Changes of the maxillary arch produced by different self-ligating appliance systems during the leveling and aligning phases / 实用口腔医学杂志

Objective:To evaluate the changes in the transverse dimension and the perimeters of the maxillary archs produced by 3 self-ligating appliance systems during the leveling and aligning phases. Methods: 45 patients who had class I skeletal pattern and upper arch crowding 3-6 mm were divided into 3 groups with 15 subjects in every group. The dental casts were analyzed. Results: Statistically significant increases were recorded of all dentoalveolar widths (with the exception of intermolar width measured lingually) and arch perimeters. The increase in arch perimeter showed a significant negative relationship with the individual perimeter of the maxillary arch before treatment. No significant change was found in arch depth. Conclusion: The self-ligating appliance systems produce statistically significant increases in the transverse dentoalveolar width and the perimeter of the maxillary arch during the leveling and aligning phases of treatment.

A Study on Basal and Dental Arch Width in Skeletal Class III Malocclusion / 대한치과교정학회지

The purpose of this study was to compare the arch width of the hyperdivergent group with that of the neutral group in Class III malocclusion based on the vertical patterns and to compare the arch width of Class III neutral group with that of normal occlusion group based on sagittal patterns. The subjects consisted of 118 pairs of study casts, divided into three groups; 37 Class III hyperdivergent group(18 males and 19 females, SN-Mn plane angle>39.5 degrees), 40 Class III neutral group(20 males and 20 females, SN-Mn plane angle: 32+/-2.5 degrees) and 41 Class I normal occlusion group(20 males and 21 females). The intercanine, interpremolar, and intermolar width of the maxillary and mandibular study casts were measured, then the ratios of dental width to basal width and mandibular width to maxillary width were obtained. Basal arch width and dental arch width were measured to obtain the pure basal arch relation in transverse plane as ruled out the transverse dental compensation. The results were as follows: 1. There were no significant differences in any ratios between Class III hyperdivergent group and Class III neutral group as different vertical pattern. 2. As the ratios of dental arch width to basal arch width between normal occlusion group and Class III neutral group were compared, the maxillary teeth flared buccally to the basal bone, and the mandibular teeth tilted lingually to the basal bone in Class III neutral group. 3. The ratios of mandibular arch width to maxillary arch width in basal arch level were significantly different in all regions. Maxillary basal arch width of Class III neutral group was narrower than that of normal occlusion group. 4. The ratios of mandibular arch width to maxillary arch width in teeth level were not significantly different between normal occlusion group and Class III neutral group. In spite of discrepancies of maxillary and mandibular basal arch width, the dental arch width of Class III malocclusion group compensated very well. At the presurgical orthodontic treatment in clinic, it would not be desirable to decompensate for compensated dental arch width too much, for obtaining an appropriate arch compatibility and good results for orthognathic surgery.

An evaluation of the adequacy of PONT's index / 대한치과교정학회지

Dental arch expansion in one of the method used to solve the dental crowding problem by non-extraction. Many formulae using tooth size have been suggested to predict ideal inter-premolar and inter-molar width. The purpose of this study was to evaluate the adequacy of some of some upper dental arch width prediction methods, namely Pont's method, Schmuth's method and Cha's method. The sample consisted of the casts of 119 Korean young adults who had no muscular abnormality, no skeletal discrepancy, and Angle's Class I molar relationships. Measurements were obtained directly form plaster casts; they included mesiodistal crown diameters of the four maxillary incisors, as well as maxillary inter-first-premolar and inter-first-molar arch widths as specified by Pont. The correlation coefficients between the sum of incisors(SI) and upper dental arch width were calculated. The differences between predicted width and actual width wee classified as overestimated, properestimated, and underestimated. The data obtained from each group were analyzed for statistical differences. The results were as follows : 1. Upper dental arch width indices were calculated from SI in normal occlusion (81.96 : premolar index, 62.55 : molar index). 2. Low correlations between SI and arch width were noted in normal occlusion (0.50 in the inter-premolar width, 0.39 in the inter-molar width). 3. Pont's formula and Schmuth's formula tended to overestimate the inter-premolar. A more even distribution of estimates was noted in Cha's formula. 4. Cases within 1mm range of observed inter-premolar width were 45% in the Pont's formula, and 39% in the Schmuth's formula. 5. All formulae had a tendency to underestimate the inter-molar width, but Cha's formula had better predictability than others. 6. Cases within 1mm range of observed inter-molar width were 40% in the Cha's formula, 29% in the Pont's formula, and 13% of Schmuth's formula. The data presented in this study dose not support the clinical usefulness of ideal arch width prediction methods using the mesiodistal width of maxillary incisors.