Mixed dentition space analysis for a northern Italian population: new regression equations for unerupted teeth.

OBJECTIVE: The aim of this study was to determine linear regression equations for a Northern Italian population to predict mandibular permanent premolars and canines widths, and particularly, second premolar widths, using the sum of the widths of the four mandibular incisors, canines and first premolars. MATERIALS AND METHODS: Mesiodistal tooth widths were measured from 230 dental casts obtained from Northern Italian patients (130 females and 100 males). Student's t-test or Wilcoxon test for independent and paired samples were used to determine right/left side and male/female differences. Correlation coefficients and linear regression equations were constructed to evaluate the relationship between 1) the combined mesiodistal widths of the permanent mandibular incisors (independent variable) and the combined mesiodistal widths of the canine and premolars (dependent variable); 2) the combined mesiodistal widths of the incisors, canines and first premolars (independent variable) and the widths of the second premolars (dependent variable). Significance value was set a priori at 0.05. RESULTS: A linear regression equation was found, y=0.585x+7.927 (r=0.734) considering right and left sides of mandibular arch together, to predict canines and premolars widths. For second premolar width, the linear regression equation was y=0.201x+2.149 (r=0.641), even when considering the right and left sides of the mandibular arch together. CONCLUSIONS: New regression equations were derived for a Northern Italian population.