Evaluation of Relationship between Mesiodistal Width of Permanent Canines and Premolars with Permanent Lower First Molars and Incisors for Space Analysis

 One of the simplest methods to predict mesiodistal width of permanent canines and premolars is using Tanaka and Johnston’s prediction formula; however, dental size varies according to race.  The study aimed to examine the relationship between incisors mesiodistal width and mandibular first molar’s with mesiodistal width of maxillary and mandibular canines and premolars and to determine the reliability of Tanaka and Johnston prediction formula. 

 In the present cross-sectional study, 200 pairs of a dental cast of 12-25 years old were selected and the greatest mesiodistal width of canines and premolars crown in each jaw and incisors and mandibular first molars were measured with a digital caliper with 0.01 resolution. Data were analyzed using regression analysis, t-test and SPSS 22 software. (p value < 0.05)

 there was a significant statistical difference between actual width and Tanaka and Johnston prediction formula in the group under study (p value < 0.001). Moreover, a new linear equation for the prediction of mesiodistal width of maxillary and mandibular canines and premolars based on mesiodistal width of lower incisors and mandibular first molars was developed using regression analysis.

 In statistical terms, Tanaka and Johnston’s prediction formula is not applicable for the population under study because maxillary estimated measures were a little high and mandibular estimated measures were a little low.