Influence of Bracket Type Combined with Delayed Light Activation on Bracket-Adhesive Shear Bond Strength
This study examined the effect of bracket type and varying delayed polymerization times in combination with bracket manipulation on adhesive temperature change, shear bond strength (SBS), degree of conversion (DC), and adhesive remnant index (ARI) score when using a resin adhesive. Specimens from four bracket types: stainless steel with a mesh base (SSm), polycrystalline with a dovetail base (PCd), polycrystalline with a micro-shard base (PCsh), and monocrystalline with a micro-sphere base (MCsp), were divided into three groups of clinically relevant delay times (0.5, 5, 10 min) to simulate the delay that frequently occurs between bracket placement and manipulation followed by light polymerization. Based on an analysis of variance (α=0.05), bracket type was not a significant factor in mean temperature change of the resin cement; however, delay time was found to be a significant factor (p<0.05). There was no significant difference in SBS as a function of delay time. The PCsh bracket type had higher SBS values than other bracket types. Delayed polymerization time and bracket type were not significant factors in DC or ARI. A Spearman correlation (α=0.05) showed a positive correlation between SBS and ARI at the 0.5 min time delay across bracket types. The results of this study suggest that clinically relevant delay times of 0.5, 5, and 10 min do not negatively impact the SBS of a resin adhesive. A majority of brackets fell into the ARI 1 category, meaning that >50% of the resin adhesive remained on the bracket base. The PCsh bracket type showed significantly higher SBS, and thereby may be more appealing to clinicians.
Table of Contents
Introduction -- Materials and methods -- Results -- Discussion -- Conclusions -- Literature cited -- Appendix 1 -- Appendix 2