Comparison between dental and basal arch forms in normal occlusion and Class III malocclusions utilizing cone-beam computed tomography / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to investigate the relationship between the mandibular dental and basal arch forms in subjects with normal occlusion and compare them with those of Class III malocclusion using cone-beam computed tomography (CBCT). METHODS: CBCT images of 32 normal occlusion (19 males, 13 females; 24.3 years) and 33 Class III malocclusion subjects (20 males, 13 females, 22.2 years) were selected. Facial axis and root center points were identified from the left to right mandibular first molars. Distances between the facial axis and root center points for each tooth were calculated, and 4 linear and 2 ratio variables were measured and calculated for each arch form. The variables were compared between groups by independent t-test. Pearson correlation coefficient was applied to assess the relationships between dental and basal variables within each group. RESULTS: The mandibular dental and basal intercanine widths were significantly greater in the Class III group than in normal occlusion subjects (p < 0.05). The dental and basal intercanine widths as well as the dental and basal intermolar widths were strongly correlated in normal occlusion and moderately correlated in Class III malocclusion. CONCLUSIONS: The dental arch form demon strated a strong positive correlation with the basal arch form in the normal occlusion group and moderate correlation in the Class III malocclusion group. These results might be helpful for clinicians to have a better understanding of the importance of basal arch form in the alveolar bone.

Comparison of arch form between Koreans and Egyptians / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate morphologic differences in the mandibular arch between Egyptian and Korean subjects. METHODS: The Egyptian sample consisted of 94 mandibular casts (35 Class I, 32 Class II and 27 Class III). The Korean sample consisted of 462 mandibular casts (114 Class I, 119 Class II, and 135 Class III). The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth. The subjects were grouped according to arch form to compare the frequency distribution of the 3 arch forms between the ethnic groups in each Angle classification. RESULTS: Egyptians had significantly narrower intermolar and intercanine widths (p < 0.001), and shallower intermolar and intercanine depths (p < 0.001) than Koreans. There was an even frequency distribution of the 3 arch forms within the Egyptian group (p = 0.46). However, in the Korean group, the most frequent arch form was the square arch form (46.7%), while the frequency of the tapered arch form was significantly lower (18.8%). CONCLUSIONS: These results might provide helpful information in evaluating morphologic differences between ethnic groups in selection of preformed superelastic archwires.