It has been claimed that eugenol has a detrimental effect on resin composites and dentin bonding systems. The aim of the present study was to examine whether zinc oxide-eugenol (ZOE) cement would reduce the efficacy of a bonding system. Human third molars were selected for the study, and cylindrical posts of a resin composite (Z100) were bonded vertically to a standardized flat dentinal surface, prepared on the buccal surface of the teeth and treated with Scotchbond Multi-Purpose. The tooth surfaces involved were either freshly cut, or had been exposed to ZOE cement for 6 days, with and without a subsequent thorough cleansing with ethanol. The bond strength in shear was measured after 24 hours. The results showed that ZOE cement had no negative effect on the bond strength of the resin composite (Z100) to dentin when this bonding system was used. The mean shear bond value for the specimens covered with ZOE cement for 6 days was 28.1 MPa. For specimens covered with ZOE cement and cleansed with 96% ethanol, the mean shear bond value was 23.5 MPa. The corresponding value for the controls was 19.0 MPa. These findings suggested that eugenol-containing temporary filling materials may be used safely prior to inserting resin based restorative materials, when Scotchbond Multi-Purpose is employed as the bonding agent.

– Silver and copper amalgams show a pronounced cytotoxic effect on monolayer cultures of human epithelial cells (NCTG 2544). Analyses of the medium from silver amalgam cultures showed that, zinc was released in substantial amounts (14 μg/ml after incubation for 24 h). Small amounts of mercury and possibly also some silver were released, whereas release of copper and tin could not be. detected. Toxicity tests showed that 10 μg Zn2+/ml reduced the number of cells by 96% after incubation for 24 h. In the copper amalgam cultures about. 100 μg copper and 5 μg, cadmium per ml medium were found after 24 h. Only small amounts of mercury were released, Toxicity tests showed an increasing effect of Cu2+ and Cd2+ with tune. With 50 μg Cu2+/ml the number of cells was reduced by 73% after incubation for 24 h, and after 3 d a similar effect was found with 25 μg/ml. With 10 μg Cd2+/ml no cells were left after 24 h, whereas after 3 d 1μg/ml reduced cell growth by more than 80 %.

– An in vitro method was used to investigate the ability of animal cells to (a) grow in the proximity of various dental materials, (b) adhere to and grow on the surface of the same materials during long‐term contact. Disks (30 × 1 mm), made from the different materials, were placed in the center of plastic Petri dishes and incubated with human epithelial cells (NCTC 2544) and mouse fibroblasts (L 929). The growth around and on the surface of the disks was followed by measuring the amount of deoxyribonucleic acid (DNA) and/or cell number. The cultures were stained with crystal violet to visualize the distribution of the cells. In the presence of gold alloy, growth was similar to that obtained in control cultures, whereas the other materials tested showed various degrees of a toxic effect. With the two heat‐cured acrylics tested, a transient toxic effect was observed on the surface of the disks. In the presence of silicate cement, various degrees of growth inhibition were observed, both on the surface of and around the disks. A toxic effect of silver amalgam was evident on the surface of and in the close proximity of the disks, whereas Addent 12® and copper amalgam appeared to have a general toxic effect. The present method might thus be of value in the evaluation of the tissue compatibility of biomaterials.

To investigate the mechanism for the toxicity of silicate cement as observed in a cell culture system, the effects of pH and fluoride were tested on human epithelial cells (NCTG 2544). At pH 7.3, fluoride concentrations from 15 to 25 [xg/ml (0.79 to 1.3 mM) had a growth inhibitory effect. When pH of the incubation medium was lowered in the range 7.0 to 6.4, an enhanced cytotoxic effect of fluoride was found, and even at 5 to 10 |xg'ml growth inhibition occurred. Concomitant with the enhanced cytotoxicity of fluoride at low pH, there was an increased utilization of glucose and formation of lactate. Upon lowering the pH of the incubation medium from 7.4 to 6.7 a twofold increase in the intracellular concentration of fluoride was found. Previously, we have described the growth inhibitory effect of silicate cement in a cell culture system (HELGELAND & LEIRSKAR 1972), During incubation, zinc, silicon, fluoride and phosphate were released from the silicate cement disks (HELGELAND & LEIRSKAR 1973), pH decreased and magnesium and calcium were adsorbed from the medium.In the present experiments the importance of acidification and the release of fluoride for the observed cytotoxicity of silicate cement was studied. The effects of fluoride and pH on glucose metabolism, growth and morphology of human epithelial cells in culture were tested separately and in combination. Also, the influence of pH on the cellular uptake of fluoride was measured. Material and methods CELL CULTURE PROCEDURES

abstract— Human epithelial cells (NCTG 2544) were grown as monolayer cultures in the presence of silicate cement disks (Bio‐trey 9®). A cytotoxic effect was found on the surface of the disks after 24 h, whereas a corresponding effect was obvious around the disks after incubation for 3 d. In the silicate cement cultures more glucose was utilized and more lactate formed per cell than in control cultures. In the presence of silicate cement, pH of the culture medium decreased during incubation, reaching 6.3–6.4 after 6 d. Phosphate, silicon, zinc, and fluoride were released into the medium from the silicate cement disks. The medium concentration of sodium, however, remained constant, and aluminum was not detected. The concentrations of calcium and magnesium decreased, and experiments with 45Ca showed that calcium was bound to the silicate cement disks.