Effect of immediate dentin sealing on the fracture strength of indirect overlay restorations using different types of luting agents (A comparative in vitro study)

OBJECTIVE: This study evaluates the effects of immediate dentin sealing (IDS) on the fracture resistance of lithium disilicate overlays using three different types of resin-luting agents (preheated composite, dual-cure adhesive resin, and flowable composite). MATERIALS AND METHODS: Forty-eight maxillary first premolars of equal size were prepared using a butt joint preparation design. The teeth were separated into two primary groups, each with 24 teeth: Group DDS – delay dentin sealing (DDS) (non-IDS) teeth were not treated. Group IDS – dentin sealing was applied immediately after teeth preparations. Each group was subsequently separated into three separate subgroups of eight teeth. Subgroups DDS+Phc and IDS+Phc – cemented with preheated composite (Enamel plus HRi, Micerium, Italy), subgroups DDS+Dcrs and IDS+Dcrs – cemented with dual-cured resin cement (RelyX Ultimate, 3M ESPE, Germany), and subgroups DDS+Fc and IDS+Fc – cemented with flowable composite (Filtek Supreme Flowable, 3M ESPE, USA). The fracture resistance of each sample was evaluated using a test of a single load till failure, which was automatically recorded in Newton by a computer-controlled universal testing system. RESULTS: The fracture resistance of the subgroup IDS+Phc was the highest mean value, in which the overlay was cemented with preheated composite (1954 N), and the lowest mean was noted in the subgroup DDS+Fc, by which the overlay cemented with flowable composite without IDS (887 N). All IDS subgroups had a high mean fracture load. Both the Bonferroni test and the one-way ANOVA test identified a significant difference between all groups of 0.05. CONCLUSION: In general, teeth with IDS were stronger than teeth without IDS. When the preheated composite is used as a luting agent improves overall fracture resistance, followed by resin cement and flowable composite, respectively. However, the result showed that the ceramic overlays with and without IDS are strong enough to withstand the normal mastication force. Overlays was failed in a more catastrophic, irreparable mode of fracture than the clinical situation.