# Compressive Strength Comparison of Different Orthodontic Metal Bracket Systems
## 4 Discussion  
To ensure reproducible results, standardization, and the isolated measurement of compression forces for accurately assessing the plastic deformation of metal brackets, our study was designed as in vitro research. In our study, the compression of bracket wings using Weingart forceps (Dentaurum, Ispringen, Germany) was selected as the method to compare bracket debonding. This approach was supported by [PERSON] et al. 's study results showing unwanted torque forces could be avoided through compression debonding, which does not exert additional loads on the periodontal ligament and alveolar bone [7,8], which was found to be the healthiest method for enamel and periodontal tissues. In our study, compressive debonding forces were investigated, and no previous studies were found evaluating plastic deformation and yield point using this method. Considering that mesiodistal compression of the bracket wings creates a relatively bilateral tensile force in the bracket-adhesive-enamel system before debonding, only the Mini Diamond bracket in our study exhibited a lower average debonding force than the OmniArch bracket in [PERSON] et al. 's study (121.71 N \(\pm\) 20.52 N) [19]. All other brackets demonstrated higher bond strength. The onset of plastic deformation was less than half the average of the Mini Diamond model, the lowest in our study. These higher values in our study could be attributed to the use of different teeth, brackets, and debonding methods. Consistent with [PERSON] et al. 's results, all specimens in our study exhibited an ARI Score of 3, indicating that resin remained entirely on the enamel surface under the influence of a relative tensile force. The bond strength values obtained in our study differ from [PERSON] et al. [20] results. In our study, isolated compression forces were applied in vitro, so the forces calculated in Newtons did not fully impact the bracket-adhesive-enamel system, with a significant portion absorbed by plastic deformation. Considering the differences in teeth, bracket brands, separation tools, and the application of isolated compression forces, the higher bond strength values in our study can be understood. In this research, forces were applied to the bracket wings in the mesiodistal direction. Although most samples dropped due to plastic deformation, the average values were much higher for the samples that resulted in debonding in our study. Unlike [PERSON] et al. 's findings [21], all samples in our study that debonded under compression force had an ARI Score of 3. However, these values must be considered in the context of different experimental settings, brackets, devices, and debonding instruments. In addition, [PERSON] et al. found that an ARI Score of 3 caused the least damage to the enamel [22], and [PERSON] [5] noted that the amount of residual composite resin depends on the method used for bracket removal. Although it may not be clinically feasible to remove brackets with isolated compression as in an in vitro environment, it appears to be a safe method for preserving enamel surfaces. In addition, the results we obtained are different from the results of an average debonding strength of 107.8 kg/cm\({}^{2}\)) (10.57 MPa) for the shear group and 67.8 kg/cm\({}^{2}\) (6.64 MPa) for the diametral compression group found by [PERSON] et al. [23]. This difference  
Figure 9: Sample specimens with ARI score of 3.  
can be attributed to the use of metal brackets in our study instead of ceramic brackets and the ductility of metal materials. Additionally, in our study, isolated compression forces were applied using a Weingart Plier (Dentaurum, Ispringen, Germany). Therefore, the tests resulted more in plastic deformation than debonding. Hence, the assumption that diametral compression in metal brackets would correspond proportionally to tensile forces is invalid for our brackets. Therefore, the values of samples resulting in failure in our study were much higher than those of [PERSON] et al. [23]. In another study using the Mini Diamond bracket, [PERSON] et al.