Effect of intermaxillary tooth-size discrepancy on accuracy of prediction equations for mixed dentition space analysis.

AIM: Correlation-statistical methods are widely used for prediction of size of unerupted permanent canines and premolars in mixed dentition space analysis. The present study was planned to evaluate the effect of selecting dental study casts with no intermaxillary tooth-size discrepancy on the accuracy of predicting mesiodistal widths (MDWS) of permanent canines and premolars. STUDY DESIGN: Bolton ratios were calculated for all the screened study dental casts fulfilling the inclusion criteria. Subjects were divided into two groups. Group A: all subjects with no intermaxillary tooth-size discrepancy within +/-2 SD (Standard deviation) of the mean values. Group B: increased percentage of subjects with intermaxillary tooth-size discrepancy beyond +/-2 SD (Standard deviation) of the mean values. STATISTICS: Linear regression equations were established for both maxilla and mandible in both the groups, with different tooth combinations as independent variables. Validation of best possible regression equations was done on an independent set of 40 subjects. The actual and predicted values of MDWS of permanent canines and premolars were compared by paired samples t test in both groups, for both arches. RESULTS: The accuracy of equations derived from group A was higher than those derived from group B. The difference between actual and predicted values was statistically insignificant in group A and statistically significant in group B. CONCLUSION: The results confirm the accuracy of simple linear regression equations derived from a sample of children with no intermaxillary tooth-size discrepancy.