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Effects of Salivary Bicarbonate Content and Film Velocity on pH Changes in an Artificial Plaque Containing Streptococcus oralis, After Exposure to Sucrose

Department of Oral Biology, Faculty of Dentistry, University of Manitoba, 780 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E OW2

W.-Y. Chen

Department of Oral Biology, Faculty of Dentistry, University of Manitoba, 780 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E OW2

C. Dawes

Department of Oral Biology, Faculty of Dentistry, University of Manitoba, 780 Bannatyne Avenue, Winnipeg, Manitoba, Canada R3E OW2

Chewing-gum stimulation of salivary flow (at the time of the pH minimum following exposure of plaque to carbohydrate) has been shown to cause a rapid increase in plaque pH. The objective of this study was to determine whether the rise in plaque pH is primarily due to the increased buffering capacity of stimulated saliva, or to the fact that an increased flow rate increases the concentration gradient for acid to diffuse from the plaque into the overlying salivary film, which will be moving at a higher velocity. This was investigated with an in vitro technique in which artificial plaque (0.5 or 1.5 mm deep) containing S. oralis cells was exposed to 10% sucrose for one min. The pH values at the proximal and distal undersurfaces of the plaque were then monitored during the passage of a 0.1-mm-thick film of a sucrose-free artificial saliva over the surface, at a range of film velocities (0.8-8 mm/min) that have been estimated to occur in vivo. When a minimum plaque pH had been achieved, the salivary film velocity was either (a) kept the same, with or without 15 mmol/L HC03 (the concentration measured in chewing-gum-stimulated saliva), (b) increased to 86.2 mm/min, or (c) increased to 86.2 mm/min with 15 mmol/L HC03 added to the artificial saliva. The findings suggest that after sucrose ingestion, the rapid rise from minimum plaque pH values, which can occur with gum-chewing stimulation of salivary flow, is due to the combined effects of the increase in salivary film velocity, and of a greater availability of bicarbonate. The former appeared to be more important in the thinner plaque (0.5 mm deep) than in the thicker one (1.5 mm deep).

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Journal of Dental Research, Vol. 70, No. 9, 1235-1238 (1991)
DOI: 10.1177/00220345910700090201


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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Macpherson, L.M.D. Articles by Dawes, C. Search for Related Content PubMed PubMed Citation Articles by Macpherson, L.M.D. Articles by Dawes, C. Social Bookmarking                         What's this?