The purpose of this study was to examine histologically occlusal amalgam restorations with both defective and sound margins for comparison of their caries status. Thirty extracted teeth with occlusal amalgam restorations were sectioned so that a ditched and a clinically sound margin could be examined on the same tooth in the mouth. Histological examination showed a low prevalence of caries lesions in the outer enamel. However, lesions were present in the enamel of the cavity wall in 54% of specimens, whether the margin was defective or sound. If the results of this study are applicable to all occlusal amalgams with defective margins, it would appear that a defective margin alone is not an indication that a restoration needs to be replaced.
The clinical marginal fracture characteristics of three commercial dental amalgams were evaluated and compared with a number of their mechanical properties to determine which properties would relate best to clinical performance. It was found that compressive strength, tensile strength, transverse strength, transverse deflection, and flow as determined by ADA Specification No. 1 were ineffective, whereas the rheological properties of dynamic creep, static creep, and slow compressive strength appeared effective in relating to marginal fracture.
Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights.