Jokstad A
Department of Anatomy, School of Dentistry, University of Oslo, Norway.
Acta Odontol Scand. 1991 Apr;49(2):65-71. doi: 10.3109/00016359109005888.
In a 5-year clinical trial it was observed that the marginal degradation of class-II amalgam restorations could be related to the bulk of the restoration. The association between the occlusal cavity depth and the marginal degradation was observed after 6 months and varied for the different types of alloy. Ridit scores of the marginal degradation were correlated to various indices of the cavity sizes, to assess the possible reason for this association. The possibilities of the relationship being an indirect effect caused by longer condensation times or by poorer condensation due to the use of larger condenser sizes were rejected. Furthermore, the possibility that the association was the result of potential buildup of stresses on the restoration margins caused by flexible cusps and axial walls was not apparent. A possible mechanism may be that marginal degradation is the result of short-term or long-term expansion, or even extrusion of amalgam. Expansion may theoretically be caused over short periods by temperature changes or over long periods by corrosion or phase shifts in the amalgam. The theory does not exclude the role of creep or corrosion and may furthermore explain the lack of correlation between in-vitro tests and in-vivo performance of amalgam restorations.
在一项为期5年的临床试验中观察到，Ⅱ类汞合金修复体的边缘降解可能与修复体的体积有关。6个月后观察到咬合洞深度与边缘降解之间的关联，且不同类型的合金有所不同。边缘降解的Ridit评分与洞大小的各种指数相关，以评估这种关联的可能原因。冷凝时间较长或因使用较大尺寸的冷凝器导致冷凝较差所引起的间接影响这种关系的可能性被排除。此外，由灵活的牙尖和轴壁在修复体边缘上引起的应力潜在积累导致这种关联的可能性并不明显。一种可能的机制可能是边缘降解是汞合金短期或长期膨胀甚至挤出的结果。理论上，膨胀可能在短期内由温度变化引起，或在长期内由汞合金的腐蚀或相转变引起。该理论并不排除蠕变或腐蚀的作用，并且还可以解释汞合金修复体的体外测试与体内性能之间缺乏相关性的原因。
