Date of Award

9-17-2021

Department

Department of Orthodontics

First Advisor

Marie M. Tolarová

Abstract

Background and Purpose. Orthodontic treatment helps to ensure proper function of teeth and to create healthy smiles. To this aim, the orthodontist’s goal is establishment of an esthetic harmony between soft and hard tissues of the face. Dimensions of facial width and height are crucial for accurate diagnosis and formulation of an efficient treatment plan. A knowledge of genetic determinants of these dimensions in Class II patients will deepen our understanding of etiology of skeletal Class II malocclusions and would make it possible to personalize a patient’s treatment plan. The purpose of our pilot study was to analyze, if specific variants of PAX 3, PAX 5, PAX 7 and PAX 9 genes are associated with Class II malocclusion but not with Class I malocclusion or vice versa. Methods. Patient data (extraoral photographs, intraoral photographs, and iCAT CBCT images obtained as part of patients’ routine orthodontic examinations) was collected for patients who had come to the Orthodontic Clinic, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, from July 2019 to July 2021. For 72 patients who met the inclusion criteria for Class I or Class II groups in our study, saliva samples were collected, and DNA was isolated and analyzed using rtPCR genotyping for PAX 3 SNP: rs974448, PAX 5 SNP: rs7031673, PAX 7 SNP: rs4920520 and PAX 9 SNP: rs8004560. 4 Results. Genotype A5G5 (rs7031673, PAX5) was high in Class I generally, but also in phenotypic Cluster 1 and Cluster 9. Genotype G5G5 (rs7031673, PAX5) was high in Class II generally, but also in phenotypic Cluster 8 and Cluster 10. Allele G5 was more frequent in Class II than in Class I. Genotype A7A7 (rs4920520, PAX7) was high in Class II generally. It was absent in phenotypic Cluster 1 and Cluster 9, present in phenotypic Cluster 8 and Cluster 10. Genotype A9G9 (rs8004560, PAX9) was higher in Cluster 8 than in Cluster 10 (and also higher than in Clusters 1 and 9). Allele A9 was more frequent in Class II than in Class I. Conclusions. The aim of this study was to determine genotypic differences between Class I and Class II malocclusion groups and to study genotypic associations with phenotypic clusters. We showed genotypic and phenotypic cluster differences between Class I and Class II groups. We report several genotypes tentatively identified by genotypic analysis and found in association with certain phenotypic clusters. None of these differences proved to be statistically significant, probably, due to a small size of the studied groups. However, in this pilot study, we found trends, on which we will focus in our future study using a larger sample.

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