Diagnostic Value of Plaster Models in Contemporary Orthodontics

Advances in digital technology have allowed for photographic images that can be immediately evaluated in the clinical setting. Clinical photography can currently be relied on to be of predictable diagnostic value, and unsatisfactory images can be immediately replaced. The purpose of the present study was to evaluate how information obtained from traditional plaster models contributed to the diagnosis and treatment planning of orthodontic patients who were originally evaluated by using digital photographs and radiographs alone. A sample of 20 orthodontic patients from the Department of Orthodontics at the University of Alabama at Birmingham was selected for this study. The sample was selected on the basis of Angle molar classification, comprised of 11 Class I, 7 Class II, and 2 Class III patients, to attempt to provide an average range of malocclusions as reported in the literature.¹ Four orthodontists, provided with digital photographs, a panoramic radiograph, and a traced lateral cephalometric radiograph for each patient, were asked to complete a diagnostic questionnaire and to formulate a preliminary treatment plan for each record set. The orthodontists were then shown plaster models for each patient and the questionnaire and treatment plan were allowed to be revised for a final treatment plan if the orthodontists considered this to be appropriate. Any changes that the orthodontists deemed necessary for the diagnosis and formulation of the final treatment plan were recorded. A binomial probability and a Chi square analysis were used with a P = 0.05 level of significance. The results indicated a total of 83 changes of the 1600 diagnostic values among 20 diagnostic categories recorded. The five categories that were statistically significant included the anteroposterior relationship of the molars, the anteroposterior relationship of the cuspids, the amount of overbite, the amount of overjet, and the depth of the curve of Spee in the mandible. There were no clinically significant changes in treatment recommended by the orthodontists from their preliminary to their final treatment plans following examination of the study casts. The results of this study indicate that plaster models may not be needed for the planning of treatment of every orthodontic patient.