Bacteriological studies of developing supragingival dental plaque

Abstract

The predominant flora of plaque developing on an area of about 1 sq cm. on the middle third of the buccal surface of the upper first molar of one individual was studied. Samples were taken at 5 and 15 min, 1, 2, 4 and 8 hr, and 1, 2, 4, 8 and 16 days; the tooth surface was cleaned prior to each period. Plaque samples were handled and cultured under anaerobic conditions utilizing various growth media. AH isolates from blood agar plates in Brewer jars with 30 to 100 colonies were characterized. Streptococcus sanguis, the single‐most predominant organism, and Actinomyces viscosus were consistently found. Streptococcus mitis, Staphylococcus epidermidis, Actinomyces israelii, Peptostreptococcus sp. and Veillonella alcalescens were found at more than one time period. High proportions of “suspected pairs” (mixtures of 2 or more intimately‐associated organisms), were regularly detected. Bacterial population changes with time were observed. Many isolates, particularly those present in plaques up to 8 hr, agglutinated in the presence of saliva. Less than half of the isolates, including Gram‐positive saccharolytic rods, staphylococci and some S. sanguis strains, formed plaque in vitro on wires in the presence of sucrose or glucose. The data suggest that the nature of the early microflora observed is determined by bacterial attachment which may be influenced by, amongst others, salivary constituents. Subsequent cell multiplication leads to a large bacterial increase in which proportional changes may occur as a result of differences in bacterial growth.