## 1 Introduction
These materials are intended for restorative (not orthodontic) applications and their composition is modified by adding reversible addition-fragmentation chain transfer (RAFT) agents to an organic matrix [1]. The DC values of these materials were shown to be comparable to those of conventional composites and not affected by curing light intensity (high intensity or conventional) [13]. To the best of our knowledge, RAFT polymerization is currently used only in restorative composites from a specific manufacturer and has not yet been implemented in orthodontic adhesives. Resin-based orthodontic adhesive systems are the most widely used materials for bonding brackets [2; 6; 14]. Since bracket bonding is a clinically sensitive and time-consuming procedure [5], there is a need to simplify this process and to reduce chair time [23; 29; 30]. As a result, practitioners may be inclined to use rapid (3 s) light curing, originally introduced as an option for restorative resin composites, as a time-saving measure. Additionally,light curing of orthodontic adhesive systems is complicated by the presence of a non-transparent bracket material [9]. The effectiveness of light curing, represented as DC of these materials, is affected by the presence of brackets. DC values increase over time to a material-dependent extent due to the continuation of post-cure polymerization, but this increase is typically unable to fully compensate for an initially lower DC value [31]. Several studies have examined the effect of light curing intensity on the shear bond strength of orthodontic brackets [32,33]. While some found no significant difference in bond strength between conventional and rapid high-intensity curing [33], others concluded that reducing the curing time to 3 s significantly lowered bond strength [32]. A lower DC value can influence the bond strength between the adhesive and enamel, affecting the risk of enamel damage during bracket debonding and the adhesive clean-up process [34]. [PERSON] et al. [2] found no significant differences in the percentage of bonding failures when using a 3200 mW/cm\({}^{2}\) LED light for 6 s compared to a 1200 mW/cm\({}^{2}\) LED light for 20 s, suggesting that rapid high-intensity curing may be a clinically viable procedure. Previous studies [30,35,36] confirmed the positive influence of extending the curing time and intensity on the DC of orthodontic adhesive systems. However, concerns have been raised about the efficacy of high irradiance delivered over a short duration in achieving adequate polymerization [1]. To our knowledge, research on the effects of rapid high-intensity curing on the DC of orthodontic adhesive systems, especially in the presence of bracket material, is scarce. Although some studies [2,35] showed that rapid high-intensity curing provides clinically acceptable bond strength of orthodontic adhesive systems, research on restorative composites indicates that it may alter polymerization kinetics and compromise mechanical properties [3,14]. Also, orthodontic adhesive systems lack specific compositional adjustments specifically designed for rapid high-intensity curing. Therefore, the present study compared the short-term and 24 h post-cure DC values of orthodontic adhesive systems, both in the absence of a bracket (control group) and under a metal bracket, using two light curing protocols: rapid high intensity and conventional. The null hypotheses were: (1) there is no significant difference in the DC of the tested orthodontic adhesive systems between the conventional and rapid high-intensity curing protocols; and (2) the presence of a metal bracket does not influence the DC of the tested orthodontic adhesive systems.