Role of mast cells in oral inflammation

Mast cells play important roles in the maintenance of many physiological functions as well as in the pathophysiology of diseases. Mast cells are involved in the inflammatory mechanisms of many systemic diseases. In this pandemic period, their role in physiological and pathological host inflammatory reactions in tissue disruption following SARS-CoV-2 infection has been stressed. A review of the literature was carried out by entering the key words "Mast Cells" AND "Oral Diseases" AND "Role of Mast Cells in Periodontitis". The results show us that mast cells are definitely involved in many oral diseases including periodontitis. Further in vivo and in vitro studies are needed to further investigate the specific role of the cells in physiological and pathological inflammation.

Minimally invasive digital implant-prosthetic procedure in "all on 4" rehabilitation in patients with special needs: a three-year follow-up

The present study describes an innovative procedure for resolving implant-prosthetic cases in patients with edentulous special needs. In 2017 a 56-year-old female patient came to the Department of Dentistry of Vita-Salute San Raffaele Hospital, Milan, Italy, requiring implant-prosthetic rehabilitation of the dental arches given the difficulty in wearing removable prostheses. The first level radiological examinations were evaluated, two technical photographs were taken with specific reference, the 2D Digital Smile Design (Smile Design) was then carried out, the provisional prosthesis was performed and the CBCT requested with repere and provisional prostheses to realize the computerized implant project and an atraumatic flapless guided surgery. Professional oral hygiene sessions were performed quarterly, and the 3-year follow-up revealed no complications affecting the prosthetic or implant component. We can therefore conclude that the proposed method, exploiting digital technologies and flows and minimally invasive flapless surgical methods, can be considered elective in the treatment of patients with special needs.

The efficacy of the diode laser at 800-980 nm as an aid to non-surgical therapy in periodontitis treatment: a review of literature

The aim of this literature review is to assess the effectiveness of diode laser at a wavelength of 800-980 nm in addition to non-surgical periodontal therapy in periodontitis treatment. The authors performed an electronic research on Pubmed inserting as keywords: (laser OR laser therapy OR diode laser) and (periodontitis OR periodontal disease). The field has been narrowed to select only Randomized controlled clinical trials (RCT) performed from 2010 to 2020. The result of this research was 84 articles, of which eight were included in the review because they respect the inclusion criteria. The clinical, immunological, and microbiological parameters studied in the various clinical random trials were analysed. It has been shown that four out of eight studies have achieved greater benefits, in terms of clinical parameters, with the use of diode laser compared to Scaling and Root Planing. However, the greater increase in clinical parameters in diode laser-treated patients compared to the control group was mainly detected in the short term rather than in the long term. In terms of microbiological parameters, no improvement was detected after six months. Only one study reported six-month improvements in immunological parameters in patients treated with DL compared to the Scaling and Root Planing only group. In conclusion, considering the limitations of this review of literature, there is no evidence that the diode laser at 800-980 nm in addition to non-surgical periodontal therapy is more effective than SRP alone in the long term.

How to consider implant-prosthetic rehabilitation in elderly patients: a narrative review

With the beginning of the twenty-first century, population aging has emerged as a major worldwide phenomenon. The dentist must respond to this demographic change by taking into consideration the possibility of restoring oral function in the elderly patient with the use of dental implants. This article aims to provide a narrative review of the literature regarding the implant survival rate in geriatric patients and the relative importance and advantages of implant-prosthetic rehabilitation through a scientific analysis of the literature through online databases and dental journals. Tooth loss can have a significant impact on patients' oral function and significantly affects quality of life, self-esteem, and nutritional status. Although many studies in the past have reported that implant success is age-dependent, more recent studies suggest that they are safe and predictable for geriatric patients, improving quality of life, with similar results to those of younger age groups. Advanced age does not necessarily represent a contraindication for implant placement and osseointegration and success is influenced by patient and site-specific factors. Aging is a process that affects each patient differently, consequently, there should be a specific therapeutic approach for everyone, which must consider the functional and cognitive status of the patient, his medical condition, and his social situation-economic and motivational.

Anti-discoloration system: a new chlorhexidine mouthwash

Chlorhexidine is defined as biocompatible, which is why it is used as a mouthrinse for the patient before starting dental procedures (2). It has the ability to bind well to teeth and mucous membranes and is released for twelve hours, which is why it is used as a treatment for gingivitis and also in post-operative wound healing. The long-term side effects of chlorhexidine are pigmentations. To remedy this, various types of antidiscoloration have been tried out over time. Nowadays there are other types of anti-discoloration systems such as, for example, in our study we used a test group containing an anti-discoloration system called SPPD. A single-center, prospective, double-blind randomized clinical trial on 84 patients. The investigated treatments consisted of 4 mouthwashes (CHX 0.12% SPDD alcohol free; CHX 0.20% SPDD alcohol free; CHX 0.12% alcohol free with ADS; CHX 0.20% alcohol free with ADS). Despite the limitations of the study, all the mouthwashes tested showed good efficacy in reducing the amount of plaque. Comparing the two experimental concentrations (0.12% and 0.20%) tested here demonstrates that the 0.20% chlorhexidine concentration slightly surpasses its 0.12% equivalent with regard to the PI and BI parameters. The SPDD is an innovative anti-discoloration system and gives the mouthwash a great taste.

Comparison of hygiene levels in metal-ceramic and stratified zirconia in prosthetic rehabilitation on teeth and implants: a retrospective clinical study of a three-year follow-up

The aim of this retrospective clinical study was to evaluate and compare oral hygiene levels in patients subjected to fixed metal-ceramic or stratified zirconia prostheses, either on teeth or on dental implants. Twenty patients, including 10 with metal-ceramic prostheses and 10 with stratified zirconia, were engaged for the study. Considering the prosthesis positioning phase as zero time, all patients were examined twice a year for a follow-up period of 3 years. During each session, to assess oral cavity state of health, both the Plaque Index (IP) and the Bleeding Index (BOP) were recorded. All patients were instructed in home hygiene maintenance and subjected to professional oral hygiene sessions customized according to prothesis type (on natural teeth or dental implants) and materials (metal ceramic or stratified zirconia). Statistically significant evidence was found in IP values, with an increase in the initial stages in zirconia prostheses and in the final stages in metal-ceramic ones. BOP levels showed a reduction during the follow-up period, but no statistically significant differences were found between examined groups. An adequate patient education in hygiene maintenance associated with professional oral hygiene sessions with special tools could positively affect fixed prostheses' maintenance, both on natural teeth and on dental implants.

Anaphylaxis is a rare reaction in COVID-19 vaccination

Anaphylaxis is a severe multisystem reaction that occurs rapidly after the introduction of an antigen that would otherwise be a harmless substance. It is characterized by airway and respiratory problems, cardiovascular collapse, mucosal inflammation, and other complications, all severe symptoms that can cause death. IgE-dependent anaphylaxis involves mast cells (MCs) which are the main sources of biologically active mediators that contribute to the pathological and lethal phenomena that can occur in anaphylaxis. Antibody-mediated anaphylaxis can follow multiple pathways such as that mediated by MCs carrying the FcεRI receptor, which can be activated by very small amounts of antigen including a vaccine antigen and trigger an anaphylactic reaction. In addition, anaphylaxis can also be provoked by high concentrations of IgG antibodies that bind to the FcγR receptor present on basophils, neutrophils, macrophages and MCs. For this reason, the IgG concentration should be kept under control in vaccinations. Activation of MCs is a major cause of anaphylaxis, which requires immediate treatment with epinephrine to arrest severe lethal symptoms. MCs are activated through the antigen binding and cross-linking of IgE with release of mediators such as histamine, proteases, prostaglandins, leukotrienes and inflammatory cytokines. The release of these compounds causes nausea, vomiting, hives, wheezing, flushing, tachycardia, hypotension, laryngeal edema, and cardiovascular collapse. mRNA and viral vector vaccines have been cleared by the United States, Food and Drug Administration (FDA), generating hope of prevention and cure for COVID-19 around the world. Scientists advise against giving the vaccine to individuals who have had a previous history of anaphylaxis. The US Centers for Disease Control and Prevention (CDC) advises people with a previous history of any immediate allergic reaction to remain under observation for approximately 30 minutes after COVID-19 vaccination. To date, vaccines that prevent SARS-CoV-2 infection have not raised major concerns of severe allergic reactions, although, in some cases, pain and redness at the injection site and fever have occurred after administration of the vaccine. These reactions occur in the first 24-48 hours after vaccination. It has been reported that probable forms of anaphylaxis could also occur, especially in women approximately 40 years of age. But after tens of millions of vaccinations, only a few patients had this severe reaction with a low incidence. Anaphylactic and severe allergic reactions can also occur to any component of the vaccine including polysorbates and polyethylene glycol. To date, there is no precise information on allergic reactions to COVID-19 vaccines. Individuals with MCs and complement with higher activation than others may be at greater allergic risk. Moreover, the reactions called anaphylactoids, are those not mediated by IgE because they do not involve this antibody and can also occur in COVID-19 vaccination. These not-IgE-mediated reactions occur through direct activation of MCs and complement with tryptase production, but to a lesser extent than IgE-mediated anaphylaxis. However, at the moment it is not known exactly which component of the vaccine causes the allergic reaction and which vaccine causes the most side effects, including anaphylaxis. Thus, individuals who have a known allergy to any component of the vaccine should not be vaccinated. However, should an anaphylactic reaction occur, this requires immediate treatment with epinephrine to arrest severe lethal symptoms. In conclusion, the purpose of this editorial is to encourage the population to be vaccinated in order to extinguish this global pandemic that is afflicting the world population, and to reassure individuals that anaphylactic reactions do not occur with a higher incidence than other vaccinations.

Frequent and Persistent Salivary Gland Ectasia and Oral Disease After COVID-19

The clinical picture of coronavirus disease 2019 (COVID-19) in various target organs has been extensively studied and described. However, relatively little is known about the characteristics of oral cavity involvement. This is surprising, considering that oral mucosal and salivary gland cells are known targets for the direct replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and that the presence of the virus in saliva is a source of transmission of the infection. The aim of our study was to investigate the presence and prevalence of oral manifestations in COVID-19 survivors. We profiled the oral involvement in 122 COVID-19 survivors that were hospitalized and followed up at a single-referral university hospital in Milan, Italy, between July 23, 2020 and September 7, 2020, after a median (interquartile range) time from hospital discharge of 104 (95 to 132) d. We found that oral manifestations, specifically salivary gland ectasia, were unexpectedly common, with oral manifestations being detected in 83.9% while salivary gland ectasia in 43% of COVID-19 survivors. Salivary gland ectasia reflected the hyperinflammatory response to SARS-CoV-2, as demonstrated by the significant relationship with C-reactive protein (CRP) and lactate dehydrogenase (LDH) levels at hospital admission, and with the use of antibiotics during acute disease. Both LDH levels and antibiotic administration survived as independent predictors of salivary gland ectasia at multivariable analysis. Temporomandibular joint abnormalities, facial pain, and masticatory muscle weakness were also common. Overall, this retrospective and prospective cohort study of COVID-19 survivors revealed that residual damage of the oral cavity persists in the vast majority of patients far beyond clinical recovery, and suggests that the oral cavity represents a preferential target for SARS-CoV-2 infection. Further studies are needed to clarify the connection between SARS-CoV-2 infection and oral disorders.

The British variant of the new coronavirus-19 (Sars-Cov-2) should not create a vaccine problem

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly contagious virus that infects humans and a number of animal species causing coronavirus disease-19 (COVID-19), a respiratory distress syndrome which has provoked a global pandemic and a serious health crisis in most countries across our planet. COVID-19 inflammation is mediated by IL-1, a disease that can cause symptoms such as fever, cough, lung inflammation, thrombosis, stroke, renal failure and headache, to name a few. Strategies that inhibit IL-1 are certainly helpful in COVID-19 and can represent one of the therapeutic options. However, until now, COVID-19 therapy has been scarce and, in many cases, ineffective, since there are no specific drugs other than the vaccine that can solve this serious health problem. Messenger RNA (mRNA) vaccines which are the newest approach, are already available and will certainly meet the many expectations that the population is waiting for. mRNA vaccines, coated with protected soft fatty lipids, use genetic mRNA (plus various inactive excipients) to make a piece of the coronavirus spike protein, which will instruct the immune system to produce specific antibodies. The soft fatty lipids allow the entry of mRNA into cells where it is absorbed into the cytoplasm and initiates the synthesis of the spike protein. In addition, vaccination also activates T cells that help the immune system respond to further exposure to the coronavirus. mRNA induces the synthesis of antigens of SARS-CoV-2 virus which stimulate the antibody response of the vaccinated person with the production of neutralizing antibodies. The new variant of the coronavirus-19 has been detected in the UK where, at the moment, the London government has imposed a lockdown with restrictions on international movements. The virus variant had already infected 1/4 of the total cases and in December 2020, it reached 2/3 of those infected in the UK. It has been noted that the spreading rate of the British variant could be greater than 70% of cases compared to the normal SARS-CoV-2 virus, with an R index growth of 0.4. Recent studies suggest that coronavirus-19 variation occurs at the level N501Y of the spike protein and involves 23 separate mutations on the spike, 17 of which are linked to the virus proteins, thus giving specific characteristics to the virus. In general, coronaviruses undergo many mutations that are often not decisive for their biological behavior and does not significantly alter the structure and the components of the virus. This phenomenon also occurs in SARS-CoV-2. It is highly probable that the variants recently described in the UK will not hinder vaccine-induced immunity. In fact, the variant will not break the vaccine although it may have some chance of making it a little less effective. Therefore, it is pertinent to think that the vaccine will work against the SARS-CoV-2 variant as well. In today's pandemic, the D614G mutation of the amino acid of corronavirus-19, which emerged in Europe in February 2020 is the most frequent form and causes high viral growth. The previously infrequent D614G mutation is now globally dominant. This variant, which is being tested by many international laboratories, is rapidly spreading across the countries and a series of vaccinated subjects are testing to see if their antibodies can neutralize the new variant of SARS-CoV-2. This variant has a very high viral growth and is less detectable with the RT-PCR technique in the laboratory. It has been reported that the British variant that increases viral load does not cause more severe effects in the respiratory tract and lung disease, therefore, it is certain that the variant is growing rapidly and must be kept under control; for this reason, laboratory data is expected impatiently. The study on the many variants that coronavirus-19 presents is very interesting and complete and clearer data on this topic will be ready in the near future. In addition, it is still unclear whether the different variants discovered in many countries, including Africa, share the same spike protein mutation and therefore, this is another study to elaborate on. In order to be certain and to not have unexpected surprises, we need to reduce the spread and the transmission speed of viral variants that could appear around the world, creating new pandemics. For this reason, the scientific community is on the alert since laboratory tests on serum antibodies from COVID-19 survivors have been reported to be less effective in attacking the variant. In light of the above, the scientific community must be on the alert as larger variants of the spike protein could escape vaccine-induced antibodies, which for now are of great help to the community and can save millions of lives. Deepening the study of spike protein mutations will help to better understand how to combat coronavirus-19 and its variants.

Mast cells activated by SARS-CoV-2 release histamine which increases IL-1 levels causing cytokine storm and inflammatory reaction in COVID-19

SARS-CoV-2 virus is an infectious agent commonly found in certain mammalian animal species and today also in humans. SARS-CoV-2, can cause a pandemic infection with severe acute lung injury respiratory distress syndrome in patients with COVID-19, that can lead to patient death across all ages. The pathology associated with pandemic infection is linked to an over-response of immune cells, including virus-activated macrophages and mast cells (MCs). The local inflammatory response in the lung that occurs after exposure to SARS-CoV-2 is due to a complex network of activated inflammatory innate immune cells and structural lung cells such as bronchial epithelial cells, endothelial cells and fibroblasts. Bronchial epithelial cells and fibroblasts activated by SARS-CoV-2 can result in the up-regulation of pro-inflammatory cytokines and induction of MC differentiation. In addition, endothelial cells which control leukocyte traffic through the expression of adhesion molecules are also able to amplify leukocyte activation by generating interleukin (IL)-1, IL-6 and CXC chemokines. In this pathologic environment, the activation of mast cells (MCs) causes the release of histamine, proteases, cytokines, chemokines and arachidonic acid compounds, such as prostaglandin D2 and leukotrienes, all of which are involved in the inflammatory network. Histamine is stored endogenously within the secretory granules of MCs and is released into the vessels after cell stimulation. Histamine is involved in the expression of chemokine IL-8 and cytokine IL-6, an effect that can be inhibited by histamine receptor antagonists. IL-1 is a pleiotropic cytokine that is mainly active in inflammation and immunity. Alveolar macrophages activated by SARS-CoV-2 through the TLR produce IL-1 which stimulates MCs to produce IL-6. IL-1 in combination with IL-6 leads to excessive inflammation which can be lethal. In an interesting study published several years ago (by E. Vannier et al., 1993), it was found that histamine as well as IL-1 are implicated in the pathogenesis of pulmonary inflammatory reaction, after micorganism immune cell activation. IL-1 in combination with histamine can cause a strong increase of IL-1 levels and, consequently, a higher degree of inflammation. However, it has been reported that histamine alone has no effect on IL-1 production. Furthermore, histamine enhances IL-1-induced IL-6 gene expression and protein synthesis via H2 receptors in peripheral monocytes. Therefore, since MCs are large producers of histamine in inflammatory reactions, this vasoactive amine, by increasing the production of IL-1, can amplify the inflammatory process in the lung infected with SARS-CoV-2. Here, we have proposed for the first time an emerging role for histamine released by MCs which in combination with IL-1 can cause an increase in lung inflammation induced by the viral infection SARS-CoV-2.

Management of the delicate phase of the temporary crown: an in vitro study

The fundamental moment of prosthetic rehabilitation is the "temporary". Although the meaning of the term diminishes its importance, the provisional has fundamental biological, aesthetic and functional functions. The oral cavity must maintain an adequate level of oral hygiene to carry out this delicate phase in the best possible way; a result achieved only with the collaboration of the prosthetic dentist with the hygienist and the patient, as if they were a biological system in motion. The different methods of hygiene are effective in maintaining a good level of oral health; but they could, if too aggressive, affect the prosthetic restoration. Our objective in vitro is to understand, after applying a known bacterial load, which hygiene method is the most effective in removing bacterial biofilm but at the same time is less aggressive towards resinous material.

Role of induced pluripotent stem cells (IPSCS) in bone tissue regeneration in dentistry: a narrative review

Several conditions as trauma, cancer surgical resection, fractures, congenital malformations and periodontitis could bring alveolar bone defects. To avoid more invasive and less predictable regenerative procedures, Stem cells of different origins as pluripotent Embryonic Stem Cells (ESCs), undifferentiated multipotent Mesenchymal Stem Cells (MSCs) and Induced Pluripotent Stem Cells (iPSCs) were proposed as possible alternative. IPSCs have potential for proliferation and differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. According with their ability to involve in several cells type, Induced Pluripotent Stem Cells (iPSCs) could be proposed as alternative in regeneration either of mineralized tooth components or supporting tissue. The aim of this brief review is to describe clinical applications of Induced Pluripotent Stem Cells (iPSCs) in oral bone regeneration to employ their use in tissue regeneration in dentistry.

Immediate versus delayed loading of post-extraction implants in the aesthetic zone: a prospective longitudinal study with 4-year follow-up

The aim of this randomized clinical trial was to compare the outcome of immediate versus delayedloading protocol using a new conical connection implant in post-extractive sockets with 4-year followup. Patients requiring single-tooth extraction for root fractures or periodontal disease in the maxillary or mandibular anterior or premolar areas were selected for the present study. After extraction, implants were placed immediately in fresh sockets. After randomization process, in group A immediate loading was performed while in group B a delayed loading protocol was followed. In both groups mean marginal bone loss was measured through intraoral digital radiographs at 3, 6, 12, 24, 36 and 48 months from loading. After a 48-month follow-up period, a success and survival rate of 96.55% was found in both groups. At 48-month follow-up, for group A a mean marginal bone loss of 0.14 ± 0.15mm was found, while for group B a value of 0.12 ± 0.12 mm was measured. No statistically significant differences between groups were found at each time point (P>0.05). When used in post-extractive immediate and delayed loading implant rehabilitations, the new conical connection implant showed a predictable outcome at 48-month follow-up. However, further clinical studies are needed to evaluate soft tissues adaptation, patient satisfaction, and long-term follow-up.

The smokeless tobacco: a survey in a cohort of young Italians through a social-media questionnaire

This observational survey aimed to demonstrate the use of the Snus kind of smokeless tobacco, among young Italian adults from alpine areas. A customized anonymous questionnaire was purposely created using the Google Forms platform and made it available for 4 weeks through social media supports to a cohort of young adults living in a mountain area in Italy. Out of four hundred recipients, 332 interviewees returned the survey. Participants had a mean age of 22.8, range 17-40 years. One hundred fifty regular consumers used Snus for more than 5 years. Gingival changes were reported in 92 subjects, associated with gingival bleeding in 14 subjects. 79 subjects reported discoloration of the mucosa. The 50% of the habitual users developed an addiction to Snus and 90% didn't smoke conventional cigarettes. In Italian young adults the use of Snus tobacco could be an adjunctive risk factor for the oral mucosa. It is essential to extend and spread the awareness about this addictive habit among dental professionals, to give to the patients a reliable and effective oral and systemic education.

Experimental analysis of the influence of cortical bone layers and bone quantity on implant primary stability

The systematic analysis of parameters impacting implant primary stability is difficult to achieve with human cadavers or animal models, particularly for complex trans-sinus procedures to determine the effects of cortical layers and bone engagement on implant stability before and after a simulated load in vitro. Solid rigid polyurethane blocks, partially intersected by an 8-mm-thick space, were created to imitate tri-cortical situations, the presence of the sinus cavity, and the posterior maxilla with different degrees of bone atrophy. Implants were inserted through the cavity at an angle of 30˚ (scenarios 1 and 2) to imitate the clinical protocol. Controls simulating uni-cortical anchorage and no sinus cavity were also included (controls 1 and 2). Four parameters were measured: peak insertion torque, insertion work, resistance to lateral bending loads and extraction torque. Scenarios 1 and 2 displayed similar peak insertion torque to control 2, where all three groups anchored equal amounts of bone surrogate. The distribution of surrogate bone in contact with trans-cavity implants influenced both extraction torque and the degree of lateral bending. Sufficient peak insertion torque can be attained with a trans-sinus tricortical implant anchorage providing sufficient apical and coronal bone is engaged.

How to reduce the likelihood of coronavirus-19 (CoV-19 or SARS-CoV-2) infection and lung inflammation mediated by IL-1

SARS-CoV-2, also referred to as CoV-19, is an RNA virus which can cause severe acute respiratory diseases (COVID-19), with serious infection of the lower respiratory tract followed by bronchitis, pneumonia and fibrosis. The severity of the disease depends on the efficiency of the immune system which, if it is weak, cannot stem the infection and its symptoms. The new CoV-19 spreads in the population at a rate of 0.8-3% more than normal flu and mostly affects men, since immune genes are more expressed on the X chromosome. If CoV-19 would spread with a higher incidence rate (over 10%), and affect the people who live in closed communities such as islands, it would cause many more deaths. Moreover, people from the poorest classes are most at risk because of lack of health care and should be given more assistance by the competent authorities. To avoid the aggravation of CoV-19 infection, and the collapse of the health system, individuals should remain at home in quarantine for a period of approximately one month in order to limit viral transmission. In the case of a pandemic, the severe shortage of respirators and protective clothing, due to the enormous demand and insufficient production, could lead the CoV-19 to kill a large number of individuals. At present, there is no drug capable of treating CoV-19 flu, the only therapeutic remedies are those aimed at the side effects caused by the virus, such as inflammation and pulmonary fibrosis, recognized as the first causes of death. One of the COVID-19 treatments involves inhaling a mixture of gaseous hydrogen and oxygen, obtaining better results than with oxygen alone. It was also noted that individuals vaccinated for viral and/or bacterial infectious diseases were less likely to become infected. In addition, germicidal UV radiation "breaks down" the oxygen O2 which then aggregate into O3 (ozone) molecules creating the ozone layer, capable of inhibiting viral replication and improving lung respiration. All these precautions should be taken into consideration to lower the risk of infection by CoV-19. New anti-viral therapies with new drugs should also be taken into consideration. For example, microbes are known to bind TLR, inducing IL-1, a pleiotropic cytokine, highly inflammatory, mediator of fever and fibrosis. Therefore, drugs that suppress IL-1 or IL-1R, also used for the treatment of rheumatoid arthritis are to be taken into consideration to treat COVID-19. We strongly believe that all these devices described above can lead to greater survival and. therefore, reduction in mortality in patients infected with CoV-19.

RANK/RANKL/OPG signaling pathways in necrotic jaw bone from bisphosphonate-treated subjects

Osteonecrosis of the jaw (ONJ) is a chronic complication affecting long-term bisphosphonate-treated subjects, recognized by non-healing exposed bone in the maxillofacial region. The pathophysiological mechanism underlying ONJ has not been fully elucidated. The aim of the present study was to investigate the role of RANK/RANKL/OPG signaling pathway and, in parallel, to evaluate angiogenic and matrix mineralization processes in jaw bone necrotic samples obtained from bisphosphonate-treated subjects with established ONJ. Necrotic bone samples and native bone samples were processed for Light and Field Emission in Lens Scanning Electron Microscope (FEISEM) analyses, for Real-Time RT-PCR to evaluate the gene expression of TNFRSF11A (RANK), TNFSF11 (RANKL), and TNFSF11B (OPG) and for immunohistochemical analyses of VEGF and BSP expression. Morphological analyses performed by Light microscope and FEISEM show empty osteocytic lacunae and alteration of lamellar organization with degradation of the mineralized bone matrix in necrotic bone samples. A significant increase in TNFRSF11A, TNFSF11, TRAF6 and NFAT2 gene expression, and a reduction of TNFSF11B gene transcription level compared is also showed in necrotic bone compared to control samples. No significant difference of VEGF expression is evidenced, while lower BSP expression in necrotic bone compared to healthy samples is found. Even if the pathogenesis of bisphosphonate-associated ONJ remains unknown, a link between oral pathogens and its development seems to exist. We suppose lipopolysaccharide produced by bacteria colonizing and infecting necrotic bone and the surrounding viable area could trigger RANK/RANKL/OPG signaling pathway and, in this context, osteoclasts activation could be considered as a protective strategy carried out by the host bone tissue to delimitate the necrotic area and to counteract infection.