Effects of Vertical Positions of Anterior Teeth on Smile Esthetics in Japanese and Korean Orthodontists and Orthodontic Patients

Abstract

The perception of a pleasing smile may differ between the countries in Asia or may be converging on a more internationally pleasing one. The aim of this study was to evaluate the influence of vertical positions of anterior teeth on smile esthetics as assessed by Japanese and Korean orthodontists as well as by orthodontic patients. A standard composite smile was constructed from different females' intraoral and extraoral photographs. Vertical positions of anterior teeth were modified digitally in 1-mm increments, from 5 mm upper lip coverage of the incisors to 5 mm gingival exposure. Using a visual analog scale, 41 Japanese orthodontists and 96 Japanese orthodontic patients, 25 Korean orthodontists, and 72 Korean orthodontic patients rated the attractiveness of 11 smiles with altered gingival displays. Overall, the Japanese and Korean raters assigned similar esthetic scores between the corresponding groups. The male orthodontic patients assigned higher scores to the smiles with upper lip coverage of the teeth than the corresponding females did in both countries. The female patients assigned clinically significant higher scores to the smiles from 2 mm upper lip coverage of the teeth to 0 mm gingival exposure in both countries. In both countries, the orthodontists and the female patients shared the similar preference in the smile evaluation of vertical positions of anterior teeth, whereas the male orthodontic patients were more tolerant of upper lip coverage of the anterior teeth than the orthodontists and the female patients. This study proposes 0 mm to 2 mm of upper lip coverage of the teeth as a threshold of acceptability for esthetic smile evaluations in female orthodontic patients. For male orthodontic patients, the paper proposes negative gingival display as a threshold of acceptability for esthetic smile evaluations.