Periodontitis is a chronic inflammatory condition that destroys the tooth‐supporting tissues and eventually leads to tooth loss. As one of the most prevalent oral conditions, periodontitis endangers the oral health of 70% of people throughout the world. Periodontitis is also related to various systemic diseases, such as diabetes mellitus, atherosclerosis, and rheumatoid arthritis, which not only has a great impact on population health status and the quality of life but also increases the social burden. Porphyromonas gingivalis (P. gingivalis) is a gram‐negative oral anaerobic bacterium that plays a key role in the pathogenesis of periodontitis. Porphyromonas gingivalis can express various of virulence factors to overturn innate and adaptive immunities, which makes P. gingivalis survive and propagate in the host, destroy periodontal tissues, and have connection to systemic diseases. Porphyromonas gingivalis can invade into and survive in host tissues by destructing the gingival epithelial barrier, internalizing into the epithelial cells, and enhancing autophagy in epithelial cells. Deregulation of complement system, degradation of antibacterial peptides, and destruction of phagocyte functions facilitate the evasion of P. gingivalis. Porphyromonas gingivalis can also suppress adaptive immunity, which allows P. gingivalis to exist in the host tissues and cause the inflammatory response persistently. Here, we review studies devoted to understanding the strategies utilized by P. gingivalis to escape host immunity. Methods for impairing P. gingivalis immune evasion are also mentioned.

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Background. Endo-periodontal lesions are bacterial infectious diseases involving both the periodontal and pulp tissues with poor outcomes. It is hard for clinicians to predict their prognosis. The aim of this study is to investigate the factors affecting the prognosis of endo-periodontal lesions. Methods. A total of 140 teeth diagnosed with grade 2-3 endo-periodontal lesions in patients with periodontitis were recruited in this study. They were divided into high and low responder groups, according to the clinical symptoms and parameters of the teeth involved after nonsurgical treatment of both the endodontic and periodontal components. Clinical parameters and symptoms were compared before and after treatment, and gender, age, smoking, and all clinical parameters were compared between high and low responder groups using univariate analyses. Logistic regression was applied to evaluate the independent effects on endo-periodontal lesion prognosis. Results. Compared with the clinical parameters at baseline, the values of tooth mobility (TM), periapical index (PAI), and discomfort when chewing were decreased after endodontic therapy, and the values of periodontal probing depth (PD), clinical attachment level (CAL), sulcus bleeding index (SBI), TM, simplified oral hygiene index (OHI-S), full-mouth periodontitis severity, PAI, and discomfort when chewing were decreased after periodontal therapy. Univariate analysis revealed that smoking, PD, CAL, TM, PAI, clinical crown-root ratio (CR), full-mouth periodontitis severities, and the number of root canals were significantly different between the high and low responder groups (P<0.05). The logistic regression analysis showed that smoking, PD, CAL, full-mouth periodontitis severities, and the number of root canals remained significantly associated with grade 2-3 endo-periodontal lesions in patients with periodontitis (P<0.05). Conclusionsand Practical Implications. High PD and CAL, multirooted teeth, smoking, and serious full-mouth periodontitis indicated a poor prognosis for teeth with grade 2-3 endo-periodontal lesions.

Background Sialidase has an important role in the pathogenesis of periodontitis and Porphyromonas gingivalis is a sialidase‐producing organism implicated in periodontitis development. The aim of this study was to evaluate the anti‐virulence and anti‐inflammatory properties of the sialidase inhibitor, 2‐deoxy‐2,3‐didehydro‐N‐acetylneuraminic acid (DANA), in vitro and in vivo. Methods The effects of DANA on P. gingivalis sialidase and cell viability were determined, and the effects of DANA on P. gingivalis virulence were evaluated by assessment of growth curves, cell morphology, biofilm formation, fimbriae gene expression, and gingipains and lipopolysaccharide (LPS) activity. Anti‐inflammatory effects of DANA on LPS‐induced macrophages were assessed by measurement of tumor necrosis factor‐alpha (TNF‐α), interleukin (IL‐1β), inducible nitric oxide synthase (iNOS) secretions. The effect of DANA on P. gingivalis–induced periodontitis in rats was analyzed by radiography, stereoscopic microscopy, histopathology, and immunohistochemistry. Results Sialidase inhibition rate of 1mM DANA was 72.01%. Compared with untreated controls, treatment with DANA inhibited P. gingivalis growth and biofilm formation, and significantly decreased expression of the fimA, fimR, and fimS genes, as well as gingipains activity. DANA did not influence macrophage viability, but significantly inhibited TNF‐α, IL‐1β, and iNOS production in LPS‐stimulated macrophages. In the periodontitis rat model, DANA prevented alveolar bone absorption and inhibited TNF‐α and IL‐1β production. Conclusion DANA can reduce the growth, the biofilm formation and the virulence of P. gingivalis and exhibits anti‐inflammatory effects, as well as effects against rat periodontitis, suggesting that DANA should be considered for development as a new adjunctive treatment for periodontitis.

Background Periodontitis is a chronic multi-factorial infectious disease, and there is a significant difference in the prognosis of severe periodontitis patients after non-surgical periodontal treatment. Therefore, a retrospective study was conducted to find common and specific factors affecting the prognosis of periodontitis stage III-IV after non-surgical periodontal treatment according to various tooth sites.Methods A total of 977 teeth from 266 patients of periodontitis stage III-IV were enrolled, including 330 anterior teeth, 362 maxillary posterior teeth and 285 mandibular posterior teeth. The enrolled teeth were divided into two groups according to the residual pockets (PD ≥ 5 mm) at 3 months post-treatment. The association of risk factors with the prognosis of periodontitis stage III-IV were analyzed with multivariate analysis. All tests were two-sided and parameters were statistically significant (P < 0.05).Results The PD values of each site and the deepest PD values of each tooth were significantly decreased at 3 months post-treatment, and the residual pockets were mainly distributed in mesio/disto-buccal and mesio/disto-lingual. The multivariate analysis revealed that gender, probing depth (PD), sulcus bleeding index (SBI) and plaque index (PLI) at baseline and crown-root ratio in anterior teeth had significant correlation with periodontitis stage III-IV (P < 0.05). In maxillary posterior teeth the significant factors were smoking, PD, PLI and furcation involvement (FI) at baseline, PLI at 3 months post-treatment, grades of periodontitis and crown-root ratio. And PD, PLI and FI at baseline, PLI at 3 months post-treatment and crown-root were significant in mandibular posterior teeth.Conclusions The mean PD and PLI at baseline and crown-root ratio were common prognostic factors of anterior teeth, maxillary posterior teeth and mandibular posterior teeth. The gender and SBI at baseline were specific prognostic factors of anterior teeth. The common prognostic factors of posterior teeth were FI at baseline and PLI at 3 months post-treatment. While the specific prognostic factors of maxillary posterior teeth were smoking and the grades of periodontitis compared with mandibular posterior teeth .