Effect of confined surface on the dimensional changes of high copper amalgam

Dimensional changes for two high copper amalgams were measured for free samples and restricted samples having smooth and rough inner surfaces. The samples were prepared according to ADA specification No. 1. The experiment was conducted at 50C in air for maximum period 30 weeks. The amalgam tested had high expansions for unrestricted cylinders [82 un/cm for Dispersallcy and 134 um/cm for Optaloy11]. While the expansion in the restricted glass-tube showed very low values for Dispersallcy 3 um/cm and 30 um/cm for Optaloy11. There was no significant difference between the samples prepared in a glass tubes having smooth and tough surfaces. This present study, which is principally concerned with the dimensional changes of two high copper amalgam in a confined glass tubes having smooth and tough surfaces has arrived to the following conclusions: 1] There are wide differences between the expansion of the dental amalgam as a free sample and in a restricted sample stimulating the cavity in the tooth regardless to the surface conditions. 2] For restricted samples, Dispersalloy showed about 2.1-3.6 Um/cm. 3] Most of the amalgam expansions for bathe conditions recorded in the first 10 weeks of the experiment. A phase changes of gamma I towards Beta I in dental amalgam restorations has resulted in dimensional changes. As observed clinically, these dimensional changes may be partly cause some of the extrusion of amalgam restorations. For this reason, the dimensional stability as amalgam is an important aspect for clinical behavior. A phase change of gamma I to beta I in the silver-tin mercury system occurs slowly at body temperature [37C] and more rapidly at 50 to 60C [7,2].Most of the works were done to study the dimensional changes that occurs during hardening for the first 24 hours [3-8]. As well as more after 40 weeks at 42. 37. 60C in air for the samples [3-8].The present work was conducted to study the effect of confined surface on the dimensional stability of two high - copper amalgam alloys

in vitro study: the effect of coca-butter application on the surface property of some glass ionomer cements

The purpose of the present work was to study the effect of coca butter application over the cement against the surface property for three brands of glass ionomer cement. The effect of water storage on the surface property of the cement was also studied. Scratch resistance test for cement surface was performed using a vicker Hardness apparatus under a load of 200 gm. And a speed of 0.5 m/min. Width of the scratch was measured using a stereo-microscope. The results showed that application of coca butter on cement surface had no effect for increasing scratch resistance. There was no significant difference among all the brands of cement tested for the scratch width. For all the brands investigated, the width of the scratch was not varied after four month of water storage

Clinical evaluation of different impression materials

Four impression materials were chosen as representatives of the different impression materials. The ease of manipulation, ease of separation from the cost and reaction of the patient to each impression material were evaluated and recorded. In this study, ten completely edentulous patients were selected from the prosthetics clinic and four impressions, with different impression materials were taken for each patient in one visit. The different impression materials were evaluated from the above mentioned points of view. Polysulphide could be considered as the most convenient impression material for both the patient and the operator. As regards appearance of the costs, polysulphide was the best

Interface bond strength and leakage of repaired composite resin

The bond strength of repaired composite resin [Lumicon] was examined under different conditions. Exposure to saliva for short period, 2 minutes, did not affect the bond strength, but 24 hours exposure to saliva or tea before repair caused a significant drop in the repair bond. The type of surface finish, smooth or rough, did not alter the results. It also seems that maturation of the composite rather than contamination which influence the repair strength. There was no dye leakage at the repair interface under any of the experimental conditions