In vitro evaluation of surface properties of Pro Seal® and Opal® SealTM in preventing white spot lesions.

OBJECTIVES: To evaluate the surface properties of two commercially available sealants (Pro Seal® (PS) and Opal® SealTM (OS)) in terms of fluoride(F) release, biofilm formation of Streptococcus mutans and Lactobacillus and the ability to resist acid penetration. SETTING: University of Nebraska Medical Center. MATERIAL & METHODS: Discs of similar diameter and thickness were made from OS and PS. Discs were soaked in double-distilled water, and F released was measured with fluoride meter daily for 14 consecutive days, then at 21 and 28 days. Biofilm formation was evaluated with Streptococcus mutans and Lactobacilli grown on sealant discs using confocal microscopy. Extracted human teeth (n=8) with sealant-coated buccal surfaces and untreated lingual surfaces were exposed to 0.1M lactic acid(pH=4.5) to test the acid penetration. After 1-4 weeks of exposure, teeth were subjected to microhardness testing and SEM microscopy. RESULTS: PS released significantly higher levels of F than OS. PS showed more S. mutans adherence than OS, whereas Lactobacillus did not show any differences in adherence. Both sealants protected enamel surfaces, showing statistically significant difference in the depth of acid penetration compared to their unsealed control sides. CONCLUSION: F release was adequate to aid in remineralization, although clinically it would not likely aid in preventing demineralization as there was no prolonged release of F by both sealants tested. S. mutans adherence to OS surface was less compared to PS surface, which could be of relevance in biofilm formation and white spot lesions. Both sealants protected enamel surfaces from acid penetration.

Altered antigenicity in periodontitis patients and decreased adhesion of Porphyromonas gingivalis by environmental temperature stress.

Periodontopathogenic bacteria survive various environmental changes during the progression of periodontal disease. Alterations in metabolism and protein expression will have to take place to adapt their physiological functions to environmental stress. We examined the effects of an elevation of 2 degrees C in temperature on the adhesive ability and antigenicity of Porphyromonas gingivalis. Elevation of growth temperature of P. gingivalis from 37 degrees C to 39 degrees C remarkably suppressed the expression of surface filamentous structures, such as fimbriae, as well as the adhesive capacities to salivary components and Streptococcus oralis. Sera of severe periodontitis patients revealed a marked increase in serological activity with 39 degrees C cells than with 37 degrees C cells. The alteration of protein profiles of bacterial surface components by temperature elevation was demonstrated by SDS-PAGE, and their Western blot profiles were also different from those of cells grown at 37 degrees C. Although a uniform trend was not found in the altered patterns, sera from severe periodontitis patients detected more antigenic proteins in cells grown at 39 degrees C than 37 degrees C cells. These observations suggest that P. gingivalis downregulates the expression of fimbriae and alters its adhesive capacity and antigenicity by the temperature stress that could occur during the disease progression.

Use of PCR and sodium dodecyl sulfate-polyacrylamide gel electrophoresis techniques for differentiation of Prevotella intermedia sensu stricto and Prevotella nigrescens.

Primers were designed from 16S rRNA sequences of Prevotella intermedia sensu stricto and Prevotella nigrescens and were used to discriminate these two species by PCR. The results were compared with those from the PCR technique using primers designed from arbitrarily primed PCR products by Guillot and Mouton (E. Guillot and C. Mouton, J. Clin. Microbiol. 35:1876-1882, 1997). The specificities of both assays were studied by using P. intermedia ATCC 25611, P. nigrescens ATCC 33563, 174 clinical isolates of P. intermedia sensu lato, and 59 reference strains and 58 clinical isolates of other Prevotella species and/or common oral flora. In addition, the usefulness and reliability of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the differentiation of the two species were examined by comparing the results with those from PCR assays. The controversial lipase test for distinguishing these species was also carried out. Unambiguous differentiation was made by both PCR assays, and the results matched each other. The SDS-PAGE assay was found to misidentify a few strains tested, compared with the results of PCR assays. The lipase test was positive for both species, including the reference strains of P. intermedia and P. nigrescens. We conclude that both PCR assays are simple, rapid, reliable, and specific methods which could be used in clinical studies and that the lipase test is not valuable in the differentiation. The reliable discrimination of the two species by SDS-PAGE is questionable.