Objective: To test the applicability of the Tanaka and Johnston equation for prediction of the mesiodistal width of unerupted permanent teeth in a Sudanese population and to develop a new prediction equation for this specific population if necessary.
Design: A descriptive, cross-sectional study.
Settings: School-based study.
Subjects and methods: Two hundred and fifty subjects (118 males and 132 females) age 13 - 19 years were randomly selected from two public secondary high schools in Khartoum State. Mesiodistal widths of the upper and lower permanent canines, first and second premolars (CPM) as well as the mandibular permanent incisors (MPI) were measured manually on the dental casts using a digital caliper. The predicted values of the mesiodistal widths were statistically compared with the respective actual sum of the canine and premolars of the same quadrant.
Results: Moderate correlation coefficients were found between the sum of the mesiodistal width of the MPI and the sum of the CPM in males (0.618 for mandibular arch and 0.626 for maxillary arch) and females (0.726 for mandibular arch and 0.680 for maxillary arch). A low coefficient of determination was recorded (0.45 and 0.48) in both jaws for combined genders.
Conclusions: The Tanaka and Johnston equations overestimated the actual mesiodistal width of CPM in both arches for males and females. New prediction equations with more accurate regression parameters were proposed for the Sudanese population.
Keywords: Mixed dentition; Tanaka and Johnston equations; space analysis.