title: Plaque pH in caries-free and caries-active young individuals before and after frequent rinses with sucrose and urea solution.
abstract: OBJECTIVE
  To examine pH in the approximal dental biofilm after acid and alkali formation from sucrose and urea, after an adaptation period to these substances, in caries-free (CF) and caries-active (CA) individuals. Saliva flow and buffer capacity, and aciduric bacteria in saliva and plaque were also examined.
  
  
  METHODS
  Twenty adolescents and young adults (15-21 years) with no caries (n = 10, D(m + i)MFS = 0) or ≥1 new manifest lesions/year (n = 10, DmMFS = 3.4 ± 1.8) participated. After plaque sampling, interproximal plaque pH was measured using the strip method before (baseline) and up to 30 min (final pH) after random distribution of a 1-min rinse with 10 ml of 10% sucrose or 0.25% urea. This procedure was repeated after a 1-week adaptation period of rinsing 5 times/day with 10 ml of the selected solution. After a 2-week washout period the second solution was similarly tested. Mutans streptococci, lactobacilli and pH 5.2-tolerant bacteria were analyzed by culturing.
  
  
  RESULTS
  In the CF group, acid adaptation resulted in lowering of baseline and final plaque pH values after a sugar challenge, and in increased numbers of bacteria growing at pH 5.2, which was increased also after alkali adaptation. In the CA group, the final pH was decreased after acid adaptation. No clear effects of alkali adaptation were seen in this group.
  
  
  CONCLUSIONS
  One-week daily rinses with sucrose and urea had the most pronounced effect on the CF group, resulting in increased plaque acidogenicity from the sugar rinses and increased number of acid-tolerant plaque bacteria from both rinses.
authors.affiliation: Department of Oral Microbiology and Immunology, Institute of Odontology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Haidar
authors.initials: H
authors.lastname: Hassan
authors.forename: Peter
authors.initials: P
authors.lastname: Lingström
authors.forename: Anette
authors.initials: A
authors.lastname: Carlén
mesh_terms: D000143:Acids; D000293:Adolescent; D000468:Alkalies; D058491:Bacterial Load; D018441:Biofilms / Q000187:drug effects; D002021:Buffers; D004245:DMF Index; D003731:Dental Caries / Q000382:microbiology / Q000503:physiopathology*; D003773:Dental Plaque / Q000382:microbiology / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000302:isolation & purification; D008297:Male; D009067:Mouthwashes / Q000494:pharmacology*; D012463:Saliva / Q000378:metabolism; D012636:Secretory Rate / Q000502:physiology; D016037:Single-Blind Method; D013295:Streptococcus mutans / Q000302:isolation & purification; D013395:Sucrose / Q000494:pharmacology*; D013549:Sweetening Agents / Q000494:pharmacology*; D014508:Urea / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D000143:Acids; D000468:Alkalies; D002021:Buffers; D009067:Mouthwashes; D013549:Sweetening Agents; D013395:Sucrose; D014508:Urea