An In Vitro Study to Compare the Shear Bond Strength of Orthodontic Brackets Bonded to Permanent Teeth by Using Conventional Acid-Etching and Self-Etching Primers

The objective of the present study was to evaluate and compare the bond strength of orthodontic brackets bonded to permanent teeth with a conventional acid-etching and self-etching primer systems. Also, the study aims to evaluate the mode of bond failure after debonding the brackets.

It was an experimental study. Fifty extracted permanent premolars were collected, checked, and cleaned. Teeth were split equally into two groups, group A and B. Orthodontic brackets were bonded using conventional acid-etching and self-etching primer systems for group A and B, respectively. Shear bond strength (SBS) was measured with a universal testing machine, and the mode of bracket-adhesive failure was determined by using adhesive remnant index (ARI). Data were analyzed with a statistical software. Independent sample t-test was used to compare the SBS and Mann–Whitney U test was used to assess whether there is a significant difference of ARI score between the groups.

Although the SBS with self-etching primer was within clinically acceptable range, the overall mean SBS for group A (14.71 MPa) was significantly greater than group B (9.24 MPa) (P =0.024). There was no significant difference in ARI scores between conventional acid-etching and self-etching groups (P =0.801).

The SBS of the conventional acid-etching was significantly higher than the self-etching primer. The SBS of self-etch was within the acceptable range to withstand the forces of mastication. The majority of the brackets recorded ARI score of 1 indicating a cohesive failure with no significant difference between acid-etch and self- etch groups.