Evaluating the relation of posterior occlusal plane to ala-tragal line according to age and sex

Abstract

Introduction: Occlusal plane orientation affects the esthetic, function, and success of removable or fixed prostheses. The most prevalent index for determination of this plane is the ala-tragus line while there are controversies in the exact location of tragus reference point. Aims: This study aimed to determine the best point on tragus as the posterior reference of ala-tragal line in relation to occlusal plane according to age and sex. Materials and methods: The study included 136 participants of both sexes who were randomly divided into three age groups: 20-35, 36-50, and older than 50. Fox plane was stabilized on incisal edge-occlusal table of maxillary teeth. A lateral photograph was obtained from each participant sitting in predetermined standard position. Using Auto-Cad software, three lines were traced from nasal ala base to superior, middle, and inferior borders of the tragus, and evaluated for being parallel to occlusal plane. Results: The coordination between occlusal plane and ala was 20.5% for superior, 35.6% for middle, and 43.9% for inferior border of tragus. There was a significant difference in the relationship between sex and plane position (p=0.003), while the relationship between age and plane could not reach statistical significance (p=0.65). The results were analyzed using chi-square test, and ANOVA (p<0.05). Conclusions: Ala-inferior border of tragus line was the most parallel, and ala-superior border of tragus line was the least parallel line to the occlusal plane. The parallelism between occlusal plane and ala-superior border was more prevalent in women, while the men demonstrated significantly more parallelism with inferior border of tragus.