Letters From Our Readers

To: Editor, The Angle Orthodontist

Re: Response to: Factors associated with spontaneous mesialization of impacted mandibular third molars after second molar protraction. Un-Bong Baik, Jin Hye Kang, Ui-Lyong Lee, Nikhilesh R. Vaid, Yoon-Ji Kim, Dong-Yul Lee. Angle Orthod. 2020; 90: 181–186.

We thank Drs. Merin Kuriakose and Sandhya Jain for their comments and questions regarding our article. Our responses to the points that were raised are as follows:

1. We had initially considered the available space in the retromolar area at pretreatment as a possible factor that affected the amount of third molar's spontaneous mesialization. However, it showed statistically non-significant results and was thus excluded from the regression model.

2. We agree that the vertical skeletal pattern would affect the spontaneous movement of the third molars following second molar protraction. However, we did not analyze patients' skeletal patterns in this study. As such, we are currently conducting a study to analyze the association between the second and third molar movements and vertical skeletal patterns as well as the subsequent changes following molar protraction by using lateral cephalograms.

3. There were cases of periapical cyst in the second and third molars (figure below). As it was not possible to perform second molar protraction, those cases were not included in the study.

4. It is possible that alveolar bone resorption might affect the spontaneous mesialization of the third molar. However, we presumed that the alveolar bone resorption occurred as a result of the second molar protraction and that it would have minimal effects on the third molars. In cases that showed significant bone resorption distal to the second molar, the bone resorption was only confined to the second molar's distal root area; the alveolar bone mesial to the third molars was intact. However, further investigation is warranted to provide a clear answer to this issue.