Dentin bond strengths of two ceramic inlay systems after cementation with three different techniques and one bonding system.

STATEMENT OF PROBLEM: Cementation of inlay restoration is critical. Because of its high organic content, dentin is a less favorable substrate for bonding than enamel. Therefore it is important to improve dentin adhesion when placing ceramic inlay restorations.

PURPOSE: The purpose of this study was to compare the dentin bond strengths of 2 different ceramic inlay systems after cementation with 3 different techniques and 1 bonding system.

MATERIAL AND METHODS: One hundred twenty freshly extracted caries- and restoration-free molar teeth used in this study were stored in saline solution at room temperature. Standardized Class I preparations were made in all teeth. Each preparation had a length of 6 mm, a width of 3 mm, a depth of 2 mm, and 6-degree convergence of the walls. Teeth were randomly assigned to 2 groups of 60 each to evaluate the bonding of 2 ceramic systems, Ceramco II (Group I) and IPS Empress 2 (Group II), to dentin. Each of the 2 groups were further divided into 3 cementation technique groups of 20 each (Group I A, B, and C and Group II A, B, and C). Groups I A and B and Groups II A and B used dentin bonding agent (DBA) Clearfil Liner Bond 2V, and resin cement (Panavia F). Groups I C and II C served as control groups and used Panavia F without the dentin-bonding agent. In Groups I A and II A, the DBA was applied immediately after the completion of the preparations (D-DBA). Impressions were then made, and the ceramic inlays were fabricated according to the manufacturers' guidelines. In Groups I B and II B the DBA was applied just before luting the inlay restorations (I-DBA). In Groups I C and II C, no bonding agent was used before the cementation of the inlay restorations (No DBA). Cementation procedures followed a standard protocol. After cementation, specimens were stored in distilled water at 37 degrees C for 24 hours. The teeth were sectioned both mesial-distally and buccal-lingually along their long axis into three 1.2 x 1.2 mm wide |-shaped sections. The specimens were then subjected to microtensile testing at a crosshead speed of 1 mm/min, and the maximum load at fracture (in kilograms) was recorded. Two-way analysis of variance and Tukey honestly significant difference tests were used to evaluate the results (P<.05). Scanning electron microscopy analysis was used to examine the details of the bonding interface. The fractured surfaces were observed with a stereomicroscope at original magnification x22 to identify the mode of fracture.

RESULTS: Although no significant difference was found among the 2 ceramic systems with regard to dentin bond strengths (P>.05), the difference between the cementation techniques was found to be significant (P<.001). Comparison among techniques showed that the dentin bond strength in the D-DBA technique had a significantly higher mean (40.27 +/- 8.55 Kg) than the I-DBA (30.20 +/- 6.78 Kg) and No DBA techniques (32.43 +/- 8.58 Kg). As a result of scanning electron microscopy analysis, a distinct and thicker hybrid zone with more, and longer resin tags were found in specimens treated with the D-DBA technique than with the other 2 techniques. Most failures (353 of 360) were adhesive in nature at the bonding resin/dentin interface. Only 7 specimens showed cohesive failure within the bonding resin.

CONCLUSION: Within the limitations of this in vitro study, the cementation of the ceramic inlays tested with the D-DBA technique used resulted in higher bond strengths to dentin.