A comparison of bond strengths measured using cantilever bending and micro-tensile methods

Objectives

The purpose of this study was to evaluate the cantilever-bending test as a bond-strength measurement method for enamel/composite adhesion.

Materials and methods

The buccal surface of bovine incisors were flattened and subsequently placed with composite Z250 (3M ESPE) incrementally after either self-etching adhesive (SE) or etch-and-rinse adhesive (SB) was applied. Then, they were cut with a low-speed cutter to obtain stick-shape samples. The samples were divided into four groups (n = 30 each) according to the adhesive and test method: SET, SE-B, SB-T and SB-B, where T denotes the microtensile test and B denotes the cantilever-bending test. The failure mode of each sample was examined under the microscope. Those samples with the fracture surface lying entirely or partially in the adhesive layer were considered to have provided successful measurements. The results from the two test methods were compared.

Results and discussion

The cantilever-bending method produced a comparable success rate of bond strength measurement to that of the microtensile method. The bond strengths of SE and SB from the cantilever-bending test were 58% and 40% higher, respectively, than those measured with the microtensile method. The adhesive SE exhibited almost the same bond strength as SB, irrespective of the test method.

Conclusions

Cantilever bending can be used as an alternative method for bond strength measurement. The ratio of bending to tensile strength is around 1.5.