A study of patient facial expressivity in relation to orthodontic/surgical treatment

Abstract

A dynamic analysis of the faces of patients seeking an aesthetic restoration of facial aberrations with orthognathic treatment requires (besides the routine static study, such as records, study models, photographs, and cephalometric tracings) the study of their facial expressions. To determine a classification method for the units of expressive facial behavior, the mobility of the face is studied with the aid of the facial action coding system (FACS) created by Ekman and Friesen. With video recordings of faces and photographic images taken from the video recordings, the authors have modified a technique of facial analysis structured on the visual observation of the anatomic basis of movement. The technique, itself, is based on the defining of individual facial expressions and then codifying such expressions through the use of minimal, anatomic action units. These action units actually combine to form facial expressions. With the help of FACS, the facial expressions of 18 patients before and after orthognathic surgery, and six control subjects without dentofacial deformation have been studied. I was able to register 6278 facial expressions and then further define 18,844 action units, from the 6278 facial expressions. A classification of the facial expressions made by subject groups and repeated in quantified time frames has allowed establishment of "rules" or "norms" relating to expression, thus further enabling the making of comparisons of facial expressiveness between patients and control subjects. This study indicates that the facial expressions of the patients were more similar to the facial expressions of the controls after orthognathic surgery. It was possible to distinguish changes in facial expressivity in patients after dentofacial surgery, the type and degree of change depended on the facial structure before surgery. Changes noted tended toward a functioning that is identical to that of subjects who do not suffer from dysmorphosis and toward greater lip competence, particularly the function of the orbicular muscle of the lips, with reduced compensatory activity of the lower lip and the chin. The results of our study are supported by the clinical observations and suggest that the FACS technique should be able to provide a coding for the study of facial expression.