Shear bond strength of amalgam reinforced with a bonding agent and/or dentin pins

The use of dentin pins can cause crazing in dentin. Bonding agents represent a more conservative approach to retention but may not ensure a comparable shear bond strength.

This study compared the shear bond strength of amalgam to dentin with the application of dentin pins, a bonding agent, and a combination of both forms of retention.

Forty-five freshly extracted, intact molar teeth of similar size were ground flat approximately 2 mm coronal to the cemento-enamel junction and then embedded in acrylic resin blocks. The teeth were randomly divided into 3 groups of 15 specimens each. In group 1, Panavia-Ex was applied to exposed dentin surfaces, and the amalgam was condensed with a copper ring. In group 2, two Pinlock dentin pins were placed 3 mm apart; Panavia-Ex was applied to the dentin, and the amalgam was condensed. In group 3, two Pinlock pins were placed 3 mm apart, and the amalgam was condensed. All materials were mixed and applied according to the manufacturers' directions. After the amalgam had set for 10 minutes, the specimens were stored at 37 degrees C for 24 hours, after which they were thermocycled 1500 times at 5 degrees to 55 degrees C with a dwell time of 30 seconds. Specimens then were loaded in shear mode in a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. A 1-way analysis of variance and a Tukey multiple range comparison test were used for statistical analysis (P<.05).

Significant differences were found among all groups. The highest bond strength (181.86 kg/cm(2)) was obtained for group 2 specimens, which were restored with 2 dentin pins and the bonding system tested.

Within the limitations of this study, the combined use of dentin pins and Panavia-Ex significantly increased the retention of the amalgam core material.