Chemostat flow cell system: an in vitro model for the evaluation of antiplaque agents.

We developed an experimental in vitro model of dental plaque to assess the potential efficacy of antiplaque agents. The model used a chemostat, which provided a continuous source of 5 species of oral bacteria grown in an artificial "saliva-like" medium. This mixture was pumped through six flow cells, each containing two types of surfaces on which plaque formed and was subsequently measured. Formation of bacterial plaque on hydroxyapatite surfaces was assessed by measurement of the DNA and protein content of the plaque film. The amount of bacterial plaque formed on germanium surfaces was measured by attenuated total reflectance (ATR/FT-IR) spectroscopy. Plaque viability was also assessed by a fluorescent staining technique. The quantity of plaque formed on both types of surfaces gradually increased with the duration of flow (from 24 to 72 h) through the cells during a 72-hour experimental period. The flow cells were then pulsed with experimental treatment solutions for 30 s, twice daily. Parallel to results of human clinical studies, the model was capable of discriminating among water, a placebo mouthrinse, and an active antimicrobial mouthrinse formulation containing 0.03% triclosan. It therefore offers a valuable alternative to animal model testing and allows for more rapid evaluations under well-controlled experimental conditions.

Recent advances in plaque, gingivitis, tartar and caries prevention technology.

A dentifrice containing triclosan/PVM/MA, copolymer/NaF (Total) combination was compared with dentifrices containing triclosan without the copolymer system. A variety of laboratory, animal and human studies indicated that Total provided higher uptake and retention of triclosan on teeth, and was more effective in reducing plaque in chemostat and flow cell models. The retention of triclosan in dental plaque was significantly higher with Total as compared with other dentifrices 2 hours post brushing. The triclosan retained in the plaque after using Total was effective against plaque bacteria for up to 12 hours. Other dentifrices did not provide a sustained antibacterial effect against plaque. The results indicated that the delivery system with the copolymer significantly enhanced the efficacy of triclosan against plaque, gingivitis and plaque related diseases in vivo.

In vitro antiplaque effects of a triclosan/copolymer mouthrinse.

The influence of a mouthrinse containing 0.03% triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) and 0.25% copolymer (polyvinylmethylether maleic acid copolymer), compared to a matching placebo rinse, on in vitro plaque formation was assessed in two dynamic plaque model systems. In the controlled saliva flow cell system, the triclosan-containing rinses significantly reduced total plaque compared to the placebo rinse, with no significant differences when copolymer was removed from the active rinse formula. In the continuous culture system (chemostat flow cell model), the mean plaque was significantly reduced when compared with placebo. The results of these studies indicate that a triclosan mouthrinse, in the presence or absence of copolymer, is effective in reducing plaque in vitro.

Antiplaque effects of dentifrices containing triclosan/copolymer/NaF system versus triclosan dentifrices without the copolymer.

A dentifrice containing triclosan/PVM/MA, Colgate Gum Protection Formula Toothpaste (GPF), was found to be highly effective against oral bacteria with minimal inhibitory concentration ranging from 0.3 to 5.35 micrograms/ml. A variety of in vitro model systems simulating oral environment were used to compare dentifrices containing triclosan/PVM/MA versus the dentifrices containing triclosan without PVM/MA, such as Crest Gum Health Toothpaste (CGH) and Neo-Mentadent P Toothpaste (N-MP). The uptake of triclosan on saliva-coated hydroxyapatite (HA) disks and buccal epithelial cells was significantly higher from the GPF versus the other dentifrices. Uptake on HA disks was 132 micrograms/disk versus 11 micrograms/disk from CGH; on buccal epithelial cells the uptake was 59 micrograms/2 x 10(5) cells with GPF versus 30.0 micrograms with CGH per same number of cells. The retained triclosan on the surfaces provided a sustained and higher antibacterial effect up to 4 hours post-treatment with GPF, but not with N-MP and CGH. In dynamic plaque model systems such as the chemostat or the controlled saliva flow system, GPF was significantly (P = 0.05) more effective than N-MP or CGH in reducing plaque thickness, protein and carbohydrate contents of plaque films. Collectively, the results of these microbiological and biochemical investigations indicate that the GPF has the potential to provide superior clinical efficacy versus the dentifrices without the copolymer.

Endotoxic activity in periapical lesions.

Thirty tissue samples were examined histologically and classified as being inflamed (apical granulomas) or noninflamed (scars or noninflamed cysts). The samples were then homogenized in pyrogen-free water and treated to remove interfering substances. The presence of endotoxin was then determined by means of the limulus assay; 75 percent of the inflamed tissues were positive for endotoxin, while only 20 percent of the noninflamed tissues contained endotoxin. The presence of endotoxin was thus highly correlated (p = 0.015) with the presence of inflammation in these tissues.

In vitro and in vivo autoimmune response to enamel matrix proteins.

Enamel matrix proteins taken from neonatal C57Bl/6 mice were shown to be able to elicit in vitro proliferative responses in C57Bl/6 splenic lymphocytes taken from animals which had not been exposed to exogenous enamel proteins. Animals which had been injected with enamel matrix proteins in Freund's complete adjuvant made IgG antibodies against enamel proteins which were detected by indirect immunofluorescence. Spleen cells from the immune animals gave an augmented in vitro proliferative response to enamel proteins, while spleen cells from C57Bl/6 nu/nu mice or anti-Thy 1 and complement-treated normal C57Bl/6 spleen cells were incapable of responding to enamel proteins in vitro. Thus, enamel matrix proteins appear to be T-cell dependent autoantigens. The natural history of enamel matrix proteins is reviewed, and it is suggested, based on the anatomic details of enamel synthesis, secretion, and maturation, that enamel matrix proteins are autoantigenic because they are anatomically sequestered.