Background: The Tanaka and Johnson equation is commonly used in mixed dentition analysis. However, the analysis is based on Caucasian population making clinical decisions challenging when used in different ethnic groups. This study developed a prediction equation based on a Kenyan population.
Design: A descriptive cross-sectional study done in 68 13-17 year old Kenyans of African descent in two boarding secondary schools. Alginate impressions were taken, study models obtained, and mesiodistal tooth-widths measured on upper and lower study models from the first molar to the contralateral first molar. Descriptive, paired t-tests and independent t-tests were conducted and Pearson product-moment correlation coefficients calculated (p<0.05).
Results: The mean age was 13.78 years (SD ±0.70), females were 59%. The mesiodistal tooth-widths of the permanent canines and premolars were different between males and females (p˂0.1). The Tanaka and Johnston equation significantly under-estimated the mesiodistal tooth-widths of the permanent canines and premolars (p˂0.05). The addition of lower first permanent molars to the permanent lower incisors provided higher correlation coefficients than the Tanaka Johnston equation.
Conclusions: A new equation that includes the permanent lower incisors and first permanent molars as predictor teeth seems to be more suitable for mixed dentition analysis for this Kenyan population. A larger study is needed to validate these findings.