[A micro-computed tomographic study of the isthmus in the root canal system of mandibular first molar].
OBJECTIVE
To investigate the prevalence and configuration of the isthmuses in the apical 6 mm of the mesial and distal roots of Chinese mandibular first molar by means of micro-computed tomography.


METHODS
Thirty-six extracted human mandibular first molars were selected. Specimens were subject to micro-CT and a slice thickness of 30 microm was obtained in the apical 6 mm of the roots examined. The number of sections showing isthmuses at each apical level was recorded. Three-dimensional images of isthmuses of mandibular first molars were reconstructed and observed.


RESULTS
The mesial roots of human mandibular first molars had a high incidence of isthmus. The isthmus incidence was greatest 4-6 mm from the apex in human mandibular first molar, with prevalence figures of 49.5%-66.1% and 17.3%-17.8% in mesial and distal roots, respectively. The chi-square test indicated a significant difference in the distribution of isthmuses between the two roots (P < 0.01).


CONCLUSIONS
The mesial roots of human mandibular first molars have a high incidence of isthmus, which may have clinical implications especially when surgical endodontics is performed on the mesial roots of mandibular molars.
Gu
Li-Sha
LS
Department of Cariology and EndodonTology, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
Ling
Jun-Qi
JQ
Huang
Xiang-Ya
XY
Wei
Xi
X
Xu
Qiong
Q
D000328:Adult; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000000981:diagnostic imaging; D008963:Molar / Q000000981:diagnostic imaging*; D012390:Root Canal Therapy; D014092:Tooth Root / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography