Are photos for facial analysis in orthodontics reliable?.

摘要

Introduction: Facial anthropometry is the measurement of distances of the face. It can be performed directly in the subject present or indirectly. Among the indirect methods is photogrammetry: measuring facial distances in photographs. In order to perform the facial photographic registration, a standardized photographic technique is required, that is, the parameters of the camera, the photographic set and the parameters of the subject must be previously established. This work aims to standardize a photographic technique and to study the reliability of facial photogrammetry, comparing direct anthropometric measurements and photogrammetry with three different photographic lenses, in order to determine which one has the highest fidelity. Objective: To standardize camera parameters and image framing for facial photogrammetry. Materials and Methods: Six facial distances were measured directly and indirectly on a sample of 50 subjects. The indirect measurements were taken on photographs of the subjects using fixed photographic lenses of 35mm, 50mm and 100mm. Six photographs were taken from each volunteer; three of front and three of profile, one with each lens. The distances between the camera and the subjects was variable, so that the image frame was always 30 cm. The differences were statistically compared. Results: With a 35mm lens, only one of the six distances measured in photographs was equal to the measurement obtained directly. With a 50mm lens, three of the six distances obtained were equal to the direct measurements. With a 100mm lens, all distances measured in photographs were equal and without statistical difference in relation to the measurements obtained directly. Conclusion: Of the three photographic lenses, the 100mm lens is the one that allows the photograph more faithful to the reality, where the photogrammetric measures of the face have a difference of 0,5mm or less with the direct measurements.