[Analysis the stress variations of the root canal wall of pulpless tooth by different root canal preparation with finite-element method].
OBJECTIVE
To analyze the stress variations of the root canal wall of pulpless tooth by different root canal preparations.


METHODS
On the basis of the set up model of the mandibular first molar, modified model was established by simulation of the routine or step-back root canal preparation and filling in. Then the maximum mises stress of each part of teeth and wall of root canal were calculated by special finite-element software.


RESULTS
The stress-changing tendency is similar between two modified models but the maximum mises stress of the model by step-back technique is a little greater than one by routine. The stress of wall of mesial-buccal root canal was the greatest and one of mesial-lingual root canal was the least at three root canals. The stress-changing tendency of modified models was similar to original model. The maximum mises stress of modified models was near or less than one of original model except that of amalgam layer because of material property alteration.


CONCLUSIONS
Not only routine but step-back technique is an effective and safe method. Dentist can choose them in practice.
Hong
Jin
J
Department of Oral Medicine, Ninth People's Hospital, Shanghai Second Medical University, Shanghai 200011, China. hj1221@online.sh.cn
Xia
Wen-wei
WW
Zhu
Ya-qin
YQ
Wang
Xiao-yi
XY
Xiong
Huan-guo
HG