Periodontal Complex Research Articles

Association between periodontitis and COVID-19 infection: a two-sample Mendelian randomization study.

Epidemiological studies report associations between coronavirus disease 2019 (COVID-19) and periodontitis; however, causality has not been proven. The aim of this study is to assess the associations between COVID-19 susceptibility and periodontitis with two-sample Mendelian randomization (MR) analyses. A two-sample summary MR analysis was performed using data for outcome and exposure from the OpenGWAS database on people of European descent. Periodontal complex traits (PCTs) were chosen as a proxy for the periodontitis phenotype. The causal association between PCT3 (Aggregatibacter actinomycetemcomitans), PCT5 (Porphyromonas gingivalis), and gingival crevicular fluid (GCF) interleukin-1β (IL-1β) and COVID-19 were considered. Genome-wide association study (GWAS) data with the two largest sample sizes were selected as COVID-19 outcomes (datasets ebi-a-GCST010776 and ebi-a-GCST010777). Single-nucleotide polymorphisms (SNPs) associated with PCT3, PCT5, and GCF IL-1β at statistical significance at genome-wide level (P<5×10-8) were identified as genetic instruments. We used two-sample summary MR methods and tested the existence of a pleiotropic effect with MR-Egger. Inverse-variance weighted (IVW) estimates showed that there was a positive association between COVID-19 risk and periodontitis (ebi-a-GCST010776: odds ratio [OR] = 1.02 (95% confidence interval (CI), 1.00-1.05), P=0.0171; ebi-a-GCST010777: OR = 1.03 (95% CI, 1.00-1.05), P=0.0397). The weighted median also showed directionally similar estimates. Exploration of the causal associations between other PCTs and COVID-19 identified a slight effect of local inflammatory response (GCF IL-1β) on COVID-19 risk across the two datasets (ebi-a-GCST010776: IVW OR = 1.02 (95% CI, [1.01-1.03]), P<0.001; ebi-a-GCST010777: IVW OR = 1.03 (95% CI, [1.02-1.04]), P<0.001). The intercepts of MR-Egger yielded no proof for significant directional pleiotropy for either dataset (ebi-a-GCST010776: P=0.7660; ebi-a-GCST010777: P=0.6017). The findings suggests that periodontitis and the higher GCF IL-1β levels is causally related to increase susceptibility of COVID-19. However, given the limitations of our study, the well-designed randomized controlled trials are needed to confirm its findings, which may represent a new non-pharmaceutical intervention for preventing COVID-19.

Характеристика мікробіологічного профілю та дентальної біоплівки у віковому аспекті, її вплив на стоматологічний та пародонтальний статуси пацієнта

Summary. The oral cavity is a complex ecological system in which external factors (biological, individual, social) are closely interconnected with internal factors (tissues of the periodontal complex, dentin metabolites, microbial biofilm, local immune protection, epithelium of the oral cavity) and are in dynamic balance. The aim of the study. To investigate the level and trends of the development of scientific knowledge about oral biofilm and its management, leaving. Materials and methods. 24 еnglish-language and 37 domestic literary sources were processed. Conclusions. A detailed analysis of modern domestic and foreign literature convinces of the need for a thorough study of oral biofilms, as this will illuminate a complete picture of the etiology and pathogenesis of inflammatory diseases of the oral cavity. Having carefully studied biofilms and the mechanisms of their occurrence, we can carry out targeted treatment measures, while destroying the complex links of vital activity and interrelationships of microorganisms.The composition of dental plaque also changes at different anatomical loci in connection with the formed physical and biological properties of each site. A deeper understanding of the significance of dental plaque as a mixed biofilm may have a significant impact on clinical practice. Dental plaque cannot be completely eliminated, but the pathogenic nature of the biofilm can be reduced by reducing the bioburden and maintaining normal microflora with appropriate hygienic methods and oral care products. Key words: dentistry, periodontitis, age, periodontium, microorganisms, biofilm, periodontopathogens

Stem Cells in the Periodontium-Anatomically Related Yet Physiologically Diverse.

Periodontitis is a complex chronic disease discernible by the deterioration of periodontal tissue. The goal of periodontal therapy is to achieve complete tissue regeneration, and one of the most promising treatment options is to harness the regenerative potential of stem cells available within the periodontal complex. Periodontal ligament stem cells, gingival mesenchymal stem cells, oral periosteal stem cells, and dental follicle stem cells have structural similarities, but their immunological responses and features differ. The qualities of diverse periodontal stem cells, their immune-modulatory effects, and variances in their phenotypes and characteristics will be discussed in this review. Although there is evidence on each stem cell population in the periodontium, understanding the differences in markers expressed, the various research conducted so far on their regenerative potential, will help in understanding which stem cell population will be a better candidate for tissue engineering. The possibility of selecting the most amenable stem cell population for optimal periodontal regeneration and the development and current application of superior tissue engineering treatment options such as autologous transplantation, three-dimensional bioengineered scaffolds, dental stem cell-derived extracellular vesicles will be explored.

CYTOKINE-MEDIATED REACTIONS IN THE PATHOGENESIS OF EXPERIMENTAL PERIODONTITIS

Determining cytokinemia role in the destructive processes of the periodontal complex gives new opportunities to the development and subsequent implementation of practical methods for chronic periodontitis diagnosis, justifies including pathogenetic drugs that inhibit the secretion of pro-inflammatory mediators in treatment regimens.&#x0D; The aim of the study is to evaluate the dynamics of cytokine profile indicators and identify their correlation with the local status of periodontal tissues in animals with experimental periodontitis.&#x0D; Materials and methods. The study enrolled 65 white outbred rats weighing 180±20 g. The authors reproduced the model of experimental periodontitis according to K.D. Shkolnaya, V.G. Atrushkevich method (patent RU No. 2625295, December 07, 2017). The cytokine profile was assessed by pro-inflammatory and anti-inflammatory cytokine levels, determined by enzyme-linked immunosorbent assay, Bender MedSystems reagent kit. Local status of periodontal tissues was assessed according to the degrees of gingival hemorrhage, dental mobility and depth of periodontal pockets with a button-shaped and modified periodontal probes.&#x0D; Results. During the experimental periodontitis modeling, a high level of cytokinemia was determined. It destructively effects the periodontal connective tissue matrix, which was confirmed by an increase in the depth of periodontal pockets, gingival hemorrhage and dental mobility. A strong correlation between a high level of cytokinemia and local destructive changes in periodontal tissues was determined. This fact emphasized the conjugation of these pathophysiological mechanisms.&#x0D; Conclusion. Defined disorders of physiological balance in the cytokine balance necessitate the use of pathogenic drugs, as they have an inhibitory effect on the synthesis of pro-inflammatory cytokines and prevent further destruction of the periodontal complex. Changes in the cytokine profile indicate inflammation process, and a decrease in the level of cytokinemia indicate the resolution of infection and can be considered a criterion for the effective treatment.

The effect of the composition of Soderm®-Forte gel and the new injectable form of Rexod® on pathology findings in gingival tissue in experimental periodontitis in rats

Introduction: Periodontitis is the most important problem of modern dentistry. The development of new medicines and treatment regimens for patients with periodontal complex lesions is a strategic direction of modern pharmacology and dentistry. In this view, pride of place goes to morphological research, which allows not only to study the effect of drugs on pathomorphological changes in periodontal tissues, but also to estimate their therapeutic effectiveness. Aim of the study: to determine the nature of the effect of the composition of Soderm®-Forte gel and the new injectable form of Rexod® on the pathology findings in gingival tissue of rats with experimental periodontitis.&#x0D; Materials and methods: Experimental periodontitis (EP) was induced in rats by ligature method. The study was per­formed according to the following algorithm: animals with intact periodontium; animals with untreated EP; animals with EP treated with traditional drug therapy (TDT); animals with EP treated with combinations of TDT with Soder­m®-Forte gel and TDT with Soderm®-Forte gel and the new injectable form (NIF) of Rexod®. For pathomorphological examination, biopsy specimen was taken from the gingival margin of the lower incisors. The ImageJ software was used for computer morphometry.&#x0D; Results and discussion: Examination of the gum samples revealed moderate therapeutic effects of the TDT. The com­binations of TDT with Soderm®-Forte gel and, to a greater extent, TDT with Soderm®-Forte gel and the NIF of Rexod® showed high pharmacotherapeutic efficacy, manifested in rapid regeneration of the gingival tissues.&#x0D; Conclusion: The combination of TDT, Soderm®-Forte gel and the NIF of Rexod® shows the most beneficial effect on the pathological processes in the gum. The pharmacotherapeutic effect of the studied combination promotes the earliest regeneration of damaged gum tissues and reduces the risk of persistent pathology changes in them.

Morphological reorganization of periodontic tissues under experimental opioid influence for twelve weeks

Peculiarities of pathomorphological changes of periodontal components of rats under the long-term opioid influence during twelve weeks in the experiment have been studied.Objective – to determine the features of structural changes in the tissues of the periodontal complex of rats under conditions of long-term experimental action of opioids for twelve weeks.Methods. Adult male rats were administered the opioid analgesic nalbuphine for 12 weeks, in gradually increasing doses every 2 weeks. The initial dose was 0.212 mg / kg, 11-12 weeks - 0.3 mg / kg. Components of the dental organ of the upper and lower jaws of rats were used as material for histological examination. Sampling was performed at the end of week 12 of the experiment.Results. On histological preparations in the epithelium of the gums thinning, ulcers, desquamation, as well as the presence of areas of necrosis and inflammatory infiltrates were determined. Microscopic examinations of the epithelium of the free part of the gums in the gingival sulcus revealed foci of necrosis, accumulation of purulent bodies, damage to the epithelium of attachment and defragmentation of circular periodontal fibers, which led to the formation of periodontal pockets. Destruction of collagen fibers, purulent bodies, fibrinoid edema and fibrinoid necrosis were noted in the own plate. In the constituent components of the periodontium, the destruction of fibers with detachment from the connective tissue membrane of the dental cell, as well as signs of mucoid edema were determined. In the connective tissue of the periodontium observed thrombosis and stasis due to the coordination of blood cells, excessive proliferation of microvessels, diapedetic hemorrhage, which led to the progression of hypoxia.Conclusions. The experimental action of the opioid for 12 weeks revealed alternative changes, which were due to the deepening of dystrophy, necrosis of the soft tissues of the periodontium and severe hemomicrocirculation. Diffuse progression of the inflammatory-dystrophic process was due to insufficient activity of reparative processes, which indicated the irreversible nature of changes in the periodontium, which developed against the background of chronic opioid exposure.

Pathological Processes in Oral Cavity at Vitamin D-Resistant Rickets (Family Case Reports)

Vitamin D-resistant rickets of X-linked dominant transmission type is caused by pathology of renal tubular apparatus resulting in impaired absorption of calcium and phosphorus in the small intestine; it proceeds with the injuries of varying severity to skeletal system as well as dental and periodontal complex. The purpose of the study is to describe a family case of vitamin D-resistant rickets.

Hertwig's epithelial root sheath cells show potential for periodontal complex regeneration.

Although researchers have been exploring therapeutic strategies of treating serious periodontal tissue loss, including the application of stem cells, tissue regeneration of the periodontal complex involving cementum, periodontium, and alveolar bone has hardly been achieved. Aiming at tackling the problem of severely damaged periodontal complex, it is worth trying to make advantages of Hertwig's epithelial root sheath (HERS) cells to tissue regeneration mimicking the physiological developmental process with their ability of cementum, bone, and periodontium formation. HERS cells and dental follicle cells (DFCs) were acquired from Sprague Dawley rats' molar germs and identified by immunofluorescence. Alizarin red assay, ALP staining, AKP test, real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot were conducted to confirm the osteogenic potential, epithelial-mesenchymal transition (EMT) character of harvested HERS cells and epithelial-mesenchymal interaction (EMI) with DFCs. An animal model of periodontal defect was constructed to testify the tissue regeneration ability in vivo. Micro-CT and histological examinations were interpreted to unveil the tissue repair outcomes. HERS cells expressed strong epithelial cell markers CK14 and E-cadherin. The in vitro experiments overall showed the concretely enhanced osteogenic differentiation ability in either HERS group or HERS+DFC group. Meanwhile, the in vivo conduction of rat mandibular periodontal repair experiment showed regenerative effectiveness of periodontal complex structure in both HERS and HERS+DFC group in situ, testified by Micro-CT and histological analysis. HERS cells show potential for periodontal tissue regeneration which suggests the future possibilities of being considered as one of the cell choices for severely damaged periodontal tissue repair.

Long-acting PFI-2 small molecule release and multilayer scaffold design achieve extensive new formation of complex periodontal tissues with unprecedented fidelity

The faithful engineering of complex human tissues such as the bone/soft tissue/mineralized tissue interface in periodontal tissues requires innovative molecular cues in conjunction with tailored scaffolds. To address the loss of periodontal bone and connective tissues following periodontal disease, we have generated a polydopamine and collagen coated electrospun PLGA-PCL (PP) scaffold enriched with the small molecule mediator PFI-2 (PP-PFI-pDA-COL-PFI). In vitro 3D studies using PDL progenitors revealed that the PP-PFI-pDA-COL-PFI scaffold substantially enhanced Alizarin Red staining, increased Ca/P ratios 4-fold, and stimulated cell proliferation more than 12-fold compared to PP-controls, suggestive of its potential for mineralized tissue engineering. When applied in our experimental periodontitis model, the PP-PFI-pDA-COL-PFI scaffold resulted in a substantial 34% reduction in alveolar bone defect height, a 25% root-length gain in periodontal attachment, and the formation of highly ordered regenerated acellular cementum twice as thick as in controls. Explaining the mechanism of PFI-2 mineralized tissue regeneration in periodontal tissues, PFI-2 inhibited SETD7-mediated β-Catenin protein methylation and increased β-Catenin nuclear localization. Together, dual-level PFI-2 incorporation into a degradable, dopamine/collagen coated PLGA/PCL scaffold backbone resulted in the regeneration of the tripartite periodontal complex with unprecedented fidelity, including periodontal attachment and new formation of mineralized tissues in inflamed periodontal environments.

ДИНАМИКА ПОКАЗАТЕЛЕЙ ЦИТОКИНОВОГО ПРОФИЛЯ ПРИ ЭКСПЕРИМЕНТАЛЬНОМ ПАРОДОНТИТЕ

Abstract. The molecular level of physiological processes in the context of studying the pathogenesis of diseases is the basis for their diagnosis and treatment. Thus, the features of the pathogenesis of periodontitis are the direct participation of pro-inflammatory cytokines in the development of alterative inflammation. The study of the cytokine profile is relevant for both diagnostic and therapeutic purposes, since the dynamics of indicators of inflammatory mediators reflects the degree of activity and specificity of pathological reactions present in periodontitis. The purpose of the study Study of cytokine profile indicators in experimental periodontitis. Materials and methods. In an experiment on 50 white non-linear rats weighing 190-280 g, the model of experimental periodontitis proposed by Shkolnaya K.D., Atrushkevich V.G. was reproduced. (Patent RU No. 2625295 dated 07/12/2017). Assessment of the dynamics of the cytokine status of blood serum was carried out by the level of pro-inflammatory (IL-1β, TNF, IL-6, IL-17), anti-inflammatory (IL-4, IL-10) and regulatory (IL-2) cytokines using enzyme-linked immunosorbent assay using reagent kit "Bender MedSystems". Results. The study revealed the presence of an imbalance in the cytokine system, characterized by a violation of the physiological balance between pro-inflammatory and anti-inflammatory cytokines with a predominance of the former. Hyperproduction of cytokines persisted throughout the experiment with an increase in the above uncoupling by day 25, which indicates the formation of an immunoinflammatory process in the periodontium. Conclusion. The data obtained during the study confirm the presence of an imbalance of the cytokine network, which indicates the formation and progression of the inflammatory process of the periodontal complex, and also necessitates the introduction of drugs that inhibit the synthesis of pro-inflammatory mediators into complex therapy.

Novel approaches for periodontal tissue engineering.

The periodontal complex involves the hard and soft tissues which support dentition, comprised of cementum, bone, and the periodontal ligament (PDL). Periodontitis, a prevalent infectious disease of the periodontium, threatens the integrity of these tissues and causes irreversible damage. Periodontal therapy aims to repair and ultimately regenerate these tissues toward preserving native dentition and improving the physiologic integration of dental implants. The PDL contains multipotent stem cells, which have a robust capacity to differentiate into various types of cells to form the PDL, cementum, and alveolar bone. Selection of appropriate growth factors and biomaterial matrices to facilitate periodontal regeneration are critical to recapitulate the physiologic organization and function of the periodontal complex. Herein, we discuss the current state of clinical periodontal regeneration including a review of FDA-approved growth factors. We will highlight advances in preclinical research toward identifying additional growth factors capable of robust repair and biomaterial matrices to augment regeneration similarly and synergistically, ultimately improving periodontal regeneration's predictability and long-term efficacy. This review should improve the readers' understanding of the molecular and cellular processes involving periodontal regeneration essential for designing comprehensive therapeutic approaches.

EFFECTIVENESS OF MATRIX METALLOPROTEINASES INHIBITORS FOR PREVENTIVE TREATMENT OF GENERALIZED PERIODONTITIS

Generalized periodontitis is one of the most widespread human stomatological diseases; it is diagnosed in 11.0 % of the world's population. Despite the recognition of the microbial factor as leading in its etiopathogenesis, antimicrobial treatment of gingivitis, added with removal of dental plaque, does not prevent the further development of periodontitis. Dysbacteriosis causes inflammation which leads to an increase of proteolysis products. They are a nutrient medium for periodontal pathogenic microflora, they contribute to its growth. So, the use of anti-inflammatory drugs, such as matrix metalloproteinase inhibitors, is promising for preventive treatment of generalized periodontitis.&#x0D; The aim of the work is to conduct a clinical trial of complex treatment which includes matrix&#x0D; metalloproteinase inhibitors in patients with diffuse gingivitis and generalized periodontitis of chronic course.&#x0D; Materials and methods of the research. 60 patients with chronic course of diffuse gingivitis and generalized periodontitis of initial, I and II stages, were treated. The effectiveness of the treatment was evaluated in the early and distant term (after 1 year) according to data of the clinical and radiological examination, computer tomography, biochemical examination of oral fluid for matrix metalloproteinases-8 and -9 (MMP-8, -9) and immunohistochemical study of gingival biopsies for cytoplasmic expression of matrix metalloproteinase-1 (MMP-1).&#x0D; Results of the research. According to the data of the clinical examination, complete elimination of inflammatory symptoms in periodontal tissues was achieved in 93.3% of patients in the comparison group in 12-14 days and in 96.7% in the base group in 10-12 days. In patients in whom the developed therapeutic scheme was used, the best dynamics of the index assessment of the state of hygiene, gingiva and periodontal complex was established. The main difference between the research groups was the preservation of obtained results in 1 year after treatment in patients of the base group (p ˂ 0.05). In particular, a year later, the results of bone mineral density measurement for patients of the base group did not change from baseline, while in the comparison group there was their significant decrease (p ˂ 0.05), indicating the progression of inflammatory-destructive process in periodontal tissues.&#x0D; After treatment, a significant reduction in the level of MMP-8 and MMP-9 in the oral fluid of patients of both groups was achieved (p ˂ 0.05). In patients of the base group, in contrast to the comparison, these results were the same in the distant term (p ˂ 0.05). When assessing the cytoplasmic expression of MMP-1 in epithelial and stromal cells after treatment, zero result was in 96.7% of patients in the base group and in 80.0% – in the comparison group, and after 1 year – in 90.0% vs 63.3% respectively.&#x0D; It should be noted that the differences between the base and comparison groups were most observed for patients with gingivitis and generalized periodontitis of initial stage without destructive processes in periodontal tissues. It suggests the greatest effectiveness of the proposed treatment in the early stages of pathological process.&#x0D; Thus, based on the fact that the activity of matrix metalloproteinases characterizes the course of the inflammatory process in periodontal tissues, a decrease in their level according to biochemical and immunohistochemical studies in the base group against the comparison indicates a better anti-inflammatory effect of the developed treatment to prevent the progression of generalized periodontitis.&#x0D; Conclusion. The obtained results allow recommending the use of matrix metalloproteinase inhibitors as a preventive pathogenetic treatment for the patients with chronical course of gingivitis and generalized periodontitis of the initial stage, to inhibit the inflammatory component of the pathological process.&#x0D; Prospects for further research. It should be studied the indication for repeated courses of matrix metalloproteinase inhibitors in patients with periodontal disease.

The influence of the composition of the gel Soderm®-Forte and the metabolic energy corrector cytoflavin on the course of the inflammatory process in the conditions of experimental periodontitis

The study explored the possibility of combining the multitargent means of gel Soderm®-Forte and the metabolic energy corrector Cytoflavin in conditions of inflammatory pathology of periodontal tissues on a model of induced experimental periodontitis in rats. It is shown that the conduct of complex pharmacotherapy with drugs with antimicrobial, anti-inflammatory, energy-correcting and antioxidant orientation helps to reduce inflammatory phenomena in periodontal tissues, normalize osmotic exudation of the gingival fluid of the sulcular region and restore the index assessment of the tissues of the periodontal complex.&#x0D; The paper substantiates and shows the significance of the use of these drugs that can have a prolonged therapeutic effect on the peripheral microvascular network in the region of the gingival groove, reducing the exudative component in the postcapillary venules and arterioles by lowering perfusion pressure and reducing their permeability and improving protective effects under hypoxia.

Changes of ultrastructural organization in periodontal complex components in experimental periodontitis and its correction with quercetin

The article presents the results of study the changes of ultrastructural organization in the periodontal complex under conditions of experimental bacterial-immune periodontitis development and treatment effect of flavonol quercetin. Experimental bacterial-immune periodontitis in experimental animals was caused by injection of complex mixture of microorganisms diluted with egg protein into periodontal tissue. The evaluation of the ultrastructural character changes in the gingival area of the periodontal complex was carried out on the basis of electron microscopic examination. In a result study on the 7th day of the experiment were observed changes that manifested disorders of the connective tissue and vessels structure. It were also marked increased diffusive leukocytic infiltration of the connective tissue of the mucosal gingival lamina propria. There was some improvement in respect of the electron microscopic structure of the microcirculatory vessels on the 14th and 30th days of the experiment. The performed studies of hemocapillaries submicroscopic organization of the animal’s gums mucous membrane in conditions of application quercetin for experimental periodontitis has shown that flavonol improved structural organization considerably. The use of quercetin improves the organization of all ultrastructured components of the periodontal complex in experimental periodontitis.

DISBALANCE OF BIORADICAL PROCESSES AS THE MAIN CAUSE OF DISORGANIZATION OF CONNECTIVE TISSUE STRUCTURES IN EXPERIMENTAL PERIODONTITIS

Abstract: Relevance. The features of the dynamics of free radical processes, as well as the metabolism of collagen structures of the connective tissue matrix against the background of periodontitis will reveal deeper pathogenetic mechanisms and application points for the introduction of new therapeutic and diagnostic technologies into practice. The purpose of the study. Assessment and establishment of interrelations between the intensity of bio-radical processes and collagen metabolism in dynamics in experimental periodontitis. Materials and methods. The study used 45 white nonlinear rats, on which the model of periodontitis proposed by Shkolnaya K. D., Atrushkevich V.G. (Patent RU No. 2625295 dated 12.07.2017) was reproduced. The total activity of free radical oxidation and the antioxidant potential of the body were monitored by the biochemiluminescence method, and markers of collagen metabolism were recorded. Results. The study revealed a sharp predominance of oxidative processes and the inability of the antioxidant potential to suppress free radical peroxidation, as evidenced by the persistently high levels of total luminescence intensity and biohemiluminescence light sum that persist throughout the experiment, despite dynamic changes. Reactive oxygen species in conditions of progressive chronic inflammation have a damaging effect on collagen fibers, which means they lead to the inevitable destruction of the periodontal complex, which is expressed in the growth of CO and PSO. In addition, there is a significant direct correlation between the dynamics of the intensity of free radical oxidation and the indicators of collagen metabolism. Conclusion. Thus, oxidative stress, progressing against the background of periodontitis, leads to disorganization of connective tissue structures of the periodontal. In turn, the study confirms the validity of the use of markers of the intensity of free radical oxidation and collagen metabolism to diagnose the severity of the disease and prognosis, as well as the need for the use of antioxidant drugs as part of complex therapy.

THE MAIN RISK FACTORS FOR DEVELOPMENT OF PERIODONTAL COMPLICATIONS AT THE STAGE OF NON-REMOVABLE PROSTHODONTIC TREATMENT IN PATIENTS WITH CHRONIC PERIODONTITIS

The absence of objective morpho-functional indicators of the periodontal tissues state increases the risk of complications at the stage of preparing and prosthodontic treatment of patients with periodontal diseases. The analysis of more than 100 academic papers on the research topic was carried out, the results of which are presented in this review. According to the literature data, the most common complications in non-removable prosthodontic treatment are acute inflammatory reactions, occlusal trauma and functional periodontal overload with significant morphological disorders. The Understanding of physiology and individual variations of the regenerative process in periodontal complex will help the dentist to avoid most complications during prosthodontic treatment and to achieve a long-term positive effect after its completion

The Effect of Phosphatase and Tension Homolog (PTEN) on Homeostasis of the Periodontal Ligament

Aim: Phosphatase and tension homolog (PTEN) has been known to maintain homeostatic control over the body. The roles of PTEN in periodontal complex are unknown. The purpose of this study was to investigate the role of PTEN in periodontal structures by removing PTEN from osteoblasts and odontoblasts. Materials and Methods: The function of this endogenous PTEN was evaluated by conditionally eliminating the PTEN gene using an Osteocalcin (OCN) Cre driver. The resulting OCN-Cretg/+; Ptenfl/fl mice were examined using micro-CT and histology, immunohistochemical analyses for osteogenic markers in the periodontal ligament (PDL) and bone turnover. Results: Bone apposition was increased around molar areas accompanying deposition of cementum in micro CT. Osteoprogenitor markers except for OCN in the PDL maintained their expression in both wild-type and OCN-Cretg/+; Ptenfl/fl mice. Both alkaline phosphatase activity and osteoclast activity increased in the PDL of OCN-Cretg/+; Ptenfl/fl mice compared to those in wild-type mice. Conclusions: Loss of PTEN causes an increase of bone turnover in the periodontal surrounding tissues with an increase of cementogenesis. These findings underscore the effect of PTEN on homeostasis of the periodontal ligament.

CYTOKINOGENESIS DISORDERS IN MECHANISMS OF THE EXPERIMENTAL PERODONTITIS DEVELOPMENT AND THEIR CORRECTION BY FLAVONOL

The aim: Evaluation of changes in proinflammatory and anti-inflammatory units of the cytokine profile in the mechanisms of development of experimental bacterial-immune periodontitis and elucidation of the effect of flavonol quercetin on its parameters. Materials and methods: Experimental periodontitis was caused by introducing into the tissues of the periodontal complex a mixture of microorganisms diluted with egg protein. In order to enhance the immune response, a complete Freund’s adjuvant was injected into the rat’s paw at the same time. For correction, intramuscular injections of water-soluble quercetin at a dose of 100 mg / kg body weight were performed for 7 days (7th to 14th day). Results: The use of flavonol quercetin led to a decrease in the serum content of experimental animals with pro-inflammatory cytokines. With regard to anti-inflammatory cytokines, their content in the blood of animals during the development of this simulated inflammatory process changed in the opposite direction. Quercetin effectively eliminated the imbalance of the immune system and increased the level of IL-10 and IL-4 in the serum. After injections of quercetin, the relation of pro- and anti-inflammatory cytokines in the serum of animals on 14th day of the study was reduced compared to their content in rats that did not receive correction. Conclusions: The formation and course of experimental bacterial-immune periodontitis is accompanied by a complex of pathological changes in immunocytokinogenesis, which is manifested by a progressive increase in serum concentrations of proinflammatory cytokines and a decrease in anti-inflammatory cytokines. Flavonol quercetin reduces the concentration of pro-inflammatory and increases the content of anti-inflammatory cytokines.

MORPHOLOGICAL CHANGES OF PERIODONTAL COMPONENTS UNDER EXPERIMENTAL LIPOPOLYSACCHARIDE PERIODONTITIS COMBINED WITH HYPERTHYROIDISM.

The aim: Investigate structural changes in the tissues of the periodontal complex under the condition of experimental lipopolysaccharide periodontitis combined with hyper¬thyroidism. Materials and methods: The studies were performed on adult white male rats, which simulated periodontitis combined with hyperthyroidism. Periodontal tissues were subjected to morphological examination on the 22nd day of the experiment. Collection of material for microscopic examinations was performed according to the generally accepted method; histological specimens were studied using a light optical microscope. Results: Morphological studies of the components of the periodontal complex of experimental animals with experimental periodontitis established the reorganization of its structural elements. Damage to the epithelium in the area of attachment of the circular ligament and erosive-ulcerative changes of the gums led to a deepening of the gingival sulcus with the formation of a deep periodontal pocket. Intense hyperkeratosis was observed in the area of the bottom of the periodontal pocket. In the own plate of the mucous membrane of the gums - significant edema, collagen fibers were disorganized, defragmented. There were pronounced destructive-degenerative and inflammatory changes of the epithelial and own plates of all areas of the gums and periodontium, damage to the nuclei and cytoplasm of keratinocytes, fibroblasts, and leukocytes. Conclusions: Experimental periodontitis combined with hyperthyroidism is accompanied by pronounced signs of destructive and inflammatory changes in the soft and dense tissues of the periodontal complex, as well as disruption of stromal-vascular interactions, which progress from reversible to irreversible disruption of periodontal connective tissue.

Food hardness can regulate orthodontic tooth movement in mice.

Orthodontic treatment is often accompanied with prescription of softer foods to patients. The question to ask is, is this prescribed load regimen congruent with Wolff's law, and does it provide an adequate mechanical stimulus to maintain the functional health of periodontal complex? This question was answered by studying the effects of mice chewing on soft food (SF) and hard food (HF) while undergoing experimental tooth movement (ETM). Three-week-old C57BL/6mice (n=18) were fed either hard pellet (HF; n=9) or soft-chow food (SF; n=9). ETM was performed on mice at 8weeks of age, and mice were euthanized at 1min, 2weeks, and 4weeks (8, 10, and 12weeks old, respectively). A logistic regression model was applied to the experimental data to extrapolate the prolonged effects of ETM on the physical features of the dentoalveolar joint (DAJ). By 12weeks, mice that chewed on SF expressed wider periodontal ligament space than those that chewed on HF. Mice that chewed on SF demonstrated increased alveolar socket roughness with larger alveoli and decreased bone volume fraction but with significantly lower bone mineral density and reduced overall tooth movement. These altered physical features when contextualized within the DAJ illustrated that (a) the regions farther away from the "site of insult" also undergo significant adaptation, and (b) these adaptations vary between mesial and distal sides of the periodontal complex and topographically differentiate in the direction of the ETM. These insights underpin the main conclusion, in that there is a need to "regulate chewing loads" as a therapeutic dose following ETM to encourage regeneration of periodontal complex as an effective clinical outcome. The discussed multiscale image analyses also can be used on patient cone beam computed tomography data to identify the effectiveness of orthodontic treatment within the realm of masticatory function.