Porphyromonas gingivalis induces periodontitis, causes immune imbalance, and promotes rheumatoid arthritis.

Periodontitis induced by bacteria especially Porphyromonas gingivalis (P. gingivalis) is the most prevalent microbial disease worldwide and is a significant risk factor for systemic diseases such as rheumatoid arthritis (RA). RA and periodontitis share similar clinical and pathologic features. Moreover, the prevalence of RA is much higher in patients with periodontitis than in those without periodontitis. To explore the immunologic mechanism of periodontitis involved in RA, we established a mouse model of periodontitis and then induced RA. According to the results of paw thickness, arthritis clinical score, arthritis incidence, microscopic lesion using H&E staining, and micro-CT analysis, periodontitis induced by P. gingivalis promoted the occurrence and development of collagen-induced arthritis (CIA) in mice. Furthermore, periodontitis enhanced the frequency of CD19+ B cells, Th17, Treg, gMDSCs, and mMDSCs, whereas down-regulated IL-10 producing regulatory B cells (B10) in CIA mice preinduced for periodontitis with P. gingivalis. In vitro stimulation with splenic cells revealed that P. gingivalis directly enhanced differentiation of Th17, Treg, and mMDSCs but inhibited the process of B cell differentiation into B10 cells. Considering that adoptive transfer of B10 cells prevent RA development, our study, although preliminary, suggests that down-regulation of B10 cells may be the key mechanism that periodontitis promotes RA as the other main immune suppressive cells such as Treg and MDSCs are up-regulated other than down-regulated in group of P. gingivalis plus CIA.

[Observation of genetic diversity in dental plaque of elder people with root caries].

PURPOSE: Bacterial community in dental plaque of elder people was analyzed to learn about the microhabitat composition and diversity. METHODS: Dental plaque samples were collected from 25 elders. PCR-based denaturing gradient gel electrophoresis (PCR-DGGE) was used to evaluate the microbial diversity by displaying PCR-generated 16SrDNA fragments that migrate at different distances, reflecting the different sequence of fragment. SPSS12.0 software was used to analyze the variance of genotypes between different groups of bacteria. RESULTS: Genotypes of bacteria in dental plaques in the root caries group was significantly more than the other two groups. Crown caries group and caries-free group had no significant difference. CONCLUSIONS: The genetic diversity of the dental plaque microflora in the root caries group is significantly higher than coronal caries group and caries-free group.

[Analysis of community composition in dental plaque of elder people with root caries].

OBJECTIVE: To analyze the community in dental plaque of elder people with root caries. METHODS: Total DNAs were extracted from the root caries dental plaques of nine elders over 60 years of age. Polymerase chaid reaction-based denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the microbial composition, DGGE bands were excised from the gels for sequencing and identification. RESULTS: The dominant genus in root caries dental plaque of elder people were: Acinetobacte [0.9% (1/114)], Actinobaculum [1.8% (2/114)], Actinomyces [15.8% (18/114)], Aggregatibacter [0.9% (1/114)], Capnocytophaga [14.0% (16/114)], Corynebacterium [0.9% (1/114)], Haemophilus [0.9% (1/114)], Mobiluncus [0.9% (1/114)], Naxibacter [0.9% (1/114)], Neisseriaceae [10.5% (12/114)], Porphyromonas [0.9% (1/114)], Prevotella [12.3% (14/114)], Selenomonas [6.1% (7/114)], Staphylococcus [1.8% (2/114)], Oralis streptococcus [6.1% (7/114)], Mutans streptococcu [7.9% (9/114)], Tannerella [0.9% (1/114)], Treponema [1.8% (2/114)], Veillonella [10.5% (12/114)] and two uncultured unknown genus [1.8% (2/114)]. Uncultred genotypes accounted for 19.30% of the total. Gram-positive bacteria genotype accounted for 31.6% (36/114), and Gram-negative bacteria genotype accounted for 66.7% (76/114). CONCLUSIONS: There were many bacteria genotypes in root caries dental plaque in the elderly, which were widely distributed. Gram-negative bacteria accounted for the majority. Genotype-specific pathogenic bacteria were not found.

[Quantitative evaluation of residual endodontic microorganisms after mechanical root canal preparation different chemical preparations by real-time PCR].

PURPOSE: To establish a quick, sensitive method for quantifying root canal flora and investigate the effects of different root canal preparations on the pathogenic bacteria at RNA level. METHODS: A total of 24 single-rooted teeth with chronic apical periodontitis were selected and prepared using 3% H2O2 combined with 1% NaClO, EDTA combined with 3% H(2)O(2),1% NaClO, respectively,the samples were taken before and after root canal preparation. After isolation of total RNA from the root canal samples, cDNA was synthesized by reverse transcription, and detected by real-time PCR. The data were analyzed with SAS 6.12 software package. RESULTS: The number of bacteria in the root canal reduced dramatically after mechanical preparation and irrigated using 3% H(2)O(2) and 1% NaClO(P<0.01). Further combined with EDTA, its effect was better than that of simply irrigated using 3% H(2)O(2) and 1% NaClO(P<0.05). CONCLUSIONS: Real-time PCR can be employed in the identification of bacteria flora in the root canal, both methods of root canal preparation can effectively reduce the number of bacteria flora.

[Comparison of the sucrose dependent cell adherence of Streptococcus mutans isolates from caries-active and caries-free children].

PURPOSE: To study the sucrose dependent cell adhesive ability of Streptococcus mutans islolated from the caries-active and caries-free children. METHODS: 60 isolated Streptococcus mutans strains were selected and identified from the dental plaque of 10 caries-active children and 10 caries-free children (3 to 5 years), in which 39 strains were from caries-active group(dmfs>or=6) and 21 strains from caries-free group(dmfs=0). With the use of ultraviolet spectrophotometer, the sucrose dependent cell adherence to glass wall of the sucrose-containing testing tubes was analyzed. One-way ANOVA was used by SPSS12.0 software package to determine the statistical difference of the adhesive ability between the two groups. RESULTS: The average adhesive ratio of the Streptococcus mutans strains isolated from caries-active group was 55.49%+26.16% in the 1% sucrose-containing culture medium, while the average adhesive ratio of the Streptococcus mutans strains isolated from caries-free group was 27.01%+18.39%. The difference between the two groups was statistically significant (P<0.01). CONCLUSION: In the sucrose-containing circumstance, the sucrose dependent cell adhesive ability of the Streptococcus mutans isolated from the caries-active children was significantly higher than that from the caries-free children. This indicated that the adhesive ability may be related to the caries-causing tendency.

[In vitro evaluation of the sealing ability of an iodoform-calcium phosphorate cement root canal filler].

PURPOSE: To evaluate the sealing ability of an injectable iodoform-calcium phosphate cement(CPC) root canal filler in vitro. METHODS: Sixty-two single-rooted human extracted teeth were selected and root canals were instrumented to 40# with K file. Fifty-eight teeth were randomly divided into two experimental groups. The root canals were filled by lateral condensation of gutta-purcha with iodoform-CPC or zinc-oxide-eugenol-iodoform paste used as sealer respectively. Other four teeth were used as control. When the sealer was solidified, the apical portion of tooth was soaked into 2% methylene blue for 6 days. After the tooth was longitudinally sectioned, the dye length was measured for apical microleakage.The data obtained were analysed with group t test. RESULTS: The average microleakage in iodoform-CPC group(8.400mm) was significantly larger than that in the control group(5.300mm), P=0.021. CONCLUSIONS: We conclude that iodoform-CPC does not provide a sealing ability as good as zinc-oxide-eugenol-iodoform paste in vitro.

[Preliminary evaluation of the clinical results of calcium phosphorate cement root canal sealer].

PURPOSE: To investigate the clinic effect of calcium phosphorate cement as a root canal sealer-filler material. METHODS: 136 teeth with chronic periapical disease were instrumented and obturated with laterally condensed gutta-percha and either calcium phosphate cement(CPC) or iodoform paste. The patients were recalled and observed according to the clinic symptom and radiography after 1 week,3 months, 6 months and 1 year. The data was processed using SAS6.2 software package for Chi-square test and Wilcoxon rank test. RESULTS: The patients of CPC group had mild reaction after treatment and the successful rate of 3-month was higher compared with the control group(with iodoform paste), however there was no different clinical effects between the two groups after one year. CONCLUSION: Calcium phosphate cement root canal sealer can be acceptable for root canal filling , but the long term clinical results are needed be investigated.