tensile peel strength of cantilever Ni/Cr resin bonded bridegs

ABSTRACT

To measure the tensile peel strength of Ni/Cr cantilever resin-bonded bridges. Ten extracted upper sound human premolars were prepared with the wrap around preparation with occlusal rest for construction of Ni/Cr resin-bonded bridges. The metal retainers were then sandblasted with 50 micro m Aluminium oxide grit, cleaned in an ultrasonic bath for three minutes and bonded to the extracted teeth using Panavia 21 resin according to the manufacturer instructions and tested on an Instron universal testing machine for tensile peeling bond strength. The results of this study showed that the range of tensile peel strength was ranged between 15.3-31.9 Newton [mean 22.5 N], which is virtually much less than the published tensile bond strength values, yet resin-bonded bridges do fail at these loads. This study provided quantitative values of the tensile peeling strength by which resin-bonded bridges thought to be failing intraorally. These values showed to be well below the tensile bond strength or shear bond strength, yet it was enough to break the resin cement and to debond the resin-bonded bridges. The suggested mechanism is that the metal framework will be deformed during function, causing stress concentration in the resin layer followed by initiation of a crack, which will propagate through the bonded surface-causing breakdown by cohesive failure. This study supports the hypothesis that resin-bonded bridges do peel out of the abutment as the likely cause of failure at normal functional masticatory loads