Reaction of the human dental pulp to silver amalgam restorations. The effect of enclosing amalgam of initially high plasticity in intermediate depth or deep cavities.

From earlier studies using amalgam of known physical and sealing properties it was concluded that the initially high mercury content was the main reason for pulpal changes and that clinical leakage had been less important. The purpose of the present investigation was to study how a possible sealing insufficiency may contribute to the pulpal changes beneath restorations of silver amalgam. The influence of bacteria at the tooth/filling interface upon pulpal changes was also studied. The material consisted of 21 contralateral pairs of premolars. Intermediate depth cavities were prepared in 13 pairs and deep cavities in 8 pairs. All cavities were filled with silver amalgam by the wet technique. The restoration in one tooth of each pair was sealed off by glued metal foil protected by a cemented orthodontic band. After 1 week the teeth were extracted and examined histologically. In the pulp of teeth with restorations exposed to the oral environment, the frequency of dilated capillaries and inflammatory cells in the odontoblast - cell-rich zone boundary, associated with the dentinal tubules involved in the cavity preparation, was insignificantly higher statistically than in those with seal-off restorations. A few scattered bacteria were found on the cavity wall in some cases. It was concluded that, in the short run, the pulp reaction was influenced by sealing insufficiency, which may develop during the experimental period as a result of external factors such as tooth deformation and/or changes in temperature. No influence from bacteria on the cavity wall could be established.