Layperson's preference of the transverse occlusal plane in asymmetric facial model.

OBJECTIVE: Facial asymmetries are common, especially deviated nose and chin. The clinician must consider these variables when establishing the smile, placement and angulation of the occlusal plane. The purpose of this article is to determine if nose and chin deviations affect the perception of laypeople towards different angulations of the occlusal plane cant. MATERIALS AND METHOD: An asymmetric facial model was created from a symmetric facial model used in a previous study. Nose and chin were deviated 3 mm to the left and eight different pictures were created, each with different degrees of occlusal plane cant in both direction. Using a visual Likert scale delivered via Websurvey within the private practice setting, 120 randomly selected laypersons evaluated each image according to their own beauty preferences. RESULTS: In an asymmetric face, nose and chin deviated 3 mm to the left, a minor occlusal plane angulation of 2° can be perceptible regardless of the direction of the cant. CONCLUSIONS: The occlusal plane should be as parallel to the interpupillary line as possible. If occlusal cant is present, less than 2° of angulation it is preferable, regardless of the direction of the nose and chin. CLINICAL SIGNIFICANCE: In the presence of an asymmetric face, the occlusal plane should be as parallel as possible to the interpupillary line. The direction of the deviation of the nose and the chin are irrelevant factors to determine the occlusal plane. An inclination of the occlusal plane can cause vertical discrepancy, which could subsequently create malocclusion. A complete dentofacial analysis can aim at assessing the angulation of the occlusal plane not only for esthetic outcomes, but for also allowing correct occlusal function.

Comparison of a non-destructive technique using three-dimensional imaging and histoanatomical chemical dissolution for dental morphology analysis.

AIM: The present work aims to compare a digital dental histoanatomical analysis method with chemical enamel dissolution for the study of dental morphology. MATERIAL AND METHODS: Extracted maxillary anterior teeth were scanned under microcomputed tomography (µCT) (µCT 40; Scanco Medical), segmented, and reconstructed three-dimensionally (Amira, version 5.5.2; VSG). Following the digital acquisition of dental morphology, all specimens were acid treated with 5% formic acid for careful dissolution of the enamel layer. Six measurements (three buccopalatal and three mesiodistal) per specimen were performed, both digitally following the µCT scan and physically both before and after enamel dissolution. The obtained measurements were subjected to statistical analysis through concordance coefficient measurements and linear regression. RESULTS: A straight line correlation behavior with no statistically significant difference was found between both methods, with a concordance correlation coefficient of 97%. CONCLUSION: The digital, nondestructive, µCT-layered, three-dimensional reconstruction method presented comparable results to acid-etched enamel dissolution, confirming that both options are reliable for the histoanatomical analysis of enamel and dentin morphologies.