Eric Leforestier

In vitro action of Bordeaux red wine on the microhardness of human dental enamel

Several studies have demonstrated that the regular and large consumption of wine is associated with increased risk of tooth erosion. Here, the effect of Bordeaux red wine on enamel was estimated by measuring changes in its Vickers microhardness. Thirty premolars were used; microhardness tests were performed on buccal areas before and after 10, 30, 90 and 120 s immersion in the wine (pH=3.9). Enamel surfaces were also observed by scanning electron microscopy. No statistically significant difference was found between the mean Vickers microhardness obtained at t=0 and 90 s, but slight signs of enamel demineralisation were observed with the scanning electron microscope. It appears that wine has no disastrous effect on the microhardness of dental enamel when the two are in contact for less than 90 s. When the exposure is for at least 120 s, it may become harmful, as the decrease in the microhardness of enamel was then significant (P<0.05).

Shear Bond Strength of Self-Etching Adhesive Systems to Er:YAG Laser-Prepared Dentine with and without Pulpal Pressure Simulation

OBJECTIVE This study was conducted to study the role of pulpal pressure on the shear bond strength of composite resin bonded to Er:YAG laser-prepared or bur-prepared dentine surfaces using a self-etching adhesive system. MATERIALS AND METHODS The occlusal surfaces of 80 human third molars were ground flat to expose the dentine. The dentine was prepared using either a carbide bur or an Er:YAG laser at 350 mJ/pulse and 10 Hz (fluence 44.5 J/cm(2)). Clearfil SE Bond was then applied with or without pressure. Rods of composite resin were bonded to dentine surfaces and shear bond tests were carried out. RESULTS When the Clearfil SE Bond was used without pressure, the difference between the shear bond strength values of bur-prepared and laser-prepared dentine surfaces was significant. When the Clearfil SE Bond was used with pressure, the difference of shear bond strength values was not significant between the two types of surface preparation. CONCLUSION The absence of smear layer formation during the preparation of the dentine by the Er:YAG laser did not improve the adhesion values of self-etching adhesive systems.

Physicochemical and mechanical approaches to dentine/resin adhesive interface

Abstract 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 Spearman 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.