VITAL MICROORGANISMS IN EARLY SUPRAGINGIVAL DENTAL PLAQUE AND IN STIMULATED HUMAN SALIVA

The aim of this study was to compare the percentage of vital microorga nisms (=microbial vitality) of saliva with that of supragingival plaqu e both collected at various times during the early phases of de novo p laque formation. Between intervals of optimal oral hygiene, 14 healthy participants refrained from all oral hygiene measures for periods of 1, 4, 8 and 72 h. Stimulated whole saliva was collected at the beginni ng (= baseline) and the end of each period. Vestibular plaque was remo ved from teeth 13-16, and 23-26. Analysis of the pooled plaque (p) and saliva (s) samples comprised the total number of bacterial counts and colony-forming units to estimate the percentage of viable microorgani sms (PE(p); PE(s)). The microbial vitality (VFp; VFs) was determined b y using a fluorescence staining to differentiate vital from dead bacte rial cells. The bulk of the PE(s) values reached 5-30%. At baseline VF s ranged between 70% and 90%. The VFs values recorded at baseline or i n the presence of Ih and 4 h-old plaque, were significantly (alpha = 0 .05) higher than the corresponding VFp values ranging from 5% to 30%. It was concluded that there is a considerable discrepancy between the microbial vitality of a very early dental plaque and that of whole sur rounding saliva sampled at the same time. Unfavourable local environme ntal conditions prevailing at cervical tooth surfaces are suggested to restrain the survival of the majority of the first bacteria adhering to a particular tooth area during the early phases of supragingival pl aque formation.