Objective: To compare Shear Bond Strength (SBS) values obtained from the incisal, middle and cervical thirds of superficial bovine incisor dentin. Methods: Ten freshly extracted bovine mandibular central incisors were used to obtain dentin substrates. A slow-speed saw with a diamond disk under cooling water was used to separate the crowns from the roots at the CEJ level. From each crown, six sections were obtained by making a longitudinal section along the middle of the crown and three transverse sections between the crown incisal, middle and cervical thirds (N=60). The sections were embedded in chemically-polymerized methacrylate with the facial surface exposed. The exposed surface was ground flat on a model trimmer until superficial dentin was revealed, and the surfaces finished to 600-grit SiC sandpaper. The prepared specimens were stored in de-ionized water at 4°C until ready to be bonded. Specimens were treated with 37.5 % phosphoric acid and Optibond Solo Plus (Kerr), and polymerized for 20s according to manufacturer's instructions. The specimens were subsequently placed in a bonding jig (Ultradent), filled with resin composite Z100 (3M-ESPE) and polymerized for 40s. Samples were stored at 37°C and 100% humidity for 24 h, after which SBS was measured using an Ultratester testing machine (Ultradent) at a test speed of 1mm/min and expressed in MPa. A one-way ANOVA was used for data analysis. Results: No statistically significant differences were observed among groups (P<0.233).
SBS | Mean (SD) | Median |
Incisal third | 36.9 (13.8) | 38.60 |
Middle third | 42.6 (11.8) | 44.80 |
Cervical third | 37.1 (9.5) | 36.55 |
Conclusion: Within the limitations of this study, although not statistically significant, the higher SBS to the middle third may indicate that the location of bonding should be specified when using bovine teeth for SBS studies.