars were restored with onlays fabricated by using the Cerec System. The teeth were divided into 4 groups: in groups 1, 2 and 3 the proximal cervical margin was located coronally to the CEJ so that enamel was still present; in group 4 the proximal cervical margin was located in dentin. Vita-Cerec porcelain was the restorative material in groups 1 and 4; compressed HT-Hybrid composite in group 2 and glass-ceramic in group 3. Marginal adaptation of the onlays was examined by SEM before and after a combined occlusal loading and thermocycling test (72.5 N, 500,000X, 1.6 Hz; 1250X 5 degrees C - 55 degrees C - 5 degrees C, 4 minutes interval). In addition, a dye-penetration test was performed. The SEM evaluation and the penetration test revealed marginal adaptation values of the composite-luting agent both to enamel and the three restorative materials close to 100%. Marginal adaptation scores did not differ between porcelain, glass-ceramic and HT-composite and the three materials were equally adequate for being used with the Cerec method.