Bond strengths to enamel and dentin with indirect and direct resin composites

To investigate the differences in shear bond strengths between indirect and direct resin composites attached to enamel and dentin.

Sixty human molar teeth stored in distilled water since extraction were used in this study. Thirty of the teeth were prepared to form a flat enamel surface ground to 600 grit and 30 of the teeth were prepared to form a flat dentin surface ground to 600 grit. Cylinders constructed from Triad indirect resin composite were bonded to 15 enamel and 15 dentin surfaces and additional cylinders constructed from TPH direct resin were bonded to the remaining 15 enamel and 15 dentin substrates. Bond strengths were determined by shearing the specimens with an Instron testing machine.

Mean shear bond strengths observed in this study were: Triad to enamel, 27.64 +/- 7.35 MPa; TPH to enamel, 27.43 +/- 3.37 MPa; Triad to dentin, 21.83 +/- 3.10 MPa; and TPH to dentin, 21.27 +/- 4.85 MPa. Two-way ANOVA demonstrated that significant differences existed between the four test groups and that this difference was primarily related to the surface to which the cylinders were attached (P = 0.000). No significant differences were discovered in shear bond strengths between restorative materials (P = 0.767) or between restorative materials bonded to a specific, common surface (P = 0.891). Turkey's post hoc test demonstrated that the shear bond strength of Triad to enamel was significantly greater than the shear bond strength of either Triad to dentin (P = 0.012) or TPH to dentin (P = 0.005). This test also pointed out that the shear bond strength of TPH to enamel was significantly greater than the shear bond strength of either TPH to dentin (P = 0.007) or Triad to dentin (P = 0.016). Finally, it was noted that the shear bond strength of Triad to enamel was essentially the same as TPH to enamel (P = 1.000) and that the bond strength of Triad to dentin was essentially the same as TPH to dentin (P = 0.990).