Background: Prediction of the mesio-distal width of the unerupted premolars and canine is an important point to the practitioner.
Objectives: The main goal of this study was to find the relationship of the teeth size to be used when needed in treatments planning.
Materials and Methods: 200 plaster casts including 5600 teeth were measured and studies. A caliper with accuracy of 0.1 mm was used for measuring teeth and most teeth were measured twice and the average value was considered as the teeth size. In all cases, the vernier calipers jaws were moved along the teeth longitudinal axis and the biggest width was measured in the contact point area.
Results: Tables of mesiodistal widths of the permanent teeth and some equations were prepared. The measurement difference varied from 0 to 0.04 mm. the average value of difference was 0.016 mm with SD of 0.02 mm. All teeth in male are bigger than those in female and this different is most evident in canine teeth, especially the lower jaw canine teeth.
Conclusions: At the end of this study an equation was found which was used to measure the total value of mesiodistal width of canine and premolar teeth of upper and lower jaws in a simple and exact way.