Evaluating the Accuracy of Two Mixed Dentition Space Analysis Methods and Developing Modified Equations for an Iranian Population: A Cross-Sectional Study

Aim: Common mixed dentition space analysis methods, such as Moyers and Tanaka-Johnston, may not be accurate for all populations. Therefore, the current study aimed to assess the applicability of these methods to Iranians and develop customized equations to predict maxillary and mandibular permanent dentition sizes. Methods: In this cross-sectional study, pre-treatment digital study models of 246 Iranian patients (163 females and 83 males) were obtained from the Orthodontics Department at Shahid Beheshti University of Medical Sciences, Tehran, Iran. After taking digital impressions using Shining 3D Scanner®, mesiodistal widths of mandibular and maxillary permanent incisors, canines, and premolars were measured using Maestro 3D Ortho Studio® software. Paired and independent t-tests were used to compare actual dimensions and widths estimated through Moyers and Tanaka-Johnston methods. Spearman’s test was used to identify correlations between the tooth dimensions, which were implemented to develop predictive linear equations. The significance level was set at P<0.05. Results: The dimensions predicted using Moyers and Tanaka-Johnston methods were significantly overestimated compared to actual measurements (P<0.001 for all). The inter-method comparisons also showed significant differences between the sizes yielded from the two methods (P<0.001 for all). Conclusion: The mesiodistal widths of unerupted permanent canines and premolars predicted using Moyers and Tanaka-Johnston methods were not highly accurate among an Iranian population. Therefore, six new linear equations were developed tailored to this specific population. Nevertheless, further validation studies are necessary to verify the equations’ applicability and accuracy.