MICROBIAL GENERATION TIME DURING THE EARLY PHASES OF SUPRAGINGIVAL DENTAL PLAQUE-FORMATION

The objective of this investigation was to determine the microbial gen eration time during early human supragingival plaque formation. On 2 o ccasions, 13 participants refrained from all oral hygiene measures for periods of 1, 2, 4, 8, 24 and 72 h. Plaque was sampled from defined a reas of the teeth 13, 14, 15, 23, 24 and 25. Two independent methods w ere used to estimate the total number of viable cells: colony-forming units BCVF, total bacterial counts (BC) as enumerated by microscopic e xamination, and the percentage of vital bacteria using a vital fluores cence technique (VF) were recorded. The total number of vital microorg anisms was calculated by BCVF (= BCxVF). The generation time based on either colony-forming units or BCVF increased significantly with plaqu e age. During the first interval (1-4 h), the microbial multiplication took slightly less than 1 h. After the establishment of a more mature plaque (24-72 h), the replicating time was between 12.5 h (BCVF) and 14.8 h (colony-forming units). It was concluded that the microbial gen eration time recorded at the initial stages of plaque formation is con siderably lower than that found in older plaque.