Statement of Problems: Ethnic and sex differences in the  mesiodistal width of the teeth have been proved in different studies. The prediction methods of the canine and premolar width have been obtained from other populations, which are in controversy with the results of previous Iranian studies.
Purpose: The aim of this study was to determine the accuracy of the Tanaka-Johnston prediction equations and Moyer’s prediction tables in the prediction of un-erupted canines and premolars in a South Iranian population. Also, new regression equations and tables are presented to predict the width of the un-erupted canines and premolars based on the sum of the mesiodistal width of the lower incisors
Materials and Method: For this cross-sectional study, a total of 715 dental casts were recruited from southern Iranian population. The greatest mesiodistal widths of all the teeth were measured using digital caliper with the accuracy of 0.01 mm. All the data were compared with Moyers’s and Tanaka-Johnston predictions using Pearson Correlation, independent t-test and paired sample t-test. New regression equations were presented with multiple linear regression tests and new prediction tables were presented with LMS chart maker software.
Results: Tanaka-Johnston equations and Moyer’s prediction tables revealed a significant difference with the mesiodistal dental width of southern Iranian population and the predictions were overestimated in this population. Also, there was a significant difference between the mesiodistal width of the teeth of males and females. So, new regression equations and tables (based on the sum of the lower incisors) were introduced for different jaws and sexes in this study. The suggested regression for prediction of the maxillary canine and premolars based on the summation of mesiodistal width of the lower incisors was y=0.529x+9.161 and for prediction of the mandibular canine and premolarsit was  y=0.567x+7.827.
Conclusion: Tanaka-Johnston and Moyer’s prediction tables overestimate the actual size of southern Iranian’s teeth width; Moyers prediction tables are not accurate in the prediction of the width of the canines and premolars in none of the percents. So, application of these methods is not suggested for Iranian population.