No abstract

The application of Fortify (Bisco, Lombard, IL), an unfilled resin, to the surface of composite resin restorations is intended to fill in defects in the surface that persist despite polishing, improve marginal integrity, and increase these materials' resistance to abrasion. The aim of this study was to observe the surface texture by scanning electron microscopy and measure the microhardness of the surface. For each sample of composite resin covered with glaze, 40 measurements were made of the thickness of the resin. Measurements of the Vickers microhardness included three samples of composite resin, three samples of glaze, and six samples of composite resin covered with glaze. A relationship was established between microhardness and thickness. Scanning electron microscopy showed a noticeable improvement in the surface texture. Nevertheless, areas were seen in which glaze seemed very thin or even completely absent. Measurements of the thickness ranged from 0-70 microm. The mean microhardness of composite resin was 65.8 +/- 0.7, while the mean hardness of glaze was 7.3 +/- 0.7. The microhardness of the double layer was reduced, depending on the thickness of the glazing resin. The capacity of glaze to mask surface defects of composite resin was shown, but it was difficult to obtain a regular surface with liquid resin. The application of this product caused a decrease of the microhardness of the composite resin's surface.

The Quantec rotary system produced cleaner canal walls than conventional manual instrumentation, particularly in the middle and apical thirds. This finding may imply that stresses applied to the cutting regions of Quantec instruments by accumulation and compression of the smear layer are minimized.

No abstract

The original canal shape was maintained better in the apical third of curved canals when using the Hero system in a crown-down technique when compared to a hand preparation technique with stainless steel instruments.

Burned bones were studied using Scanning Electron Microscopy. The samples were cut from a maxillary-mandibular block taken during an autopsy. These fragments were heated in a furnace under controlled temperature conditions for 60 minutes. The temperatures ranged from 150 to 1150 degrees Celsius. The results are as following: (i) there are significant alterations of the bone, more and more obvious as the temperature increases, (ii) it appears to be difficult to establish a precise correlation between the temperature and the scanning electron microscopy patterns.

No 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.