# Root resorption pattern and root length of mandibular primary molars in children: a cross-sectional radiographic study

## TL;DR

This study analyzed root resorption patterns in children's mandibular primary molars using radiographs and found gender-specific differences and asymmetric resorption in second molars.

## Contribution

The study provides new insights into gender-based differences and asymmetric root resorption patterns in mandibular primary molars.

## Key findings

- Boys showed delays in root resorption of first and second mandibular primary molars.
- Girls exhibited significant increases in root resorption compared to boys.
- Second mandibular primary molars showed asymmetric resorption with mesial roots resorbing first.

## Abstract

To determine the root resorption pattern and calculate the root resorption length of mandibular primary molars in children.

A cross-sectional and descriptive study was conducted of 367 panoramic radiographs of healthy nonorthodontic children, 169 girls with a mean age of 9.39 years and 198 boys with a mean age of 9.02 years. The length of the mesial and distal roots of the primary molar was calculated using a computer program (PixelStick®) that measures the pixels indicated in the image. Student’s t test, the Mann‒Whitney U test and the Kruskal‒Wallis test were used for comparisons, and p < 0.05 indicated statistical significance.

A 0.84 mm delay in root resorption of the first mandibular primary molar (74) in boys was described. There was also a delay in the resorption of the mesial root of 0.89 mm and 1.12 mm from the distal root of the second mandibular primary molar (75) in boys and a significant increase in root resorption in girls (p < 0.05). The mesial and distal roots of the first mandibular primary molar were resorbed equally; however, the mesial root of the second mandibular primary molar was resorbed before the distal root.

Delays in root resorption were detected in boys, whereas advances in root resorption were detected in girls. The root resorption pattern of the first mandibular primary molar was symmetrical; however, the resorption pattern of the second mandibular primary molar was asymmetric, with the mesial root being resorbed first. Clinical and radiographic monitoring of mandibular primary molars with unevenly resorbed roots is recommended to avoid the complications associated with over retained molars.

The online version contains supplementary material available at 10.1007/s40368-025-01052-3.