歯科用アマルガムにおよぼす繰返し圧縮荷重の影響 (in vitro)

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Marginal deterioration is one of the most serious problems in amalgam restoration. It has been said to be correlated with creep rate with some exceptions through many of laboratory and clinical works. The authors, on the other hand, previously reported that the marginal breakdown of amalgam restorations showed an aspect of intergranular fracture detouring around the residual γ alloy particles, and such a fracture in hardened amalgam could experimentally be confirmed to occur by repeated compressive loading of small stress and not by static loading. In the present study, effects of the repeated compressive loading in air or artificial saliva at 37℃ were examined on creep rate and compressive strength for four different types of commercial amalgams. Accumulative dynamic creep and marginal breakdown by repeated loading were also checked for a six-month period. Considerable degree of the marginal breakdown could be seen in only one week for all the repeatedly loaded specimens, and then it gradually increased with time. Marked marginal deterioration appeared on conventional lathe cut amalgam, Luna Alloy, after six months in artificial saliva. Single composition type of spherical high-copper amalgam, Dialloy, exhibited larger marginal breakdown both in air and artificial saliva than conventional spherical, Hi Atomic M, supplied by the same manufacturer, while admixed type of high-copper amalgam, Dispersalloy, showed the smallest breakdown. Accumulative dynamic creep, which refers to the accumulated deformation of the amalgam specimen by the repeated loading during ageing, reached almost the maximum value in one week and exhibited no significant changes with time after that period in air. Compressive strength also much increased by repeated compressive loading. On the contrary, static creep for the specimen after repeatedly loaded became significantly smaller than that for the specimen aged without any loading for the same period, except for Luna Alloy which showed the largest marginal breakdown. Such changes in creep and compressive strength might mainly be due to the reduction of the internal porosity of amalgam specimen by repeated compressive loading. No differences could be found statistically in compressive strength or static creep between the specimens in air and those in artificial saliva. Accumulative dynamic creep, however, increased with time in artificial saliva with significant difference from that in air, showing a quite similar tendency to the increase of marginal breakdown for each amalgam in artificial saliva. These deteriorations seemed to be attributed to the stress corrosion induced by the repeated compressive loading for a long time in artificial saliva.
九州歯科学会の論文
1983-02-25

歯科用アマルガムにおよぼす繰返し圧縮荷重の影響 (in vitro)

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