This study was an attempt to clarify whether the bactericidal effects of photodynamic therapy (PDT) are wavelength or dose-dependent. We also attempted to create an optimised protocol for a light-based bactericidal modality to eliminate periodontal pathogens. Cultures of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Porphromonas gingivalis, Prevotella intermedia, and Streptococcus sanguis, were exposed to a He-Ne laser (632.8 nm) with a 30 mW power output, a 100 mW diode laser at 665 nm, or a 100 mW diode laser at 830 nm, in the presence or absence of methylene blue (MB) as a photosensitiser. A control group was also used with exposure to MB alone without laser exposure. The cultures were analysed by viable counts. The results indicated that exposure to the 100 mW laser light could eliminate up to 40% of bacteria on average. In particular, the most effective killing occurred with exposure to laser light in combination with the MB photosensitiser. The results of kinetic studies indicated that the best PDT response rate was achieved with a 60 s (energy density 21.2 J/cm(2)) exposure to the 665 nm wavelength diode laser in the presence photosensitiser. In this condition, approximately 95% of A. actinomycetemcomitans and F. nucleatum, and 99-100% of the black-pigmented bacteria ( P. gingivalis and P. intermedia) and S. sanguis were eliminated. These results showed that both wavelength and energy density are important factors, and that a low power laser of optimal wavelength and dosage, in combination with an appropriate photosensitiser, is a practical bactericidal modality. We concluded that using a diode laser of proper power and wavelength to deliver 60 s of irradiation could be a useful adjunct with mechanical debridement in the prevention of the re-colonisation of subgingival lesions by pathogenic microorganisms.

No study available has utilized the new classification scheme (the consensus report of the American Academy of Periodontology 1999) to determine the prevalence of Actinobacillus actinomycetemcomitans in different periodontal conditions. The purpose of this study was to investigate prevalence and proportions of A. actinomycetemcomitans serotypes in subgingival plaque samples from a young Taiwanese population with aggressive periodontitis, chronic periodontitis and no periodontal disease. A total of 221 subgingival plaque samples from 171 diseased subjects (70 had aggressive periodontitis, and 101 had chronic periodontitis) (mean age 25.0 +/- 8.2 yr) and 50 periodontally healthy subjects (mean age 18.4 +/- 9.5 yr) were screened for A. actinomycetemcomitans. Serotypes of A. actinomycetemcomitans were determined by an indirect immunofluorescence assay using serotype-specific polyclonal antisera to A. actinomycetemcomitans strains ATCC 29523 (serotype a), ATCC 43728 (serotype b) and ATCC 33384 (serotype c). Prevalence (% of positive samples) of A. actinomycetemcomitans was 84.3% in aggressive periodontitis, 60.4% in chronic periodontitis, and 64.0% in periodontally healthy subjects. Proportions of A. actinomycetemcomitans (mean percentage per total bacteria) in periodontally healthy subjects were significantly lower than in aggressive periodontitis subjects. The proportion of serotype b in subjects with aggressive periodontitis and subjects with chronic periodontitis were significantly greater than that in periodontally healthy subjects. The proportion of serotype c in periodontally healthy subjects was much higher than that in chronic periodontitis subjects. The results of this study suggest that prevalence and proportions of A. actinomycetemcomitans are significantly greater in patients with aggressive periodontitis than in those with chronic periodontitis. Serotype b is the predominant serotype of A. actinomycetemcomitans in patients with diseased periodontal conditions. Serotype c is a more common serotype detected in periodontally healthy subjects.

No abstract

Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes capable of degrading most components of the extracellular matrix. Recently, evidence has shown that MMPs may play a role in tissue degradation in inflamed dental pulp. To date very little is known regarding the mechanism of extracellular matrix destruction at the site of bacterial infection. The purpose of this study was to determine the effects of the supernatants from Porphyromonas endodontalis and Porphyromonas gingivalis on the production and secretion of MMPs by primary human pulp and periodontal ligament (PDL) cell cultures in vitro. The results were evaluated by substrate gel zymography from long-term cultures. The main gelatinase secreted by human pulp and PDL cells migrated at 72 kDa and represented MMP-2. Minor gelatinolytic bands were also observed at 92 kDa regions that correspond to MMP-9. After an 8-day culture period, P. endodontalis and P. gingivalis were found to elevate MMP-2 production both in human pulp and PDL cell cultures. In addition, the stimulation was in a dose- and time-dependent manner. Both human pulp and PDL cells, however, treated with either P. endodontalis or P. gingivalis had no effect on the pattern of MMP-9 produced or secreted in either cell extracts or conditioned medium fractions. These results indicate that black-pigmented Bacteroides species play an important role in tissue destruction and disintegration of extracellular matrix in pulpal and periapical diseases. Thus, activation of MMPs may be one of the distinct host degradative pathways in the pathogenesis of microbial-induced pulpal and periapical lesion. An understanding of the actions of these black-pigmented Bacteroides species on pulp and PDL cells may result in new therapies to augment current treatment of pulpal and periapical lesions.