Posterior composite Class II restorations: in vitro comparison of preparation designs and restoration techniques

The aim of this study was to evaluate conservative preparation designs for the restoration of Class II lesions with posterior resin composite. Fourteen primary and 14 permanent molars were obtained. Conservative modified MO and DO preparations were placed in half the teeth; conventional MO and DO preparations were placed in the remaining teeth. Randomly, a glass-ionomer liner was placed over the exposed dentin in one preparation of each tooth; a calcium hydroxide liner was placed in the remaining preparations. Posterior resin composite was placed in all teeth, and the teeth were loaded with a 17-kg force. Teeth were thermocycled, stored in 37°C water, then immersed in 50% silver nitrate solution and placed in developer. The teeth were sectioned and photographed. Microleakage was calculated according to the depth of dye penetration, on a 6-degree scale. Results demonstrated the conservative modified restorations and conventional restorations, when glass-ionomer liner was used, to have less marginal microleakage, in both primary and permanent teeth, than their calcium hydroxide counterparts.