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.