The influence of polishing on the marginal integrity of amalgam restorations

The influence of the polishing procedure on the marginal integrity of amalgam restorations was investigated in a clinical study. In this study two operators each made 150 class I or II restorations in a group of forty-eight adult patients. The restorations were made in a series of six per patient. Within each series, two restorations were made of three different high copper amalgam alloys. Only one restoration of each pair was polished. From each restoration a black and white photograph was taken after finishing and after 0.5, 1.0 and 1.5 years. The marginal integrity of each restoration at the four time periods was quantified with a 6-point photo rating scale. The quantifications were analysed as to their variance for the factors alloy, polishing procedure, operator and patient. After finishing, all four factors had a significant influence on the marginal integrity. From 0.5 to 1.5 years, the influence of the factors alloy, polishing procedure and patient were very significant. The influence of the patient on marginal integrity was more or less equal to that of the alloy. The size of the polish influence was relatively small. Therefore, it was concluded that the contribution of the polishing procedure to the prevention of marginal deterioration was questionable.