The B.S.S.O. M.Orth. prize of the Royal College of Surgeons of England: 1997.

Abstract

Objectives: To test the use of Moyers prediction method and Tanaka and Johnston’s equations for use in a Nepalese population and to construct new probability tables and prediction formulae based on the actual tooth sizes in a sample of the Nepalese population.

Design: Cross-sectional.

Source and setting: Dental, medical and nursing science students at the B.P. Koirala Institute of Health Sciences, Dharan, Nepal.

Subjects and methods: The sample consisted of 100 Nepalese males and 100 females aged between 17 and 23 years. Subjects without any previous orthodontic treatment, fully erupted permanent teeth and with no dental anomalies were recruited. Dental study models were taken and measurements of the mesio-distal widths of teeth were carried out using digital caliper. The measured values were compared with predicted values derived from Moyers method and Tanaka and Johnston equations. Independent t tests were used to examine differences between genders. Correlation coefficients and linear regression equations were used to compare the actual Nepalese tooth widths with predicted values

Results: Moyers method at 50% tends to underestimate the actual width of the canine and premolars in males by 0.3 mm and overestimate the width in females by 0.2 mm. The Tanaka and Johnston method tends to overestimate the actual width of the canine and premolars in both males (0.7 mm) and females 1.0 mm.

Conclusion: The newly developed regression equations are more accurate for prediction of width of unerupted permanent teeth in a Nepalese population. Further studies are required based on larger sample size, to confirm the applicability of the new regression equations proposed.