Mandibular molar C-shaped root canals in 5th millennium BC China.
OBJECTIVE
The aim of this study was to analyze the occurrence and variations in C-shaped canals in ancient Chinese teeth and compare the differences of these features between ancient and age-matched modern populations.


DESIGN
Approximately 5000-year-old craniofacial bone remains were collected from the fossils of 38 individuals (total: 68 mandibular second molars) excavated from the Jiaojia site. The control group comprised of an equal number of randomly selected modern samples. We used cone-beam computed tomography to scan the mandible along the apex-crown axis and analyzed the canal morphology, based on Fan's categorization criterion, at 2 mm, 5 mm, and 8 mm to the apical level. Grooves on the lingual and buccal sides were also recorded.


RESULTS
The proportion of C-shaped roots among ancient samples on the left and right sides were 48.57 % (17/35 teeth) and 54.55 % (18/33 teeth), respectively, and 51.47 % (35/68 teeth) in the total sample. Conversely, in the control group, 44.12 % (15/34) and 38.24 % (13/34) occurred on the left and right sides, respectively, and 41.18 % (28/68) in the total sample. Among the C-shaped canals from the Jiaojia site samples, the classification type changed between two adjacent levels in 84.31 % of samples. Approximately 35 (51.5 %) teeth had a fused root, 20 (29.41 %) had one shallow buccal and one deep lingual groove. The occurrence of C-shape variation was not significantly correlated with time (p＞0.05).


CONCLUSIONS
This study identified a high rate of C-shaped root canals among individuals of Jiaojia who lived approximately 5000 years ago.
['Ren|Hui Ying|HY|', 'Zhao|Yong Sheng|YS|', 'Yoo|Yeon-Jee|YJ|', 'Zhang|Xiao Wen|XW|', 'Fang|Hui|H|', 'Wang|Fen|F|', 'Perinpanayagam|Hiran|H|', 'Kum|Kee-Yeon|KY|', 'Gu|Yu|Y|']
D002681:China D054893:Cone-Beam Computed Tomography D003786:Dental Pulp Cavity D005580:Fossils D006801:Humans D008334:Mandible D008963:Molar D014092:Tooth Root
C-shaped root canal Craniofacial bone remains Mandibular second molar Cone-Beam computed tomography