محمد سعد طعمة الدحيدحاوي

The fundamental objective of this research is to explore the impact of copper content on corrosion resistance of dental amalgam. Five alloys have been casted made out of steady level of tin (30wt %) and the copper content is fluctuate from 5 to 25wt% with interim of 5%. Copper is increased in the expense of silver. The specimens were prepared according to ADA specification No. 1 and have been stored at 37±1 ºC. The corrosion test has been carried out according to ASTM standard ( G5 – 87) and at 37±1 ºC. Two types of electrochemical tests were made an Open Circuit Potential (OCP) – time measurements, and Potentiodinamic polarization in artificial saliva at 37 ± 1 oC. From the obtained results, it‟s obviousthat the Ecorr is shifted to the positive side and a reduction in the mean corrosion current densities with copper content increasing , hence, increasing corrosion resistance with increasing copper content by 46 % compared to low copper dental amalgam.

Admixed alloy powder composed of low copper and metallic glass silver copper eutectic triturated with gallium or gallium tin alloy. The restorative is reinforced with ceramic powder of ZrO2 in both nano and micron sized to improve the mechanical properties and manipulation of the filling. The specimens were prepared according to ADA specification No. 1. Reduction of the liquid reduces the expansion and the addition of the ZrO2 at micronized particles stabilize the dimensional change up to 0.138 of 1% addition at 0.4g of GaSn while the nano ZrO2 enhance the manipulation of the filling paste. Compressive strength enhanced by 19% at 2 percent compared to that without addition at 1h, for 24h the best enhancement for 1 percent nano ZrO2 was 81%. The best creep resistance is at 3 percent micronized ZrO2 by 74% compared to that without addition and 76 % as compared to dental amalgam

Specimens of a gallium-based dental alloy were prepared with different liquid parts (Ga, GaSn) and different ZrO2 addition particle sizes (nano and micro) and their effect on the corrosion resistance of the filling was explored. The solid part was admixed from a low copper alloy and metallic glass of silver copper eutectic (1/3rd Low Cu + 2/3rd Ag–Cu eutectic). The low copper alloy comprising 66 wt% Ag, 30 wt% Sn, 4 wt% Cu and Zn was added at a constant weight of 1.2 g per cast. The specimens were prepared according to ADA specification no. 1 and stored at 37±1°C. The corrosion test was carried out according to ASTM standard (G5 – 87) and at 37±1°C. Two types of electrochemical tests were made: Open Circuit Potential (OCP) – time measurements, and potentiodynamic polarization in artificial saliva at 37±1°C. The results obtained show that Ecorr is shifted in the positive direction and the mean corrosion current densities decrease with ZrO2, and with a change from Ga to GaSn.

the aim of the present investigation is to study the effect of copper content on mechanical properties of dental amalgam. For this purpose five alloys have been casted composed of constant percentage of tin 30wt% and the copper content is vary as follow(5, 10, 15, 20, 25) and the rest was silver. The specimens were prepared and tested according to ADA specification No. 1. Mechanical properties (compressive strength, diametral tensile strength, creep, dimensional change, and hardness) were investigated and it is found that all mechanical properties enhanced by increasing copper content. The compression strength is increased by 37.4% at one day and 35.2% at 7 days test. The diametral tensile strength is increased by 18.1% at one day and 13.5% at 7 days test. Creep resistance is increased by 71.1%. Vickers microhardness increases by 29.4% at one day test and 27.3% at 7 days test. Increasing copper content stabilizes the dimensional change of dental amalgam. All as compared to low copper content amalgam.