EFFECT OF CHLORHEXIDINE VARNISH ON STREPTOCOCCI IN DENTAL PLAQUE FROMOCCLUSAL FISSURES

The treatment of tooth surfaces with chlorhexidine varnish may to long lasting suppression of mutans streptococci in dental plaque. Microbiol ogical observations following varnish treatment suggest that this prol onged suppression might be caused by bacterial interference. To invest igate whether physiologically related organisms, such as other Strepto coccus species, compete with mutans streptococci in the ecosystem, we have analyzed streptococcal populations on the tooth surface before an d after chlorhexidine varnish treatment. Occlusal surfaces with high n umbers of mutans streptococci were selected in human volunteers and tr eated with chlorhexidine varnish. Analyses of sequentially collected p laque samples confirmed that S. oralis-group streptococci returned to baseline levels shortly after the chlorhexidine application, while Act inomyces naeslundii populations reached prestudy or even higher levels only several days after treatment. Mutans streptococci, however, were below the detection level in the 14-day samples, except in 1 individu al. The pattern of recolonization by individual Streptococcus species after chlorhexidine application closely resembled that of cleaned enam el surfaces: S. oralis and S. sanguis were primary colonizers while S. gordonii became dominant at a later stage. It is concluded that after intensive chlorhexidine treatment, a normal oral microflora reestabli shed, characterized by low proportions of mutans streptococci.