The Moyer's and Hixon-Oldfather's Mixed-dentition Analyses in African-American Patients

Recently, there has been a tendency to initiate orthodontic treatment at an earlier age than previously. One advantage in doing this is that one can use the growth of the patient as an adjunctive tool in treatment, leading to a more facially balanced result. With this increasing trend to treat in the mixed dentition, it is imperative that orthodontists make accurate assessments of tooth size arch length discrepancies, in order to achieve a successful diagnosis and treatment plan. It is essential that the orthodontist have an accurate method for measuring the sizes of the unerupted permanent teeth. Moyer’s and Hixon-Oldfather determined that the size of the unerupted permanent teeth could be estimated based on the sizes of the permanent erupted mandibular incisors or utilizing radiographs. Objectives: This study was to determine if there was a difference between Moyer’s and Hixon-Oldfather’s analyses applied to the African-American population. Methods: Replication of Moyer’s and Hixon-Oldfather’s analyses, using 60 pre-treatment study casts of African-Americans were utilized. The sample consisted of 30 males and 30 females. The casts were of completely erupted permanent dentitions from first molar to opposite first molar, with Class I malocclusions, good alignment, minor rotations and crowding, and occlusal restorations only. Statistical analyses of the means and standard deviations, one sample t-test, and Pearson’s correlation coefficient analyses were utilized. Results: This study found that the mean widths of the canines and premolars in the sample were significantly different when compared to Moyer’s and Hixon-Oldfather’s predictions. Moyer’s predictions were shown to be less reliable in predicting the widths of the premolars for African-Americans than the Hixon-Oldfather method. A strong correlation existed between the Hixon-Oldfather predictions and the sample data. Conclusions: Based on the results of this investigation, it was evident that new prediction tables should be formulated specifically for the African-American population.