Study of the Composition of Dental Plaque
Condition: Dental Caries; Dental Plaque; Periodontal Disease
MeSH terms: Dental Caries; Periodontal Diseases; Dental Plaque
Study type: Observational

Summary: 
      This study will examine the composition of dental plaque-a naturally occurring substance that
      sticks to the teeth and can cause tooth decay and gum disease. A better understanding of how
      plaque builds up in the mouth may help in developing improved ways of controlling it.

      Healthy normal volunteers between the ages of 18 and 65 who work at the National Institutes
      of Health main campus in Bethesda, Maryland, may participate in this study. Candidates will
      be screened for eligibility with a medical and dental history.

      This study involves a maximum of five visits to the dental clinic. At the first visit,
      participants will have a dental examination, and a mold will be made of the mouth. To make
      the mold, a small plastic tray containing impression material will be placed in the
      volunteer's mouth and held in place for about 2 minutes to set. The tray will then be removed
      and a mold will be made from the impression. The mold will be used to make the mouthpiece
      used in study 1, described below, and the tooth fittings used in study 2, also described
      below. Volunteers will participate in one of these two studies.

      Study 1. Volunteers in study 1 will have their mouthpiece checked at the second visit, have a
      teeth cleaning, and have the mold put in place. The mouthpiece will be worn for up to 8
      hours, during which time soft foods can be eaten. Mouthwash should not be used while the
      device is in place. At the volunteer's third (last) visit, the mouthpiece will be removed and
      the volunteer will spit into a tube to collect saliva for examination for bacteria.

      Study 2. Volunteers in study 2 will have their teeth cleaned at the second visit and the
      tooth fittings placed onto the back teeth with a dental adhesive. The fittings will be worn
      for up to 72 hours, during which time volunteers can eat a regular diet and brush their
      teeth. Mouthwash should not be used while the fittings are in place. At the third, fourth and
      fifth visits, some of the fittings will be removed and, if necessary, the tooth surface will
      be polished. The last of the fittings will be removed at the fifth visit and the volunteer
      will spit into a tube to collect saliva for examination for bacteria.
    

Detailed description: 
      Dental caries and periodontal disease are closely associated with dental plaque, the biofilm
      that results from microbial colonization of the tooth surface. Various experimental models
      have been described for the initial phase of colonization, including one that utilizes enamel
      chips positioned within the oral cavity for periods of time up to 24 hours. Scanning electron
      microscopy of chips removed after 4 hrs in vivo revealed individual bacteria attached to the
      pellicle-coated surface. Growth of these pioneer organisms resulted in microcolonies that
      merged to form a spreading monolayer of cocci and rods. Over 80% of the bacteria present in
      early biofilms were identified as members of four closely related viridans streptococcal
      species, Streptococcus sanguis, S. oralis, S. mitis and S. gordonii. Veillonella spp, and
      Actinomyces naeslundii each composed about 5%. Interestingly, veillonellae, actinomyces and
      streptococci all increased during the first 24 hrs of colonization thereby suggesting
      important roles for these bacteria in normal daily plaque accumulation [early biofilm
      development].

      One of the major uncertainties raised by the wide-spread ability of cells of oral bacteria to
      interact physically in vitro is whether these coaggregations function in vivo. Using direct
      immunofluorescence, we have demonstrated the coincident juxtaposition in dental plaque of
      streptococci and actinomyces, suggesting that these known coaggregating partners may use
      coaggregation as a means to colonize enamel. Our overall goal is to determine spatial
      organization of different viridans streptococci in biofilms that form during initial
      colonization of the tooth surface. These bacteria include two groups with distinctive
      properties. One group contains strains of S. sanguis and S. gordonii with GalNAc-sensitive
      adhesions and the other contains strains of S. oralis and other species with complementary
      receptors for intrageneric coaggregation. The models for biofilm formation will include an in
      vitro flow-cell model in which streptococci with known adhesive properties attach and grow on
      a saliva-coated surface and an in vivo model in which enamel chips are colonized within the
      oral cavity for periods of time up to 72 hours. The results of these studies should provide
      significant insights into the involvement of interbacterial adhesion in biofilm development.
      Our goal from these studies is to investigate the spatial organization of streptococci and
      their coaggregation partner actinomyces and veillonellae in biofilms formed in vivo compared
      to in vitro. We hope to make significant advances in understanding the distribution of these
      species in initial dental plaque formation. Since the streptococci are the predominant
      organism in early dental plaque, we propose that understanding their contribution to
      microbial communities will lead to important advances in designing effective oral health
      regimens.
    

Keywords: Bacterial Colonization; Plaque; Mouth; Saliva; Adhesion; Dental Plaque Formation; Dental Caries