Changes in condylar position during orthodontic treatment depending on the amount of incisor retraction: a cone-beam computed tomography study.

OBJECTIVES: Orthodontic treatment may be associated with temporomandibular disorders through changes in the condylar position. This study aimed to evaluate changes in the condylar position among different amounts of maxillary incisor retraction during orthodontic treatment using cone-beam computed tomography images. MATERIALS AND METHODS: Fifty-four participants were enrolled and divided into minimal (n = 14), moderate (n = 20), and maximal (n = 20) retraction groups based on the amount of incisor retraction (< 1, 1-6, and > 6 mm, respectively). Changes in condylar position before (T0) and after (T1) orthodontic treatment were assessed for the superior, anterior, posterior, and medial joint spaces (SJS, AJS, PJS, and MJS, respectively). Changes in joint spaces were compared between T0 and T1 in each group using paired t-tests and among the three groups using analysis of variance. RESULTS: Anterior movement of the condyle was observed in the maximal retraction group with a 0.2 mm decrease in ΔAJS and a 0.2 mm increase in ΔPJS, significantly greater than those in the minimal retraction group. The AJS and PJS showed statistically significant differences between T0 and T1 (P < 0.05) in the maximal retraction group. CONCLUSIONS: The condyle may show a statistically significant but clinically insignificant forward movement in the maximal incisor retraction group, whereas it was relatively stable in the minimal and moderate incisor retraction groups. CLINICAL RELEVANCE: More attention should be paid to the signs and symptoms of the condyle in patients with excessive incisor retraction during orthodontic treatment.

Posttreatment stability of an anterior open-bite by molar intrusion compared with 2-jaw surgery - a retrospective study.

OBJECTIVES: This study aimed to compare post-treatment stability in patients with anterior open-bite (AOB) between those treated surgically (orthognathic 2-jaw surgery) and non-surgically (molar intrusion using orthodontic miniscrews). MATERIALS AND METHODS: All subjects had initial overbite (OB) < -1 mm and lateral cephalograms taken before treatment (T0), immediately after AOB correction (T1), after orthodontic treatment (T2), and at least 1 year after treatment (T3). The non-surgical group was enrolled retrospectively; then, the surgical group was matched by OB, sex, and age to the non-surgical group (n = 21 each). Changes in cephalometric measurements during treatment (T1-T0), finishing (T2-T1), and retention (T3-T2) periods were compared between two groups. RESULTS: OB increased by 4.5-5.1 mm during the treatment period with 3.3 mm upward movement of the maxillary first molar (U6) in both groups. Changes in OB were not significantly different between the groups: 0.5-0.9 mm increase during the finishing period but 1.0 mm decrease during the retention period (P > 0.05). U6 moved 0.5 mm downward in non-surgical group and 0.1 mm upward in the surgical group during the finishing period, and 1.0 mm and 0.4 mm downward in the non-surgical and surgical groups, respectively, during the retention period. CONCLUSIONS: Post-treatment stability of AOB was similar for surgical and non-surgical methods (76.8 - 78.7%), although U6 moved more downward in the non-surgical group than in the surgical group. CLINICAL RELEVANCE: AOB without severe skeletal deformity can be treated by either molar intrusion or orthognathic surgery with similar treatment outcome and stability.

BBS7-SHH Signaling Activity Regulates Primary Cilia for Periodontal Homeostasis.

Objectives: Mechanical stimuli are essential for the maintenance of periodontal ligament (PDL) homeostasis. Although there are several studies on atrophic changes in PDL due to occlusal hypofunction, the underlying mechanism is still unknown. Here, we aimed to explore the changes of gene expression in occlusal hypofunctional PDL and elucidate the related role in maintaining the PDL homeostasis. Methods: To investigate the transcriptomic difference between control and hypofunctional PDL tissue from patients, RNA sequencing was performed on 34 human teeth. The atrophic changes in PDL were evaluated by histological analysis. The effect of the Bardet-Biedl syndrome 7 (BBS7) knockdown was evaluated by the RT-qPCR, Western blot, wound healing, and tubule formation assay. Results: We detected that the expression of BBS7 was downregulated in occlusal hypofunctional PDL through RNA sequencing. Dynamic changes, including the number of periodontal ligament cells, alignment of collagen fibers, diameter of blood vessels, appearance of primary cilia, and torturous oxytalan fibers, were observed following occlusal hypofunction. Furthermore, Sonic hedgehog signaling (Shh) activity was closely associated with BBS7 expression in PDL cells. In addition, the cell migration and angiogenesis were also suppressed by BBS7 knockdown in vitro. Conclusion: We suggest that BBS7 plays an essential role in maintaining Shh signaling activity for PDL homeostasis.

Spontaneous repair of iatrogenic root perforation by an orthodontic miniscrew: A case report.

BACKGROUND AND OVERVIEW: Orthodontic miniscrews have become popular tools for providing temporary anchorage during orthodontic treatment. Although they are easy to insert, damage to the periodontal ligament or dental root during insertion is an unfavorable iatrogenic complication. Root perforation during miniscrew insertion in human teeth has been reported in a few articles. In this article, the authors describe the spontaneous repair of an iatrogenic root perforation in a mandibular first molar that occurred during insertion of an orthodontic miniscrew in a young girl undergoing orthodontic treatment. CASE DESCRIPTION: A 15-year-old girl with malocclusion was undergoing orthodontic treatment when the mesial root of her mandibular right first molar was damaged by an orthodontic miniscrew. The miniscrew and corresponding bracket were immediately removed to avoid any unnecessary forces on the tooth. Because the pulp remained vital without any additional damage and infection for 6 months, orthodontic treatment was resumed and completed in 9 months without any pulp damage or unfavorable symptoms. Serial periapical radiographs and cone-beam computed tomographic images showed that the injured area was surrounded by reparative tissue without any apical lesion. CONCLUSIONS AND PRACTICAL IMPLICATIONS: The findings of this case suggest that immediate removal of unnecessary forces provides an environment for spontaneous repair in cases of iatrogenic root perforation by orthodontic miniscrews, even when the damage involves the pulp. If force stimulation is avoided for a certain period, which was 6 months in this case, it may be possible to complete the orthodontic treatment without unfavorable symptoms.