Microtensile Bond Strength to Root Canal vs Pulp Chamber Dentin: Effect of Bonding Strategies

The aim of this in vitro study was to compare the microtensile bond strength (MTBS) between root canal and pulp chamber dentin with two bonding strategies (self-etching primer and total-etch technique). The pulp chamber of four human canines was accessed and the pulp chamber and root canal prepared with spiral drills. The teeth were cut into halves parallel to the long axis of the tooth and randomly assigned to two groups: Clearfil SE Bond + AP-X(SE) (Kuraray) and SingleBond + Filtek Z250(SB) (3M ESPE). After 24 h in water storage, the specimens were cut perpendicular to the root into 1.0-mm slices with a low-speed diamond saw. Specimens were trimmed to obtain hourglass shapes with a bond area of 1.0 mm2 (n = 12). Three specimens were obtained from the cervical root canal dentin (R) and from the coronal pulp chamber dentin (C). The MTBS was measured in a Bencor device with an Instron machine at a crosshead speed of 0.5 mm/min. The data was analyzed with two-way ANOVA and Tukey LSD post hoc (p 0.05). MTBS in MPa (mean ± SD) were: SB.C = 25.3 (± 6.5)a; SB.R = 16.9 (± 6.0)b; SE.C = 16.9 (± 3.4)b; SE.R = 16.8 (± 5.3)b. Means with the same letter are not statistically different at p 0.05. When data were pooled for "dentin region", coronal pulp chamber dentin resulted in statistically higher bond strengths than root canal dentin (p 0.013). Bonding to pulp chamber dentin seems to be more predictable than to root canal dentin. In the former region, the total-etch technique may result in a higher bond strength. Palabras clave: microtensile bond strength, root canal, dentin bonding, one-bottle bonding system, acid etching, self-etching primer