Early replacement of ankylosed first molar via mesial root movement facilitates bone formation and normal eruption of the third molar.

Ankylosis of a molar during active growth leads to a significant vertical bone defect, extrusion of the opposing molar, and inclination of adjacent teeth. Treatment timing is an essential factor for the patient's quality of life. Early extraction of the ankylosed molar and protraction of the second molar is challenging because of the difficulty of tooth movement and the uncertainty of the normal eruption of the third molar. In view of the uncertainty of eruption of the mandibular third molar, it is essential to assess the potential for eruption according to the developmental stage of the third molar and to secure sufficient space for eruption. In this case report, a girl with an ankylosed right mandibular first molar and an advanced vertical bone defect was treated via early extraction of the ankylosed molar along with the intrusion of the maxillary molar and mesial root movement of the second molar before the initiation of third molar root formation. Restoration of the vertical bone defect was noted at the end of treatment. In addition, spontaneous eruption of the third molar was observed, which was in contrast to the mesioangular impaction of the contralateral third molar. This case emphasizes the importance of treatment timing to increase the chance of utilization of the third molar.

Effects of bodily retraction of mandibular incisors versus mandibular setback surgery on pharyngeal airway space: A comparative study.

OBJECTIVE: The purpose of this study was to compare the changes induced in the pharyngeal airway space by orthodontic treatment with bodily retraction of the mandibular incisors and mandibular setback surgery without extraction. METHODS: This retrospective study included 63 adult patients (32 men and 31 women). Thirty-three patients who had been treated via four-bicuspid extraction and bodily retraction of the mandibular incisors (incisor retraction, IR group) were compared with 30 patients who had been treated via mandibular setback surgery (MS group) without extraction. Lateral cephalograms were acquired and analyzed before (T1) and after treatment (T2). RESULTS: The superior pharyngeal airway space did not change significantly in either group during treatment. The middle pharyngeal airway space decreased by 1.15 ± 1.17 mm and 1.25 ± 1.35 mm after treatment in the IR and MS groups, respectively, and the decrease was comparable between the two groups. In the MS group, the inferior pharyngeal airway space (E-IPW) decreased by 0.88 ± 1.67 mm after treatment (p < 0.01). The E-IPW was larger in the MS group than in IR group at T1, but it did not differ significantly between the two groups at T2. No significant correlation was observed between changes in the pharyngeal airway space and the skeletal and dental variables in each group. CONCLUSIONS: The middle pharyngeal airway space decreased because of the posterior displacement of the mandibular incisors and/or the mandibular body. The E-IPW decreased only in the MS group because of the posterior displacement of only the mandibular body.

Maxillomandibular arch width differences at estimated centers of resistance: Comparison between normal occlusion and skeletal Class III malocclusion.

OBJECTIVE: To evaluate the differences in maxillomandibular transverse measurements at either the crown or the estimated center of resistance (CR), and to compare values between normal occlusion and Class III malocclusion groups. METHODS: Dental casts and computed tomography (CT) data from 30 individuals with normal occlusion and 30 with skeletal Class III malocclusions were evaluated. Using the casts, dental arch widths (DAWs) were measured from the cusp tips, and basal arch widths (BAWs-cast) were measured as the distance between the points at the mucogingival junction adjacent to the respective cusp tips. The BAWs determined from CT (BAWs-CT) images were measured from the estimated CRs of the teeth. RESULTS: None of the DAW measurements or maxillomandibular DAW differences showed statistically significant intergroup differences. In contrast, the maxillary BAWs-CT and BAWs-cast were lesser in the Class III malocclusion group than in the normal occlusion group. The mandibular BAWs-CT were significantly greater in the Class III malocclusion group than in the normal occlusion group. Moreover, the maxillomandibular BAW differences on both CT and cast showed significant intergroup differences in all transverse measurements. CONCLUSIONS: The maxillomandibular DAW differences showed no significant intergroup differences. In contrast, the maxillomandibular BAW differences on both CT and cast showed significant intergroup differences in all transverse measurements. The maxillomandibular BAW differences at the estimated CRs, measured using CT or casts, can reveal underlying transverse maxillary basal arch deficiencies in patients with skeletal Class III malocclusions.