showed that dex tranase produced by a culture of Penicillium funiculosum was able to remove plaques grown in vitro. These plaques were products of cariogenic streptococci in su crose containing broths. Later the same investigators working with Keyes 2 showed that dextranase reduced plaque formation and retarded caries development in albino hamsters previously infected with cariogenic organisms. Smooth surface lesions in the third molars did not form when administration of dextranase was begun prior to the eruption of this tooth.The present communication is concerned with the capacity of dextranase to prevent smooth surface caries completely in all molar teeth of golden hamsters fed a test diet containing 56% sucrose. The formation of plaque in the gingival sulcus and the development of periodontal pathosis was greatly reduced during the test period. Also a curative experiment is described in which dextranase removed preformed plaque in hamsters after 2 days of treatment.

The antimicrobial and cariostatic activities of the dihydrochloride and dihydrofluoride salts of alexidine (1,6-bis-[2-ethylhexylbiguanido]hexane) were compared to those of chlorhexidine acetate and sodium fluoride in rats implanted orally with Streptococcus mutans 6715 and fed a cariogenic diet. Experimental caries was significantly reduced by the continuous administration of low concentrations of biguanides via the drinking water, but this was accompanied by increased staining of the molars. Very high biguanide concentrations, applied infrequently, directly to the molars, effectively reduced caries and resulted in less staining. A combination of alexidine dihydrochloride and sodium fluoride offered no advantage over either drug alone. Alexidine salts prevented the progressive increase in implanted S. mutans, whereas chlorhexidine acetate practically eliminated the micro-organism from the oral cavity. Sodium fluoride had no effect on the implanted flora. It was concluded that alexidine salts are comparable in cariostatic activity to chlorhexidine. The tooth staining accompanying the use of bisbiguanides can be reduced by adjusting the concentration of the drug and its frequency of application.