Quantitative Longitudinal Analysis of Root Growth in Maxillary First Molars

Objectives: To measure for the first time longitudinal growth of the buccal roots of permanent maxillary first molars, compare mesial and distal root lengths (MRL, DRL) and compare symmetry of antimeres in male subjects.

Methods: Longitudinal periapical radiographs of upper first molars of 31 male subjects from the Iowa Facial Growth Study were captured and measured in millimeters with software from Image Pro Express. Duplicate measurements were taken from the cemento-enamel junction to root tip on the mesial aspect of the mesial root and the distal aspect of the distal root. Intra-class correlation coefficients indicated strong agreement between the duplicate measurements with a single-observer at each tooth surface (between .98 and .99 for each surface). Descriptive statistics were computed and a paired-samples t-test was used to compare differences between mesial and distal root length and symmetry of antimeres. A 0.05 level of significance was chosen.

Results: The male subjects demonstrated MRL that were significantly longer than DRL at ages 6-14 and above age 20 (p<0.05) for tooth #3 and tooth #14. Root lengths of antimeres showed no significant difference in length at both the mesial and distal surfaces at ages 6-14 and above age 20 (p>0.05). Root growth velocity peaked in tooth #3 for mesial and distal roots at age 8, and velocity peaked in tooth #14 at age 8 for the distal root and age 10 for the mesial root.

Conclusions: In males, growth of the permanent maxillary first molar roots showed that the mesial root surface length was significantly longer than the distal root surface length, and that there was no significant difference in growth between the antimeres.

*This study was supported by a University of Iowa Dental Research Award.