Geometrical Aspects on Bi-Material Microtensile Tests

Recently the bond strength of composite resin to tooth has received attention from researchers of dental materials. Limitations imposed by the biological substrate, such as the size of the specimen, fostered the development of a tensile test with small dimensions. Due to the reduced size of the specimens, the test is called microtensile test. The specialized literature has not presented standards for the test parameters and the relatively large scatter of published bond strength data probably reflects the lack of standards for the test parameters. The objective of this study is to evaluate how specimen geometry and loading conditions affect the estimation of bond strength. A numerical simulation of the test using a Finite Element Model was performed to determine the associated variations on the stress field imposed by variations in the geometry of the specimen and loading conditions. The Finite Element pre-processing and post-processing was performed on Patran® and the Finite Element processing was performed on Marc®. Results from numerical simulations show that geometrical parameters and loading conditions have a significant influence on the stress field. Some suggestions of standards for the microtensile test considering the non-uniform stress field are presented.