• Piyarat Apivatanagul
• Vachara Phetcharakupt

Objective The purpose of this study was to verify the prediction of the summation of canine first premolar and second premolar widths by calculating from first molar width utilized Vachara and Piyarat’s predicting equations compared with Moyers’ probability chart.

Materials and methods Tooth size of 200 models (100 males and 100 females) from the Department of Orthodontics, Faculty of Dentistry, Chulalongkorn University were measured. The summation of canine and premolar widths from models, were calculated by Vachara and Piyarat’s predicting equation and Moyers’ probability chart. The prediction values were compared with actual value by Paired T-test at the level of significance 0.05 and were test for correlation coefficiency.

Result The study found statistically significant difference in the upper arch of males and lower arch of females between Moyers’ probability chart and calculating from the predicting equation (P < 0.01), and between Moyers’ probability chart and the measurement from models (P < 0.01), but there was no statistically significant difference between calculating from the predicting equation and the measurement from models. In the lower arch of male group and the upper arch of female group, there were no statistically significant difference in all variables. However, when considered the difference between both methods and the actual value, the correlation coefficiency between the predicting equation and the measurement from the models was closer than Moyers’ probability chart.

Conclusion From this study found that the calculating result from Vachara and Piyarat predicting equation was closer to the real measurement of the summation of canine and premolars width than the Moyers’ probability chart, especially in upper jaw of the male and lower jaw of the female.

(CU Dent J 2003;26:173-9)