## 4 Discussion  
The in vitro testing of the SBS is of translational clinical importance and allows the selection of an ideal combination of materials for effective orthodontic bonding. Clinicians seek to perform the most reliable and stable bonding procedures without inducing any harm to the tooth during intentional debonding at the completion of active treatment [16]. The SBS of orthodontic brackets is impacted by the bracket base design [4]. Moreover, MBs and CBs mostly have mechanical surface roughening or etching to enhance the mechanical retention of the composite to the bracket base. Three-dimensional (3D) printing is a new technique used to fabricate 3D-printed custom brackets [16]. This system delivers precise and individualized bracket base characteristics, assuring an excellent match to the tooth surface through the form-fit properties between the custom bracket base and the tooth surface [16]. The curvature of the bracket base should seamlessly fit the surface of the tooth, leaving a thin layer of resin between the bracket base and the tooth enamel. Any discrepancy in this fit will impact the innate mechanical properties of the resin and, thus, could lead to a fragile interface with a resultant inadequate bond strength [7; 17]. Thus, it is pertinent to evaluate the SBS values of 3D-printed resin brackets and to compare them with those of conventional CB and MB groups. In the present study, the SBS for the 3 DBs with various bonding variables was significantly lower (\(p<0.001\)) than that for the CB and MB groups. All the SBSs were above the minimal force levels recommended in the published literature for a successful clinical debonding procedure [16; 23; 24]. Orthodontic brackets need to remain bonded to the enamel during the extent of the orthodontic treatment. A very low bond strength will lead to inefficient bonding with resultant debonding. On the contrary, a very high bond strength will likely lead to enamel fracture during debonding. Moreover, a clearly noticeable high bond strength may not be clinically appropriate because of the significant risk of enamel damage during the debonding procedure [25]. [PERSON] et al. [26] reported enamel fracture incidents with bond strength measurements as low as 9.7 MPa in samples during in vitro bond testing. Even though the enamel can often resist greater forces compared to the force level reported, it is desirable to follow the instructions for debonding as instructed by the manufacturer to avoid enamel damage [25]. Although all the 3D-printed brackets' mean SBS value in the present study was higher than the ideal mean SBS value suggested by [PERSON] et al. [26] (9.7 MPa) and that of [PERSON] et al. [24] (10.76 MPa), there were only two incidences of damage to the tooth enamel during the debonding procedure from each group represented. Moreover, the SBSs of all the 3 DB groups were significantly lower than the SBSs of the MB and CB groups, which suggests a lower risk of enamel damage during bracket debonding. The lower SBSs could result from the flexible resin of the 3 DB compared to the more rigid MBs and CBs, which will require slightly more force to engender a composite fracture. In addition, no significant difference existed in SBSs between the MB and CB groups, which has also been supported by other studies [27; 28]. The ARI provides information on the efficiency of debonding, that is, the potential for enamel fracture or enamel damage when debonding occurs [29]. ARI scores are impacted by the type of bracket, the debonding procedure, the adhesive type, and the bonding procedure used [25]. Composite resin remaining after the debonding procedure mandates additional cleaning, which may include superficial enamel removal; however, carefully removing the residual resin is likely less risky than damage during the debonding procedure [27; 30; 31]. In the present study, in all the 3 DB groups debonded, less than 50% composite remained, which may be due to the lower SBSs for the 3 DB compared to the MB and CB groups.