Periodontal tissues in health and disease: introduction

Preventive effects of melatonin on periodontal tissue destruction due to psychological stress in rats with experimentally induced periodontitis

OBJECTIVE AND BACKGROUND

Psychological stress is a potential modifiable environmental risk factor causally related to the exacerbation of periodontitis and other chronic inflammatory diseases. This animal study aimed to investigate comprehensively the preventive efficacy of systemic melatonin administration on the possible effects of restraint stress on the periodontal structures of rats with periodontitis.

METHODS

Forty-eight male Sprague Dawley rats were randomly divided into six groups: control, restraint stress (S), S-melatonin (S-Mel), experimental periodontitis (Ep), S-Ep, and S-Ep-Mel. Periodontitis was induced by placing a 3.0 silk suture in a sub-paramarginal position around the cervix of the right and left lower first molars of the rats and keeping the suture in place for 5 weeks. Restraint stress was applied simultaneously by ligation. Melatonin and carriers were administered to the control, S, Ep, and S-Ep groups intraperitoneally (10 mg/body weight/day, 14 days) starting on day 21 following ligation and subjection to restraint stress. An open field test was performed on all groups on day 35 of the study. Periodontal bone loss was measured via histological sections. Histomorphometric and immunohistochemical (RANKL and OPG) evaluations were performed on right mandibular tissue samples and biochemical (TOS (total oxidant status), TAS (total antioxidant status), OSI (oxidative stress index), IL-1β, IL-10, and IL-1β/IL-10) evaluations were performed on left mandibular tissue samples.

RESULTS

Melatonin significantly limited serum corticosterone elevation related to restraint stress (p < .05). Restraint stress aggravated alveolar bone loss in rats with periodontitis, while systemic melatonin administration significantly reduced stress-related periodontal bone loss. According to the biochemical analyses, melatonin significantly lowered IL-1β/IL-10, OSI (TOS/TAS), and RANKL/OPG rates, which were significantly elevated in the S-Ep group.

CONCLUSION

Melatonin can significantly prevent the limited destructive effects of stress on periodontal tissues by suppressing RANKL-related osteoclastogenesis and oxidative stress.

Is the efficacy of cone beam computed tomography in the diagnosis of tooth ankylosis influenced by dose reduction protocols?

OBJECTIVE

To evaluate the diagnostic efficacy of cone beam computed tomography (CBCT) examinations acquired with varying dose protocols in the diagnosis of simulated tooth ankylosis (TA).

STUDY DESIGN

Tooth ankylosis was simulated in 15 of 30 teeth, and CBCT examinations were acquired at 3 mA levels (8, 6.3, and 5) and 3 voxel sizes (0.08, 0.125, and 0.2 mm). Four radiologists independently assessed the presence of TA using a 5-point scale. Sensitivity, specificity, and area under the curve (AUC) obtained through receiver operating characteristic analysis were compared among mA levels and voxel sizes using two-way analysis of variance (α = 0.05). Intra- and interexaminer reliability levels were assessed with the weighted kappa examination.

RESULTS

Sensitivity was low (0.32-0.49), and specificity was reasonably high (0.71-0.83). Mean values of AUC were low, ranging between 0.54 and 0.67, which reveals poor overall discrimination between health and disease. The detection of TA was not significantly influenced by mA level or voxel size (P > .05). Intra- and interexaminer agreements ranged from slight to moderate (0.160-0.535) and from fair to substantial (0.236-0.697), respectively.

CONCLUSIONS

Despite the limited efficacy of CBCT for TA detection, when indicated as a complementary examination, mA reduction should be considered for dose optimization purposes.

A novel method of objectively detecting tooth ankylosis using cone-beam computed tomography: A laboratory study

Purpose

The aim of this study was to objectively detect simulated tooth ankylosis using a novel method involving cone-beam computed tomography (CBCT).

Materials and Methods

Tooth ankylosis was simulated in single-rooted human permanent teeth, and CBCT scans were acquired at different current levels (5, 6.3, and 8 mA) and voxel sizes (0.08, 0.125, and 0.2). In axial reconstructions, a line of interest was perpendicularly placed over the periodontal ligament space of 21 ankylosed and 21 non-ankylosed regions, and the CBCT grey values of all voxels along the line of interest were plotted against their corresponding X-coordinates through a line graph to generate a profile. The image contrast was increased by 30% and 60% and the profile assessment was repeated. The internal area of the resulting parabolas was obtained from all images and compared between ankylosed and non-ankylosed regions under different contrast enhancement conditions, voxel sizes, and mA levels using multi-way analysis of variance with the Tukey post hoc test (α=0.05).

Results

The internal area of the parabolas of all non-ankylosed regions was significantly higher than that of the ankylosed regions (P<0.05). Contrast enhancement led to a significantly greater internal area of the parabolas of non-ankylosed regions (P<0.05). Overall, voxel size and mA did not significantly influence the internal area of the parabolas (P>0.05).

Conclusion

The proposed novel method revealed a relevant degree of applicability in the detection of simulated tooth ankylosis; increased image contrast led to greater detectability.

Estimation of soluble CD14 levels in gingival crevicular fluid and serum in diseased and healthy periodontium

OBJECTIVE

To estimate the levels of sCD14 in gingival crevicular fluid and serum under periodontally-healthy and diseased conditions.

METHODS

The subjects were divided into three groups of 15, each as follows: healthy, gingivitis, and periodontitis. Periodontal parameters including Probing pocket depth, Clinical attachment level, Bleeding index, and Plaque index. Gingival crevicular fluid and serum samples were collected and analyzed for sCD14 levels using commercially-available ELISA kits.

RESULTS

The mean concentration of sCD14 in GCF was significantly lower in the gingivitis (134.5 ± 26.85 ng/mL) and periodontitis (103.23 ± 20.36 ng/mL) groups than in the healthy group (172.77 ± 46.33 ng/mL); p < 0.001. The mean serum concentration of sCD14 in the healthy group was 1528.13 ± 387.37 ng/mL, which was significantly less than that of the periodontitis group (2051.50 ± 381.10 ng/mL); p = 0.011.

CONCLUSIONS

The serum sCD14 levels in the periodontitis groups were significantly higher than those in the healthy controls. The levels of sCD14 in GCF were significantly lower in the gingivitis and periodontitis groups than in the healthy group.

Neutrophil proteolytic activation cascades: a possible mechanistic link between chronic periodontitis and coronary heart disease

Cardiovascular diseases are chronic inflammatory diseases that affect a large segment of society. Coronary heart disease (CHD), the most common cardiovascular disease, progresses over several years and affects millions of people worldwide. Chronic infections may contribute to the systemic inflammation and enhance the risk for CHD. Periodontitis is one of the most common chronic infections that affects up to 50% of the adult population. Under inflammatory conditions the activation of endogenous degradation pathways mediated by immune responses leads to the release of destructive cellular molecules from both resident and immigrant cells. Matrix metalloproteinases (MMPs) and their regulators can activate each other and play an important role in immune response via degrading extracellular matrix components and modulating cytokines and chemokines. The action of MMPs is required for immigrant cell recruitment at the site of inflammation. Stimulated neutrophils represent the major pathogen-fighting immune cells that upregulate expression of several proteinases and oxidative enzymes, which can degrade extracellular matrix components (e.g. MMP-8, MMP-9 and neutrophil elastase). The activity of MMPs is regulated by endogenous inhibitors and/or candidate MMPs (e.g. MMP-7). The balance between MMPs and their inhibitors is thought to mirror the proteolytic burden. Thus, neutrophil-derived biomarkers, including myeloperoxidase, may activate proteolytic destructive cascades that are involved in subsequent immune-pathological events associated with both periodontitis and CHD. Here, we review the existing studies on the contribution of MMPs and their regulators to the infection-related pathology. Also, we discuss the possible proteolytic involvement and role of neutrophil-derived enzymes as an etiological link between chronic periodontitis and CHD.

Cementum and Periodontal Ligament Regeneration

The unique anatomy and composition of the periodontium make periodontal tissue healing and regeneration a complex process. Periodontal regeneration aims to recapitulate the crucial stages of wound healing associated with periodontal development in order to restore lost tissues to their original form and function and for regeneration to occur, healing events must progress in an ordered and programmed sequence both temporally and spatially, replicating key developmental events. A number of procedures have been employed to promote true and predictable regeneration of the periodontium. Principally, the approaches are based on the use of graft materials to compensate for the bone loss incurred as a result of periodontal disease, use of barrier membranes for guided tissue regeneration and use of bioactive molecules. More recently, the concept of tissue engineering has been integrated into research and applications of regenerative dentistry, including periodontics, to aim to manage damaged and lost oral tissues, through reconstruction and regeneration of the periodontium and alleviate the shortcomings of more conventional therapeutic options. The essential components for generating effective cellular based therapeutic strategies include a population of multi-potential progenitor cells, presence of signalling molecules/inductive morphogenic signals and a conductive extracellular matrix scaffold or appropriate delivery system. Mesenchymal stem cells are considered suitable candidates for cell-based tissue engineering strategies owing to their extensive expansion rate and potential to differentiate into cells of multiple organs and systems. Mesenchymal stem cells derived from multiple tissue sources have been investigated in pre-clinical animal studies and clinical settings for the treatment and regeneration of the periodontium.

Analysis of interleukin-8 gene variants reveals their relative importance as genetic susceptibility factors for chronic periodontitis in the Han population

Interleukin (IL)-8, an important chemokine that regulates the inflammatory response, plays an important role in periodontitis. Previous studies indicate that certain IL-8 gene polymorphisms are associated with periodontitis susceptibility in some populations. However, the literature is somewhat contradictory, and not all IL-8 polymorphisms have been examined, particularly in Han Chinese individuals. The aim of this study was to investigate the association of every IL-8 SNP with chronic periodontitis in Han Chinese individuals. We analyzed 23 SNPs with minor allele frequency (MAF)≥0.01, which were selected from 219 SNPs in the NCBI dbSNP and preliminary HapMap data analyses from a cohort of 400 cases and 750 controls from genetically independent Han Chinese individuals. Single SNP, haplotype and gender-specific associations were performed. We found that rs4073 and rs2227307 were significantly associated with chronic periodontitis. Further haplotype analysis indicated that a haplotype block (rs4073-rs2227307-rs2227306) that spans the promoter and exon1 of IL-8 was highly associated with chronic periodontitis. Additionally, the ATC haplotype in this block was increased 1.5-fold in these cases. However, when analyzing the samples by gender, no significant gender-specific associations in IL-8 were observed, similar to the results of haplotype association analyses in female and male subgroups. Our results provide further evidence that IL-8 is associated with chronic periodontitis in Han Chinese individuals. Furthermore, our results confirm previous reports suggesting the intriguing possibilities that IL-8 plays a role in the pathogenesis of chronic periodontitis and that this gene may be involved in the etiology of this condition.

The plasminogen activation system in periodontal tissue (Review)

The plasminogen activation system (PAS) plays an essential role in tissue proteolysis in physiological and pathological processes. Periodontitis is a chronic infection associated with increased proteolysis driven by plasminogen activation. In this comprehensive review, we summarise the effects of PAS in wound healing, tissue remodelling, inflammation, bacterial infection, and in the initiation and progression of periodontal disease. Specifically, we discuss the role of plasminogen activators (PAs), including urokinase PA (uPA), tissue-type PA (tPA), PA inhibitor type 1 (PAI-1) and 2 (PAI-2) and activated plasminogen in periodontal tissue, where their concentrations can reach much higher values than those found in other parts of the body. We also discuss whether PA deficiencies can have effects on periodontal tissue. We conclude that in periodontal disease, PAS is unbalanced and equalizing its function can improve the clinical periodontal tissue condition.

Potential effect of neutrophil functional disorders on pathogenesis of aggressive periodontitis

INTRODUCTION

Leukocytes play a key role in maintaining the balance between an effective host defence response to microorganisms and periodontal tissue destruction. Neutrophil dysfunction has been associated with increased susceptibility to periodontal diseases. We undertook this study to determine to what extent neutrophil dysfunction constitutes to the pathogenesis of aggressive periodontitis (AgP) in tropical country like ours.

MATERIALS AND METHODS

Age- and sex-matched groups consisting of 20 subjects each of generalized aggressive periodontitis (GAP)-cases and nonperiodontitis (NP)-controls. diabetes mellitus, HIV infection, prolonged antibiotic use and smoking were excluded. Each neutrophil function was assessed using the chemotactic assay using case in, phagocytosis assay, candidacidal assay (for intracellular killing) and NBT assay (for respiratory burst failure).

STATISTICAL ANALYSIS USED

Student's t-test, Fisher's exact test and Chi-square test.

RESULTS

In the study 17 out of 20 subjects (85%) had at least one abnormal neutrophil assay either hypofunctional or hyperfunctional of which 16 (80%) had hypofunctional assays and 8 (40%) had hyperfunctional assays. Defective phagocytosis was the commonest (50%) followed by chemotactic defect (45%), defective respiratory burst (40%) and defective intracellular killing (30%). Mean of chemotaxis assay was significantly less in AgP when compared to controls (103 vs 129 µm, p=0.002), similarly for phagocytic defect (3.45 vs 4.65, p≤0.001) and with candidacidal assay (26.80 vs 37.35, p<0.001).

CONCLUSION

The prevalence of neutrophil dysfunction, predominantly hypofunctional, was significantly very high in GAP patients with few even having hyperactive respiratory burst function. Multiple level neutrophil defects could account for the aggressive nature of AgP even in apparently healthy subjects.

Gingival fibroblasts inhibit MMP-1 and MMP-3 activities in an ex-vivo artery model

The main arterial pathologies can be associated with a deregulation of remodeling involving matrix metalloproteinases (MMPs), whereas gingival healing is characterized by an absence of fibrosis or irreversible elastin/collagen degradation. The aim of our study was to evaluate the effect of gingival fibroblasts on MMP-1 and MMP-3 secretion in an organotypic artery culture. MMP-1 and MMP-3 secretions and activities (dot blots, zymography, ELISA) were evaluated in coculture of rabbit artery in the presence or not of gingival fibroblasts. MMP-1/TIMP-1 and MMP-3/TIMP-1 complexes forms were measured by ELISA. Complementary studies were performed using human aortic smooth muscle cells cocultured with adventitial, dermal, or gingival fibroblasts. Our results indicated that MMP-1 and MMP-3 free-forms activities were significantly reduced in coculture. This inhibition was linked to a significant increase of TIMP-1 leading to formation of TIMP-1/MMPs complexes. Due to the presence of gingival fibroblasts, the decrease in MMP-1 and MMP-3 efficiency thus contributes to diminish the degradation of artery. This cellular therapy strategy could be promising in artery pathologies treatment.