Validation of Mixed Dentition Analysis Method for Northern Thai Population

Abstract

The purpose of this study is to determine the accuracy of the Tanaka-Johnston mixed dentition analysis method and develop a new predictive model for Northern Thai population.

A total of 400 sets of dental study casts (145 males and 255 females) were obtained from the Department of Pediatrics and Orthodontics at the Chiang Mai University School of Dentistry, Thailand. The models were obtained from patients that were age 11 to 23 years that consisted of a full permanent dentition. A digital caliper was used to measure the mesiodistal widths of all teeth on dental study models. The sum of the predicted widths for the canines and premolars using the Tanaka-Johnston method in maxilla and mandible were compared with the observed widths. Models for predicting the total width of canines and premolars was generated using linear regression. The coefficient of determination and root mean square error were used to assess the fit and prediction accuracy of the models.

Tanaka-Johnston method underestimated the mesiodistal widths of permanent canines and premolars in both arches of the Northern Thai population ( P<0.0001). Sexual dimorphism was significantly different between Northern Thai males and females for the widths of mandibular incisors, canines and premolars (P<0.05).

The data demonstrated the inaccuracy of Tanaka-Johnston method when applied to Northern Thai population. To help predict crowding in young children, new mixed dentition analysis methods were developed and validated. The data support development of these new methods which increase the predictive accuracy for Northern Thai population.