Long-Term CBCT Evaluation of Mandibular Third Molar Changes after Distalization in Adolescents

Round 1

Reviewer 1 Report

Dear Authors 

the paper is well written and can be accepted for publication after minor revisions. In particular some topics need more attention:

1) Please consider in your paper the fundamental role of oral hygiene in patients with oral devices. Please cite PubMed ID28696070

2) Please consider the fundamental role of chlorexidine in maintenance of a low bacterial loading in the oral cavity, strongly recommended in such cases. Please cite DOI10.23805/JO.2019.12.01.20

3) You should hypothesize that your method can be valid also in patient with major orthodontic diseases, that requires extraoral bone grafting. Please cite PubMed ID31140209

After these changes the paper can be acceptable for publication

Author Response

Thank you for your valuable comments. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this clinical study, the authors sought to assess the mandibular molar changes after distalization using Class III elastics and modified C-palatal plates (MCPPs) in the maxilla and to use CBCT to analyze the third molar position after long-term retention in 35 subjects. 

Although a well-written study, a few issues must be addressed.

Please see the enclosed PDF for further details.

Comments for author File: Comments.pdf

Author Response

Thank you for your valuable comments. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript investigated retrospectively and evaluated by CBCT how the mandibular third molar position changed in adolescents with bimaxillary protrusion by distalization using modified C-palatal plates (MCPP) and Class III elastics without non-extraction.

Three-dimensional analysis was performed from CBCT images of 26 mandibular third molars in 14 subjects at three time points: before orthodontic treatment, after treatment, and after long-term retention. In addition, 39 mandibular third molars in 21 Class I normal occlusion subjects who had CBCT taken for purposes other than the present study were selected as a control group for their condition after long-term retention.

The main evaluation items were the positional changes such as the angulation of the tooth axis and vertical positioning of the mandibular third molar.

The results showed that distal tipping at the crown of mandibular first and second molars was significantly greater after treatment compared to before treatment, but there was no significant change for the mandibular third molar. For vertical positioning, the post-retention group was significantly more extruded than the pre-treatment group. The retention group had a significantly smaller angulation and a significantly lower vertical alignment as well as a more buccal position than the control group.

Based on these findings, the authors concluded that the distalization in orthodontic treatment with non-extraction may result in mandibular third molar that fail to erupt and become embedded in the long term.

It is very interesting and important to evaluate the long-term mandibular third molar positional change after orthodontic treatment, especially distalization with non-extraction.

In addition, from the standpoint of oral surgeon, the type of orthodontic treatment could lead to the decision making of tooth extraction based on the eruption status of the impacted mandibular third molar, I think the conception of this study is excellent.

However, I have some concerns that should be addressed regarding the some issues including significant one.

 

Major:

#1. Page 4, line 134-136, in this study, I believe that more than one measurer is preferable, but why did you choose single examiner? If the above and general versatility is desired, it would be better to make the ICC inter-rater reliability (ICC2).

#2. Page 5, line 162-164, Figure 4, regarding the angulation of mandibular third molars, it is considered difficult to determine the tooth axis at a young age, such as 12 years old, when the tooth is almost incomplete. How was it actually determined?

#3. In clinical practice, we often experience cases of horizontally impacted mandibular third molars in radiographic findings in patients around 20 years of age with no orthodontic treatment and no dental malocclusion.　I found it disconcerting that the angulation of mandibular third molar was 71.37 ± 10.3° in the control group in Table 4. As you mentioned in the Limitation, I believe that the results of the control group will vary greatly depending on how the subjects are selected. Since the intercanine width was different in Table 4, other factors not shown here are expected to be different. In other words, the background may be different. Since this is the core of this study, careful handling of this issue is necessary. The control group in this study has a small number of subjects, so it is probably best to avoid generalization.

 

Minor:

#1. Page 7, line 189, in the sample size estimation, what specific conditions did you estimate? (alpha, power, effect size, etc.)

#2. Page 7, line 191, in statistical analysis, did you consult a statistical expert? In addition to normality and equal variance, MANOVA is said to require that correlations between outcome variables be uniform across study groups. With the small number of subjects in this study, are the above conditions met in this study? Also, what were the response variables?

Furthermore, you used MANOVA for the comparison between the T3 group and the control group, is this the correct test method? What exactly did you use as the response variable?

#3. Page 10, line 270-275, what did you think of this difference in the maxilla and mandible?

#4. Page 10-11, line 283-294, although the analysis in this study was performed in three dimensions, I recognized that the core of the results was mostly sufficient for two-dimensional analysis. What makes you think it is better than panoramic X-P or cephalogram evaluation?

Author Response

Thank you for your valuable comments. Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript has been improved

Reviewer 3 Report

Thank you for sincerely answering my questions.