Dentinal and pulpal uptake of mercury from lined and unlined amalgam restorations in minipigs

The aim of the present investigation was to examine dentin and pulp in amalgam-restored teeth in minipigs with respect to presence of mercury, and to evaluate whether lining of restored cavities with a resin-modified glass ionomer cement had any effect on the penetration of mercury. Class I and V cavities were cut in 49 posterior and canine teeth of 4 minipigs. 35 cavities were restored with amalgam and 14 with composite material. 26 of the amalgam cavities were lined with a resin-modified glass ionomer cement. Following observation periods of 17-28 months, the pigs were killed and the jaws sectioned. After decalcification, the teeth were processed for light or electron microscopy examinations. Mercury was visualized by autometallography. Silver-enhanced mercury was found in all teeth with amalgam, whereas teeth with composites were devoid of mercury. Mercury could be traced in the odontoblast processes, in the body of odontoblasts, and on rare occasions in the nerve tissue of the pulp from lined and from unlined amalgam restorations. The present study thus demonstrates transport of mercury through dentinal tubules to the pulp, and that lining of cavities with a resin-modified glass ionomer cement does not prevent penetration of mercury.