Influence of Self-Etching Primers on Bond Strength of Orthodontic Brackets

Objective: To compare the influence of six different self-etching primers (SEPs) on shear bond strength (SBS) of orthodontic brackets bonded with the same orthodontic composite-resin.

Methods: 140 extracted human bicuspids were collected (0.1%wt/vol, thymol), pumiced using rubber cup with fluoride-free paste (10s), washed (30s) and dried. The teeth were randomly divided into seven groups (n=20/gp). Group I: (Control), in which the enamel was etched (37% H3PO4; 15s), washed (30s) and dried. In remaining groups the enamel was conditioned with SEPs according to each manufacturer.  Group II: Transbond Plus; group III: AdheSE; group IV: Primers A and B; group V: Clearfil Mega Bond FA; group VI: Force Bond; and group VII: PeakSE and PeakLC Bond. Stainless steel brackets were bonded to all teeth with Transbond XT (light-cured, 20s).  Samples were stored (37°C, 24hrs), tested (0.5mm/min), and statistically analyzed [Mean, SD, Range; Scheffè, ANOVA (р<0.05)]. The adhesive remnant index (ARI) was also evaluated and statistically analyzed with c2.

Results: All groups yielded higher SBS than the average (5.9 to 7.8MPa) suggested optimum to accomplish the orthodontic treatment; nonetheless, group I (26.5±8.1MPa) presented significantly higher value than other groups [Except group II (21.1±6.2MPa)]. There were not significant differences amongst groups II, V (19.0±4.3MPa), VI (18.3±4.4MPa), and VII (19.6±5.1MPa). Groups I, II and VII were significantly higher than group III (13.4±4.1MPa), and group IV (8.8±2.6MPa) was significantly lower than groups II, V, VI and VII. There was not significant difference between groups III and IV. Concerning ARI scores, significances were found between groups, lower amount of residual adhesive was observed in groups with lower values of SBS and vice versa.

Conclusions: Although the values of SBS obtained in all groups might be clinically acceptable, SEPs influenced the bond strength. The advantages and properties of each conditioner should be highly comprehended previous bonding orthodontic brackets.