Early formation of dental plaque on plastic films

This study was designed to gain further information on early plaque formation using a previously described method employing plastic films for the collection of the initial deposits. To prevent the loss of loosely adhering material during processing of dental plaque for microscopic observation, the method was further developed by introducing an agar protection of the deposits formed on plastic films prior to fixation, dehydration and embedding procedures. Four human subjects with healthy gingiva developed microbial plaque during periods of 4 and 8 hours on plastic films applied on the buccal surfaces of premolars and cuspids. After 4 hours the plastic films were covered by a surface coating of an acellular material in or on which bacteria, epithelial cells and leukocytes were observed. The microorganisms were almost exclusively identified as Gram‐positive cocci. The deposit in the 8 hour samples exhibited the same general morphology, but with more cellular components. Bacterial aggregation to each other or to epithelial cells was frequently mediated by filamentous appendages on the bacterial cell walls. The frequent observation of a close association between bacteria and epithelial cells suggests that the latter may play an important role as a vehicle for transporting microorganisms to the solid surfaces in the mouth in the initial stage of plaque formation.