Cigarette smoke inhalation increases the alveolar bone loss caused by primary occlusal trauma in a rat model

Cytokine expression in gingival crevicular fluid around teeth opposing dental implants and 3-unit fixed partial dentures in a cross-sectional study

OBJECTIVE

This study aimed to study the cytokines in gingival crevicular fluid (GCF) of the teeth opposing to dental implants and 3-unit fixed partial dentures (FPDs).

MATERIALS AND METHODS

A total of 74 participants were recruited for this cross-sectional study. Based on the status of lower first molars, the participants were divided into dental implants group and 3-unit FPDs group. Social index and oral hygiene were recorded. Occlusal loading was evaluated with a T-scan. GCF was sampled from the upper first molar and assessed with a commercial cytokine assay kit.

RESULTS

Forty three dental implants patients and 31 3-unit FPDs patients received all of the clinical and laboratory evaluation. The dental implants group had a higher occlusion force distribution on first molars region. IL-10, IL-17, RANK had a higher mean in dental implants group and was associated with occlusion force of first molar. There was a weakly association between IL-10 and dental implants in the binary logistic regression analyses.

CONCLUSIONS

In this study, the teeth opposing implants have a higher level of cytokines in the GCF than teeth opposing to 3-unit FPDs in periodontal healthy participants because of the poor osseoperception of dental implants. IL-10 might reflect a higher occlusion force in dental implants region.

CLINICAL RELEVANCE

This study provided that different tooth restoration methods could influence the periodontal status of the contact teeth.

Study on the role of pyroptosis in bone resorption induced by occlusal trauma with or without periodontitis

BACKGROUND AND OBJECTIVE

Occlusal trauma is considered to be a contributing factor to bone loss associated with inflammatory periodontal disease. We hypothesized that pyroptosis, a recently discovered inflammation-induced programmed cell death pathway, plays a role in occlusal trauma.

MATERIALS AND METHODS

The occlusal trauma model was established using a cemented 1-mm elevated computer-aided design and manufacturing (CAD/CAM) metal crown. The periodontitis model was established by periodontal wire ligation with lipopolysaccharide (LPS) injection. The rats were sacrificed at 1, 2, 3, and 4 weeks. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression of pyroptosis-, inflammation-, and osteoclast-related markers. Micro-computed tomography (micro-CT) was used to determine bone morphology parameters. Tissue morphology was evaluated using hematoxylin and eosin staining (H&E). Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP) staining. The expression and distribution of factors related to pyroptosis and inflammation were evaluated by immunohistochemistry (IHC). The colocalization of dead cells and cysteinyl aspartate-specific proteinase-1 (caspase-1)-positive cells was analyzed by immunofluorescence.

RESULTS

Quantitative real-time polymerase chain reaction and IHC results showed that occlusal trauma induced the expression of pyroptotic factors during the early stages, while occlusal trauma with periodontitis upregulated the expression of pyroptotic factors at the later stages. The results of qRT-PCR, TRAP staining, and micro-CT showed that occlusal trauma with periodontitis increased the production of proinflammatory cytokines, leading to severe bone loss. Glyburide, an NOD-like receptor pyrin domain containing protein 3 (NLRP3)inhibitor, reduced the expression of pyroptosis markers induced by occlusal trauma with periodontitis and reversed bone resorption.

CONCLUSIONS

Pyroptosis was involved in bone loss induced by occlusal trauma with or without periodontitis, while glyburide reversed inflammation and bone resorption.

Wnt4 regulates bone metabolism through IKK-NF-κB and ROCK signaling under occlusal traumatic periodontitis

BACKGROUND AND OBJECTIVE

Occlusal trauma is one of the most important local contributing factors of periodontitis. It has been reported that Wnt4, a noncanonical Wnt ligand, can inhibit osteoclast formation and inflammation and promote bone formation in vivo. However, the prospects of Wnt4 application in occlusal trauma and periodontitis have not yet been described. This study aimed to investigate the function and the corresponding mechanism of Wnt4 to regulate bone metabolism in occlusal trauma and periodontitis.

MATERIAL AND METHODS

Osteogenic-induced MC3T3-E1 cells were treated with or without Porphyromonas gingivalis lipopolysaccharide (Pg. LPS) under cyclic uniaxial compressive stress. After treatment with mouse recombinant protein Wnt4 (rWnt4), the expression of osteogenic markers and activation of the IKK-NF-κB signaling pathway were evaluated in vitro. To investigate whether Wnt4 can promote osteogenesis via the ROCK signaling pathway, the expression of RhoA was evaluated in vitro. Finally, we evaluated the change in bone quantity and the activation of the IKK-NF-κB and ROCK signaling in mice with occlusal trauma and periodontitis to demonstrate the therapeutic efficacy of rWnt4 injection.

RESULTS

Stimulation of traumatic force and Pg. LPS stimulation suppressed the expression of osteoblast markers, but their expression was rescued after rWnt4 treatment in vitro. In addition, the inhibition of the ROCK signaling pathway induced by force loading was reversed when rWnt4 was applied in vitro. Micro-CT, H&E, and TRAP staining of the mandibles showed increased bone loss in the occlusal trauma-aggravated periodontitis group, whereas it was rescued after rWnt4 injection. The expression levels of IκBα and p65 were upregulated in occlusal trauma and periodontitis-bearing mice, whereas the expression levels of Runx2 and RhoA were downregulated. After rWnt4 injection, remarkably upregulation of Runx2 and RhoA expression was observed in occlusal trauma and periodontitis- bearing mice.

CONCLUSION

Wnt4 not only inhibits IKK-NF-κB signaling but also activates ROCK signaling to inhibit osteoclast formation and promote bone regeneration in occlusal trauma and periodontitis-bearing mice.

Effect of nicotine exposure on the rate of orthodontic tooth movement: A meta-analysis based on animal studies

Background

Nicotine exposure has been reported to modify bone cell function and the osseous metabolism with potential effects on the rate of orthodontic tooth movement.

Objectives

To systematically investigate and quantitively synthesize the most recent available evidence from animal studies regarding the effect of nicotine exposure on the rate of orthodontic tooth movement.

Search methods

Unrestricted searches in 7 databases and hand searching were performed until July 2020 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ProQuest Dissertations and Theses Global).

Selection criteria

We searched for controlled studies on healthy animals investigating the effect of nicotine on the rate of orthodontic tooth movement.

Data collection and analysis

Following study retrieval and selection, relevant data was extracted and the risk of bias was assessed using the SYRCLE’s Risk of Bias Tool. Exploratory synthesis and meta-regression were carried out using the random effects model.

Results

From the initially identified records, 5 articles meeting the inclusion criteria were selected and no specific concerns regarding bias were identified. Quantitative data synthesis showed that the rate of orthodontic tooth movement in the nicotine exposed rats was higher than in the control group animals (2 weeks of force application; 0.317 mm more movement in nicotine exposed rats; 95% Confidence Interval: 0.179–0.454; p = 0.000). No effect of the concentration or the duration force application was demonstrated following exploratory meta-regression.

Conclusion

Rats administered with nicotine showed accelerated rates of orthodontic tooth movement. Although, information from animal studies cannot be fully translated to human clinical scenarios, safe practice would suggest that the orthodontist should be able to identify patients exposed to nicotine and consider the possible implications for everyday clinical practice.

Occlusion Heightened by Metal Crown Cementation is Aggressive for Periodontal Tissues

PURPOSE

To investigate the effect of experimental traumatic occlusion (ETO) induced by metal crowns on alveolar bone loss.

MATERIALS AND METHODS

Metal crowns were custom-made for the lower first molars with occlusal discrepancy of 0.4 and 0.7 mm from the maximum intercuspation. Thirty-six animals were randomly divided into three groups (n = 12 animals per group): 0.4-mm hyperocclusion group, 0.7-mm hyperocclusion group and the sham group (no metal crown). Twenty-eight days after crown cementation, the animals were euthanized and gingival tissue was collected to assess cytokine levels of IL-17, IL-6, and TNF-α using enzyme-linked immunosorbent assay (ELISA). Mandibles were stained with 1% methylene blue and alveolar bone levels were quantified. Western blotting was used to quantify the expression of receptor activator of nuclear factor κ B (RANK), and its ligand (RANKL), secreted osteoclastogenic factor of activated T cells (SOFAT) and TNF-α-converting enzyme (TACE). Also, mandibles were histologically processed and stained with hematoxylin and eosin, from which the presence of osteoclast-like cells, multinucleated cells containing ≥3 nuclei was counted at 100× magnification. The data were analyzed using one-way ANOVA and Tukey tests.

RESULTS

Experimental occlusal trauma for 28 consecutive days significantly increased alveolar bone loss and multinucleated cell counts (p < 0.05). RANK, RANKL, SOFAT, TACE, IL-6, and TNF-α were significantly higher in gingival tissues of ETO groups (p < 0.05). IL-17 titers were unchanged among the groups (p > 0.05).

CONCLUSION

Experimental traumatic occlusion activates and sustains bone resorption pathways in the periodontium inducing alveolar bone resorption. As the intensity of occlusal trauma increased, alternative osteoclastic pathways were activated, such as TACE and SOFAT.

Traumatic compressive stress inhibits osteoblast differentiation through long chain non-coding RNA Dancr

BACKGROUND

Occlusal trauma is an important local contributing factor aggravating periodontal pocket and alveolar bone absorption in periodontal diseases. Our previous studies have found that occlusal trauma inhibited osteogenic differentiation through nuclear factor (NF)-κB signaling. To further investigate the underlying mechanism, the aim of this study was to explore the role of long chain non-coding differentiation antagonizing non-protein coding RNA (Dancr) in the inhibitory effect of traumatic stress on osteoblast differentiation.

METHODS

We took the MC3T3-E1 cells as object in vitro research and stimulated cells with simple stress load, Dancr-siRNA + stress load, Dancr overexpression-plasmid + stress load. Quantitative real-time polymerase chain reaction was used to detect the RNA expression levels of Dancr, alkaline phosphatase (Alp) and Runt-related transcription factor 2 (Runx2). The protein expressions of Alp and Runx2 were tested by Western blot and the activity of Alp was qualitatively demonstrated by Alp staining. In addition, Western blot was performed to investigate the role of Dancr in affecting NF-κB signaling pathway.

RESULTS

Traumatic compressive stress inhibited the expressions of Alp, Runx2, andDancr in MC3T3-E1 cells. Stress-induced inhibition of osteoblast differentiation was promoted after silencing Dancr. Overexpression of Dancr could alleviate the inhibitory effect of traumatic force on osteoblast differentiation to some extent. Furthermore, NF-κB signaling was activated after silencing Dancr, and the activated effect of traumatic force on NF-κB signaling could be alleviated through overexpression of Dancr to some extent.

CONCLUSION

Traumatic compressive stress can indirectly activate the NF-κB signaling through downregulation of Dancr, thereby inhibiting osteogenic differentiation.

Occlusal trauma inhibits osteoblast differentiation and bone formation through IKK-NF-κB signaling

BACKGROUND

Occlusal trauma is an important factor promoting bone loss caused by periodontal diseases. Although there are reports of traumatic force promoting bone resorption in periodontal diseases, no studies examining the inhibition of bone formation by traumatic force and the underlying mechanism have been reported. The aim of this study was to investigate the mechanism whereby traumatic force inhibits bone formation.

METHODS

MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without stimulation with Pg. LPS. The expression of osteoblast markers and the activation of IKK-NF-κB signaling were evaluated in vitro. Then, MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without IKK-2 Inhibitor VI. The expression of osteoblast markers was determined. Then, the classic Wnt signaling pathway (β-catenin, Gsk3β, p-Gsk3β, and Dkk1) was further evaluated in vitro. Finally, occlusal trauma was induced in Wistar rats with or without the injection of IKK-2 Inhibitor VI, to evaluate changes in bone mass and IKK-NF-κB and Wnt/β-catenin signaling in vivo.

RESULTS

After stimulation with Pg. LPS and traumatic force, IKK-NF-κB signaling was significantly activated in vitro. The expression of osteoblast markers and the activity of alkaline phosphatase in MC3T3-E1 cells declined after traumatic force loading and were rescued when IKK-NF-κB signaling was blocked. Wnt/β-catenin signaling was accordingly inhibited upon force loading, but this inhibition was reversed when IKK-NF-κB was antagonized in vitro. X-ray and Micro-CT analysis of the mandibles of the rats as well as HE and TRAP staining showed that bone loss induced by occlusal trauma declined after IKK-NF-κB was inhibited. The expression of p65 and IκBα was increased when occlusal trauma was induced in Wistar rats, whereas β-catenin, OCN, and Runx2 levels were decreased. After blocking IKK-NF-κB, significant upregulation of β-catenin, OCN, and Runx2 was observed in rats suffering from occlusal trauma.

CONCLUSIONS

IKK-NF-κB signaling could be activated by traumatic force or occlusal trauma. Its activation promoted the degradation of β-catenin, ultimately inhibiting osteogenic differentiation in vitro and bone formation in vivo.

Effect of tobacco on periodontal disease and oral cancer

INTRODUCTION

Periodontal disease and oral cancer are common health hazards. Epidemiological investigations show that smoking, periodontal disease and oral cancer are closely related. Tobacco is one of the major risk factors for periodontitis and oral cancer.

METHODS

A systematic literature review was performed. To identify relevant studies, the following online databases were searched using specific keywords: PubMed, Web of Science and CNKI.

RESULTS

Tobacco not only possesses an addictive effect, but it aggravates periodontal disease by promoting the invasion of pathogenic bacteria, inhibiting autoimmune defense, aggravating the inflammatory reaction, and aggravating the loss of alveolar bone. According to current evidence, tobacco significantly aggravates the development and progression of periodontal disease and oral cancer, and periodontal disease may be related to the prevalence of oral cancer.

CONCLUSIONS

Clinicians should strongly recommend that smokers undertake a strategy to stop smoking to avoid the exacerbation of nicotine-related periodontal disease and to reduce the incidence of oral cancer.

Resveratrol suppresses the alveolar bone resorption induced by artificial trauma from occlusion in mice

OBJECTIVE

Besides inflammatory bone loss, trauma from occlusion (TO)-induced alveolar bone loss increases the risk of future tooth loss. We have shown that resveratrol, a polyphenol, possesses anti-inflammatory characteristics and a suppressive effect on osteoclastogenesis. Therefore, we investigated the effects of resveratrol on TO-induced bone loss in mice.

MATERIAL AND METHODS

Trauma from occlusion was induced by overlaying composite resin onto the maxillary first molar of C57BL/6 mice. TO-induced mice were administered either resveratrol or vehicle for 15 days from 5 days before TO induction. The mice administered vehicle only served as controls. The effect of resveratrol on bone resorption was assessed histologically. Gene expression in gingival and periodontal ligament tissues was analyzed. In vitro effect of resveratrol on the differentiation of RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells was analyzed.

RESULTS

Resveratrol administration significantly decreased the bone loss and suppressed the elevated expression of osteoclastogenesis-related gene in periodontal ligament tissue by TO. Resveratrol treatment also suppressed the differentiation of both RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells.

CONCLUSION

Resveratrol administration suppressed the TO-induced alveolar bone loss by suppressing osteoclast differentiation, suggesting that resveratrol is effective in preventing both inflammation and mechanical stress-induced alveolar bone resorption.

Effects of passive inhalation of cigarette smoke on structural and functional parameters in the respiratory system of guinea pigs

Objective:

To evaluate the effects of passive inhalation of cigarette smoke on the respiratory system of guinea pigs.

Methods:

Male guinea pigs were divided into two groups: control and passive smoking, the latter being exposed to the smoke of ten cigarettes for 20 min in the morning, afternoon and evening (30 cigarettes/day) for five days. After that period, inflammatory parameters were studied by quantifying mesenteric mast cell degranulation, as well as oxidative stress, in BAL fluid. In addition, we determined MIP, MEP, and mucociliary transport (in vivo), as well as tracheal contractility response (in vitro).

Results:

In comparison with the control group, the passive smoking group showed a significant increase in mast cell degranulation (19.75 ± 3.77% vs. 42.53 ± 0.42%; p < 0.001) and in the levels of reduced glutathione (293.9 ± 19.21 vs. 723.7 ± 67.43 nM/g of tissue; p < 0.05); as well as a significant reduction in mucociliary clearance (p < 0.05), which caused significant changes in pulmonary function (in MIP and MEP; p < 0.05 for both) and airway hyperreactivity.

Conclusions:

Passive inhalation of cigarette smoke caused significant increases in mast cell degranulation and oxidative stress. This inflammatory process seems to influence the decrease in mucociliary transport and to cause changes in pulmonary function, leading to tracheal hyperreactivity.

Chronic periodontitis and smoking. Prevalence and dose-response relationship

OBJECTIVES

To determine the prevalence and dose-response relationship of chronic periodontitis among smokers in Pakistan.

METHODS

  This is a cross-sectional study among participants seeking dental care in Karachi Medical and Dental College, Karachi, Pakistan. A total of 443 participants with a mean age of 44.3 (±6.5) participated in the study from April 2011 to December 2011. Males comprised 64.7%, and females comprised 35.2%. Participants were interviewed on social demographics and oral habits. Participants with shallow pockets (3.5-5.5 mm) and deep pockets (greater than 5.5 mm) were considered suffering from chronic periodontitis. The characteristics of participants were assessed using frequency distribution for categorical variables and mean (standard deviation) for continuous variables. 

RESULTS

Among 443 participants, smokers were distributed as 55.1% and non-smokers as 44.9%. Smoking was found to be significantly related to young adults (p less than 0.007), male gender (p less than 0.001), and lower education level (p less than 0.01). Overall prevalence of chronic periodontitis among smokers was estimated at 81.6%. Heavy smoking was found to have significantly high prevalence (p less than 0.001) and severity (p less than 0.001) of periodontitis as compared with moderate and light smokers. The multivariate unadjusted model depicted 3.5 times higher risk of chronic periodontitis among smokers (p less than 0.001).

CONCLUSION

Chronic periodontitis had a high prevalence among smokers. Heavy smoking was found to have a higher risk for having periodontitis.

Evaluation of bone loss due to primary occlusal trauma in two experimental models of occlusal overload

Abstract Introduction Primary occlusal trauma (OT) is an injury of the periodontium with normal height as a result of occlusal forces which exceed their adaptive capacity. Objective To evaluate, histometrically, the alveolar bone loss in the furcation region of rats experimentally submitted to 2 models of occlusal overload. Material and method 45 animals randomly divided into 3 groups: Occlusal Interference (OI, n = 15) - fixing an orthodontic wire segment on the occlusal surface of the first lower molar; Occlusal Overload (OO, n = 15) - wearing of the cusps of the lower contralateral molars, the second and third molars next to the first molar that had its dimensions maintained; Negative Control (NC, n = 15) - evaluation of the initial dimensions of the periodontal ligament (PL). Five animals / group were sacrificed after 14, 21 and 28 days. Result Intergroup evaluation showed significant bone loss in OI (p<0.001) and OO (p<0.01) compared to NC. OI had significantly higher bone loss compared to OO at 14 (p<0.01), 21 (p <0.01) and 28 days (p<0.01). The intragroup evaluation showed no significant influence of time on bone loss in OI and OO, regardless of the technique used (p>0.05). The thickness of the PL remained stable in NC (p>0.05). Conclusion OI and OO were effective in the experimental reproduction of OT, and OI promoted greater alveolar bone loss compared to OO, showing that the impact of occlusal overload in OI increased the extent of the OT injury.

Autophagy Has a Beneficial Role in Relieving Cigarette Smoke-Induced Apoptotic Death in Human Gingival Fibroblasts

The deleterious role of cigarette smoke has long been documented in various human diseases including periodontal complications. In this report, we examined this adverse effect of cigarette smoke on human gingival fibroblasts (HGFs) which are critical not only in maintaining gingival tissue architecture but also in mediating immune responses. As well documented in other cell types, we also observed that cigarette smoke promoted cellular reactive oxygen species in HGFs. And we found that this cigarette smoke-induced oxidative stress reduced HGF viability through inducing apoptosis. Our results indicated that an increased Bax/Bcl-xL ratio and resulting caspase activation underlie the apoptotic death in HGFs exposed to cigarette smoke. Furthermore, we detected that cigarette smoke also triggered autophagy, an integrated cellular stress response. Interesting, a pharmacological suppression of the cigarette smoke-induced autophagy led to a further reduction in HGF viability while a pharmacological promotion of autophagy increased the viability of HGFs with cigarette smoke exposures. These findings suggest a protective role for autophagy in HGFs stressed with cigarette smoke, highlighting that modulation of autophagy can be a novel therapeutic target in periodontal complications with cigarette smoke.

FOXO1 Is Involved in the Effects of Cigarette Smoke Extract on Osteoblastic Differentiation of Cultured Human Periosteum-derived Cells

Cigarette smoke is associated with delayed fracture healing, alterations in mineral content, and osteoporosis, however, its effects on osteoblastic differentiation of osteoprogenitor cells are not fully understood. In the present study, we examined the effects of cigarette smoke extract (CSE) on osteoblastic differentiation of cultured human periosteum-derived cells. We found that CSE inhibited alkaline phosphatase (ALP) activity, mineralization and Runx2 transactivation of the periosteum-derived cells. Nucleofection of RUNX2 into the periosteum-derived cells increased expression of endogenous osteocalcin (OC) and ALP genes in osteogenic induction medium and increased OC expression in non-osteogenic medium. Treatment of the periosteum-derived cells with CSE resulted in decreased phosphorylation of AKT and forkhead box protein O1 (FOXO1). The AKT phosphorylation-resistant mutant, FOXO1-A3, inhibited transcriptional activity of RUNX2 in the periosteum-derived cells. The current study suggests one mechanism by which CSE exposure leads to inhibition of osteoblastic differentiation of cultured human periosteum-derived cells.