RESUMO
Background: Lower incisors are the first teeth to erupt, their sizes are reliable and little changes occur on the lower arch during mixed dentition. These teeth can be used to predict the size of remaining unerupted teeth. Tanaka Johnston's analysis is the most widely used method of mixed dentition analysis worldwide. The aim of the study was to assess the accuracy of Tanaka-Johnston's methods of mixed dentition analysis among orthodontic patients in Tanzania. Methods: A cross-sectional study design was carried out at MUHAS dental clinic involving models from orthodontic patients. Data collection involved actual teeth size measurement and prediction using Tanaka-Johnston's method. Comparison between the actual measurements and the predicted measurements was assessed using students' paired t-tests. Prediction equations for the present study were generated using a simple linear regression analysis. Results: Tanaka Johnston's method significantly overestimated the combined width of upper canines and premolars in the female group (p=0.000). However, the method underestimated the lower jaw measurements in both sexes (p<0.05). New prediction equations for the present study were generated for each sex and arch separately. For the upper jaw, it was Y=11.97+ 0.56X for males and Y = 10.97+0.49X for females. While for the lower jaw, it was Y= 10.8 +0.51X for males and Y=11.39+0.47X for females. Conclusion: Tanaka-Johnston's methods of mixed dentition analysis was found to be inaccurate in estimating the size of unerupted canines and premolars in the study sample. Therefore, new prediction formulas were generated.