Analysis of gaze point retention times for closed­mouth and smiling facial images

A favorable esthetic appearance of the teeth is strongly desired by patients nowadays, and new esthetic materials and treatment methods have been developed and clinically applied. 3 However, the way in which people look at others’ teeth cur­ rently remains unknown. A psychologist, Yarbus, reported that when images of the face were pre­ sented to subjects, their lines of sight were concen­ trated on the region around the eyes ; however, the lips were closed in those images, and the gaze point for closed­lip and smiling facial photographs is unclear. Studies on esthetic consciousness relating to teeth have mainly been performed using subjec­ tive evaluations, such as questionnaires. 5­12 Ques­ tionnaire surveys reported that most people felt that the appearance of the mouth was important for jobs, and considered white teeth to be ideal. Regarding the interest in esthetics relating to the mouth, no image has clearly been recognized as favorable. The level of demand for each esthetic element is determined by age, and varies markedly among individuals. 7 Interest in esthetics relating to teeth is subjective and diverse ; therefore, it is diffi­ cult to express criteria observed in esthetic ques­ tionnaire surveys in numerical forms. However, analysis of the line of sight using eye­tracking has recently been applied in various fields. Eye­ tracking is a method used to acquire information re­ garding the site gazed at, the duration of gazing, and the order of gazing, by tracking the subjects’ line of sight. Because unconscious movement of the line is also measured, human behavior not ob­ servable by a questionnaire or interview can be in­ vestigated. People generally shift their lines of sight to an object of interest and form its image at the central fovea, the area on the retina with the best vision, i.e., central vision, and collect visual in­ formation. Furthermore, the visual cognitive behav­ ior of humans can be investigated by measuring gaze point movements because the direction of the line of sight is mostly consistent with the site of the gaze point. Identifying the facial area where people are look­ ing requires investigation of their interest in each facial region by quantifying unconscious gazing. This will help us understand the need of esthetic Analysis of gaze point retention times for closed­mouth and smiling facial images