Assistant Professor of Orthodontic Dept. School of Dentistry Yazd University of Medical Sciences



Aim: To compare the prediction of unerupted permanent canine and premolar size of a comparable sample size of Iranian (Yazd) population with that of the study of Tanaka and Johnston.
Materials and Methods: Teeth on study casts of an unselected sample from a 11 to 25 years old (n 120; 60 males and 60 females) were measured in the mesiodistal dimension. An Iranian mixed dentition analysis based on the Tanaka and Johnston method was constructed with new linear regression equations for prediction of the mesiodistal widths of unerupted canines and premolars. Digital calipers were used to measure the mesiodistal widths of all teeth on study models fabricated from alginate impressions. The predicted widths of the canines and the premolars in both arches were compared with the actual measured widths.
Results: Sexual dimorphism was evident between Iranian (Yazd) males and females in incisors, canines, and premolars in the mesiodistal dimension.
Conclusions: To predict the space (in mm) required for alignment of unerupted canine and premolars in Iranian(Yazd) children, divide the sum of the mesiodistal dimensions of the four mandibular incisors by two and add the respective constants for males (upper, 12.91; lower, 10.51) or females (upper, 9.09; lower, 8.22).