Bacterial Arrangement on the Teeth

Dental caries and periodontal disease are closely associated with the oral biofilm known as dental plaque. Much is known about the makeup of this biofilm, especially at its early stage of development (i.e. up to 12 hrs following tooth cleaning). The primary initial colonizers are streptococci, and actinomyces. These bacteria coaggregate frequently with one another by a mechanism that involves binding of protein adhesins on the surface of one cell to complementary cell surface receptor polysaccharides (RPS) on streptococci.

Coaggregation profiles are known for a wide range of oral actinomyces and streptococci. However, despite the potential significance of these interactions in biofilm formation, little is known about their occurrence within oral biofilms in situ.

Objective

The objective of this study is to determine and compare the influence of coaggregation on the spatial organization of bacteria in supragingival dental plaque formed under conditions of normal salivary flow (Arm 1 of the protocol) or increased salivary flow (Arm 2 of the protocol).

Study Population

The study population will consist of up to twenty-five (25) healthy adult subjects 18 years of age and older. All subjects will participate in Arm 1 of the protocol. In addition, at least three volunteers from Arm 1 will participate in Arm 2 of the protocol.

Study Design

This will be an observational, longitudinal protocol to determine the spatial organization of bacteria found within dental plaque of normal healthy subjects. Enrolled subjects will have a standard oral examination (including oral cancer screening) performed in the NIDCR clinic by protocol-listed dental clinicians. A mandibular stent will be custom fabricated based on impressions taken during the exam. Enamel chips cut from previously extracted third molars will be sterilized by ethylene oxide then inserted into the stent on each side over the molar area. We currently have enough extracted third molars in storage to accommodate tooth chips for the entire protocol if four subjects complete the study as projected. If additional chips are needed, the NIDCR is currently in the process of preparing a protocol that will provide extracted teeth, if needed, for this and other protocols. In Arm 1 of the study, a custom-fitted stent will be worn in the mouth of each subject, and chips removed for analysis after 4 or 8 hours of wearing. The bacterial biofilm on the chips will be stained with fluorescent antibodies against specific microbial adhesins or receptors, after which the spatial organization of labeled cells within the biofilm will be documented by laser confocal microscopy. Chips may be used for bacterial isolation and subjects will be asked to provide saliva samples, and site-specific plaque samples (curette scrapings, gum swabs) for molecular taxonomic analysis. Decisions on which subjects will have these samples taken will be based on the reactivity of available antibodies with bacterial communities. Subjects from Arm 1 of the study who are chosen to participate in Arm 2, will chew a gum base for 10 minutes to increase salivary flow while wearing their stent. The stent from these individuals will be removed after 4 hours of additional wear and analyzed as above. Prior to participation in Arm 2 of the protocol, subjects will be advised that the experiments are supported by a CRADA agreement. Through this agreement, only coded research information will be exchanged. The samples will remain with the NIH research team. Individuals may participate in the first arm only, or in both arms of the study, as indicated in their consent document.

Outcome Measures

Outcome measures for this protocol will be the qualitative and quantitative description of the oral bacterial community during development of initial plaque.