Influence of occlusal vertical dimension on lip positions at smile in completely dentulous adults

AIM: The study was conducted to evaluate the effect of increased vertical dimension on the lip positions at smile in dentulous subjects. SETTINGS AND DESIGN: Invivo - comparative study. MATERIALS AND METHODS: Thirty individuals aged between 22 and 30 years were selected for the study. Poly-vinyl siloxane (Jet Bite, Coltene, Switzerland) interocclusal bite records of varying thickness of +1, +2, +3, and +4 mm were made using articulated stone casts for all the participants, respectively. Posed smile photographs at different increased vertical dimensions of +1, +2, +3, and +4 mm were captured with D-SLR camera (Nikon D3200 of 18 megapixels with macro lens, Japan) mounted on tripod stand keeping a uniform distance of five feet from the face. Head positioning device (Genoray CBCT Machine Papaya 3D Plus, Unicorn DenMart, India) was used to stabilize the head position of the participants. Interlabial gap height, intercommissural width, smile index (width/height ratio), incisal edge-to-upper lip distance, incisal edge-to-lower lip distance, and display zone area measurements were made in AutoCAD software (Autodesk, Inc., California, USA). STATISTICAL ANALYSIS USED: One-way repeated measures ANOVA tests (α = 0.05) and Bonferroni's post hoc tests were performed for statistical analysis. RESULTS: With increasing occlusal vertical dimension, the interlabial gap height, incisal edge-to-lower lip distance, and display zone area increased significantly (P < 0.001). The smile index decreased significantly as the occlusal vertical dimension increased (P < 0.001). No significant difference was found in intercommissural width and incisal edge-to-upper lip distance. CONCLUSION: It was found that an increase in occlusal vertical dimension led to an increase in interlabial gap height, incisal edge-to-lower lip distance, and display zone area measurements, whereas the width of smile and incisal edge-to-upper lip distance did not change with increasing occlusal vertical dimension.