Shear bond strength of universal adhesive bonding to primary dentin using rubbing and sonic activation with and without etching strategies: an in vitro study

Objective: This in vitro study sought to compare the influence of manual rubbing versus sonic activation on the shear bond strength (SBS) of a universal adhesive (All-Bond Universal) when applied to primary dentin, both with and without prior acid etching. A total of 66 extracted, caries-free primary canine teeth were divided into six groups ( n = 11 each) based on the application method of All-Bond Universal: (I) no etching and no activation; (II) no etching with rubbing activation; (III) no etching with sonic activation; (IV) etching without activation; (V) etching with rubbing activation; and (VI) etching with sonic activation. Composite resin cylinders were then bonded to the prepared dentin surfaces, and SBS was measured using a universal testing machine. Statistical analysis was performed using ANOVA, Tukey’s, and Bonferroni tests (α = 0.05). The highest SBS was observed in the no-etching/rubbing activation group, while the lowest SBS was found in the etching/no-activation group. Both etching mode ( P < 0.001) and activation method ( P < 0.001) significantly influenced SBS; specifically, regardless of whether etching was used, both activation techniques enhanced bond strength compared to no activation. Across etching conditions, the mean SBS was significantly greater in the activation groups than in the non-activation groups ( P < 0.05). The rubbing group showed a significantly higher mean SBS than the no-activation group ( P = 0.049), but no significant difference was observed between the rubbing and sonic groups ( P = 1.00). When activation mode was disregarded, the etched groups exhibited a significantly lower mean SBS than the non-etched groups ( P < 0.001). Activation by rubbing was most effective for the enhancement of SBS of All-Bond Universal to primary dentin. Activation by Sonic ranked second. Etching is not required prior to adhesive application.