Experimental Inoculation of Aggregatibacter actinomycetemcomitans and Streptococcus gordonii and Its Impact on Alveolar Bone Loss and Oral and Gut Microbiomes.

Oral bacteria are implicated not only in oral diseases but also in gut dysbiosis and inflammatory conditions throughout the body. The periodontal pathogen Aggregatibacter actinomycetemcomitans (Aa) often occurs in complex oral biofilms with Streptococcus gordonii (Sg), and this interaction might influence the pathogenic potential of this pathogen. This study aims to assess the impact of oral inoculation with Aa, Sg, and their association (Aa+Sg) on alveolar bone loss, oral microbiome, and their potential effects on intestinal health in a murine model. Sg and/or Aa were orally administered to C57Bl/6 mice, three times per week, for 4 weeks. Aa was also injected into the gingiva three times during the initial experimental week. After 30 days, alveolar bone loss, expression of genes related to inflammation and mucosal permeability in the intestine, serum LPS levels, and the composition of oral and intestinal microbiomes were determined. Alveolar bone resorption was detected in Aa, Sg, and Aa+Sg groups, although Aa bone levels did not differ from that of the SHAM-inoculated group. Il-1ß expression was upregulated in the Aa group relative to the other infected groups, while Il-6 expression was downregulated in infected groups. Aa or Sg downregulated the expression of tight junction genes Cldn 1, Cldn 2, Ocdn, and Zo-1 whereas infection with Aa+Sg led to their upregulation, except for Cldn 1. Aa was detected in the oral biofilm of the Aa+Sg group but not in the gut. Infections altered oral and gut microbiomes. The oral biofilm of the Aa group showed increased abundance of Gammaproteobacteria, Enterobacterales, and Alloprevotella, while Sg administration enhanced the abundance of Alloprevotella and Rothia. The gut microbiome of infected groups showed reduced abundance of Erysipelotrichaceae. Infection with Aa or Sg disrupts both oral and gut microbiomes, impacting oral and gut homeostasis. While the combination of Aa with Sg promotes Aa survival in the oral cavity, it mitigates the adverse effects of Aa in the gut, suggesting a beneficial role of Sg associations in gut health.

Correlation between crestal alveolar bone loss with intracanal bacteria and apical lesion area in necrotic teeth.

OBJECTIVE: This study aimed to analyze the correlation between crestal alveolar bone loss with the presence of some bacterial species in root canals and the apical lesion area of necrotic teeth. DESIGN: Data from 20 patients with diagnosis of pulp necrosis and acute apical abscesses, without active periodontal diseases, were evaluated. Patients with history of antibiotic usage three months prior to the study, with exposed pulp cavity, and with probing depth >3 mm were not included. The root size, the distance between the bone crest to the tooth apex in the mesial and distal surfaces, and the apical lesion area were measured from standard periapical radiographies by a calibrated examiner. Root canal samples were collected using sterilized paper points. In multirooted teeth, the largest root canal was sampled. Culture, microbial isolation and identification by phenotypic methods were performed. Spearman correlation and exact Fischer test were calculated between higher/lower existing bone crests, according to the median and the presence of specific bacteria. RESULTS: No statistically significant differences were found between occurrence of pathogenic bacteria, such as Porphyromonas gingivalis, Porphyromonas endodontalis, and Prevotella intermedia, and groups with higher/lower degree of bone loss (p > 0.05). A negative significant correlation was found between Parvimonas micra and periodontal bone loss (p = 0.02). Additionally, no statistically significant association was found between crestal bone loss and the apical lesion area. CONCLUSIONS: It was concluded that, in patients without active periodontitis, the presence of pathogenic bacteria in the root canal was not correlated with periodontal bone loss.

RANKL Triggers Treg-Mediated Immunoregulation in Inflammatory Osteolysis.

The chronic inflammatory immune response triggered by the infection of the tooth root canal system results in the local upregulation of RANKL, resulting in periapical bone loss. While RANKL has a well-characterized role in the control of bone homeostasis/pathology, it can play important roles in the regulation of the immune system, although its possible immunoregulatory role in infectious inflammatory osteolytic conditions remains largely unknown. Here, we used a mouse model of infectious inflammatory periapical lesions subjected to continuous or transitory anti-RANKL inhibition, followed by the analysis of lesion outcome and multiple host response parameters. Anti-RANKL administration resulted in arrest of bone loss but interfered in the natural immunoregulation of the lesions observed in the untreated group. RANKL inhibition resulted in an unremitting proinflammatory response, persistent high proinflammatory and effector CD4 response, decreased regulatory T-cell (Treg) migration, and lower levels of Treg-related cytokines IL-10 and TGFb. Anti-RANKL blockade impaired the immunoregulatory process only in early disease stages, while the late administration of anti-RANKL did not interfere with the stablished immunoregulation. The impaired immunoregulation due to RANKL inhibition is characterized by increased delayed-type hypersensitivity in vivo and T-cell proliferation in vitro to the infecting bacteria, which mimic the effects of Treg inhibition, reinforcing a possible influence of RANKL on Treg-mediated suppressive response. The adoptive transfer of CD4+FOXp3+ Tregs to mice receiving anti-RANKL therapy restored the immunoregulatory capacity, attenuating the inflammatory response in the lesions, reestablishing normal T-cell response in vivo and in vitro, and preventing lesion relapse upon anti-RANKL therapy cessation. Therefore, while RANKL inhibition efficiently limited the periapical bone loss, it promoted an unremitting host inflammatory response by interfering with Treg activity, suggesting that this classic osteoclastogenic mediator plays a role in immunoregulation.

Different engagement of TLR2 and TLR4 in Porphyromonas gingivalis vs. ligature-induced periodontal bone loss.

This study was conducted to investigate the roles of different Toll-like receptor (TLR) signaling in Porphyromonas gingivalis (P. gingivalis)-induced and ligature-induced experimental periodontal bone resorption in mice. Wild-type (WT), TLR2 knockout (KO), TLR4KO, and TLR2&4 KO mice with C57/BL6 background were divided into three groups: control, P. gingivalis infection, and ligation. Live P. gingivalis or silk ligatures were placed in the sulcus around maxillary second molars over a 2-week period. Images were captured by digital stereomicroscopy, and the bone resorption area was measured with ImageJ software. The protein expression level of gingival RANKL was measured by ELISA. The gingival mRNA levels of RANKL, IL-1ß, TNF-α, and IL-10 were detected by RT-qPCR. The results showed that P. gingivalis induced significant periodontal bone resorption in WT mice and TLR2 KO mice but not in TLR4 KO mice or TLR2&4 KO mice. For all four types of mice, ligation induced significant bone loss compared with that in control groups, and this bone loss was significantly higher than that in the P. gingivalis infection group. RANKL protein expression was significantly increased in the ligation group compared with that in the control group for all four types of mice, and in the P. gingivalis infection group of WT, TLR2 KO, and TLR4 KO mice. Expression patterns of RANKL, IL-1ß, TNF-α, and IL-10 mRNA were different in the P. gingivalis infection group and the ligation group in different types of mice. In summary, P. gingivalis-induced periodontal bone resorption is TLR4-dependent, whereas ligation-induced periodontal bone resorption is neither TLR2- nor TLR4-dependent.

The role of 5-lipoxygenase in Aggregatibacter actinomycetemcomitans-induced alveolar bone loss.

AIM: Leukotrienes (LTs) are pro-inflammatory lipid mediators formed by the enzyme 5-lipoxygenase (5-LO). The involvement of 5-LO metabolites in periodontal disease (PD) is not well defined. This study aimed to assess the role of 5-LO in experimental PD induced by Aggregatibacter actinomycetemcomitans (Aa). MATERIAL AND METHODS: In vivo experiments were carried out using SV129 wild-type (WT) and 5-LO-deficient (5lo-/- ) mice inoculated with Aa. Osteoclasts were stimulated in vitro with AaLPS in the presence or not of selective inhibitors of the 5-LO pathway, or LTB4 or platelet-activating factor (PAF), as PAF has already been shown to increase osteoclast activity. RESULTS: In 5lo-/- mice, there were no loss of alveolar bone and less TRAP-positive osteoclasts in periodontal tissues, after Aa inoculation, despite local production of TNF-α and IL-6. The differentiation and activity of osteoclasts stimulated with AaLPS were diminished in the presence of BLT1 antagonist or 5-LO inhibitor, but not in the presence of cysteinyl leukotriene receptor antagonist. The osteoclast differentiation induced by PAF was impaired by the BLT1 antagonism. CONCLUSION: In conclusion, LTB4 but not CysLTs is important for Aa-induced alveolar bone loss. Overall, LTB4 affects osteoclast differentiation and activity and is a key intermediate of PAF-induced osteoclastogenesis.

Different engagement of TLR2 and TLR4 in Porphyromonas gingivalis vs. ligature-induced periodontal bone loss

Abstract This study was conducted to investigate the roles of different Toll-like receptor (TLR) signaling in Porphyromonas gingivalis (P. gingivalis)-induced and ligature-induced experimental periodontal bone resorption in mice. Wild-type (WT), TLR2 knockout (KO), TLR4KO, and TLR2&4 KO mice with C57/BL6 background were divided into three groups: control, P. gingivalis infection, and ligation. Live P. gingivalis or silk ligatures were placed in the sulcus around maxillary second molars over a 2-week period. Images were captured by digital stereomicroscopy, and the bone resorption area was measured with ImageJ software. The protein expression level of gingival RANKL was measured by ELISA. The gingival mRNA levels of RANKL, IL-1β, TNF-α, and IL-10 were detected by RT-qPCR. The results showed that P. gingivalis induced significant periodontal bone resorption in WT mice and TLR2 KO mice but not in TLR4 KO mice or TLR2&4 KO mice. For all four types of mice, ligation induced significant bone loss compared with that in control groups, and this bone loss was significantly higher than that in the P. gingivalis infection group. RANKL protein expression was significantly increased in the ligation group compared with that in the control group for all four types of mice, and in the P. gingivalis infection group of WT, TLR2 KO, and TLR4 KO mice. Expression patterns of RANKL, IL-1β, TNF-α, and IL-10 mRNA were different in the P. gingivalis infection group and the ligation group in different types of mice. In summary, P. gingivalis-induced periodontal bone resorption is TLR4-dependent, whereas ligation-induced periodontal bone resorption is neither TLR2- nor TLR4-dependent.

Neutrophil Functions in Periodontal Homeostasis.

Oral tissues are constantly exposed to damage from the mechanical effort of eating and to microorganisms, mostly bacteria. In healthy gingiva tissue remodeling and a balance between bacteria and innate immune cells are maintained. However, excess of bacteria biofilm (plaque) creates an inflammation state that recruits more immune cells, mainly neutrophils to the gingiva. Neutrophils create a barrier for bacteria to reach inside tissues. When neutrophils are insufficient, bacteria thrive causing more inflammation that has been associated with systemic effects on other conditions such as atherosclerosis, diabetes, and cancer. But paradoxically when neutrophils persist, they can also promote a chronic inflammatory state that leads to periodontitis, a condition that leads to damage of the bone-supporting tissues. In periodontitis, bone loss is a serious complication. How a neutrophil balance is needed for maintaining healthy oral tissues is the focus of this review. We present recent evidence on how alterations in neutrophil number and function can lead to inflammatory bone loss, and how some oral bacteria signal neutrophils to block their antimicrobial functions and promote an inflammatory state. Also, based on this new information, novel therapeutic approaches are discussed.

Arthritis-induced alveolar bone loss is associated with changes in the composition of oral microbiota.

Rheumatoid arthritis (RA) and periodontitis (PD) are chronic inflammatory disorders that cause bone loss. PD tends to be more prevalent and severe in RA patients. Previous experimental studies demonstrated that RA triggers alveolar bone loss similarly to PD. The aim of this study was to investigate if arthritis-induced alveolar bone loss is associated with modification in the oral microbiota. Checkerboard DNA-DNA hybridization was employed to analyze forty oral bacterial species in 3 groups of C57BL/6 mice: control (n = 12; without any challenge); Y4 (n = 8; received oral inoculation of Aggregatibacter Actinomycetemcomitans strain FDC Y4) and AIA group (n = 12; chronic antigen-induced arthritis). The results showed that AIA and Y4 group exhibited similar patterns of bone loss. The AIA group exhibited higher counts of most bacterial species analyzed with predominance of Gram-negative species similarly to infection-induced PD. Prevotella nigrescens and Treponema denticola were detected only in the Y4 group whereas Campylobacter showae, Streptococcus mitis and Streptococcus oralis were only found in the AIA group. Counts of Parvimonas micra, Selenomonas Noxia and Veillonella parvula were greater in the AIA group whereas Actinomyces viscosus and Neisseira mucosa were in large proportion in Y4 group. In conclusion, AIA is associated with changes in the composition of the oral microbiota, which might account for the alveolar bone loss observed in AIA mice.

NOD2 contributes to Porphyromonas gingivalis-induced bone resorption.

The NOD-like receptors are cytoplasmic proteins that sense microbial by-products released by invasive bacteria. Although NOD1 and NOD2 are functionally expressed in cells from oral tissues and play a role triggering immune responses, the role of NOD2 receptor in the bone resorption and in the modulation of osteoclastogenesis is still unclear. We show that in an experimental model of periodontitis with Porphyromonas gingivalis W83, NOD2(-/-) mice showed lower bone resorption when compared to wild type. Quantitative polymerase chain reaction analysis revealed that wild-type infected mice showed an elevated RANKL/OPG ratio when compared to NOD2(-/-) infected mice. Moreover, the expression of 2 osteoclast activity markers-cathepsin K and matrix metalloproteinase 9-was significantly lower in gingival tissue from NOD2(-/-) infected mice compared to WT infected ones. The in vitro study reported an increase in the expression of the NOD2 receptor 24 hr after stimulation of hematopoietic bone marrow cells with M-CSF and RANKL. We also evaluated the effect of direct activation of NOD2 receptor on osteoclastogenesis, by the activation of this receptor in preosteoclasts culture, with different concentrations of muramyl dipeptide. The results show no difference in the number of TRAP-positive cells. Although it did not alter the osteoclasts differentiation, the activation of NOD2 receptor led to a significant increase of cathepsin K expression. We confirm that this enzyme was active, since the osteoclasts resorption capacity was enhanced by muramyl dipeptide stimulation, evaluated in osteoassay plate. These results show that the lack of NOD2 receptor impairs the bone resorption, suggesting that NOD2 receptor could contribute to the progression of bone resorption in experimental model of periodontitis. The stimulation of NOD2 by its agonist, muramyl dipeptide, did not affect osteoclastogenesis, but it does favor the bone resorption capacity identified by increased osteoclast activity.

IgG sera levels against a subset of periodontopathogens and severity of disease in aggressive periodontitis patients: a cross-sectional study of selected pocket sites.

AIMS: To evaluate the association among serum immunoglobulin G (IgG) responses to Aggregatibacter actinomycetemcomitans (Aa) serotypes a, b and c, Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf) and clinical parameters in Aggressive Periodontitis (AP) subjects. Associations between periodontal pathogens and clinical and immunological parameters were also evaluated. METHODS: Thirty-eight subjects diagnosed with generalized AP (GAP) and localized AP (LAP) were included. Ten healthy controls were also evaluated. Clinical parameters were assessed and percentages of subgingival levels of Aa, Pg and Tf (beyond bacterial load), were determined by quantitative real-time polymerase chain reaction. Serum IgG antibody levels against Aa, Pg and Tf were evaluated by enzyme-linked immunosorbent assay. RESULTS: Percentages of Aa, Pg and Tf were significantly higher in AP than in controls. The response to Aa serotype c was higher in LAP subjects than in controls. There were no differences in microbial composition or antibodies responses between GAP and LAP, except for IgG response to Tf. Pg levels were correlated with probing depth (PD), BoP and CAL in GAP but not in LAP subjects. Tf levels correlated with PD and CAL in GAP subjects. In GAP, the infection levels of Aa and Pg correlated with the corresponding IgG levels to Aa serotype c and Pg. CONCLUSION: Given the evidences that IgG response in AP patients correlated with bacterial infection level in GAP, but not in LAP, and that LAP patients lack a response to Tf, despite harbouring this species, our data suggest a difference in host immune defence between these two forms of aggressive periodontitis.

Effect of Lithothamnium sp and calcium supplements in strain- and infection-induced bone resorption.

OBJECTIVE: To investigate the effect of Lithothamnium sp (LTT) supplement, a calcium-rich alga widely used for mineral reposition, on strain-induced (orthodontic tooth movement [OTM]) and infection-induced bone resorption (periodontal disease [PD]) in mice. MATERIALS AND METHODS: Mice were divided into two bone resorption models: one with an orthodontic appliance and the other with PD induced by the oral inoculation of Aggregatibacter actinomycetencomitans (Aa). Both groups were fed a regular diet (vehicle), LTT-rich diet (LTT), or calcium-rich diet (CaCO3). Alveolar bone resorption (ABR), the number of osteoclasts, and the levels of tumor necrosis factor α (TNF-α), calcium, and vitamin D3 were evaluated. RESULTS: The number of osteoclasts was reduced in LTT and CaCO3 mice, which led to diminished OTM and infection-induced alveolar bone loss. In addition, LTT- and calcium-treated groups also presented decreased levels of TNF-α in periodontal tissues and increased levels of calcium in serum. CONCLUSIONS: These results indicate that the LTT supplement influences ABR, probably due to its calcium content, by affecting osteoclast function and local inflammatory response, thus modulating OTM and PD.

Evaluation of the host response in various models of induced periodontal disease in mice.

BACKGROUND: The aim of this study is to characterize and evaluate the host response caused by three different models of experimental periodontitis in mice. METHODS: C57BL/6 wild-type female mice were distributed into six experimental groups and sacrificed at 7, 15, and 30 days after the induction of periodontal disease: 1) group C: no treatment control group; 2) group L: periodontal disease induced by ligature; 3) group G-Pg: oral gavage with Porphyromonas gingivalis (Pg); 4) group G-PgFn: oral gavage with Fusobacterium nucleatum + Pg; 5) group I-Pg: heat-killed Pg injected into the palatal mucosa between the molars; and 6) group I-V: phosphate-buffered saline injected into the palatal mucosa. The samples were used to analyze the immune-inflammatory process in the gingival tissue via descriptive histologic and real-time polymerase chain reaction analyses. The alveolar bone loss was evaluated using microcomputed tomography. The data were analyzed using the Kruskal-Wallis test, followed by a post hoc Dunn test and analysis of variance, followed by a Tukey test using a 5% significance level. RESULTS: Only the ligature model displayed significant alveolar bone loss in the initial period (7 days), which was maintained with time. The group injected with heat-killed Pg displayed significant alveolar bone loss starting from day 15, which continued to progress with time (P <0.05). A significant increase (P <0.05) in the gene expression of proinflammatory cytokines (interleukin-6 and -1ß) and proteins involved in osteoclastogenesis (receptor activator of nuclear factor-κB ligand and osteoprotegerin) was observed in the ligature group on day 7. CONCLUSION: The ligature and injection of heat-killed Pg models were the most representative of periodontal disease in humans, whereas the oral gavage models were not effective at inducing the disease under the experimental conditions.

Quercetin inhibits inflammatory bone resorption in a mouse periodontitis model.

Periodontitis is a disease that leads to bone destruction and represents the main cause of tooth loss in adults. The development of aggressive periodontitis has been associated with increased inflammatory response that is induced by the presence of a subgingival biofilm containing Aggregatibacter actinomycetemcomitans. The flavonoid quercetin (1) is widespread in vegetables and fruits and exhibits many biological properties for possible medical and clinical applications such as its anti-inflamatory and antioxidant effects. Thus, in the present study, the properties of 1 have been evaluated in bone loss and inflammation using a mouse periodontitis model induced by A. actinomycetemcomitans infection. Subcutaneous treatment with 1 reduced A. actinomycetemcomitans-induced bone loss and IL-1ß, TNF-α, IL-17, RANKL, and ICAM-1 production in the gingival tissue without affecting bacterial counts. These results demonstrated that quercetin exhibits protective effects in A. actinomycetemcomitans-induced periodontitis in mice by modulating cytokine and ICAM-1 production.

Adjunctive antimicrobial photodynamic treatment of experimentally induced periodontitis in rats with ovariectomy.

BACKGROUND: The aim of this study is to compare antimicrobial photodynamic therapy (aPDT) as an adjunctive therapy to scaling and root planing (SRP) for the treatment of experimentally induced periodontitis in rats with ovariectomy (OVX) that are or are not treated with estrogen replacement. METHODS: A total of 270 female rats were divided into three groups: 1) normal rats; 2) rats with OVX; and 3) rats with OVX with estrogen replacement. Periodontal disease was induced through the introduction of a cotton thread around the mandibular left first molar. After 7 days, the ligature was removed, and the rats were randomly divided into the following treatment groups: 1) SRP plus saline solution; 2) SRP plus low-level laser therapy (LLLT); and 3) SRP plus toluidine blue O irrigation followed by LLLT. Ten rats from each group were euthanized at days 7, 15, and 30 after dental treatment. Bone loss (BL) in the furcation region was evaluated using histometric and immunohistochemical analyses. RESULTS: aPDT treatment resulted in reduced BL compared with SRP treatment at all time points. Additionally, rats treated with aPDT exhibited reduced numbers of tartrate-resistant acid-phosphatase-positive cells and more proliferating cell nuclear antigen-positive cells in all treatment groups regardless of estrogen status. Whereas rats treated with aPDT showed weak immunoreactivity to the receptor activator of nuclear factor-κ B ligand at day 7 post-treatment, strong osteoprotegerin immunoreactivity was observed at day 15 post-treatment. CONCLUSION: aPDT is an effective adjunctive therapy for the treatment of periodontitis in rats with OVX that are or are not given estrogen replacement therapy.

Clinical and microbiological changes after minimally invasive therapeutic approaches in intrabony defects: a 12-month follow-up.

OBJECTIVES: This 12-month randomized, controlled trial evaluated the clinical effects and microbiological changes of minimally invasive nonsurgical and surgical approaches for the therapy of intrabony defects. MATERIALS AND METHODS: Twenty-nine subjects with intrabony defects in single-rooted tooth were randomly assigned to; (1) minimally invasive nonsurgical technique (MINST) or (2) minimally invasive surgical technique (MIST). Quantities of Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Porphyromonas gingivalis, determined by using real-time PCR, were evaluated at baseline, 3, 6, and 12 months after the treatments. Clinical recordings--probing depth (PD), position of the gingival margin (PGM), and relative clinical attachment level (RCAL)--were obtained at baseline and 12 months post-therapy. The primary outcome variable of the study was RCAL. RESULTS: Both treatment modalities resulted in an improvement in all clinical recordings, with significant PD reductions (p < 0.05), RCAL gains (p < 0.05), and no change in the PGM (p > 0.05) after 12 months in both MINST and MIST groups. No clinical differences were observed between groups (p > 0.05). Regarding the microbiological outcomes, at the re-examinations, a significant decrease was observed for T. forsythia and P. gingivalis when compared with baseline (p < 0.05) for both treatments. The amount of A. actinomycetemcomitans did not reduced decrease throughout the study (p > 0.05). Intergroup differences in the microbiological assay were not found at any time point (p > 0.05). CONCLUSIONS: Both MINST and MIST provided comparable clinical results and microbiological changes in the treatment of intrabony defects over 12 months follow-up. CLINICAL RELEVANCE: This randomized, controlled, parallel trial revealed that both therapeutic modalities may promote clinical and microbiological benefits at 12 months post-therapy.

Frequency of periodontal pathogens in equivalent peri-implant and periodontal clinical statuses.

OBJECTIVES: This study tested the hypotheses that there is: (1) higher bacterial frequency in peri-implantitis/periodontitis, followed by mucositis/gingivitis and peri-implant/periodontal health; (2) similar bacterial frequency between comparable peri-implant and periodontal clinical statuses. DESIGN OF STUDY: The presence of Porphyromonas gingivalis, Tannerella forsythia, Campylobacter rectus, Prevotella intermedia, Treponema denticola and Aggregatibacter actinomycetemcomitans was evaluated in peri-implant (n=53) and periodontal (n=53) health; mucositis (n=50), gingivitis (n=50), peri-implantitis (n=50) and periodontitis (n=50). RESULTS: The pattern of peri-implant bacterial frequency was not as expected (peri-implantitis>mucositis>health). Except for P. intermedia (p>0.05), bacterial frequency was higher in peri-implantitis than health (p<0.05). The frequency of P.gingivalis and red complex species were higher in peri-implantitis than mucositis (p<0.05). In periodontal samples, T. forsythia and T. denticola showed the expected pattern of frequency (periodontitis>gingivitis>health). The frequencies of C. rectus and T. forsythia were higher in healthy teeth/gingivitis than healthy implants/mucositis, respectively (p<0.05). The frequency of P. gingivalis and A. actinomycetemcomitans were similar between periodontitis and peri-implantitis (p>0.05) while all other species occurrences were higher in periodontitis than peri-implantitis (p<0.05). CONCLUSIONS: Bacterial frequency increased from peri-implant/periodontal health to peri-implantitis/periodontitis but not from mucositis/gingivitis to peri-implantitis/periodontitis. There was a trend towards higher bacterial frequency in teeth than implants.

Host responses induced by different animal models of periodontal disease: a literature review.

Periodontitis is an infectious disease characterized by chronic inflammation of the periodontium, and it is mediated and modulated by the host immune system. In the presence of microorganisms or other antigens, immune cells (macrophages/monocytes, dendritic cells, lymphocytes, neutrophils), endothelial cells and fibroblasts secrete cytokines and trigger immune and inflammatory reactions. However, when synthesized at high levels, cytokines modify the pattern of cellular response, participating substantially in the development of chronic inflammatory pathologies, such as periodontal disease. Understanding the origin and progression of bone resorption is one of the primary goals of the field of periodontics, aiming to arrest the disease progression and to optimize future treatments. For this purpose, the development of experimental models is an important and necessary step before entering into clinical trials with new therapies. The purpose of this study is to characterize/evaluate the tissue changes induced by various models of experimental periodontitis through a literature review.

Experimental arthritis exacerbates Aggregatibacter actinomycetemcomitans-induced periodontitis in mice.

AIM: This study aimed to investigate whether chronic antigen-induced arthritis (AIA) influences infection-induced periodontitis (PD) in mice and whether PD modifies the clinical course of AIA. The contribution of anti-TNF-α therapy was also evaluated. MATERIALS AND METHODS: The PD was induced in C57BL/6 mice by oral infection with Aggregatibacter actinomycetemcomitans. AIA was induced after infection. Anti-TNF-α and chlorhexidine therapies were used to investigate the role of TNF-α and oral infection on PD and AIA interaction. Maxillae, knee joints, lymph nodes and serum samples were used for histomorphometric, immunoenzymatic and/or real time-PCR analyses. RESULTS: Antigen-induced arthritis exacerbated alveolar bone loss triggered by PD infection. In contrast, PD did not influence AIA in the evaluated time-points. PD exacerbation was associated with enhanced production of IFN-γ in maxillae and expression of the Th1 transcription factor tBET in submandibular lymph nodes. Increased serum levels of IL-6 and C-reactive protein were also detected. Anti-TNF-α and antiseptic therapies prevented the development and exacerbation of infectious-PD. Anti-TNF-α therapy also resulted in reduced expression of IFN-γ, TNF-α and IL-17 in maxillae. CONCLUSIONS: Altogether, the current results indicate that the exacerbation of infection-induced PD by arthritis is associated with an alteration in lymphocyte polarization pattern and increased systemic immunoreactivity. This process was ameliorated by anti-TNF-α and antiseptic therapies.

Bacterial intensity and localization in primary molars with caries disease.

AIM: The aim was to assess the characteristics and outcomes of infections affecting the structures of carious primary molars. MATERIALS AND METHODS: Forty primary molars were used and classified according to the following clinical situation: With profound caries lesion, with bone loss at the furcation region, with perforation of the pulp chamber floor, and residual roots. The teeth were demineralized, cut, and stained with both haematoxylin-eosin and Brown and Brenn staining techniques. Assessment was performed using optical microscopy. RESULTS: Statistical analysis of the data by means of the Chi-square test suggests that there was a significant relationship (P<0.001) between the intensity and localization of infection and the level of destruction of dental structures. A significant difference was also observed in the intensity and localization of infection between the groups regarding crown, furca, and root (P<0.001). CONCLUSION: More intense and profound the infection, more severe is the dental destruction. The groups of residual roots showed the most severe bacterial infection compared to other groups.

A.actinomycetemcomitans-induced periodontal disease promotes systemic and local responses in rat periodontium.

AIM: To characterize the histologic and cellular response to A. actinomycetemcomitans (Aa) infection. MATERIAL & METHODS: Wistar rats infected with Aa were evaluated for antibody response, oral Aa colonization, loss of attachment, PMN recruitment, TNF-α in the junctional epithelium and connective tissue, osteoclasts and adaptive immune response in local lymph nodes at baseline and 4, 5 or 6 weeks after infection. Some groups were given antibacterial treatment at 4 weeks. RESULTS: An antibody response against Aa occurred within 4 weeks of infection, and 78% of inoculated rats had detectable Aa in the oral cavity (p < 0.05). Aa infection significantly increased loss of attachment that was reversed by antibacterial treatment (p < 0.05). TNF-α expression in the junctional epithelium followed the same pattern. Aa stimulated high osteoclast formation and TNF-α expression in the connective tissue (p < 0.05). PMN recruitment significantly increased after Aa infection (p < 0.05). Aa also increased the number of CD8(+) T cells (p < 0.05), but not CD4(+) T cells or regulatory T cells (Tregs) (p > 0.05). CONCLUSION: Aa infection stimulated a local response that increased numbers of PMNs and TNF-α expression in the junctional epithelium and loss of attachment. Both TNF-α expression in JE and loss of attachment was reversed by antibiotic treatment. Aa infection also increased TNF-α in the connective tissue, osteoclast numbers and CD8(+) T cells in lymph nodes. The results link Aa infection with important characteristics of periodontal destruction.