title: Penetration of Streptococcus sobrinus and Streptococcus sanguinis into dental enamel.
abstract: The aim of this pilot study was to assess the difference in virulence of acidogenic and aciduric oral streptococci in an in vitro caries model using their penetration depths into dental enamel. 30 caries-free extracted molars from 11- to 16-year-olds were cleaned ultrasonically for 1 min with de-ionized water and, after air-drying, embedded in epoxy resin. After 8-h of setting at room temperature, the specimens were ground on the buccal side with SiC-paper 1200 (particle size 13-16 μm). Enamel was removed in circular areas sized 3 mm in diameter; the mean depth of removed enamel was 230 ± 60 μm. 15 specimens each were incubated anaerobically under standardized conditions with 24 h-cultures of Streptococcus sanguinis 9S or Streptococcus sobrinus OMZ 176 in Balmelli broth at 37 ± 2 °C; the pH-values of the broths were measured at the beginning and end of each incubation cycle. After 2, 4, 6, 8, and 10 weeks 3 teeth each were fixed in 2.5% glutaraldehyde in cacodylate buffer for 24 h, washed 3× and dehydrated 30-60min by sequential washes through a series of 30-100% graded ethanol. The teeth were cut in half longitudinally; afterward, two slits were made to obtain fracture surfaces in the infected area. After critical-point-drying the fragments were gold-sputtered and viewed in a scanning electron microscope at magnifications of ×20-20,000. After 10 weeks of incubation, penetration of S. sanguinis of 11.13 ± 24.04 μm below the break edges into the enamel was observed. The invasion of S. sobrinus reached depths of 87.53 ± 76.34 μm. The difference was statistically significant (paired t test: p = 0.033). The experimental penetration depths emphasize the importance of S. sanguinis versus S. sobrinus in the context of the extended ecological plaque hypothesis.
authors: Research Laboratory for Dental Materials, Center of Dentistry, University Hospital, Jena, Germany. Electronic address: susanne.kneist@med.uni-jena.de.
authors: Susanne
authors: S
authors: Kneist
authors: Center of Electron Microscopy, University Hospital, Jena, Germany.
authors: Sandor
authors: S
authors: Nietzsche
authors: Research Laboratory for Dental Materials, Center of Dentistry, University Hospital, Jena, Germany.
authors: Harald
authors: H
authors: Küpper
authors: Research Laboratory for Dental Materials, Center of Dentistry, University Hospital, Jena, Germany.
authors: Gerhard
authors: G
authors: Raser
authors: Department of Operative Dentistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
authors: Brita
authors: B
authors: Willershausen
authors: Department of Operative Dentistry, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
authors: Angelika
authors: A
authors: Callaway
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003731:Dental Caries / Q000382:microbiology*; D003743:Dental Enamel / Q000382:microbiology*; D006801:Humans; D010865:Pilot Projects; D013291:Streptococcus / Q000235:genetics / Q000502:physiology*; D016986:Streptococcus sobrinus / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins
keywords: Caries model experiment; Cariogenic bacteria; Human enamel; Penetration depths; Plaque hypotheses