That study, however, was conducted with pre-coated APC brackets bonded with an acid-etch adhesive system. Although these brackets provide a reduction in the number of bonding procedures and improve kinase inhibitor Cisplatin tolerance to humidity, they are expensive and are less commonly used than conventional brackets. Thus, in the present study, conventional brackets were used. In the present study, no significant difference in SBS values was observed among the groups. Although not significant, an increase in SBS values was observed when the self-etch system was used, following pretreatment with ozone. Previously, Endo at al31 evaluated the bond strengths on enamel and dentin with a self-etch adhesive (iBond), with or without oxygen-inhibited surface layer, and reported that oxygen inhibition had no adverse effect on enamel bond strengths.

This may be attributed to the different and complex chemical compositions of the self-etch adhesives. For the ozone+acid-etch+Transbond XT (Group 3) group, the findings of the present study are in accordance with the studies in which no reduction of bond strength values was observed. As far as the authors know, this is the first study to have tested the bond strength of a self-etch adhesive system after ozone application; thus, no comparison can be made in the self-etch group (Group 1). Although no significant difference was found in SBS values, when ARI scores were examined, it was observed that specimens not pretreated with Biozonix demonstrated lower ARI scores. In the overall evaluation, the lowest SBS values and the lowest ARI scores were observed in Group 2.

Accordingly, it can be interpreted that surface etching helps to counter the oxidizing effect of the ozone; however, the use of a self-etch adhesive system without ozone pretreatment revealed adhesion failure. ARI scores showed that the predominant failure mode for Group 2 was cohesive failure, and most of the resin remained on tooth surface. On the other hand, the ARI is an ordinal scale, which has its limitations, especially when the numbers do not represent linear gradations from one score to the next. Perhaps a more accurate adhesive retention index could have been developed in which 3D area calculation could be conducted precisely. More importantly, as Hildebrand et al32 demonstrated, ARI scores do not always correlate with SBS values, and in vitro studies do not represent clinical situations precisely.

CONCLUSIONS Although the results should be confirmed clinically, the following conclusions were drawn within the limitations of this study: Enamel pretreatment with ozone did not affect the SBS of tested adhesive systems used for bracket bonding. SBS values of the ozone pretreated AV-951 specimens were somewhat higher. The lowest SBS values and lowest ARI scores were obtained when a self-etch adhesive was used alone. In general, the ARI scores of the specimens without ozone pretreatment were lower.