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A Novel Classification System for Adult Skeletal Class III Malocclusions Based on Maxillary Occlusal Plane
Lingling Hu1, Yingjia Sun, Hui Pan
1Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine, Zhejiang Provincial Clinical Research Center for Oral Diseases, Key Laboratory of Oral Biomedical Research of Zhejiang Province, Cancer Center of Zhejiang University, Engineering Research Center of Oral Biomaterials and Devices of Zhejiang Province, Hangzhou, China.
None:
To incorporate the maxillary occlusal plane inclinations (MxOP-FH) into the vertical plane classification for skeletal Class III malocclusions. A total of 145 adult patients with skeletal Class III malocclusions (CIII group; 68 males and 77 females; mean age 23.80 y) and 30 individuals with normal occlusion (N group; 14 males and 16 females; mean age 23.96 y) were selected. The mean values of MxOP-FH (6.5 degree for low-angle, 9.7 degree for average-angle, and 11.4 degree for high-angle patients) were recommended as cutoff values to divide 6 subgroups of CIII patients. Pearson correlation analysis examined the relationship between MxOP-FH and 49 key cephalometric variables on their lateral radiographs. One-way analysis of variance and the Tukey-Kramer method compared profile characteristics between the N group and 6 new classifications. The results showed that the high-angle group, with a steeper MxOP, included features of maxilla retrusion and reduced maxillary fullness. Conversely, the high-angle group, with flatter MxOP, displayed significant increases in upper anterior dental height (UADH) and Go-Gn. Besides, the low-angle group, characterized with flatter MxOP, exhibited small values of UADH and nasolabial angle, along with large values of Go-Gn and Ar-Go. This group also showed a high chin-to-lower facial height ratio and excessive chin fullness. In conclusion, for skeletal Class III malocclusions, MxOP-FH angles of 6.5, 9.7, and 11.4 degrees might be helpful to classify 6 new subgroups. Identifying these novel subgroups is crucial in orthodontics, dentofacial orthopedics, and orthognathic diagnosis and treatment planning.
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