Validity of an orthodontic treatment priority index to measure need for treatment.

In establishing the validity of an index for identifying individuals needing orthodontic treatment, we must concern ourselves with the construct validity of the measure. Since it is clear that the relevant theory concerning need for treatment must include esthetics and the accompanying social and psychological characteristics, the construct validation of an index to measure need for treatment must include tests of hypotheses with these dimensions. If we consider a child's self-perception of occlusion as a psychological variable and another person's perception of a child's occlusion as a social variable, theory relevant to an index of need for treatment would hypothesize that each should correlate positively with need for treatment. Subjects were eighth and ninth grade students from a metropolitan area in western New York State. Fifty-two of the children were planning to obtain orthodontic treatment, and 102 were not. Data were also obtained, whenever possible, from both parents and from a sibling (if any) nearest in age to the child. Data were collected in one session by a trained interviewer who used a structured interview and also photographed the child's teeth and jaws. In addition, the child was given an orthodontic Treatment Priority Index (TPI) examination by a dentist enrolled in a graduate program in orthodontics, who had previously been trained and standardized in the use of the TPI. In addition, to the TPI, scores obtained included three psychological measures and eight social measures. Each of the psychological and social variables correlated significantly with TPI at the 0.05 level, with values ranging from 0.21 to 0.54 and a median value of 0.42. On the basis of these correlations, evidence is presented for the construct validity of the TPI when measuring need for treatment.