Method: One hundred twenty extracted premolars were randomly divided into 6 groups. All teeth were pumiced with fluoride free paste. In group I (control), the enamel was etched with 37% phosphoric acid. In the other groups, it was conditioned with SEPs according to each manufacturer’s instructions: group II, Clearfil S3 Bond (Kuraray Dental, Tokyo, Japon); group III, Transbond Plus SEP (3M Unitek, Monrovia, Calif); group IV, Optibond All-In-One (Kerr, Italy); group V, G-Bond (GC Corporation, Japon); group VI, Xeno V (Dentsply, Germany). All brackets were bonded with Transbond XT adhesive (3M Unitek, Monrovia, Calif). In each group, the teeth were bonded and debonded 3 times with the same procedure. SBS and ARI scores were evaluated for each debond. ANOVA and paired samples t tests were used to compare the SBS between self-etching primers and within each SEP at different debonding sequences.
Result: SBS values were similar across the 6 groups for the first, second and third debonding sequences (p>0.05). Between debonding sequences 1 and 2, there were no significantly different SBS in all groups. Between debonding sequences 1 and 3, there were a significant (p<0.05) decrease in the SBS of control and Clearfil S3 groups. Between debonding sequences 2 and 3 there was a significant (p<0.05) decrease in the SBS of G Bond group. Less composite remained on the teeth after each debonding sequence in group II, III, IV and V. Repeated bonding procedure can be resulted among enamel-adhesive failure in SEPs.
Conclusion: SBS values of all groups might be clinically acceptable (8-13 MPa). Since SBS values are decreased following second debond, this situation takes into consideration in clinical orthodontics.