Validation of the Indiana University School of Dentistry Index of Malocclusion Using the Discrepancy Index and the Subjective Evaluation of Experienced Orthodontists

Abstract

Indices to assess malocclusion have been developed to serve a multitude of functions, from rating 'severity of malocclusion', to prioritizing orthodontic treatment for patients. These indices have been established and used, but many with significant inadequacies in their methods. Very few indices quantitatively look at characteristics of a patient to objectively assess treatment difficulty. No current published index uses all of the pretreatment diagnostic records in its assessment. A complete index of malocclusion with the objective analysis of all pretreatment records is needed to accurately quantify treatment need. Recently, an index of malocclusion was developed and validated at IUSD that evaluates a complete set of diagnostic records. Initially this index was found to be a valid measure of patients of non-Hispanic white descent in the permanent dentition. Later it was validated to patients of both mixed and permanent dentitions of various racial profiles. In the present study, pretreatment records (dental casts, intra-oral photographs, extra-oral photographs, panoramic radiograph, and a cephalogram) of 100 patients (48 mixed dentition, 52 permanent dentition) from the Indiana University Graduate Orthodontic Department were evaluated. The patients were selected from a group of completed cases that had been previously scored with the discrepancy index (DI). This data was used to select a group of patients that, as closely as possible, represented a comprehensive range of severity. Thirty-six measurements were scored and combined into a total score representing the new index for the permanent dentition. Thirty-three characteristics were totaled in a similar fashion for patients in the mixed dentition. The scores of the new index were compared to the average examiner scores of four experienced orthodontists. Statistical analysis showed significant correlations of the new index to the average examiner scores, as well as to the DI scores. It is the conclusion of this study that the new IUSD index is a valid measure of severity of malocclusion that correlates well with DI and reflects the rankings of experienced orthodontists.