Malocclusion indices: A comparative evaluation

The precision or chance error and the bias or systematic error of three malocclusion indices were measured using the same sample of 130 dental casts taken on 11- to 15-year-old children seeking treatment at the University of Iowa Orthodontic clinic. Three objective examiners scored the casts, with double determinations, using the Handicapping Malocclusion Assessment Record (HMAR), the Occlusal Index (OI), and the Treatment Priority Index (TPI). A high degree of reproducibility within examiners was indicated by the Pearson product-moment coefficients found: r = 0.714 to 0.908. Analysis of variance was used to further check time periods (within examiners) and indicated no significant variability. Using Pearson product-moment coefficients, a high degree of reproducibility was also found between examiners when the combined scores from each examiner's first and second examinations for each index were compared: r = 0.761 to 0.890. Analysis of variance indicated a significant difference between examiners. Inspection of the scores revealed that the greatest difference in the mean scores between examiners was 1.92. Four subjective examiners ranked the 130 dental casts according to their need for treatment. Spearman rank correlation coefficients were determined on the rankings for each index versus the average subjective rank. The OI had the highest correlation of the three indices: OI r s = 0.742, TPI r s = 0.551, and HMAR r s = 0.532. Of the three indices tested in this study, no one index can be selected over the other, with regard to precision or intra- and inter-examiner differences. The Occlusal Index would be the index of choice with regard to having the least amount of bias, as indicated by the results of this study.