Vertical Dimensions of Mandible in Class II Subdivision Malocclusion with Skeletal Asymmetry

Authors

Sara Greene, University of the Pacific, Arthur A. Dugoni School of DentistryFollow
Renee Greene, University of the Pacific, Arthur A. Dugoni School of DentistryFollow
Ivan Lo
Heeyeon Suh, University of the Pacific Arthur A Dugoni School of DentistryFollow
Joorok Park, University of the Pacific Arthur A Dugoni School of DentistryFollow
Heesoo Oh, University of the Pacific Arthur A Dugoni School of DentistryFollow
Kyra Lee, niversity of the Pacific Arthur A Dugoni School of Dentistry

Lead Author Affiliation

Doctor of Dental Surgery

Lead Author Program & Year

DDS Year 3

Presentation Category

Research

Introduction/Context/Diagnosis

• Advancements in 3-dimensional imaging analysis, utilizing cone-beam computed tomography (CBCT), have allowed for further investigation of skeletal asymmetry. • While past 2-dimensional studies attributed dentoalveolar deviation to unilateral Class II malocclusion, recent 3D studies have found a primarily skeletal contribution.1 • There is much debate on the impact of condylar morphology on malocclusion in patients with Class II subdivision and significant skeletal asymmetry.2 • Some authors concluded that condylar characteristics are not correlated with skeletal asymmetry, while others reported a correlation between a greater condyle angulation and skeletal asymmetry.2-4

Methods/Treatment Plan

DESIGN: • Retrospective Study • Records collected from University of the Pacific, Arthur A. Dugoni School of Dentistry Graduate Orthodontic Clinic

INCLUSION CRITERIA: • Have complete set of initial records and photographs • Have intraoral scans with occluded models • Have initial full-volume CBCT • Have all permanent dentition (no primary teeth) • Have at least 3mm of Class II molar relationship on one side and Class I molar on the other side • Have at least 2mm Me deviation on Class II side • Have all premolars and molars present

EXCLUSION CRITERIA: • Have syndromes or history of cleft lip or palate • History of prior orthodontic care • Impacted canines

SAMPLE: • 34 subjects ○ 17 females (50%) and 17 males (50%) ○ Age range between 10-47 years; Average: 18.8 ○ Class II side: 23 Lt (68%) and 11 Rt (32%)

METHODS: • 4 calibrated judges (DDS students) independently located 29 landmarks and generated 3-dimensional analysis using Anatomage InVivo 3D Imaging Software

STATISTICS: • A paired t-test was used to evaluate vertical differences between Class II and I sides (Table 1) • A Pearson correlation and linear regression was used to evaluate the relationship between skeletal asymmetry (transverse deviation) and condylar (vertical, angular) asymmetry (Table 2)

Results/Outcome

• A significant skeletal and dental vertical differences between Class I and II sides was found for all measurements except Condyle vertical position (Table 1). • Of which, Class II side had shorter Ramus length, Condylar height, Maxilla height; superior vertical positions of Gonion and U6; larger Frontal and Lateral ramus inclination than Class I side (Table 1, Figure 4). • Vertical measurements and the amount of skeletal asymmetry showed a positive correlation for Ramus length (0.59, p=0.0002), Gonion vertical position (0.60, p=0.0002), and Condylar height (0.43, p=0.012) (Figure 1, Table 2). • A negative correlation was found for Frontal ramus inclination (-0.65, p<0.0001) (Figure 2, Table 2) • A positive correlation was found for U6 vertical position (0.73, p<0.0001) (Figure 3, Table 2).

Significance/Conclusions

• The results suggest there are skeletal (condylar, vertical, and angular) differences between Class I and Class II sides in patients with skeletal asymmetry. • Furthermore, some of these skeletal (vertical and angular) differences may be correlated with the amount of skeletal asymmetry (Me deviation). • Of which, more Me deviation to Class II side was found for Class II side with decreased Ramus length, Condylar height, superior vertical position of Gonion and U6, and increased Frontal ramus inclination than Class I side.

Format

Event