Influence of adhesion promoters and curing-light sources on the shear bond strength of orthodontic brackets

Abstract

The effect of different curing units on bond strength of orthodontic brackets is still unclear when utilizing nanofilled composites in comparison with traditional Transbond-XT. To evaluate the influence of two adhesive promoters and two curing-light units on the shear bond strength (SBS) of orthodontic brackets. The factors under study were adhesive promoters (nanofilled composite - Filtek-Z350 flowable restorative and conventional orthodontic adhesive - Transbond XT) and curing-light units (halogen lamp - Ultralux and LED device - Radii-Call). Forty lower bovine incisors were utilized. The teeth were distributed in four groups (n = 10) according to the combination between adhesive promoters and curing-light units. Scotchbond Multipurpose-Plus and Transbond-XT primer were used to bond Filtek-Z350 Flowable Restorative and Transbond-XT, respectively. After storage in distilled water for 24 h, the brackets were subjected to SBS test at a speed of 0.5 mm/min until bracket debonding. The Adhesive Remnant Index (ARI) was assigned at fractured specimens. Analysis of variance and Tukey test were utilized. The Kruskal-Wallis test was used to compare ARI scores between the groups (p<0.05). There was statistically significant difference between the adhesive promoters tested. Transbond-XT showed higher SBS means than Filtek-Z350. There was no statistically significant difference between both curing-light units tested in this study, neither between ARI scores. The conventional orthodontic adhesive presented higher bond strength than the nanofilled composite, although both materials interacted similarly to the teeth. The curing-light devices tested did not influence on bond strength of orthodontic brackets.