## 4 Discussion
Moreover, another similar finite element model study was conducted to identify the different tooth movements while forces were applied via a mini screw using different heights (0 mm, 3 mm, 6 mm and 9 mm) of the power arm. The study revealed that a longer power arm with the mesial placement of the mini screw decreased the anterior rotation, and the power arm at the height of 6 mm and distal placement of the mini screw had a minimal adverse effect on anterior dentition [48]. Root resorption is a common phenomenon during orthodontic tooth movement. A study on stress distribution on cement with the finite element model reported that maximum elemental stress was observed in cervical and neck areas which gradually decrease in the apex area [8]. These areas are more prone to root resorption [49]. Moreover, greater stresses in the apex area are mostly observed during the tipping and torquing movement [50]. It assumed that, while forces were applied, the stresses were dispersed in the cervical and mid root area before the stress extends to the apex. However, the current study did not determine the stresses in the cementum and confined it to the hard and soft bone only. In addition, root morphology is also playing an important role. A finite element model study was conducted on the stress distribution of different root morphology. The study reported that short roots show significant stress in the neck of the root area while balanced stress distribution was observed in the root with normal shape. Blunt shaped roots showed more stress distribution in the apex area of the roots, whereas dilacerated and blunt shaped roots exhibited more stresses in the middle area of the root [51]. Even though there are variant stress distributions observed, [PERSON] et al. stated that deviated roots do not always occur in root resorption during orthodontic tooth movement [52], and genetic factors might play a vital role in root resorption during orthodontic treatment [53]. However, the current study did not focus the stress distribution on different root morphology. This study has not observed any altered root morphology during the 3D assessment; therefore, the stress distribution on different tooth roots might not change even if the stress distribution was assessed. Therefore, it could be said that finite element studies have an enormous effect on orthodontic treatment. In en masse retraction studies, finite element study could explain how the placing of power arms at different heights modifies the anterior teeth retraction. However, in the current study, different power arms did not affect stress distribution, which could explain that the soft bone and hard bone have enough strength to resist the retraction forces by the mini screw implants. Moreover, none of the studies are free from limitations, and the current study is not exceptional. This study measured the stress distribution in soft and hard tissue. However, stress distribution in the periodontal ligament is also an important factor. In addition, the center of resistance is not calculated in the current study, which needs to be taken into consideration. On the other hand, the finite element model study simulates the mechanical law; therefore, clinical representation of orthodontic tooth movement is not sufficient to predict by the finite element models. Hence, clinical trials along with finite element model studies should be conducted.