The applicability of the Tanaka and Johnston analysis in a contemporary Western Australian population

Abstract Background/Objective The Tanaka and Johnston mixed dentition analysis is a widely used method to predict the size of unerupted permanent canines and premolars. The aim of the present study was to determine the applicability of the Tanaka and Johnston analysis to Western Australian adolescents and develop a new regression equation. Methods Five hundred participants (323 females, 177 males) meeting the inclusion criteria were selected from private orthodontic clinics. The mesiodistal dimensions of all permanent teeth were retrieved from pre-orthodontic treatment digital dental records using Invisalign® technology (Invisalign®, Align Technology, Santa Clara, CA, USA) and analysed using a predicted value derived from the Tanaka and Johnston analysis. Correlation and linear regression analyses were applied to develop new regression equations. Result A significant difference was found between the actual and predicted values derived from the Tanaka and Johnston analysis. A significant correlation was observed between the sum of the permanent mandibular incisors and the sum of the maxillary and mandibular canine and premolars (0.58–0.74). New regression equations and tables were derived from the study population. Conclusion The Tanaka and Johnston analysis overestimated the mesiodistal dimensions of permanent canines and premolars. The developed regression equation and tables may be used for orthodontic diagnosis and treatment planning in Western Australian adolescents.