Dental arch dimensions of adolescent Kuwaitis with untreated ideal occlusion: Variation and validity of proposed expansion indexes

Abstract

The purposes of this study were to analyze the variations in dental arch dimensions of a large representative sample of adolescent Kuwaitis with untreated almost ideal occlusion and to test the validity of proposed expansion indexes and multivariate linear regression with inclusion of lateral and posteroanterior cephalometric parameters for estimation of dental arch width. Study models and both lateral and posteroanterior cephalograms of 143 Kuwaitis, aged 13 to 14 years, clinically diagnosed with untreated almost ideal occlusion during screening of a population-based sample, were examined. Maxillary and mandibular arch dimensions were measured by using a digital caliper accurate to 0.01 mm, and cephalometric parameters were measured electronically. All dimensions were greater in boys than in girls (P <0.001) and demonstrated wide individual variations. Maxillary arch-width estimates according to 3 proposed expansion indexes differed from the actual dimensions (P <0.001), with more than 60% of the dimensions having discrepancies greater than 1.0 mm and explained variances from 0.12 to 0.20. Multivariate linear regression with inclusion of cephalometric parameters provided better estimates, with explained variances from 0.29 to 0.44. The tested expansion indexes provide poor estimates of maxillary arch widths, with low explained variances. Multivariate linear regression provides better estimates, with moderate explained variances.