Three common oral bacteria, namely Streptococcus sanguis, Actinomyces viscosus and Corynebacterium spp. were studied with regard to their ability to penetrate etched and unetched dentine and for their effect on underlying cell cultures. The test organisms were grown in cylinders above dentine slices 100 and 500 microns thick for 72 hours. The slices were in contact with tissue culture medium covering a layer of fibroblasts. Penetration of 100 microns slices was most rapid with S. sanguis, followed by A. viscosus and Corynebacterium. The pattern was similar but slightly delayed when 500 microns slices were used, but in most cases penetration had occurred by 72 hours. The presence of a smear layer had no effect on the results obtained. Following penetration, cell destruction was most extensive with S. sanguis, the most cytotoxic organism, followed by Corynebacterium and A. viscosus. In the limited number of dishes where no penetration occurred there was little effect on cell numbers.

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Abstract. This study investigated the fluoride release from three glass ionomer cements, ASPA, ChemFil and ChemBond, and a fluoride‐enriched polycarboxylate cement, Poly‐F Plus, using a simulated model cavity system. ChemFil released considerably more fluoride than the other materials at all the time intervals investigated. The release from ASPA was greater than that for either ChemBond or Poly‐F Plus. Release from ChemFil and ASPA was of a similar order to a silicate cement investigated previously and it is expected that this release should confer some protection against secondary caries.

A new in vitro method for assessing the antibacterial properties of dental restorative materials is described with ratios of test material/culture medium volume aiming to simulate conditions around a restoration in vivo. Antibacterial activity is determined by the reduction in optical density of the test culture relative to controls. The method was used for assessment of the antibacterial activity of five dental materials of different composition against five oral bacteria. Release of zinc and fluoride from these materials was also measured and correlated with antibacterial activity. There was a general trend toward greater antibacterial activity with increased zinc release, while fluoride release had a significant effect on only one organism. While all the materials, when freshly mixed, were strongly toxic to three out of the five bacteria studied, much of this activity was lost after the materials had set.