Adaptation of a standard adherence test to dentistry: the peeling test. Study of the interface between dentine and a one step dentine adhesive system
Résumé
The aim of this study was to finalise a 90° peeling test on 60 human teeth. The dentinal surfaces to be stuck were characterised by micro-hardness, wettability, optical microscopy, SEM, AFM, XPS and EDS. The so-called fifth-generation bonding agent (Prime & Bond(®) 2.1 DeTrey Dentsply) was used to perform the peeling-test. The extremity of a membrane was included in the adhesive which rendered it possible to hold. The other extremity of the membrane was connected to an Instron universal testing machine, on which the peeling system (MTS) was fixed. The cross head speed was set to 0.5mms-1. Two types of curves (force versus displacement) were obtained: for bond strengths higher than 5N (average=7N) curves were typical of cleavage; for bond strengths lower than 5N (average=2.8N) peeling was observed. The obtained curve which showed maximal stress versus strain, indicated the membrane rheology and made it possible to rank the samples with respect to their surface fracture. Correlation between failure and physico-chemical dentine composition was observed. The observation of the fracture surface with an electron microscope in combination with X-ray analysis by energy dispersive spectroscopy showed interfacial failure when cleavage was obtained and cohesive fracture when peeling was obtained. It showed some very heterogeneous fractures, from adhesive resin interfacial fractures to cohesive fractures in the adhesive resin or restorative composite resin. This work demonstrated that dentine/resin adhesive interface was highly complex. The adherence results depended not only on dentine superficial parameters, but also on the physico-chemistry, rheological behaviour of the resin and the composite and on test parameters (e.g. speed, etc.).