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A MULTICENTER INTERRACIAL STUDY OF FACIAL ESTHETICS

Edward G. Owens

A multicenter study of facial esthetics was carried out in the form of a comparative study with samples derived from six different racial groups.

The primary objective of this study was to estimate six dental, eight frontal and six profile soft tissue parameters of esthetic norms for the six racial groups within the population of five chosen centers. The secondary objective of this study was to test the hypotheses that there were no gender or interracial differences in this population. A third objective was to estimate the reproducibility of the method by evaluating differences between measurements made at a specified time interval. Finally, due to the subjective nature of any study of esthetics undertaken, an analysis comparing the subject's description of their own smile with an evaluator's description of that smile was conducted using a model built for this purpose.

A total population of 253 subjects participated in this study. The criteria for inclusion in this cross-sectional study were as follows, only subjects with no history of trauma, no congenital or acquired defects in the head and neck region, no loss or prosthetic replacement of anterior teeth and no history of orthodontics or maxillofacial surgery were included. The sample consisted of 144 males and 109 females from the chosen centers. The numbers of subjects, categorized by race, from each center was Black 44, Caucasian 42, Chinese 40, Hispanic 40, Japanese 44 and Korean 43. There were no subjects of mixed racial origin in the sample. The subjects had a mean age of 26.5 years (age range 18-41 years). Specific variables were measured from three sources.

1. The subject's history provided data concerning age, gender, racial origin, geographic location and the subject's description of their smile in one of ten ranked numbers supplied. This data was compiled in the form of a questionnaire.

2. Clinical examination recorded details of six specified variables: teeth present, left and right molar relationship (Angle classification), vertical overlap, horizontal overlap, clinical crown width of the right central incisor and the presence, absence and intrajaw location of any maxillary or mandibular exostoses.

3. Three photographic portraits of each subject were made adhering to a standardized photographic protocol. These photographs provided data for analysis of facial esthetic parameters from both frontal and profile perspectives using angular and linear relationships derived from specific anatomic landmarks traced from the photographic prints. All linear and angular measurements were computed electronically by entering the data by means of a sonic digitizer into the computer for analysis.

Within the parameters of this study the following conclusions are offered:

1. Estimates for the parameters examined in this study are comparable to previous studies in this area.

2. Most studies use parametric statistical methods to report estimates of reference ranges under the assumption that the data will follow a normal distribution. An interesting finding in this study was the observation that not all data fit the normal assumption. Statistical methodology may have to be adapted to take account of the significance of this finding, at a clinical level, in designing future studies of this nature.

3. Statistically significant interracial differences exist between the groups studied among many of the dental and soft tissue profile parameters investigated by both parametric and non-parametric methods.

4. Statistically significant gender differences exist between the groups studied among many of the dental and soft tissue profile parameters investigated by both parametric and non-parametric methods.

5. No statistically significant interracial or gender differences were found from investigation of the frontal parameters estimated in this study. This signifies the usefulness of these parameters in the evaluation of esthetics and possibly facial asymmetry on an interracial basis.

6. The reproducibility of the tracing and digitizing process used in this study is high and it is, therefore, recommended as a reliable method for analyzing data of this nature.

7. A finding of this study is that regardless of gender, subjects exhibit a tendency to over or underrate their smiles consistent with the direction of the evaluator's ratings. This indicates that perceptual differences exist, in degree, in the esthetic evaluations of potential caregivers as opposed to population of potential patients.