Physicochemical and mechanical approaches to dentine/resin adhesive interface
Résumé
The aim of this study is to determine the influence of different characteristic parameters of the human dentine surface on the interaction between dentine and adhesive resin. The dentine surface of 21 freshly extracted teeth (from patients between the ages of 13 and 77 years old) was treated with Total Etch (Vivadent etching gel) and characterised by three methods: Vickers microhardness (for mechanical characterisation); wettability (in order to characterise the dentine and adhesive interactions using the drop angle): optical and electron microscopy with image analysis (for microstructural characterisation). The average number and diameter of the tubules on the surfaces were calculated. Then 21 stubs of Z100 restorative (3M dental products) were bonded on the dentine substrate of these teeth using Syntac Sprint (Vivadent). The shear bond strength (Instron universal testing machine) at a crosshead speed of 0.5 mm s (-1) was determined. Shear bond strength and microhardness increases with the age of the tooth. The shear bond strength decreases with the per cent surface area, and average number of tubules. The wettability angle increases with the number of tubules and the per cent surface area of tubules. The results were analysed with the use of Sperman Rank. The explanation of the wettability behaviour is very complicated and it is necessary to take into account the evolution of the resin adhesive viscosity over time. The originality in this work is that the physicochemical characterisation and mechanical study were carried out on the same tooth. The fact that no significant statistical correlation is found between dentine, its specific parameters, and the shear bond strength can be explained by the observation of fracture surfaces using SEM in combination with EDX analysis. This shows some very heterogeneous fractures, from adhesive resin interfacial fracture to cohesive fractures in the adhesive resin or restorative composite resin. This work demonstrates that the dentine resin adhesive interface is highly complex. It depends not only on the superficial parameters of the dentine but also on the physicochemistry of the resin and the adherence test parameters.