Comparison of Skeletal-Class-III Facial-Subphenotypes in African- Americans, Caucasian, and Hispanics

Objectives: Objectives: The goal of this study was to determine the predominant skeletal Class III facial sub-phenotype(s) among patients of differing ethnicities. Our null hypothesis stated that African American (AfrAm), Caucasian (Cauc) and Hispanic (Hisp) populations would exhibit the same predominant skeletal-Class-III sub-phenotype.
Methods: Methods: This retrospective study was conducted with ethics approval from the University of Kentucky (UK) IRB. Photos and cephalometric data stored in the UK-Orthodontics Dolphin- Clinical-Imaging-database were used to pre-screen subjects for inclusion in the study based on ethnicity, ANB < 0.3 and Wits < -3.0. Qualified cases were coded and retraced by a single examiner for consistency. Case records were retained for further study when retracing confirmed an ANB < 0.3 and Wits < -3.0. Syndromic patients and cases of developmental delay, Cleft Lip/Palate, or other craniofacial anomalies were excluded. Cases with missing lateral-incisors were also excluded. Ten angular cephalometric measures, six ratios of a select number of linear measurements, Wits and Overjet were examined for normality, and were compared using an ANOVA across sex and ethnic groups.
Results: Results: ANB, MP-SP, MP-FH, PP-MP, SN-FOP, PP-FOP, and SN-PP angles were not statistically different by sex and ethnicity. Similarly, Wits and ratios of Co-Go/Co-Gn, Go-Gn/N-Me, LAFH/TAFH and Co-Go/S-Go did not differ by sex and ethnicity. Trends of smaller SNA and SNB angles were observed in the Caucasians compared to the AfrAm and Hisp. The Tukey-Kramer Means Comparison revealed significant differences in facial angle (FH-Npo) and Overjet between Cauc and AfrAm subjects. In addition, ratios for posterior-vertical-height (S-Go) to Mandible length (Co-Gn), and mandible-length (Ar-Gn) to posterior-vertical-height (S-Go) were significantly different by Tukey-Kramer Comparison between Cauc and AfrAm females. Co-A/Co-Gn was significantly different by Tukey-Kramer Comparison between Cauc and AfrAm males.
Conclusions: Conclusions: We rejected our null hypothesis. Geometric morphometrics are underway using (X,Y) coordinate data generated in Dolphin.