Histopathology of Natural Caries around Silver Amalgam Fillings

Abstract

The histopathology of natural secondary caries associated with silver amalgam fillings was studied and compared with the histopathology of experimental in vitro and in vivo secondary caries described in previous publications. The material consisted of 49 extracted human permanent teeth with a total of 55 silver amalgam, mostly class V, fillings. On macroscopical examination, about 75% of the teeth showed initial secondary caries, whilst 25% revealed no change of the tooth surface adjacent to the filling. The teeth were cut into longitudinal sections, 60–120 µm thick, which were examined by polarized light and microradiography. Because every complete section included an occlusal/incisal and a cervical cavity wall with an adjacent area of the tooth surface, it offered two ‘secondary caries risks’ for histological examination. However, the original number of risks was somewhat reduced during processing of sections. In principle, the histopathology of the lesions corresponded closely to that of the experimental secondary caries, but certain differences are described. In the enamel the frequency of outer lesions was 79.5%, in the cementum 90.9%. The frequency of cavity wall lesions in enamel and dentine/cementum was 69.5 and 86.7%, respectively. Outer lesions associated with a wall lesion were almost three times more frequent than outer lesions without a wall lesion. Increased radiopacity of the dentinal wall occurred in 27.8% of the risks, whilst no such change could be registered in the enamel walls. In the 21 risks of the group that had shown little or no macroscopical lesions, the microscopical changes were surprisingly frequent.