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The in vitro susceptibility of 128 bacterial strains was tested to amine fluoridestannous fluoride (AmF+SnF) and chlorhexidine (CHX) solutions, Actinobacillus actinomycetemcomitans, Streptococcus mutans, and Bacteroides intermedius were among the species investigated. The 50% and 90% minimal inhibitory concentrations (MICs) were assessed by an agar dilution method. The MIC ranges for A. actinomycetemcomitans were 2-32 μg/ml for CHX and 0.25-64 μg/ml for AmF + SnF. The respective values for S. mutans were 0.5-8 μg/ml (CHX) and 2-8 μg/ml (AmF+ SnF); and 4-8 μg/ml (CHX) and 2-4 μg/ml (AmF+SnF) for B. intermedius. Streptococcus faecalis and Staphylococcus aureus were most resistant of the control strains (MIC 64 μg/ml to CHX and 32 μg/ml to AmF+SnF, respectively) Thus, both solutions tested exerted a definite inhibitory action on the dental plaque pathogens studied. [ABSTRACT FROM AUTHOR]

Extracted third molars were used to study the effect of Nd:YAG laser irradiation combined with CO2 laser beam on dental hard tissues. The specimens were studied with SEM after lasing and the size of the impact areas and beam penetration into enamel and dentin were planimetrically analyzed. High-energy CO2 laser (e.g. 10 s irradiation with 10 W output energy) penetrated all enamel and dentin. The simultaneous addition of Nd:YAG irradiation to the CO2 beam was found to increase the effect of CO2 laser, while Nd:YAG irradiation alone, used with equivalent energy densities, did not cause any effect on enamel surface. Thus, Nd:YAG laser was found to potentiate statistically significantly the effect of CO2 irradiation, but the morphologic alterations on dental hard tissues, such as crater formation at the beam focus site, appeared to be due to CO2 irradiation alone. [ABSTRACT FROM AUTHOR]

The effects of new experimental sports drinks on dental enamel were studied in vitro using bovine tooth specimens. Profilometric analysis was used to measure the loss of tooth material after immersion of the specimens in the drinks. Thereafter the specimens' surface hardness was measured and scanning electron microphotographs were taken. In addition, 13 commercial sports drinks and experimental drinks containing either citric acid, or malic acid were tested for their capacity to dissolve hydroxyapatite in vitro. The erosive effect increased markedly with decreasing pH. The citric acid containing drinks were more erosive than malic acid containing drinks. No erosion was observed with the malic acid containing drink (pH 5.90) but the drink of similar composition containing citric acid caused an erosion 1.3 ± 1.1μm deep and a commercial citric acid containing drink caused a lesion 12.3 ± 4.5 μm deep after 120 min immersion. Softening of enamel was greater in specimens immersed in citric acid than in those immersed in malic acid containing drink. The in vitro hydroxyapatite dissolving effect of the commercial sports drink samples studied (all having a pH under 4.22) was markedly greater (0.48-4.38. mmol/l) than that of the malic acid containing experimental drink (pH 5.50, Ca++ concentration in the supernatant 0.19 mmol/l) and of the similar citric acid containing drink (0.35 mmol/l). The hydroxyapatite dissolving effect of both drinks started to be marked at a pH level of about 5.0 but increased thereafter exponentially with decreasing pH. At pH levels above 4.0 the hydroxyapatite dissolving effect of citric acid containing drinks was greater than that of malic acid containing drinks. [ABSTRACT FROM AUTHOR]