[The correlation between the enlargement of root canal diameter and the fracture strength and the stress distribution of root].
OBJECTIVE
To investigate the correlation between the extent of cutting of the root canal wall and the root fracture strength and the stress distribution.


METHODS
Fifteen pairs of root sections were into 3 groups with canal wall thickness of 1.00 mm, 0.75 mm and 0.50 mm respectively. The maximum load was tested required for fracture for each group through fracture test in a universal testing machine, and compared with that for the original canal. The stress and its distribution of the root with normal wall thickness (1.2 mm) and roots with 75%, 50% and 25% respectively of the normal wall thickness were examined by three-dimensional finite analysis. The maximum Von Mises stress of the root of each model was calculated.


RESULTS
The mean fracture strengths of the groups with canal wall thickness of 1.00 mm, 0.75 mm and 0.50 mm were (4 432.41 +/- 563.59) N, (4 137.43 +/- 680.29) N and (3 749.87 +/- 554.17) N respectively. The maximum load of fracture resistance is a linear function of the root canal wall thickness (r = 0.972, P < 0.001). The three-dimensional finite analysis revealed that the enlargement of root canal diameter brought on increase of stress of root canal wall, and the stress and its distribution altered with further decrease of the wall thickness. The stress of lateral loading was greater than that of vertical loading.


CONCLUSIONS
The results suggests that clinical root canal treatment should be designated to remove just the infected tissue and avoid over-cutting of the hard tissue.
Chen
Jun
J
Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
Yue
Lin
L
Wang
Jia-de
JD
Gao
Xue-jun
XJ
D003786:Dental Pulp Cavity / Q000473:pathology / Q000503:physiopathology*; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D066298:In Vitro Techniques; D008963:Molar; D018915:Root Canal Preparation / Q000379:methods*; D014092:Tooth Root / Q000473:pathology / Q000503:physiopathology*