Effect of Surface Finish on Bond Strength to Bovine Dentin

Objective: To assess the effect of different polishing grits when preparing dentin surfaces for Shear Bond Strength (SBS) studies. Methods: Thirty freshly extracted bovine incisors were used. Each crown was separated from the root at the CEJ level, and six sections obtained by making three mesio-distal sections between the crown thirds and one longitudinal section along the long axis. The sections were embedded in methacrylate with the facial surface exposed and grounded flat to reveal superficial dentin. The surfaces were finished to 120, 320 or 600-grit SiC sandpaper with twenty specimens for each location-grit combination obtained (N=180) and stored in de-ionized water at 4°C until ready to be bonded. Following etching and rinsing, the surfaces were coated with Optibond Solo Plus (Kerr) and polymerized for 20s. The specimens were placed in a jig which was filled with resin composite Z100 (3M-ESPE), polymerized for 40 seconds, and stored for 24 h at 37°C and 100% humidity. SBS was measured using a testing machine (Ultratester/Ultradent) at a speed of 1mm/min and expressed in MPa. A two-way ANOVA and Tukey test were used for analysis. Results: No statistically significant effect of location (P=0.254) or interaction grit-location (P= 0.629) were observed on SBS. Statistically significant effect of the grit on the SBS was detected (P<0.001) with 320-grit being statistically different from 600-grit (P=0.011) and 120-grit (P<0.001). No significant differences were observed between 600-grit and 120-grit (P=0.413).

Conclusion: Regardless of the location, 320-grit consistently showed the lowest SBS and 120-grit the highest SBS, indicating that different surface grit preparations have an effect on the in-vitro dentin bond strength.