Oxidative stress in patients with endodontic pathologies

Mitochondrial biogenesis disorder and oxidative damage promote refractory apical periodontitis in rat and human

AIM

To elucidate whether mitochondrial biogenesis disorder and damage from oxidative stress promote refractory apical periodontitis (RAP) in rat and human.

METHODOLOGY

Twenty Enterococcus faecalis-induced RAPs were established in the maxillary first molars of male Wistar rats. Concurrently, 12 periapical lesion specimens from patients presenting with RAP were obtained by apicoectomy. Radiographic examination and histologic analysis were conducted to evaluate periapical bone tissue destruction and morphological changes. The expression of key regulators of mitochondrial biogenesis, PGC-1α and Nrf2, were detected by immunohistochemistry and double immunofluorescence staining, Western blot and real-time PCR were also assayed. Mitochondrial ROS (mtROS) was identified by MitoSOX staining. Mitochondrial function was detected by the quantification of ATP production, mitochondrial DNA (mtDNA) copy number and activities of mitochondrial respiratory chain complexes. Furthermore, mitochondrial oxidative stress was evaluated by the determination of 3-nitrotyrosine (3-NT), 4-hydroxy-2-nonenal (4-HNE) and 8-hydroxy-deoxyguanosine (8-OHdG) expression levels, as well as malondialdehyde (MDA) expression and antioxidant capacity. Student's t-test was performed to determine significance between the groups; p < .05 was considered significant.

RESULTS

In the maxilla, significantly more bone resorption, greater number of periapical apoptotic cells and Tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells were observed in the RAP group compared with the control group (p < .01). PGC-1α and Nrf2 were significantly reduced in rat and human RAP lesions compared to the control group (p < .01) at both the mRNA and protein levels. Double immunofluorescence analysis of PGC-1α or Nrf2 with TOMM20 also indicated that mitochondrial biogenesis was impaired in RAP group (p < .01). Additionally, mitochondrial dysfunction was observed in RAP group, as reflected by increased mtROS, decreased ATP production, reduced mtDNA copy number and complexes of the mitochondrial respiratory chain. Finally, the expression levels of mitochondrial oxidative stress markers, 3-NT, 4-HNE and 8-OHdG, were significantly increased in the RAP group (p < .01). Consistent with this, systemic oxidative damage was also present in the progression of RAP, including increased MDA expression and decreased antioxidant activity (p < .01).

CONCLUSIONS

Mitochondrial biogenesis disorder and damage from oxidative stress contribute to the development of RAP.

An examination of the effect of exercise and creatine monohydrate on oral tissues

Although physical exercise is extremely important for health and a good lifestyle, it can trigger oxidative stress, inflammation, and muscle fatigue. The aim of this study was to determine changes in dental tissues and the mandible created by creatines monohydrate (CrM) supplementation together with low and high-intensity exercise (HIE). The study material comprised Balb/c male mices, which were separated into two groups for the application of low and HIE on a running band. CrM supplement was administered together with the exercise. At the end of the experiment period, dental tissue samples were surgically removed and examined histopathologically and immunohistochemically (TNF-α and lL-1β).As a result of the histopathological examinations, in the pulp, oedema, vascular congestion, and capillary dilatation were seen to be statistically significantly increased in the Group 3 mices that performed HIE compared to the control group (p = 0.001, p = 0.003, p = 0.001, respectively). A statistically significant increase was observed in periodontal ligament (PDL) degeneration, and disruption of the continuity and separation of collagen fibers in Group 3 compared to the control group (p = 0.001). In the immunohistochemical examination, TNF-α and IL-1β positivity was observed in Group 3, and this was significantly increased compared to the control group (p = 0.001, p = 0.000).Exposure of the mices to low and HIE caused histological and immunohistochemical changes in dental pulp and PDL, and it was determined that the use of CrM could have a protective effect against these changes. RESEARCH HIGHLIGHTS: The results of this study showed negative effects of HIE in the dental pulp and PDL, which play an important role in dental health. CrM was seen to be effective in preventing these negative effects.

Is there any association between the presence of biomarkers and apical periodontitis? A systematic review

This systematic review aimed to verify whether there is evidence of an association between apical periodontitis and the presence of systemic biomarkers. This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - PRISMA. For this, the acronym PECO was used; population (P) of adult humans exposed (E) to the presence of apical periodontitis, compared (C) to adult humans without apical periodontitis, and the outcome (O) of the presence of biomarkers was observed. The articles were searched in PubMed, Scopus, Web of Science, LILACS, Cochrane Library, OpenGray, and Google Scholar grey databases. Subsequently, studies were excluded based on title, abstract, and full article reading, following the eligibility criteria. The methodological quality of the selected studies was evaluated using the Newcastle-Ottawa qualifier. After exclusion, 656 studies were identified, resulting in 17 final articles that were divided into case-control, cross-sectional, and cohort studies. Eight studies were considered to have a low risk of bias, one had a medium risk of bias, and eight had a high risk of bias. In addition, 12 articles evaluated biomarkers in blood plasma, four evaluated them in saliva, and only one evaluated them in gingival crevicular fluid. The results of these studies indicated an association between apical periodontitis and the systemic presence of biomarkers. These markers are mainly related to inflammation, such as interleukins IL-1, IL-2, and IL-6, oxidative markers, such as nitric oxide and superoxide anions, and immunoglobulins IgG and IgM.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42023493959).

Role of induced nitric oxide synthases in orofacial nociception/discomfort after dental tooth bleaching with hydrogen peroxide

OBJECTIVE

To evaluate the role of induced nitric oxide synthase (iNOS) in nociception/orofacial discomfort in rats submitted to tooth whitening with hydrogen peroxide (H₂O₂).

DESIGN

Wistar rats were divided into three groups (n = 24/group): a sham group not submitted to whitening treatment, a saline group submitted to whitening treatment, and a test group submitted to whitening treatment and blockade of iNOS with aminoguanidine 50 mg/kg/day. After 24 and 48 h, and 7 days, the animals were euthanized to collect trigeminal ganglia and maxillae to histomorphometric analysis (size of neuronal bodies and percentage of pulp area filled by vessels) and behavior/nociception (Grimace scales, scratching and biting counting, weight loss and nociception assay). ANOVA-1- or - 2-way tests were used (p < 0.05, GraphPadPrism 5.0).

RESULTS

The aminoguanidine-treated group showed a reduction in nociceptive threshold in the masseteric region (p < 0.001), Grimace scale scores (p < 0.001), number of scratching (p = 0.011) and body mass loss (p = 0.007). After 24 and 48 h of tooth bleaching, the saline group showed a significant increase in the mean area of the blood vessels (p = 0.020) and iNOS immunostaining in odontoblasts (p = 0.002) and non-odontoblasts cells (p = 0.025). Aminoguanidine reversed both increases. Tooth bleaching reduced the mean area of neuronal bodies, and aminoguanidine significantly reversed it (p = 0.019), but an increase in GFAP immunostaining in neuronal bodies did not reduce after seven-days or after aminoguanidine treatment (p = 0.003).

CONCLUSION

iNOS blockage by aminoguanidine plays an important role in nociception and orofacial discomfort by control of inflammation in dental pulp after tooth bleaching with hydrogen peroxide (H₂O₂) 35%.

Efficacy of a Novel Intracanal Medicament on Total Antioxidant Status in Patients With Apical Periodontitis: A Randomized Controlled Clinical Trial

Introduction Successful endodontic treatment relies upon the microbial debridement of the root canal system. This can be achieved to a great extent by using intracanal medicaments, which inhibit the microbes growing in the root canal. Evaluating the capacity of oxidants in the saliva is a crucial parameter for assessing the antioxidant capacity of any individual, which decreases in inflammatory conditions. An effective intracanal medicament can increase the total antioxidant capacity of saliva, which comes down because of inflammatory conditions. Aim To evaluate the effect of two intracanal medicaments on the antioxidant capacity of saliva. Materials and methods In a randomized prospective clinical trial, 42 patients with a mean age of 18-70 years were selected based on exclusion and inclusion criteria, and the baseline value of the total antioxidant capacity of saliva was recorded. The patients were categorized into two groups as per the block randomization method (Group I: calcium hydroxide (Maarc, New Delhi, India) intracanal medicament; Group II: Hekla lava (SBL Pvt. Ltd., Germany) intracanal medicament). Access opening, working length determination, and cleaning and shaping were conducted using hand K-files and ProTaper Gold rotary files. Intracanal medicaments were placed according to the groups assigned, and temporary restoration was placed. The patients were recalled after seven days. If the tooth was asymptomatic, obturation was completed, and a saliva sample was collected to assess the total antioxidant capacity. Results The total antioxidant capacity of saliva was increased after using intracanal medicaments and endodontic therapy, and there was a statistically significant difference before and after using both the medicaments (p=0.0005; i.e., calcium hydroxide and Hekla lava. When both medicaments were compared, there was no significant difference in the antioxidant capacity of saliva among medicaments (p=0.384). Conclusion The total antioxidant capacity of saliva was increased after using both the intracanal medicaments. Hence, Hekla lava can be potentially used as an alternative intracanal medicament.

Methylenetetrahydrofolate reductase polymorphisms in dental caries-induced pulp inflammation and regeneration of dentine-pulp complex: Future perspectives

Dental caries (DC)-induced pulp infections usually undergo the common endodontic treatment, root canal therapy (RCT). Endodontically treated teeth are devitalized, become brittle and susceptible for re-infection which eventually results in dental loss. These complications arise because the devitalized pulp losses its ability for innate homeostasis, repair and regeneration. Therefore, restoring the vitality, structure and function of the inflamed pulp and compromised dentin have become the focal points in regenerative endodontics. There are very few evidences, so far, that connect methylenetetrahydrofolate reductase single nucleotide polymorphisms (MTHFR-SNPs) and dental disorders. However, the primary consequences of MTHFR-SNPs, in terms of excessive homocysteine and folate deficiency, are well-known contributors to dental diseases. This article identifies the possible mechanisms by which MTHFR-SNP-carriers are susceptible for DC-induced pulp inflammation (PI); and discusses a cell-homing based strategy for in vivo transplantation in an orthotopic model to regenerate the functional dentine-pulp complex which includes dentinogenesis, neurogenesis and vasculogenesis, in the SNP-carriers.

Association between Dental Scores and Saliva Uremic Toxins

Dental health is frequently altered in patients with chronic kidney disease. We conducted a prospective study on dental health in CKD patients with a specific interest in the association between dental health issues and the accumulation of uremic toxins in the saliva. A total of 88 patients were included in the study, with chronic kidney disease stage 2 to 5 (without kidney replacement). We analysed the total concentrations of eight uremic toxins (trimethylamine N-oxide -TMAO-, Indoxyl Sulfate, P-cresyl-sulfate, Indole 3-acetic acid, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid -CMPF-, Kynurenine, Hippuric acid and Phenylacetylglutamine) and three precursors of uremic toxins (Tyrosine, Phenylalanine and Tryptophan) in the saliva using LC-MS/MS. We observed, for the first time, the association between various dental scores: DMFT, FST, CPITN, and OHIS, and saliva uremic toxins and precursors: TMAO, indoxyl sulfate, or hippuric acid. Further prospective interventional studies are required to confirm our results.

Effects of direct pulp capping with recombinant human erythropoietin and/or mineral trioxide aggregate on inflamed rat dental pulp

OBJECTIVE

This study aimed to evaluate the dental pulp responses to recombinant human erythropoietin (rhEPO) and/or mineral trioxide aggregate (MTA) in pulp capping of inflamed dental pulp in vivo.

MATERIALS AND METHODS

In accordance with ARRIVE guidelines, pulp inflammation was induced by exposing the maxillary first molars (n = 64) of Wistar rats (n = 32) to the oral environment for two days. The exposed pulps were randomly assigned four groups based on the pulp capping material: rhEPO, MTA, MTA + rhEPO, or an inert membrane. An additional eight rats formed the healthy control group. After four weeks, the animals were euthanized, and histological, qRT-PCR, and spectrophotometric techniques were employed to analyze the left maxillary segments, right first maxillary molars, and blood samples, respectively. Statistical significance was set at p < 0.05 and < 0.001.

RESULTS

Pulp capping with rhEPO, MTA, or MTA + rhEPO resulted in lower inflammation and higher mineralization scores compared to untreated control. MTA + rhEPO group exhibited significantly decreased expression of tumor necrosis factor-alpha, and interleukin 1-beta, while MTA group showed substantially reduced expression of interferon-gamma. Both rhEPO and MTA + rhEPO groups presented elevated dentin matrix protein 1 levels compared to untreated control. Furthermore, pulp capping with rhEPO and/or MTA led to increased transforming growth factor-beta 1 expression and reductions of pro-inflammatory/immunoregulatory cytokine ratios and prooxidative markers. Pulp capping with rhEPO also resulted in increase of systemic antioxidative stress markers.

CONCLUSION

Capping with rhEPO or MTA + rhEPO resulted in a favorable effect that was similar or even superior to that of MTA.

Mitochondrial Dysfunction in the Pathogenesis and Treatment of Oral Inflammatory Diseases

Oral inflammatory diseases (OIDs) include many common diseases such as periodontitis and pulpitis. The causes of OIDs consist microorganism, trauma, occlusal factors, autoimmune dis-eases and radiation therapy. When treated unproperly, such diseases not only affect oral health but also pose threat to people's overall health condition. Therefore, identifying OIDs at an early stage and exploring new therapeutic strategies are important tasks for oral-related research. Mitochondria are crucial organelles for many cellular activities and disruptions of mitochondrial function not only affect cellular metabolism but also indirectly influence people's health and life span. Mitochondrial dysfunction has been implicated in many common polygenic diseases, including cardiovascular and neurodegenerative diseases. Recently, increasing evidence suggests that mitochondrial dysfunction plays a critical role in the development and progression of OIDs and its associated systemic diseases. In this review, we elucidated the critical insights into mitochondrial dysfunction and its involvement in the inflammatory responses in OIDs. We also summarized recent research progresses on the treatment of OIDs targeting mitochondrial dysfunction and discussed the underlying mechanisms.

Modulation of blood redox status by the progression of induced apical periodontitis in rats

This study aimed to investigate if apical periodontitis in different periods changes systemic levels of the antioxidant and pro-oxidant parameters in Wistar rats. Twenty-four rats were randomly allocated into healthy animals, apical periodontitis at 14 days (AP14) and apical periodontitis at 28 days (AP28). The first mandibular molars were accessed in the AP groups, and the pulp chamber was exposed to the oral environment, inducing the apical lesion. After 14 and 28 days, the animals were anesthetized, euthanized, and hemimandibles were collected for micro-computed tomography (micro-CT) analysis to measure lesion volume, bone volume (BV), percent of bone to total tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular space (Tb.Sp). A histological examination of the remaining bone was also performed. Finally, blood samples were collected for oxidative biochemistry analysis, investigating glutathione (GSH), Trolox equivalent antioxidant capacity (TEAC), and lipid peroxidation (TBARS). The lesion volume was greater at 28 than at 14 days, as shown by micro-CT. AP14 and AP28 had decreased BV and Tb.Th, but only AP28 showed a reduction in BV/TV. Tb.N and Tb. Sp were increased in apical periodontitis at 28 days. In the histopathological analysis, AP14 had focal regions of moderate mononuclear inflammatory infiltrate, and AP28 had an intense inflammatory infiltrate with bacterial colonies. In the biochemical evaluation, GSH, TEAC, and TBARS were increased after 14 days. However, GSH returned to control levels, TEAC was similar to AP14, and TBARS increased significantly after 28 days. Therefore, the oxidative biochemistry response was modulated according to the progression of periapical damage. After 14 days, the organism could still react to the injury. However, at 28 days, the antioxidant response decreased, associated with an increase in TBARS.

Comparative evaluation of the effect of calcium silicate and epoxy resinbased root canal sealers on postoperative pain in patients with primary endodontic lesion: A randomized clinical study

Introduction

This study's objective was to assess and compare postoperative pain response between bioceramic sealer (Nishika BG) and epoxy resin based (AH Plus) in patients with primary endodontic lesion at time interval of 24 h, 48 h, and 7 days using the Visual Analog Scale (VAS).

Materials and Methods

The study included 40 individuals with necrotic pulp and apical periodontitis. Calcium hydroxide was administered as the intracanal medication during the two-visit endodontic therapy. They were subsequently allocated randomly to either the AH Plus root canal sealer or the Nishika Canal Sealer BG, with a total of 20 participants in each group. Patients were told to use a VAS to rate their postoperative pain severity as none, minimal, moderate, or severe after 24 h, 48 h, and 7 days following obturation using the appropriate sealers.

Results

Nishika Canal Sealer BG (CS-BG) has a lower pain score as compared to the AH Plus group at 24-h time point. VAS ratings for both the groups decreased over time. According to the intergroup analysis, there was a significant difference in postoperative pain at the 24 h (P = 0.022), but not at the 48 h or 7 days (P > 0.05).

Conclusion

Although bioceramic sealer (Nishika Canal Sealer BG) resulted in significantly lower levels of pain as compared to epoxy resin-based sealer (AH Plus) at 24-h interval, there was no significant difference of postoperative pain at 48-h interval and 7-day period.

Melatonin decreases plasma TNF-α and improves nonenzymatic antioxidant defence and insulin sensitivity in rats with apical periodontitis fed a high-fat diet

AIM

To analyse the effects of melatonin (ME) treatment on oxidative stress and insulin resistance (IR) in rats with apical periodontitis (AP) fed a high-fat diet (HFD).

METHODOLOGY

Eighty 60-day-old rats were divided into eight groups: control (CN), AP, HFD with AP (HFDAP), control with ME (CNME), AP with ME (APME), HFD with ME (HFDME) and HFD with AP+ME (HFDAPME). The animals from the HFD groups were fed a HFD throughout the experimental period. On day 7, the animals from the AP groups were subjected to experimental AP, and after 70 days, the ME groups were treated for 30 days. Glycaemia, insulinaemia, homeostatic model assessment for IR index, tumour necrosis factor-α (TNF-α), and interleukin-6 were analysed in plasma using biochemical tests and enzyme-linked immunosorbent assay. Thiobarbituric acid-reactive substances (TBARS), carbonyl protein (CP), superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione (GSH) and total antioxidant capacity (ferric reducing antioxidant power [FRAP]) were analysed in the gastrocnemius muscle.

RESULTS

(1) Association of AP and HDF exacerbated IR, and ME treatment improved this alteration; (2) AP and HFD and their association showed increased TNF-α, and ME reversed it; (3) TBARS increased in the AP and HFDAP groups, and ME reversed only in the group with the association of disease and diet; (4) CP increased in all HFD groups and improved in the ME groups; (5) GSH activity decreased in all experimental groups, and ME increased this parameter only in the CN and AP groups; (6) FRAP did not change between the groups, but ME treatment increased its activity in the AP and HFD groups; (7) ME increased SOD in the CN and AP groups.

CONCLUSION

Apical periodontitis and HFD promoted IR, and the association of AP with diet promoted IR exacerbation; this resistance might have been caused by an increase in TNF-α. AP promoted more intense changes in lipid oxidative damage than in protein oxidative damage. In non-enzymatic antioxidant defence, it was observed that both AP and HFD and their association promoted a decrease in GSH levels. Overall, ME treatment reversed changes such as oxidative stress and IR.

Teeth with acute apical abscess vs. teeth with chronic apical periodontitis: a quantitative and qualitative proteomic analysis

OBJECTIVE

To quantitatively and qualitatively analyze the proteomic profile of teeth with acute apical abscesses (AAA) compared with teeth with chronic apical periodontitis (CAP) and to correlate the expression of detected human proteins with their main biological functions.

MATERIALS AND METHODS

Samples were obtained from root canals of 9 patients diagnosed with AAA and 9 with CAP. Samples were analyzed by reversed-phase liquid chromatography coupled to mass spectrometry. Label-free quantitative proteomic analysis was performed by Protein Lynx Global Service software. Differences in protein expression were calculated using the t-test (p < 0.05).

RESULTS

In total, 246 human proteins were identified from all samples. Proteins exclusively found in the AAA group were mainly associated with the immunoinflammatory response and oxidative stress response. In the quantitative analysis, 17 proteins were upregulated (p < 0.05) in the AAA group, including alpha-1-acid glycoprotein, hemopexin, fibrinogen gamma chain, and immunoglobulin. Additionally, 61 proteins were downregulated (p < 0.05), comprising cathepsin G, moesin, gelsolin, and transketolase. Most of the proteins were from the extracellular matrix, cytoplasm, and nucleus.

CONCLUSIONS

The common proteins between the groups were mainly associated with the immune response at both expression levels. Upregulated proteins mostly belonged to the acute-phase proteins, while the downregulated proteins were associated with DNA/RNA regulation and repair, and structural function.

CLINICAL RELEVANCE

The host response is directly related to the development of apical abscesses. Thus, understanding the behavior of human proteins against the endodontic pathogens involved in this condition might contribute to the study of new approaches related to the treatment of this disease.

Influence of Direct Pulp Capping with Calcium Hydroxide and Mineral Trioxide Aggregate on Systemic Oxidative Stress in Rats

Direct pulp capping is a procedure where materials are placed on exposed vital pulp tissue in order to stimulate reparative dentinogenesis and preserve pulp vitality. Carious pulp exposure and direct pulp capping are usually accompanied by pulp inflammation which can affect pro- and anti-oxidative systems locally or systemically. Therefore, this study aimed to investigate the potential influence of direct capping of inflamed rat dental pulp with calcium hydroxide (CH) and mineral trioxide aggregate (MTA) on parameters of systemic oxidative status.

Dental pulps of the first maxillary molars of Albino rats (n=32) were exposed and capped with either CH (n=8), MTA (n=8) or were left untreated (n=8). Animals with healthy pulp were used as a healthy control (n=8). After four weeks, animals were euthanized and blood samples were collected for biochemical analysis of parameters of systemic oxidative stress by spectrophotometric method.

Untreated control had the significantly higher (p <0.05) values of pro-oxidative parameters and lower (p <0.05) values of anti-oxidative parameters (superoxide dismutase and reduced glutathione) compared to healthy control. CH and MTA groups showed reduced values of pro-oxidative parameters compared to untreated control and values of anti-oxidative parameters comparable to healthy control.

Pulp exposure led to disbalance in systemic oxidative parameters while direct pulp capping with calcium hydroxide and mineral trioxide aggregate restored the levels of systemic oxidative parameters to that of animals with healthy dental pulp. These results indicate the importance of direct pulp capping and the potential influence of untreated inflamed pulp on systemic health.

Application of Proteomics in Apical Periodontitis

Apical periodontitis is an inflammatory reaction of the periradicular tissues as a consequence of multispecies microbial communities organized as biofilms within the root canal system. Periradicular tissue changes at the molecular level initiate and orchestrate the inflammatory process and precede the presentation of clinical symptoms. Inflammatory mediators have been studied at either the proteomic, metabolomic, or transcriptomic levels. Analysis at the protein level is the most common approach used to identify and quantify analytes from diseased periradicular tissues during root canal treatment, since it is more representative of definitive and active periradicular inflammatory mediator than its transcript expression level. In disease, proteins expressed in an altered manner could be utilized as biomarkers. Biomarker proteins in periradicular tissues have been qualitatively and quantitatively assessed using antibodies (immunoassays and immunostaining) or mass spectrometry-based approaches. Herein, we aim to provide a comprehensive understanding of biomarker proteins identified in clinical studies investigating periradicular lesions and pulp tissue associated with apical periodontitis using proteomics. The high throughput mass spectrometry-based proteomics has the potential to improve the current methods of monitoring inflammation while distinguishing between progressive, stable, and healing lesions for the identification of new diagnostic and therapeutic targets. This method would provide more objective tools to (a) discover biomarkers related to biological processes for better clinical case selection, and (b) determine tissue response to novel therapeutic interventions for more predictable outcomes in endodontic treatment.

The protective effects of S14G-humanin (HNG) against lipopolysaccharide (LPS)- induced inflammatory response in human dental pulp cells (hDPCs) mediated by the TLR4/MyD88/NF-κB pathway

Pulpitis is reported in large populations of patients and significantly impacts their normal life quality. It is reported that the lipopolysaccharide (LPS) in Gram-negative bacteria induces severe inflammation in dental pulp tissues. S14G-humanin is a derivative of humanin and has been recently confirmed to possess promising anti-inflammatory properties. The current study aims to explore the possibility of treating pulpitis with S14G-humanin. LPS-stimulated dental pulp cells (DPCs) were utilized to simulate an inflammatory state in the progression of pulpitis. We found the elevated expressions and production of interleukin- 6 (IL-6), tumor necrosis factor-α (TNF-α), macrophage chemoattractant protein-1 (MCP-1), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-9 (MMP-9), upregulated Pentraxin 3 (PTX3) and activated oxidative stress in LPS-treated DPCs were all reversed by treatment with 50 and 100 μM S14G-humanin. In addition, the LPS-induced elevated expression levels of toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (Myd88), and activation of the IκBα/NF-κB signaling pathway in hDPCs were significantly repressed by treatment with S14G-humanin. Conclusively, we found that S14G-humanin protected LPS-treated hDPCs by inhibiting the TLR4/MyD88/NF-κB signaling pathway.

Melatonin-doped polymeric nanoparticles induce high crystalline apatite formation in root dentin

OBJECTIVE

To investigate the effect of novel polymeric nanoparticles (NPs) doped with melatonin (ML) on nano-hardness, crystallinity and ultrastructure of the formed hydroxyapatite after endodontic treatment.

METHODS

Undoped-NPs and ML-doped NPs (ML-NPs) were tested at radicular dentin, after 24 h and 6 m. A control group without NPs was included. Radicular cervical and apical dentin surfaces were studied by nano-hardness measurements, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p < 0.05).

RESULTS

Cervical dentin treated with undoped NPs maintained its nano-hardness values after 6 m of storage being [24 h: 0.29 (0.01); 6 m: 0.30 (0.02) GPa], but it decreased at apical dentin [24 h: 0.36 (0.01); 6 m: 0.28 (0.02) GPa]. When ML-NPs were used, nano-hardness was similar over time [24h: 0.31 (0.02); 6 m: 0.28 (0.03) GPa], at apical dentin. Root dentin treated with ML-NPs produced, in general, high crystallinity of new minerals and thicker crystals than those produced in the rest of the groups. After 6 m, crystals became organized in randomly oriented polyhedral, square polygonal block-like apatite or drop-like apatite polycrystalline lattices when ML-NPs were used. Undoped NPs generated poor crystallinity, with preferred orientation of small crystallite and increased microstrain.

SIGNIFICANCE

New polycrystalline formations encountered in dentin treated with ML-NPs may produce structural dentin stability and high mechanical performance at the root. The decrease of mechanical properties over time in dentin treated without NPs indicates scarce remineralization potential, dentin demineralization and further potential degradation. The amorphous stage may provide high hydroxyapatite solubility and remineralizing activity.

Postoperative pain after endodontic treatment of necrotic teeth with large intentional foraminal enlargement

Objectives

To evaluate postoperative pain after endodontic treatment of necrotic teeth using large intentional foraminal enlargement (LIFE).

Materials and Methods

The sample included 60 asymptomatic necrotic teeth (with or without chronic apical periodontitis), and a periodontal probing depth of 3 mm, previously accessed and referred to perform endodontic treatment. After previous procedures, the position and approximate size of the apical foramen (AF) were determined by using an apex locator and K flexo-files, respectively. The chemomechanical preparation was performed with Profile 04 files 2 mm beyond the AF to achieve the LIFE, using 2.5 mL of 2.5% NaOCl at each file change. The filling was performed by Tagger's hybrid technique and EndoFill sealer. Phone calls were made to all the patients at 24, 48 and 72 hours after treatment, to classify postoperative pain. Statistical analysis was performed by different tests with a significance level of 5%.

Results

Age, gender, periradicular status and tooth type did not influence postoperative pain (p > 0.05). Only 1 patient (1.66%) reported severe pain after 72 hours. Moderate pain was reported by 7, 4 and 3 patients after 24, 48 and 72 hours, respectively (p = 0.0001). However, paired analyses showed a statistically significant difference only between 24 and 72 hours (p = 0.04). Sealer extrusion did not influence the postoperative pain (p > 0.05).

Conclusions

Acute or moderate postoperative pain was uncommon after endodontic treatment of necrotic teeth with LIFE.

Trial Registration

The Brazilian Clinical Trials Registry Identifier: RBR-3r967t

Cardiac, biochemical and histopathological analysis reveals impaired heart function in hypertensive rats with apical periodontitis

AIM

To investigate the association between experimentally induced apical periodontitis (AP) and heart function in hypertensive rats.

METHODOLOGY

Forty-eight normotensive Wistar albino and spontaneously hypertensive (SHR) rats were divided into four equal groups: control (C), normotensive with AP (AP), SHR and SHR with AP (SHR + AP). AP was induced on the first right mandibular molars by exposing the pulp chambers to the oral environment for four weeks and confirmed radiographically. Thereafter, the animals were sacrificed by cervical dislocation, whilst hearts were isolated and perfused according to the Langendorff technique gradually increasing coronary perfusion pressures 40-120 cmH₂ O. The hemimandibles were analysed radiographically (mm² and pixels) to verify the presence of AP. Biomarkers of cardiac oxidative stress (OS) were determined in coronary venous effluent and cardiac tissue homogenate. Cardiac tissue was analysed histopathologically for signs of heart damage (oedema, fibrosis and necrosis). All data were analysed by Kruskal-Wallis and one-way anova tests (p < .05).

RESULTS

The levels of the maximum left ventricular pressure development rate of the SHR + AP group were significantly increased compared to the AP and C groups, and of the SHR group compared with the C group (p < .05). The levels of the minimum left ventricular pressure development rate of the SHR + AP group were significantly decreased compared to the AP, SHR and C groups, and of the SHR group compared to the C group (p < .05). The radiographic AP area was significantly larger in the SHR + AP group than in the AP group (p < .01). The levels of superoxide anion were significantly higher in the SHR + AP group than in the AP, SHR and C groups (p < .05). The activities of superoxide dismutase in cardiac tissue homogenate were significantly lower in the SHR + AP and AP groups compared with the SHR and C groups (p < .05).

CONCLUSIONS

In rats, AP was associated with impaired cardiodynamics, disturbed cardiac OS, antioxidant defence and cardiac pathologic changes in hypertensive conditions. Hypertension was associated with an increase in the AP radiographic area. Further studies should confirm whether root canal treatment can have a cardioprotective effect and reduce cardiac OS in hypertensive conditions.

Reactive oxygen species can be traced locally and systemically in apical periodontitis: A systematic review

OBJECTIVES

The aim of this systematic review was to summarize the existing evidence on the local production and systemic traces of reactive oxygen species (ROS) in apical periodontitis (AP).

DESIGN

A search of MEDLINE-PubMed and EMBASE was conducted up to January 12 of 2021 to identify studies in 6 different languages. Eligibility was evaluated and data were extracted from the eligible studies following the predefined objective. The Newcastle-Ottawa Scale was used for quality assessment of the included studies.

RESULTS

After screening, 21 papers met the inclusion criteria. Six studies were about systemic oxidative stress, 14 studies examined local production of reactive oxygen species and one studied both. ROS modulate cell signalling and cause oxidant imbalance locally at the site of AP. Cell signalling leads to a pro-inflammatory response, activation of MMPs and formation and progression of the AP lesion. Simultaneously, these oxidative stress biomarkers are also found in blood and saliva of subjects with AP.

CONCLUSIONS

Understanding the mechanism of ROS generation, involved in chronic inflammation, can provide us with important information to enhance local and systemic healing and possibly improve diagnostic tools. Future research considerations would be to use antioxidants to accelerate the return to oxidative balance.

Calcium Silicate-Based Sealers Do Not Reduce the Risk and Intensity of Postoperative Pain after Root Canal Treatment when Compared with Epoxy Resin-Based Sealers: A Systematic Review and Meta-Analysis

This review aims to evaluate whether root canal obturation with calcium silicate-based (CSB) sealers reduces the risk and intensity of endodontic postoperative pain when compared to epoxy resin-based (ERB) sealers. The review was registered at PROSPERO (CRD42020169255). Two independent reviewers conducted an electronic search in PubMed, Scopus, EMBASE, Web of Science, Cochrane Library and LILACS until November 2020 and included only randomized clinical trials with adult health participants undergoing root canal treatment. After selection, the JBI Critical Appraisal tool was used to assess the risk of bias. A fixed-effect meta-analysis was performed to summarize the results of pain risk and pain intensity at time intervals of 24 and 48 hours. Finally, the certainty of evidence was assessed using the GRADE approach. The search resulted in 1,206 records, of which five studies (n = 421 patients) met the eligibility criteria and presented moderate to low risk of bias. There was no significant difference between groups in the risk of pain in the first 24 hours (relative risk or RR = 0.83, 95% confidence interval or CI: 0.60, 1.16, I 2 =) or 48 hours (RR = 0.56, 95% CI: 0.26, 1.21, I 2 =). Silicate-based sealers led to lower pain intensity only at 48 hours (mean and standard deviation = 0.37, 95% CI: 0.69, 0.05). All analyses revealed low heterogeneity (I 2 < 25%). The evidence presented moderate level of certainty. Currently available evidence has shown that there is no difference between CSB and ERB sealers in the risk or intensity of postoperative pain.

Melatonin-doped polymeric nanoparticles reinforce and remineralize radicular dentin: Morpho-histological, chemical and biomechanical studies

OBJECTIVES

To investigate the effectiveness of novel polymeric nanoparticles (NPs) doped with melatonin (ML) in reducing dentin permeability and facilitating dentin remineralization after endodontic treatment.

METHODS

The effect of undoped NPs and ML-doped NPs (ML-NPs) was tested in radicular dentin, at 24 h and 6 m. A control group without NPs was included. ML liberation was measured. Radicular dentin was assessed for fluid filtration. Dentin remineralization was analyzed by scanning electron microscopy, AFM, Young's modulus (Ei), Nano DMA-tan delta, and Raman analysis.

RESULTS

ML release ranged from 1.85 mg/mL at 24 h to 0.033 mg/mL at 28 d. Both undoped NPs and ML-NPs treated dentin exhibited the lowest microleakage, but samples treated with ML-NPs exhibited hermetically sealed dentinal tubules and extended mineral deposits onto dentin. ML-NPs promoted higher and durable Ei, and functional remineralization at root dentin, generating differences between the values of tan delta among groups and creating zones of stress concentration. Undoped-NPs produced closure of some tubules and porosities at the expense of a relative mineral amorphization. Chemical remineralization based on mineral and organic assessments was higher in samples treated with ML-NPs. When using undoped NPs, precipitation of minerals occurred; however, radicular dentin was not mechanically reinforced but weakened over time.

SIGNIFICANCE

Application of ML-NPs in endodontically treated teeth, previous to the canal filling step, is encouraged due to occlusion of dentinal tubules and the reinforcement of the radicular dentin structure.

Protective effect of quercetin on alteration of antioxidant genes expression and histological changes in the dental pulp of the streptozotocin-diabetic rats

OBJECTIVE

We aimed to assess the effect of quercetin as one of the most common polyphenols with anti-inflammatory and antioxidant properties on expression levels of catalase (CAT), superoxide dismutase 1 (SOD1), and glutathione peroxidase 1 (GPX1), involved in the detoxification of reactive oxygen species (ROS), and histology of dental pulp in streptozotocin-diabetic rats.

DESIGN

Type 1 diabetes mellitus (T1DM) was induced by intraperitoneal injection of streptozotocin in adult male Wistar rats. Animals (n = 24) were equally distributed into control, diabetes, and diabetes treated with quercetin groups. Rats were gavaged daily with quercetin (25 mg/kg) for forty days. To measure the mRNA levels of antioxidant genes, quantitate real-time PCR was applied. The oxidative stress parameters such as total antioxidant capacity (TAC) and histopathological assessments were performed.

RESULTS

A significant increase in the relative quantification mRNA levels of SOD1, CAT, GPX1 was detected in diabetic rat dental pulp. Besides, persistent hyperglycemia led to the enhancement of TAC level and degeneration of connective tissue of the dental pulp. Interestingly, quercetin normalized the expression mRNA levels of CAT, SOD1, GPX1 to near the normal level. Moreover, quercetin treatment normalized TAC levels.

CONCLUSIONS

Because of the crucial role of antioxidants in diabetic complications, the findings of the current study presented a molecular basis for the protective effect of quercetin on dental pulp in diabetic conditions.

Alterations of mitochondrial dynamics, inflammation and mineralization potential of lipopolysaccharide-induced human dental pulp cells after exposure to N-acetyl cysteine, Biodentine or ProRoot MTA

AIM

To investigate the effects of N-acetyl cysteine (NAC), Biodentine, ProRoot MTA and their combinations, on cell viability, mitochondrial reactive oxygen species (mtROS) production, mineralization and on the expression of genes related to inflammatory cytokine production, mitochondrial dynamics and cell apoptosis of lipopolysaccharide (LPS)-induced human dental pulp cells (hDPCs).

METHODOLOGY

Isolated hDPCs were exposed to 20 μg mL^-1 of Escherichia coli (E. coli) LPS for 24 h, before the experiment, except for the control group. Eight experimental groups were assigned: (i) control (hDPCs cultured in regular medium), (ii) +LPS (hDPCs cultured in LPS medium throughout the experiment), (iii) -LPS/Media, (iv) -LPS/BD, (v) -LPS/MTA, (vi) -LPS/NAC, (vii) -LPS/BD + NAC and (viii) -LPS/MTA + NAC. Cell viability was measured using Alamar blue assay at 24 and 48 h. Production of mtROS was evaluated at 6 and 24 h by MitoSOX Red and MitoTracker Green. The expressions of IL-6, TNF-α, Bcl-2, Bax, Mfn-2 and Drp-1 genes were investigated at 6 h using reverse transcriptase-polymerase chain reaction (RT-PCR). For differentiation potential, cells were cultured in the osteogenic differentiation media and stained using Alizarin red assay at 14 and 21 days. The Kruskal-Wallis test, Mann-Whitney U test and one-way anova were performed for statistical analysis.

RESULTS

NAC was associated with significantly greater LPS-induced hDPC viability (P < 0.05). Both Biodentine and MTA extracts promoted cell survival, whereas the combination of NAC to these material extracts significantly increased the number of viable cells at 24 h (P < 0.05). Biodentine, MTA or NAC did not alter the mtROS level (P > 0.05). NAC supplementation to the MTA extract significantly reduced the level of IL-6 and TNF-α expression (P < 0.05). Regarding mitochondrial dynamics, the use of NAC alone promoted significant Mfn-2/Drp-1 expression (P < 0.05). Most of the groups exhibited a level of Bcl-2/Bax gene expression similar to that of the control group. The increases in mineralization productions were observed in most of the groups, except the LPS group (P < 0.05).

CONCLUSIONS

The antioxidant effect of NAC was not evident under the LPS-induced condition in DPC in vitro. NAC combined either with Biodentine or MTA improved LPS-induced hDPCs survival at 24 h. The combination of NAC with MTA promoted mineralization.

Quantitative proteomic analysis in symptomatic and asymptomatic apical periodontitis

AIM

To quantitatively and qualitatively compare the host proteomic profile in samples of symptomatic and asymptomatic apical periodontitis (AP) using nano-liquid chromatography-electron spray tandem mass spectrometry.

METHODOLOGY

Samples were obtained from 18 patients with radiographically evident AP, divided into symptomatic and asymptomatic groups (nine per group) according to clinical characteristics. After sample collection, protein extraction, purification and quantification of the samples were performed, which were analysed by reverse-phase liquid chromatography coupled to mass spectrometry. Label-free quantitative proteomic analysis was performed by Protein Lynx Global Service software. Differences in expression of proteins between the groups were calculated using the Monte Carlo algorithm, considering P < 0.05 for down-regulated proteins and 1 - P > 0.95 for up-regulated proteins. Proteins were identified with the embedded ion accounting algorithm in the software and a search of the Homo sapiens UniProt database.

RESULTS

A total of 853 individual human proteins were identified. In the quantitative analysis, common proteins to both groups accounted for 143 proteins. Differences in expression between groups resulted in 51 up-regulated proteins (1 - P > 0.95) in the symptomatic group, including alpha-1-antitrypsin, protein S100-A8, myeloperoxidase, peroxiredoxin and lactotransferrin. This group also had 43 down-regulated proteins (P < 0.05), comprising immunoglobulin, neutrophil defensin, pyruvate kinase and alpha-enolase. The qualitative analysis considered only the exclusive proteins of each group. For the symptomatic group, 318 complete proteins and 29 fragments were identified, such as dedicator of cytokinesis protein, intersectin, prostaglandin, phospholipase DDHD2 and superoxide dismutase. For the asymptomatic group, 326 complete proteins and 37 fragments were identified, including azurocidin, C-reactive protein, collagen alpha, cathepsin, heat shock and laminin.

CONCLUSIONS

Quantitative differences in the expression of common proteins in cases of symptomatic and asymptomatic AP were found, which were mostly related to host immune response in both groups. Exclusive proteins in the symptomatic group were mainly related to the host response to the presence of viruses in endodontic infections, oxidative stress and proteolytic enzymes. The results provide a basis for a better understanding of cellular and molecular pathways involved in AP, establishing specific proteomic profiles for symptomatic and asymptomatic conditions.

Effect of Endodontic Treatment on Serum Glutathione (GSH) Levels in Patients with Chronic Apical Periodontitis: A Clinical Pilot Study

Aim:

To assess the before- and after-treatment levels of glutathione (GSH) in the serum of patients with chronic apical periodontitis.

Materials and Methods:

The study involved 20 systemically healthy patients with radiographic evidence of chronic apical periodontitis in at least one tooth, of which 11 were finally assessed. 10 mL of the patient’s venous blood was obtained before commencing the endodontic treatment to assess the pre-operative serum GSH levels (T0). The canals cleaned and shaped, and irrigated with 2.5% sodium hypochlorite, and filled with a calcium hydroxide based intracanal medicament. At the subsequent appointment after one week, teeth were obturated. The patients were recalled 30 days after the completion of endodontic therapy, and blood samples were assessed again at time frame T1 for serum GSH. The difference in pre- and post-treatment values for T0 and T1 was statistically analyzed.

Results:

The mean age of the subjects ( N = 11) was 21.09±3.24 years, with 19.50±0.71 years in female group and 21.44±3.50 years in the male group. The mean GSH at T0 was 11.73±8.30 units, which was increased to 14.04±13.96 units at T1. However, no significant change was observed in the GSH level from T0 to T1 (change = –2.30, t-value = –0.49, P = .635).

Conclusion:

The results of this study suggest that endodontic therapy may play a role in restoring the systemic oxidative balance, as seen by the increase in post-treatment serum GSH levels.

The effect of two calcium silicate-based and one epoxy resin-based root canal sealer on postoperative pain: a randomized controlled trial

AIM

To compare the effect of two calcium silicate-based (Endoseal MTA and EndoSequence BC Sealer) and an epoxy resin-based (AH Plus) root canal sealer on postoperative pain following single-visit root canal treatment on molar teeth.

METHODOLOGY

Patients (n = 90) having one first or second molar tooth diagnosed with asymptomatic irreversible pulpitis were randomly divided into three groups according to the sealer used (n = 30) and were treated by two endodontists having at least 10 years of experience. All patients received a single-visit root canal treatment. After the treatments, postoperative pain scores and analgesic intake were recorded at 6, 12, 24 and 48 h, and 3, 4, 5, 6 and 7 days. The data were analysed statistically using non-parametric Kruskal-Wallis tests (for the comparisons of the age and VAS scores), Friedman tests (for the assessments of the changes in pain scores over time), chi-squared tests (for the comparisons of categorical variables) and Spearman's correlation test (for the correlation assessments of the age and gender factors with postoperative pain; α = 0.05).

RESULTS

There were no significant differences amongst the groups in terms of postoperative pain at any time-points assessed (P > 0.05) nor for analgesic intake of patients amongst the groups (P > 0.05). Analgesic intake decreased significantly after 12 h in all groups (P < 0.05).

CONCLUSIONS

The sealers tested in this study were associated with similar levels of postoperative pain and were associated with a similar intake of analgesics.

Effects of alpha-lipoic acid therapy on experimentally induced apical periodontitis: a biochemical, histopathological and micro-CT analysis

AIM

To investigate the possible therapeutic effects of alpha-lipoic acid (ALA) in a model of chronic apical periodontitis in rats by analysing biochemical, histopathological and micro-CT parameters.

METHODOLOGY

The study was approved by the Animal Ethics Committee of the Near East University. Thirty-two Wistar rats were divided into four groups of eight rats each: Control Group; ALA Group; AP Group; AP + ALA Group. In the AP and AP + ALA groups, the pulp chambers of the mandibular first molars were surgically exposed and were left open to the oral environment for 4-weeks to allow the establishment of periapical lesions. The rats in the Control and AP groups were treated intraperitoneally with saline solution (with a daily dose of 100 mg kg^-1 , for 28 days after periapical lesion induction). The rats in the ALA and AP + ALA groups were treated intraperitoneally with ALA (with a daily dose of 100 mg kg^-1 , for 28 days after periapical lesion induction). After decapitation, the trunk blood was collected for the assessment of biochemical parameters. The mandibles were surgically removed and dissected for histopathologic analysis and further scanned with micro-CT. Groups of data were compared with a two-way analysis of variance (two-way anova) followed by Sidak's multiple comparison tests. Values of P < 0.05 were regarded as significant.

RESULTS

TNF-α, IL-1β, MMP-1, MMP-2 levels were significantly lower in AP + ALA group compared with AP group (P < 0.05). There was a significant difference between the AP and AP + ALA groups according to assessment of the inflammatory scores (P < 0.05). The periapical inflammatory infiltrates were significantly more severe (P < 0.05) in the AP group. The AP + ALA group exhibited lower values both in terms of surface area and volume of resorption cavities than the AP group and this difference was significant (P < 0.05).

CONCLUSION

alpha-lipoic acid treatment provided therapeutic effects on the inhibition of periapical bone loss.

Inflammatory profile of chronic apical periodontitis: a literature review

Apical periodontitis caused by root canal infection is the most frequent pathological lesion in the jaws, mainly manifested as periapical granulomas and cysts. Understanding of the formation and progression of apical periodontitis as well as the identification of inflammatory biomarkers can help increase the knowledge of pathogenic mechanisms, improve the diagnosis and provide support for different therapeutic strategies. The objective of the present article is to review inflammatory biomarkers such as cytokines, chemokines, inflammatory cells, neuropeptides, RANK/RANKL/OPG system and other inflammatory markers and to relate these systems to the development and progression of pathological conditions related to apical periodontitis.

Butyrate Stimulates Histone H3 Acetylation, 8-Isoprostane Production, RANKL Expression, and Regulated Osteoprotegerin Expression/Secretion in MG-63 Osteoblastic Cells

Butyric acid as a histone deacetylase (HDAC) inhibitor is produced by a number of periodontal and root canal microorganisms (such as Porphyromonas, Fusobacterium, etc.). Butyric acid may affect the biological activities of periodontal/periapical cells such as osteoblasts, periodontal ligament cells, etc., and thus affect periodontal/periapical tissue destruction and healing. The purposes of this study were to study the toxic effects of butyrate on the matrix and mineralization marker expression in MG-63 osteoblasts. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cellular apoptosis and necrosis were analyzed by propidium iodide/annexin V flow cytometry. The protein and mRNA expression of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-B ligand (RANKL) were analyzed by Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). OPG, soluble RANKL (sRANKL), 8-isoprostane, pro-collagen I, matrix metalloproteinase-2 (MMP-2), osteonectin (SPARC), osteocalcin and osteopontin (OPN) secretion into culture medium were measured by enzyme-linked immunosorbant assay. Alkaline phosphatase (ALP) activity was checked by ALP staining. Histone H3 acetylation levels were evaluated by immunofluorescent staining (IF) and Western blot. We found that butyrate activated the histone H3 acetylation of MG-63 cells. Exposure of MG-63 cells to butyrate partly decreased cell viability with no marked increase in apoptosis and necrosis. Twenty-four hours of exposure to butyrate stimulated RANKL protein expression, whereas it inhibited OPG protein expression. Butyrate also inhibited the secretion of OPG in MG-63 cells, whereas the sRANKL level was below the detection limit. However, 3 days of exposure to butyrate (1 to 8 mM) or other HDAC inhibitors such as phenylbutyrate, valproic acid and trichostatin stimulated OPG secretion. Butyrate stimulated 8-isoprostane, MMP-2 and OPN secretion, but not procollagen I, or osteocalcin in MG-63 cells. Exposure to butyrate (2⁻4 mM) for 3 days markedly stimulated osteonectin secretion and ALP activity. In conclusion, higher concentrations of butyric acid generated by periodontal and root canal microorganisms may potentially induce bone destruction and impair bone repair by the alteration of OPG/RANKL expression/secretion, 8-isoprostane, MMP-2 and OPN secretion, and affect cell viability. However, lower concentrations of butyrate (1⁻4 mM) may stimulate ALP, osteonectin and OPG. These effects are possibly related to increased histone acetylation. These events are important in the pathogenesis and repair of periodontal and periapical destruction.