# Lower Molar Distalization Using Clear Aligners: Bodily Movement or Uprighting? A Preliminary Study
## 4 Discussion
A potential side effect of molar uprighting is the formation of premature contacts at the level of the mesial cusps caused by the relative extrusion of molars indeed. The patient's vertical skeletal pattern is an important factor to consider when planning molar distalization as it can vary unfavorably, especially in hyperdivergent patients in whom an increase in vertical dimension during treatment is not desirable [32]. A clockwise rotation of the mandible caused by dental precontacts that appeared during the distalization movement can in fact worsen the profile and cause anterior open bite. The statistical non-significance of the variations associated with the SN-MP and PP-MP parameters demonstrates the possibility of maintaining control of verticality in the patient during orthodontic therapy and this could be determined by the thickness of the aligners and the consequent bite-block effect [29]. Regarding the skeletal variables considered, no statistically significant changes were detected not only in the vertical plane, but also in the sagittal plane. All patients included in the study had a CS5 vertebral maturation phase (according to the CVM classification) at the start of treatment; therefore, skeletal growth could be considered complete and further changes in terms of mandibular development were not likely [11]. Significant data that emerged from this study is the variation of lower incisors inclination towards lingual direction. In the dental correction of a malocclusion, it is essential to consider the need for anchorage since, as demonstrated by [PERSON] [18], every intraoral force applied in the distal direction produces an equal and opposite reaction in the opposite region, i.e., a loss of anterior anchorage, and this applies to both the arches; the same effect was documented by [PERSON] et al. [19]. Specifically, a force applied to the molars is reflected on the incisors as a loss of anchorage and therefore as a tendency to proclination. The side dental effects of molar distalization with traditional fixed orthodontic devices and with the aid of TADs are well documented in the literature [33; 34]. Aligner deflection during the distalization phase produces the same type of effect [22]. The significance of the variation in terms of endo-inclination of the lower incisor, however, suggests that the Invisual sign system allows for better control over the torque of the anterior elements, intended as a side effect of molar distalization and this is in agreement with data in the literature. However, it is advisable to use interarch elastics with class III vector during the entire distalization phase, exactly as in the upper molar distalization protocol [29]. Although the results of this study already provide useful information on the effectiveness of lower molar distalization with aligners, this topic deserves to be further explored with clinical trials and a larger sample size. Among the biases that can negatively influence the results of the study, we must remember the selection biases linked to the retrospectively of the study itself. Conducting a retrospective study on an uncommon orthodontic procedure such as this also presents difficulties, and for this reason, the participation of private orthodontic activity was requested and the retrospective design of the study seemed the most suitable one. Other limitations of the study are represented by the difficulty of evaluating the dental effects caused by the class III elastics and by the lack of monitoring of patient collaboration. Class III elastics, considered necessary to prevent the loss of anterior anchorage, were used in all patients throughout the lower molar distalization phase, but some continued to wear these elastics in later stages to reduce the risk of proclination of the lower incisors; therefore,the results relating to changes in position and inclination of the lower incisors may have been influenced.