The Matching Of Dental And Base Bone Arch And Teeth Compensatory Mechanism Of Skeletal Class â…¢ Malocclusion

ObjectiveThe aim of this article is to study the characteristics and matching of dental and base bone arch forms, tooth inclination and compensatory mechanism of skeletal Class III malocclusion and to provide references for diagnosis and treatment project.Methods33skeletal Class III malocclusion patients and47normal occlusion individuals were involved in this study. Cone beam computed tomography (CBCT) scans of samples were taken and MIMICS10.01was used to measure dental arch widths and lengths, basal bone arch widths and lengths as well as tooth inclination. Corresponding measurement differences of upper and lower jaws were also calculated. Independent samples t-test was employed for comparison of the two groups.Results1. Comparison of dental arch form:upper arch widths had no significant differences between the two groups; lower molar widths were larger in skeletal Class III malocclusion while other lower widths had the same trend. Upper arch lengths of skeletal Class III malocclusion were significantly shorter than normal occlusion; on contrast, there is no differences in lower arch lengths.2. Comparison of basal bone arch form:upper basal bone arch widths were narrower in skeletal Class III malocclusion. However, significant differences only existed in the second premolar area; lower basal bone arch widths were wider in skeletal Class III malocclusion, significant differences existed in the premolar and the first molar area. Skeletal Class III patients had shorter upper basal bone arch and significant differences existed in the second premolar and molar area; on the other hand, lower basal bone arch lengths were longer in skeletal Class III, although significant differences only existed in the first premolar and first molar area.3. Comparison of corresponding measurement differences of upper and lower jaws:basal bone arch width differences of upper and lower jaws were smaller in skeletal Class III patients than in normal occlusion individuals. Canine width differences in skeletal Class â…¢ was also smaller while other dental arch width differences had no significant differences; the arch length differences in the second premolar and the second molar area were smaller.4. Comparison of tooth inclination: upper teeth in skeletal Class â…¢ malocclusion inclined buccally while lower teeth inclined lingually; upper teeth in skeletal Class â…¢ malocclusion inclined mesially while lower tooth inclination had no differences comparing with normal occlusion patients.Conclusion1. There was transverse discrepancy in skeletal class â…¢ malocclusion except sagittal discrepancy, and this kind of abnormality existed in basal bone level. So, for the patients who had growth and development potential, promoting of maxillary basal bone should be taken into consideration.2. Upper posterior teeth in skeletal class â…¢ malocclusion inclined buccally and mesially while lower teeth inclined lingually. During presurgical orthodontics, it was necessary to decompensate posterior teeth abnormal inclination, as for posterior arch width incoordination after decompensation, surgically assisted maxillary arch expansion maybe a choice; and as for the patients whose arch width was slightly incoordinate, compensatory treatment maybe an option.3. Upper and lower teeth could inclinate towards the direction for better interarch coordination, as the same time, coordination between dental arch and the corresponding basal bone arch was reduced. This indicated that the local structures in maxillofacial had some priorities in compensation and coordination.