It is known that all techniques employed for removing adhesive remnants (AR), following the debonding of brackets, produce different degrees of polishing and introduce some form of abrasion, accompanied by various degrees of enamel loss [1,2,3,4,5,6]. Thus, the quest for a safe, efficient method for the removal of AR, after the debonding of orthodontic accessories, has resulted in the introduction of a wide variety of instruments and procedures [1, 4, 21,22,23]. One possibility is the incorporation of fluorescent agents into adhesive systems capable of allowing the clinician to check the differences in fluorescence between the adhesive material and the enamel, thereby preserving the tooth surface [9, 13, 24, 25].
However, an important step in the verification of the efficiency of an adhesive system, for use in orthodontics, is the shear bond strength test [26, 27]. In the present study, this aspect was evaluated with particular attention due to the presence of an adhesive system with fluorescent agents (Orthocem UV trace, UV group), since the other one is a widely known system already used by professionals [28, 29]. The results demonstrated that the adhesive systems used did not show significant differences in terms of shear bond strength, with values close to the results previously described in the literature . It should be emphasized that, despite the Orthocem UV Trace (UV group) being a two-step system, since it does not include the adhesive stage, this did not have an adverse effect on performance. Moreover, the presence of fluorescent agents in the UV group adhesive, similarly, had no impact on performance.
Rare earth oxides, widely used in dentistry to differentiate between dental materials and the tooth surface on visual inspection , have also been used to benefit orthodontic patients. The Eu3+ ion, one of the most popular lanthanides, is useful for the development of fluorescent, orthodontic adhesives as it emits monochromatic red light when excited with ultraviolet (UV) light. With the aim of looking for more effective solutions and making adhesives visible, for safe, complete removal after orthodontic treatment, Hamba et al.  added Eu3+ ions to yttrium oxide (Y2O3), which was a viable alternative for differentiation. Namura et al. , looked into the effect of incorporating different concentrations (0.001%, 0.002%, and 0.003%) of fluorescent dye derived from coumarin, in an adhesive system for bonding brackets to bovine teeth, and concluded that the adhesive containing 0.002% fluorescent dye possessed good shear bond strength (6.6 MPa), and also facilitated the removal of remaining material without impairing the structure of the enamel. The present study employed the UV system, though the manufacturer does not state what fluorescent agent is used, just the concentration (< 0.001% by mass). Therefore, this study obtained a shear bond strength greater than that of the abovementioned study  for all the adhesives tested, probably due to the bonding having been performed on human teeth.
The present study showed significant differences between groups for the ARI scores. Nevertheless, both groups exhibited higher frequencies of score 1 for the ARI (70%) in all systems tested, representing less than half of the adhesive remaining on the tooth surface after debonding, constituting a clinically desirable result because it reduced the amount of residual adhesive and the need for a rotary instrument for the cleanup . However, a previous clinical study demonstrated that enamel damage regularly occurred during the debonding process with the extent of the damage being highly variable depending on the bracket material and adhesive system .
The laboratory results for both tested adhesives produced values above the recommended average, between 6 and 8 MPa, which represents the minimum load for the shear bond strength of an adhesive for clinical use in orthodontics . It should also be stressed that highly accentuated shear bond strength could increase the risk of the enamel fracturing during the removal of the orthodontic accessories. Therefore, a suitable adhesive system for orthodontic use must be seen to be resistant to masticatory force  while preserving the dental structure in the accessory removal stage .
Additionally, the clinical results showed low failure rates for both adhesive systems tested (UV group = 2.5% and control group = 5%). Cal-Neto et al.  suggested that a failure rate below 10% is clinically acceptable. The UV adhesive system was compared to the gold standard in orthodontics and demonstrated similar clinical performance over a 24-month period. Despite the lack of evaluation at the end of the treatment, which is a limitation of the current study, the study was conducted considering that an average treatment time is 23.5 months .
Accordingly, this study compared a UV light-sensitive adhesive system to a conventional system, demonstrating no significant difference in shear bond strength and in clinical performance. These results show that the adhesive system with the fluorescent agent can be used and could deliver greater clinical practicality in the removal of adhesive remnants, particularly in posterior teeth, due to the differentiation of the optical characteristics of natural teeth. These characteristics could prevent potential damage to the surface layer of the enamel. Further investigation could be performed comparing the current adhesive with the fluorescent substance and the same material without it. This evaluation could address important information regarding the influence of fluorescent agents on the mechanical strength of orthodontic adhesives.