Differences in Mandibular Dentogingival Exposure as a Function of Age and Type of Facial Expression

Statement of Problem:The need to accurately and reliably assess the maximum mandibular dentogingival display is essential during the planning of dental treatment, and inaccuracies in capturing a patient’s genuine border movements in the mandible can result in a faulty treatment outcome. Purpose: Maximum smile as an expression is a frequently used to establish the extent of dentogingival display in the dental practice. In this study, the facial expressions “maximum smile,” (MS) “eyes closed smile,” (EC) and enunciation of the word “church” (CH) was used to evaluate the effect of facial expression on mandibular dentogingival display, and to assess the applicability of these findings in a clinical setting. The primary purpose of this study was to know, among the 3 stated facial expressions, the horizontal and apical differences in mandibular dentogingival display in the anterior and posterior regions. The secondary purpose of this study was to know, within each facial expression, whether age or gender is a factor in the horizontal and apical mandibular dentogingival display in the anterior and posterior regions. Material and Methods: One hundred and thirty-eight subjects were recruited to participate in the study. The group studied consisted of 85 females and 53 males. Additionally, there were 6 age groups in each study with the following subjects in each group: Age 21-30 consisted of 32 subjects, Age 31-40 consisted of 20 subjects, Age 41-50 consisted of 21 subjects, Age 51-60 consisted of 20 subjects, Age 61-70 consisted of 24 subjects, and Age 71-80 consisted of 21 subjects. After obtaining UCHC IRB approval, digital photographs of the lower half of the face of 138 dentate subjects were taken during the following three expressions: “Maximum smile” (MS) “Maximum smile with eyes closed” (EC), and saying the word “church” (CH) while holding the “ch” sound. Subjects completed a standardized demographic sheet to be statistically categorized by age, gender, and ethnicity. Photographs and the subject’s information were de-identified, and the digital photographs were analyzed. Statistical analysis used the categorical data to compare the differences in dentogingival display among the three facial expressions, and then as a function of age and gender of the subjects within each facial expression. Results: The overall presence of mandibular tooth display differed significantly between the facial expressions MS, EC and CH with respect to the number of teeth visible, calculated as a percentage (p\u3c 0.001). In the anterior mandible, expressions EC and CH showed 93% of mandibular anterior teeth, whereas MS showed 76% of mandibular anterior teeth. In the posterior mandible, EC showed 86% of the mandibular teeth, with MS showing 55% and CH showing 14% of mandibular teeth. Analysis also showed a statistically significant difference between apical extent display between facial expressions MS, EC and CH (p\u3c 0.001). In the anterior mandible, CH had the most display with an average score of 2.08, followed by EC with a score of 1.67, and lastly MS with a score of 0.93. For amount of display in the posterior mandible, EC had the most display with a score of 1.38, then MS with a score of 0.62, and CH had a minimal amount of posterior vertical display with a score of 0.19. No evidence of a statistically significant trend in percent presence value or mean score was found with respect to effect of gender and age. Conclusions:The results of this study illustrated that additional diagnostic tools such as expressions EC and CH can predictably capture a broader extent of mandibular dentogingival display. Findings from this study suggest that multiple facial expressions should be used to diagnose mandibular display, as each facial expression provides a different diagnostic element