Determination of regression equation for prediction of the size of unerupted canines and premolars in Ahwaz

One of the important aspects of diagnosis and treatment planning in the mixed dentition is estimation of the size of unerupted permanent teeth (canines and premolars). One of the most commonly used prediction methods is Tanaka and Johnston. It is based on data from a sample of children of Northern European descent. The accuracy of this method when applied to a different ethnic population is questionable. The aim of this study was to determine new regression equations for predicting the size of unerupted canines and premolars in Ahwaz. Methods & Materials: This study was a analytic and cross – sectional investigation with randomized cluster sampling in Ahwaz. Forty five students 14 to 18 years old (32 girls, 22 boys) were selected between 320 students and their plaster models was prepared. All students had all relevant teeth fully erupted, class I canine and molar relationship and presented no proximal caries or fillings, morphological anomalies, missing teeth or occlusal abrasion and bruxism. The mesiodistal crown diameters of the permanent teeth was measured with using sharpend boley gage (accuracy 0.01 mm). By using of regression, correlation analyses and T- Test, the data from this study was analyzed. In this study the following results were found. The correlation coefficient between the independent variable, lower incisor's width (LI1I2), canines and premolars. The following regression equations were found in Ahwaz for predicting mesiodistal width of the canines and premolars on based the mesiodistal width of the four mandibular incisors in simple form with 0.5 millimeters overestimation. TUCPM1PM2 = 10.5 + (The mesiodistal crown diameters of lower incisors)/2 TUCPM1PM2 = 10 + (The mesiodistal crown diameters of lower incisors)/2 The results indicated that new regression equations more closely with the 50% level Moyers probability tables for the maxilla and mandible. Because the effect of race and ethnic on teeth size we must be find relationship between different teeth group for different race and ethnic group. In this investigation there are following relationship between maxillary and mandibular canines and premolars with mandibular incisors: The mesiodistal crown diameters of lower incisors TUCPM1PM2 = 10.5 + 2 The mesiodistal crown diameters of lower incisors TLCPM1PM2 = 10 + 2 New regression equations more closely with the 50% level Moyers probability tables for the maxilla and mandible.