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[Three dimensional finite element analysis of effects on composite resin for filling in various cavity margin design].

OBJECTIVE
To evaluate the stress distribution of different angles of cavity margins with composite resin filling.


METHODS
The stress distributions of different angles of cavity margins of class I cavity of molars were analyzed by the method of three dimensional finite element. The cavity was filled with composite resin and the stress vertical force and lateral force was calculated.


RESULTS
In the 5 designed different cavity margin angles, the vertical forces and lateral forces were 18.757 MPa and 22.309 MPa respectively when the angle is 90 degrees; when the angles were 75 degrees and 60 degrees, they were 10.580 MPa, 14.265 MPa and 9.025 MPa, 13.230 MPa respectively. The vertical forces and lateral forces produced by the surface of composite resin while being stressed were up to 18.757 MPa and 22.309 MPa. The forces of the second layer evidently reduced to 2.586 MPa and 6.8 MPa.


CONCLUSION
When fill the molars with resin in clinic, the angles of cavity margins should be prepared with the slopes of 60 degrees to 75 degrees.