Creep of dental amalgam and its phases

Abstract

– The intention of the study was to evaluate creep as a function of temperature and stress, and to determine creep rate of compounds with a composition equivalent to the y, y1, and y2 phases in dental amalgam. The results were consistent with a creep model in which the deformation takes place in the y1 phase, and is dominated by glide pileups of dislocations in grain boundaries.

Relationship between creep, γ2, and marginal fracture of dental amalgams

“…Such an explanation is consistent with a previous study (Okabe et al, 1980) in which grain boundary sliding without any actual deformation of yi has been found to be operative during creep of conventional amalgams. Thus, the apparent enhancement of creep due to yi addition should strictly be attributed to Sn-rich grain boundaries and not to the yi phase as has been done in the past (Vrijhoef & Driessens, 1974a;Espevik, 1977;Mahler et al, 1977). The Sn in yi grain boundaries originates from the amalgamation reaction of Ag3Sn.…”

“…In two previous studies (Rupp, Manuszewski & Patel, 1976;Mahler, Adey & Marantz, 1977), the creep of conventional amalgams was found not to be influenced by y2. In another study (Espevik, 1977), y2 was found to enhance creep.…”

“…In attempting to clarify this conflict and to establish the exact effect of y2, the following observations need consideration. First, the y-particles are reported not to contribute to creep (Espevik, 1977;Vrijhoef & Driessens, 1974a). Second, as presented here, the creep rate of pure y2 is two orders of magnitude higher than that of yi.…”

Factors Influencing the Creep of Dental Amalgam

“…Information relevant to this physical property would be ofvalue in understanding the basic metallurgical and mechanical behavior of amalgam, as well as the relationship of this behavior to clinical performance. Because this paper will frequently refer to the various metallic phases of dental amalgam, these phases and their descriptions appear in Table 1. By measuring the creep ofthe y, y 1, and Y2 phases separately, Espevik (1977) concluded that the creep of amalgam is primarily due to creep of the y I matrix phase. Factors that have been shown to influence creep include final Hg content of the set amalgam (Mahler and Van Eysden, 1969), Sn in the y I phase (Mahler and Adey, 1979), Zn in the y1 phase (Johnson and Paffenbarger, 1980), grain size ofy 1 (Mahleret al, 1977), amount ofthe Y2 phase (Mahler et al, 1977;Osborne and Gale, 1990), and the amount ofthe y phase (Mahler et al, 1977).…”