Related Experiment Video
Updated: Jun 8, 2026
Systematic Assessment of Mammalian Skull Specimens for Dental and Temporomandibular Joint Pathology
Published on: August 22, 2022
Prevalence of 3-rooted first permanent molars among a Shanghai Chinese population
Ya Yang1, Lu-Dong Zhang, Jian-ping Ge
1Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China.
Objectives:
This study aimed to assess the prevalence of 3-rooted mandibular first molars among a Shanghai Chinese population by using periapical radiographs.
Methods:
A total of 510 patients possessing both mandibular first molars were selected. The radiographs of these cases were evaluated under optimal conditions using double magnifying glasses. The incidence of 3-rooted mandibular first molars and the correlation between occurrences in males and females and between the left and right sides were recorded and analyzed. A total of 1020 mandibular first molars were evaluated.
Results:
A total of 165 patients were found to have a 3-rooted mandibular first molar: 92 males and 73 females (P = .106). The overall incidence of patients with 3-rooted mandibular first molars was 32.35%. Of all the patients with 3-rooted molars, 67.27% (111/165) of cases occurred bilaterally. The incidence of teeth showing an extra root was 27.06%. The occurrence of such permanent 3-rooted mandibular first molars also did not differ significantly between the right side (n = 142, 13.92%) and the left side (n = 134, 13.14%; P = .573).
Conclusions:
The prevalence and bilateral incidence of 3-rooted mandibular first molars among the Shanghai Chinese population was high and such variation varied among Chinese populations living in different areas.
Related Concept Videos
01:15Teeth
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
01:21Tooth Anatomy
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.