Comparison of measured and predicted mesiodistal tooth-widths of 13-17 years old Kenyans: a descriptive cross-sectional study to develop a new prediction equation for use in the mixed dentition in a Kenyan population.

BACKGROUND: The Tanaka and Johnson equation is commonly used in mixed dentition analysis. However, the analysis is based on  a 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 years 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 statistics, 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.