Objectives: This in vitro study evaluated the marginal adaptation of compomer restorations placed using three different conditioning protocols.
Materials and methods: Thirty extracted caries-free molars with 3mm diameter cylindrical cavity preparations were divided randomly into three groups based upon the conditioning treatment used: (I) 36% phosphoric acid; (II) non-rinse conditioner (NRC, Dentsply DeTrey); and (III) no conditioning. Cavities were restored with Dyract AP using Prime&Bond NT (Dentsply DeTrey) as an adhesive. Silicone impressions of the briefly etched enamel surfaces were taken after finishing the restorations. Each sample was then longitudinally sectioned and impressions were taken. Epoxy resin replicas were prepared for SEM analysis. Qualitative and quantitative assessment were performed separately for the enamel- and dentine-restorative interface.
Results: Enamel fractures and open margins along the enamel-restorative margin were observed in some specimens in each group. No statistically significant difference was found in the percentage of gaps/cohesive failures between specimens prepared using different conditioning methods. For the dentine-restorative interface, uniform hybrid layers and long resin tags were often observed in Groups I and II. The hybrid layer in Group III was irregular and discontinuous along the interface. A significant difference (p<0.01) in the proportion of marginal gap was found between Group I (2%) and Group III (30%).
Conclusions: Pre-treating the cavity with 36% phosphoric acid significantly improved the adaptation of the compomer and adhesive to dentine compared with no etching. The marginal quality at the enamel-compomer interface was not affected by the conditioning method used.