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

ABSTRACT

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