Longevity of class II restorations with outline above/below the CEJ

In vitro studies indicate that class II restorations ending cervically below the cemento-enamel junction (CEJ) have reduced prognosis due to increased microleakage. Objectives: to evaluate whether class II restorations with cervical margins apical to the CEJ ending in dentin have an increased risk for secondary caries and clinical failure compared to restorations with margins coronal to the CEJ ending in enamel. Methods: Records from patients with at least one restoration replaced due to secondary caries were selected from an existing database. On the first bitewings after restoration placement, cervical margins of 1912 approximal restoration sites were scored in relation to the cemento-enamel junction as either coronal to the CEJ , at, or apical to the CEJ. Restorations with margins at the CEJ were considered as ending in dentin. For all restorations dates of placement, replacement and failure were recorded. Survival times were calculated and Cox-regression analysis was applied to assess influence of cervical margin extension on survival of restorations. Hazard ratios (HR) were calculated. Results: Of the 1912 restoration sites examined, 655 failed during the average 13.7 years observation time, 399 restorations with margins ending in enamel and 256 with margins ending in dentin. Cox-regression analysis revealed that restorations ending below the CEJ (HR 1.28) and the number of restoration surfaces (HR 1.15) resulted in a significantly increased risk for failure. In general, amalgam and composite restorations had comparable survival. The cracked tooth syndrome only was found in relation to amalgam restorations, whereas secondary caries was found more in relation to composite restorations (HR 1.96, p<0.001). However, no difference in secondary caries was found between restorations ending in enamel and those ending in dentin. Conclusion: Differences in survival between restorations ending in dentin or enamel were found, although a relation with secondary caries could not be established.