A digital method to predict the mesiodistal widths of canines and premolars in an Egyptian sample

Treatment planning in the mixed dentition is important for proper tooth alignment. A mixed dentition analysis, should accurately predict the mesiodistal widths of unerupted permanent teeth. The aim of the present study was to determine which sum of mesiodistal widths (MDW) of permanent teeth will be the best predictor for MDW of unerupted permanent canines and premolars.

The study was conducted on 102 Egyptians, 51 males and 51 females, mean age 16.7 +/- 0.5 years with fully erupted permanent teeth, and intact proximal surfaces. Dental casts were obtained and scanned to produce digital images that were used on a specially designed software program to measure the MDW of permanent teeth. Casts were divided into training and validation sets, where 9 models of tooth combinations were used to develop a regression equation that describes the relation between them and sum of MDW of erupted maxillary or mandibular canines, first and second premolars. The validation set was used to test the accuracy of the proposed equation.

R2 of regression models ranged from 0.3 (for models #2, 4, 5 and 8) to 0.36for model #1. The highest regression in model #1 (sum of MDW of lower first permanent molars and upper central incisors) indicated a high linear association between the sum of MDW of tooth combination model #1 and the MDWofmaxillary and mandibular permanent canines and premolars. There was no significant difference between the actual and the predicted MDW when the proposed equation was checked for its accuracy in the entire validation set (p > 0.05).

The combination of the sums of lower permanent first molars and upper permanent central incisors was the best predictor for the MD W of both maxillary and mandibular permanent canines and premolars. The newly proposed prediction equation may be considered clinically useful for mixed dentition analysis in Egyptian subjects.