Estimating the validity of Tanaka-Johnston and Moyer's analysis of a Saudi sample.

Objectives: Accurate estimation of unerupted permanent canines and premolars is a crucial step for effective orthodontic treatment planning during mixed dentition. This study aimed to evaluate the validity of Moyers' charts and the Tanaka-Johnston equation in predicting tooth sizes in a sample of the Madina population in Saudi Arabia and propose a new regression equation.

Methods: Dental casts from 219 subjects (113 males and 106 females) were analyzed. Actual mesiodistal tooth widths were measured using digital calipers with an accuracy of 0.01 mm. Moyers' and Tanaka-Johnston predictions were compared with actual measurements, and a new set of prediction equations was developed.

Results: Tanaka-Johnston predictions consistently overestimated the actual measurements, exhibiting a difference of 1.20 mm for maxillary canines and premolars and a difference of 1.25 mm for mandibular teeth. The Moyers chart showed gender-specific variations with males aligning with the 50^th percentile and females aligning with the 65^th percentile for upper arches and the 50^th percentile for lower arches. Newly derived linear regression equations were established for predicting the sum of upper and lower canines and premolars for the Madina population.

Conclusion: The study highlights limitations in the Moyers and Tanaka-Johnston methods used for the current sample as both methods overestimated tooth sizes. New regression equations were developed to offer a more accurate approach for predicting tooth sizes for the study sample.