A cone-beam computed tomography-based morphometric comparison of mandibular molars between Han Chinese and Malays

Variations in tooth and mandibular morphometry exist among ethnic groups and may have clinical and anthropological implications. This study compared the tooth length and root-to-crown ratio (RCR) of mandibular first (M1) and second (M2) molars in Han Chinese and Malays, and assessed the root length relative to mandibular height (Root-Mandible Ratio @ R: Mand).

One hundred twenty-one cone-beam computed tomography (CBCT) images were included. Relevant measurements were made using the CBCT software to obtain anatomical and clinical crown and root lengths. The measurements of the mesial and distal roots were averaged and used to calculate the RCR and R: Mand. Sixty-one CBCT scans of Malay patients were retrieved, and another 60 scans were of Han Chinese ethnicity.

There was a statistical difference in the tooth morphometry and their RCRs, with the Malays' findings being significantly higher than the Han Chinese; the exception being the clinical-RCR (c-RCR) of M2 and the R: Mand at M2. Most parameters were generally significantly larger at M1 than at M2. The mandible height at M1 was similar in both ethnic groups, but the R: Mand of M2 was significantly higher (50.69 %) in the Han Chinese because of their low mandibular height. The Han Chinese have shorter crowns and roots for M1 and M2, and mandible height compared to the Malays at M2.

The observed morphometric differences may reflect underlying genetic and/or environmental factors and possible clinical impacts on facial morphology and occlusion between the two ethnic groups.