Browsing by Author "Sintala, John Mathias"

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    The Evaluation of Dental alloys for use in high temperature and humidity environments.
    (University of Dar es Salaam, 1989) Sintala, John Mathias
    It was the purpose of this study to investigate the influence of aging of several commercial dental amalgam alloys under high temperature and relative humidity environment on mechanical strengths, creep and corrosion behaviour of the amalgams. Nine dental alloys namely Ana 2000, Sybraloy, Cupralloy, Dispersalloy, Indiloy, Solila, Cavex 68, Avalloy and New True Dentalloy were aged at 37°C with 80-100% relative humidity. Two brands were from conventional alloys and seven were from high copper alloys. Preparation of the amalgam specimens from fresh as well as aged alloys were according to manufacturer instructions and then condensed according to ADA Specification No. 1 for dental amalgam alloys. The evaluation of the mechanical strengths and creep of both fresh and aged alloys were carried out in an Instron Testing machine. The results found in this study show that the aging of alloys under Tropical climate have little effect on setting rate and ultimate strength of the resulting amalgams. A more distinct effect of aging was observed on creep property which was significantly impaired in both systems with the exception of Sybraloy. An attempt was made to investigate corrosion behaviour of amalgams made from fresh and aged alloys. The technique included potential-time and anodic polarization measurements of the corrosion effects in de-aerated artificial saliva. The results of fresh alloys show that New True Dentalloy and Cavex 68 show primary passivation related to the gamma-2 phase and show the breakdown of passivity, typical for conventional amalgams. In high copper system the peaks of anodic passive behaviour are at least one order of magnitude lower than those in conventional system. Aging had no effect on the corrosion behaviour of neither systems.