Periodontitis is a common inflammatory disease, which is initiated by bacterial infection and subsequently progressed by aberrant host response. It can result in the destruction of teeth supporting tissues and have an influence on systemic health. When periodontitis occurs, reactive oxygen species, which are overproduced mostly by hyperactive neutrophils, could not be balanced by antioxidant defense system and cause tissues damage. This is characterized by increased metabolites of lipid peroxidation, DNA damage and protein damage. Local and systemic activities of antioxidants can also be influenced by periodontitis. Total antioxidant capacity, total oxidant status and oxidative stress index have been used to evaluate the oxidative stress associated with periodontitis. Studies have confirmed that inflammatory response in periodontitis is associated with an increased local and systemic oxidative stress and compromised antioxidant capacity. Our review focuses on increased oxidative stress in periodontal disease, specifically, on the relationship between the local and systemic biomarkers of oxidative stress and periodontitis and their association with the pathogenesis of periodontitis. Also, the relationship between periodontitis and systemic inflammation, and the effects of periodontal therapy on oxidative stress parameters will be discussed.

Mesenchymal stem cells (MSCs) are considered as an attractive tool for tissue regeneration and possess a strong immunomodulatory ability. Dental tissue-derived MSCs can be isolated from different sources, such as the dental pulp, periodontal ligament, deciduous teeth, apical papilla, dental follicles and gingiva. According to numerous in vitro studies, the effect of dental MSCs on immune cells might depend on several factors, such as the experimental setting, MSC tissue source and type of immune cell preparation. Most studies have shown that the immunomodulatory activity of dental MSCs is strongly upregulated by activated immune cells. MSCs exert mostly immunosuppressive effects, leading to the dampening of immune cell activation. Thus, the reciprocal interaction between dental MSCs and immune cells represents an elegant mechanism that potentially contributes to tissue homeostasis and inflammatory disease progression. Although the immunomodulatory potential of dental MSCs has been extensively investigated in vitro, its role in vivo remains obscure. A few studies have reported that the MSCs isolated from inflamed dental tissues have a compromised immunomodulatory ability. Moreover, the expression of some immunomodulatory proteins is enhanced in periodontal disease and even shows some correlation with disease severity. MSC-based immunomodulation may play an essential role in the regeneration of different dental tissues. Therefore, immunomodulation-based strategies may be a very promising tool in regenerative dentistry.

Streptococci are primary colonizers of the oral cavity where they are ubiquitously present and an integral part of the commensal oral biofilm microflora. The role oral streptococci play in the interaction with the host is ambivalent. On the one hand, they function as gatekeepers of homeostasis and are a prerequisite for the maintenance of oral health - they shape the oral microbiota, modulate the immune system to enable bacterial survival, and antagonize pathogenic species. On the other hand, also recognized pathogens, such as oral Streptococcus mutans and Streptococcus sobrinus, which trigger the onset of dental caries belong to the genus Streptococcus. In the context of periodontitis, oral streptococci as excellent initial biofilm formers have an accessory function, enabling late biofilm colonizers to inhabit gingival pockets and cause disease. The pathogenic potential of oral streptococci fully unfolds when their dissemination into the bloodstream occurs; streptococcal infection can cause extra-oral diseases, such as infective endocarditis and hemorrhagic stroke. In this review, the taxonomic diversity of oral streptococci, their role and prevalence in the oral cavity and their contribution to oral health and disease will be discussed, focusing on the virulence factors these species employ for interactions at the host interface.

Background: The detection of special bacterial species in patients with periodontitis is considered to be useful for clinical diagnosis and treatment. The collection of subgingival plaque samples is the common way for the determination of periodontopathic bacteria. However, recently, salivary analysis has been discussed as an advantageous future diagnostic method for periodontitis because it offers simple quantitative sampling and the possibility to assess various bacteria. The aim of this cross‐sectional study is to investigate whether there is a correlation between the results of different bacterial species in saliva and subgingival plaque samples from individuals with aggressive periodontitis (AgP) and chronic periodontitis (CP).Methods: Whole saliva and subgingival plaque samples from the deepest pocket of each quadrant were collected from 43 patients with CP and 33 patients with AgP. Twenty different bacterial species from both samplings were determined by the 16S ribosomal RNA‐based polymerase chain reaction with microarray technique.Results: All bacterial species were detected in salivary and subgingival plaque samples. For Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, as well as Actinomyces viscosus, Campylobacter rectus/showae, Prevotella intermedia, Parvimonas micra, Eubacterium nodatum, and Campylobacter gracilis, a significant positive correlation between salivary and subgingival plaque samples was detected in patients with both types of periodontitis. There were no significant differences in bacteria in salivary and subgingival plaque samples between AgP and CP.Conclusion: Salivary analysis might be discussed as a potential alternative to subgingival plaque sampling for microbiologic analysis in both AgP and CP.

Background: Periodontitis is a local inflammatory disease that also has some systemic effects. We investigated the levels of interferon (IFN)‐γ, tumor necrosis factor (TNF)‐α, and interleukin (IL)‐2, ‐4, ‐5, and ‐10 in the serum of patients with periodontitis in relation to the bacterial load in the dental plaques.Methods: Serum cytokine levels in patients with generalized periodontitis and healthy control groups were determined using the cytometric bead array kit. Bacterial load in the dental plaque was determined semiquantitatively by real‐time polymerase chain reaction. The proportions of different lymphocyte subsets were determined in the peripheral blood of patients with periodontitis by flow cytometry. Finally, relationships between the bacterial load in the subgingival plaques of patients with periodontitis and levels of cytokines and counts of lymphocyte subsets were established.Results: Serum levels of IFN‐γ, TNF‐α, and IL‐10 were significantly increased, whereas those of IL‐2 were significantly decreased in patients with periodontitis compared to healthy controls. Increased serum levels of IFN‐γ and TNF‐α in patients with periodontitis were associated with the enhanced dental plaque load with Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis, respectively. Finally, as revealed by analysis of lymphocyte populations, the presence of A. actinomycetemcomitans and Trepomena denticola was associated with an increased population of CD3⁻/CD16⁺ and CD3⁺/CD8⁺ cells, respectively.Conclusion: Certain periodontal pathogens could be associated with an increased level of proinflammatory cytokines in the peripheral blood and thus increased risk of systemic diseases.