Alveolar bone thickness and lower incisor position in skeletal Class I and Class II malocclusions assessed with cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: To evaluate lower incisor position and bony support between patients with Class II average- and high-angle malocclusions and compare with the patients presenting Class I malocclusions. METHODS: CBCT records of 79 patients were divided into 2 groups according to sagittal jaw relationships: Class I and II. Each group was further divided into average- and high-angle subgroups. Six angular and 6 linear measurements were performed. Independent samples t-test, Kruskal-Wallis, and Dunn post-hoc tests were performed for statistical comparisons. RESULTS: Labial alveolar bone thickness was significantly higher in Class I group compared to Class II group (p = 0.003). Lingual alveolar bone angle (p = 0.004), lower incisor protrusion (p = 0.007) and proclination (p = 0.046) were greatest in Class II average-angle patients. Spongious bone was thinner (p = 0.016) and root apex was closer to the labial cortex in high-angle subgroups when compared to the Class II average-angle subgroup (p = 0.004). CONCLUSIONS: Mandibular anterior bony support and lower incisor position were different between average- and high-angle Class II patients. Clinicians should be aware that the range of lower incisor movement in high-angle Class II patients is limited compared to average- angle Class II patients.

Comparison of craniofacial morphology, head posture and hyoid bone position with different breathing patterns

The aim of this study was to evaluate differences in craniofacial morphology, head posture and hyoid bone position between mouth breathing [MB] and nasal breathing [NB] patients. Mouth breathing patients comprised 34 skeletal Class I subjects with a mean age of 12.8 +/- 1.5 years [range: 12.0-15.2 years]. Thirty-two subjects with skeletal Class I relationship were included in the NB group [mean 13.5 +/- 1.3 years; range: 12.2-14.8 years]. Twenty-seven measurements [15 angular and 12 linear] were used for the craniofacial analysis. Additionally, 12 measurements were evaluated for head posture [eight measurements] and hyoid bone position [four measurements]. Student's /-test was used for the statistical analysis. Probability values <0.05 were accepted as significant. Statistical comparisons showed that sagittal measurements including SNA [p < 0.01], ANB [p < 0.01], A to N perp [p < 0.05], convexity [p < 0.05], IMPA [p < 0.05] and overbite [p < 0.05] measurements were found to be lower in MB patients compared to NB. Vertical measurements including SN-MP [p < 0.01] and PP-GoGn [p < 0.01], S-N [p <0.05] and anterior facial height [p < 0.05] were significantly higher in MB patients, while the odontoid proses and palatal plane angle [OPT-PP] was greater and true vertical line and palatal plane angle [Vert-PP] was smaller in MB patients compared to NB group [p < 0.05 for both]. No statistically significant differences were found regarding the hyoid bone position between both groups. The maxilla was more retrognathic in MB patients. Additionally, the palatal plane had a posterior rotation in MB patients. However, no significant differences were found in the hyoid bone position between MB and NB patients

Cone-beam computed tomography assessment of mandibular asymmetry in unilateral cleft lip and palate patients / 대한치과교정학회지

OBJECTIVE: To determine whether there is any difference between the cleft and non-cleft sides of the mandible in unilateral cleft lip and palate (UCLP) patients, or the right and left sides in control patients; and to determine if there is any difference between the mandibular asymmetry of UCLP patients and that of control patients. METHODS: We examined cone-beam computed tomography (CBCT) scans of 15 patients with UCLP and 15 age- and gender-matched control patients. We evaluated 8 linear, 3 surface, and 3 volumetric measurements and compared the cleft/non-cleft sides of UCLP patients and the right/left sides of controls. RESULTS: There were no statistically significant gender differences in any linear, surface, or volumetric measurement. The single significant side-to-side difference in UCLP patients was a longer coronoid unit on the cleft side than on the non-cleft side (p = 0.046). Body volume was significantly lower in the UCLP group than in the control group (p = 0.008). CONCLUSIONS: In general, UCLP patients have symmetrical mandibles, although the coronoid unit length is significantly longer on the cleft side than on the non-cleft side. UCLP patients and controls differed only in body volume.

Changes in mandibular transversal arch dimensions after rapid maxillary expansion procedure assessed through cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: This study aimed at evaluating the changes in mandibular arch widths and buccolingual inclinations of mandibular posterior teeth after rapid maxillary expansion (RME). METHODS: Baseline and post-expansion cone-beam computed tomographic (CBCT) images of patients who initially had bilateral posterior cross-bite and underwent RME with a banded-type expander were assessed in this study. The patients included 9 boys (mean age: 13.97 +/- 1.17 years) and 11 girls (mean age: 13.53 +/- 2.12 years). Images obtained 6 months after retention were available for 10 of these patients. Eighteen angular and 43 linear measurements were performed for the maxilla and mandible. The measurements were performed on frontally clipped images at the following time points; before expansion (T1), after expansion (T2), and after retention (T3). Statistical significance was assessed with paired sample t-test at p < 0.05. RESULTS: T1-T2 comparisons showed statistically significant post-RME increases for all measurements; similarly, T2-T1 and T3-T1 comparisons showed statistically significant changes. The maxillary linear and angular measurements showed decreases after expansion, and mandibular linear and angular measurements increased after retention. CONCLUSION: All mandibular arch widths increased and mandibular posterior teeth were uprighted after RME procedure.