The Preventive Effect of A Magnetic Nanoparticle-Modified Root Canal Sealer on Persistent Apical Periodontitis.

Persistent apical periodontitis is a critical challenge for endodontists. Developing root canal filling materials with continuous antibacterial effects and tightly sealed root canals are essential strategies to avoid the failure of root canal therapy and prevent persistent apical periodontitis. We modified the EndoREZ root canal sealer with the antibacterial material dimethylaminododecyl methacrylate (DMADDM) and magnetic nanoparticles (MNPs). The mechanical properties of the modified root canal sealer were tested. The biocompatibility of this sealer was verified in vitro and in vivo. Multispecies biofilms were constructed to assess the antibacterial effects of the modified root canal sealer. We applied magnetic fields and examined the extent of root canal sealer penetration in vitro and in vivo. The results showed that EndoREZ sealer containing 2.5% DMADDM and 1% MNP had biological safety and apical sealing ability. In addition, the modified sealer could increase the sealer penetration range and exert significant antibacterial effects on multispecies biofilms under an external magnetic field. According to the in vivo study, the apices of the root canals with the sealer containing 2.5% DMADDM and 1% MNP showed no significant resorption and exhibited only a slight increase in the periodontal ligament space, with a good inhibitory effect on persistent apical periodontitis.

A novel antibacterial resin-based root canal sealer modified by Dimethylaminododecyl Methacrylate.

Persistent apical periodontitis, mainly caused by microorganisms infections, represents a critical challenge for endodontists. Dimethylaminododecyl methacrylate (DMADDM) is a well-studied and potent antibacterial agent used in various studies described in the literature. The aim of this study is to develop a novel antibacterial root canal sealer by incorporating DMADDM into EndoREZ and investigate the properties of the resulting material. Different mass fractions (0, 1.25%, 2.5%, and 5%) of DMADDM were incorporated into EndoREZ and the cytotoxicity, apical sealing ability and solubility of the resulting material were evaluated. Furthermore, a direct contact test, determination of colony-forming units, a crystal violet assay, scanning electronic microscopy and live/dead bacteria staining were performed to evaluate the antibacterial effect of the sealer to multispecies bacteria (Enterococcus faecalis, Streptococcus gordonii, Actinomyces naeslundii, and Lactobacillus acidophilus), in planktonic cells or biofilms. Fluorescence in situ hybridization and quantitative real-time polymerase chain reaction were carried out to assess the composition of the multispecies biofilms. No difference on the cytotoxicity, apical sealing ability and solubility between sealers containing DMADDM (1.25%, 2.5%) and EndoREZ (0%) could be determined. However, when the mass fraction of DMADDM increased to 5%, significantly different properties were found compared to the 0% (p < 0.05) group. Moreover, incorporating DMADDM into the sealer could greatly improve the antibacterial properties of EndoREZ. In addition, the composition ratio of E. faecalis could be decreased in multispecies microecology in sealers containing DMADDM. Therefore, a EndoREZ sealer material containing DMADDM could be considered useful in clinical applications for preventing and treating persistent apical periodontitis.

Resolvin D2 Induces Resolution of Periapical Inflammation and Promotes Healing of Periapical Lesions in Rat Periapical Periodontitis.

Periapical periodontitis results from pulpal infection leading to pulpal necrosis and resorption of periapical bone. The current treatment is root canal therapy, which attempts to eliminate infection and necrotic tissue. But, in some cases periapical inflammation doesn't resolve even after treatment. Resolvins belongs to a large family of specialized pro-resolving lipid mediators that actively resolves inflammation signaling via specific receptors. Resolvin D2 (RvD2), a metabolite of docosahexaenoic acid (DHA), was tested as an intracanal medicament in rats in vivo. Mechanism was evaluated in rat primary dental pulp cells (DPCs) in vitro. The results demonstrate that RvD2 reduces inflammatory cell infiltrate, periapical lesion size, and fosters pulp like tissue regeneration and healing of periapical lesion. RvD2 enhanced expression of its receptor, GPR18, dentin matrix acidic phosphoprotein 1 (DMP1) and mineralization in vivo and in vitro. Moreover, RvD2 induces phosphorylation of Stat3 transcription factor in dental pulp cells. We conclude that intracanal treatment with RvD2 resolves inflammation and promoting calcification around root apex and healing of periapical bone lesions. The data suggest that RvD2 induces active resolution of inflammation with pulp-like tissue regeneration after root canal infection and thus maybe suitable for treating periapical lesions.

Interaction of biologic therapy with apical periodontitis and periodontitis: a systematic review.

Biologic medications (BMs) are increasingly used for the management of systemic chronic inflammatory diseases. These diseases are often associated with a higher prevalence of apical periodontitis (AP) and periodontitis (P). The purpose of this systematic review was to ascertain the interactions between AP and/or P and BMs. The review was registered in the PROSPERO database (CRD42017054756). Electronic searches were performed on Pubmed Medline, Scopus and The Web of Science from their inception through to 20 March 2018. The references of the articles selected were checked. The keywords were chosen based on a pilot search, which aimed to find the most frequently prescribed BMs. The included studies were appraised qualitatively using appropriate tools. Thirty-five articles met the inclusion criteria, comprising 16 non-randomized clinical studies, 12 in vivo animal studies and 7 case reports. Quality of information was assessed as high in 18 articles, moderate in 16 articles and low in 1 article. BMs in patients suffering from chronic inflammatory diseases seems to inhibit the progression of AP and P, and to enhance the healing response to periodontal and endodontic treatment. A healthier condition of the periodontal tissues seems to be associated with a better response of the patient to BMs therapy.

Lactobacillus plantarum Lipoteichoic Acid Inhibits Oral Multispecies Biofilm.

INTRODUCTION: Apical periodontitis is an inflammatory disease in the periradicular region of teeth that results from infection by multispecies bacterial biofilm residing in the root canal system. In this study, we investigated whether Lactobacillus plantarum lipoteichoic acid (Lp.LTA) could inhibit multispecies oral pathogenic bacterial biofilm formation. METHODS: Highly pure and structurally intact Lp.LTA was purified from L. plantarum. Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans, and Enterococcus faecalis were co-cultured to form oral multispecies biofilm in the presence or absence of Lp.LTA on culture plates or human dentin slices. Preformed biofilm was treated with or without Lp.LTA, followed by additional treatment with intracanal medicaments such as calcium hydroxide or chlorhexidine digluconate. Confocal microscopy and crystal violet assay were performed to determine biofilm formation. Biofilm on human dentin slices was visualized with a scanning electron microscope. RESULTS: Biofilm formation of multispecies bacteria on the culture dishes was dose-dependently reduced by Lp.LTA compared with the nontreatment control group. Lp.LTA also inhibited multispecies biofilm formation on the dentin slices in a dose-dependent manner. Interestingly, Lp.LTA was shown to reduce preformed multispecies biofilm compared with the nontreatment group. Moreover, Lp.LTA potentiated the effectiveness of the intracanal medicaments in the removal of preformed multispecies biofilm. CONCLUSIONS: These results suggest that Lp.LTA is a potential anti-biofilm agent for treatment or prevention of oral infectious disease, including apical periodontitis, which is mainly caused by multispecies bacterial biofilm.

Canal Transportation and Centering Ability of WaveOne Gold in Combination with and without Different Glide Path Techniques.

INTRODUCTION: The aim of this study was to compare centering ability and transportation values of the Primary WaveOne Gold (PWOG; Dentsply Sirona, Ballaigues, Switzerland) instrument with or without different glide path techniques. Centering ability and transportation were also compared between the 3 different glide path preparation groups. METHODS: The mesiobuccal canals of 60 extracted human mandibular molars (curvature angles between 25° and 35° and radii ≤10 mm) were selected and randomly divided into 4 groups with 15 canals each. Canals were negotiated to patency with a #8 K-file. Canal preparations were performed by a single operator using precurved #10, 15, and 20 stainless steel manual K-files (group KF); a #10 stainless steel manual K-file followed by PathFiles #1-3 (Dentsply Sirona) (group PF); a #10 stainless steel manual K-file followed by the WaveOne Gold Glider (Dentsply Sirona) (group WOGG); and no further glide path preparation (group NG). Micro-computed tomographic imaging was used to scan teeth before and after glide path preparation. The final canal preparation was performed with PWOG; after which, all 60 specimens were scanned again using micro-computed tomographic imaging. Canal transportation and centering ratio values were determined over levels 3 mm, 5 mm, and 7 mm from the root apex after glide path preparation and again after final preparation with PWOG. One-way analysis of variance was used to statistically compare groups. The significance level was set at P < .05. RESULTS: No statistically significant difference in the mean centering ratios was found after glide path preparation when the KF, PF, and WOGG groups were compared (P > .05). The mean combined transportation values after glide path preparation were statistically significantly higher in the KF group compared with the PF and WOGG groups (P > .05). There was no statistically significant difference in the mean combined centering ratios or transportation values of the NG and 3 glide path groups in combination with PWOG over the 3 levels (P > .05). CONCLUSION: KF group showed the highest mean transportation values during glide path preparation. However, the PWOG instrument's performance regarding centering ability and transportation was not influenced by the different glide path/no glide path preparation groups.

Activation of hypoxia-inducible factor 1 attenuates periapical inflammation and bone loss.

Hypoxia (low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1 (HIF-1). Hypoxia interferes degradation of HIF-1 alpha subunit (HIF-1α), leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit (HIF-1ß) and subsequent activation of HIF-1 pathway. Apical periodontitis (periapical lesion) is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a well-characterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine (DMOG) and adenovirus-induced constitutively active HIF-1α (CA-HIF1A). Both DMOG and CA-HIF1A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B (NF-κB) and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.

The effect of endodontics and crown restoration techniques on the prognosis of treatment non-vital teeth.

OBJECTIVE: Introduction: It is generally accepted that the prognosis of endodontic treatment positively correlates with the technical quality of root filling. This seems logical in the sense that the root filling is intended to create a bacterial tight seal on the root canal, so oral bacteria cannot reach the periapical tissues and cause disease. The materials that are available to seal the root canal system are not flawed, and a number of studies using different methods have suggested that even seeming adequate root fillers may not be effective over time. The aim of the study was to evaluate the possible relationship between the quality of restorative crown of the tooth, obturation of the root canal and the periapical status of the teeth that were subjected to endodontic treatment. PATIENTS AND METHODS: Materials and methods: A series of X-ray images of randomly selected outpatient cards from patients in the dental department of the Dnipropetrovsk State Medical Academy clinic were investigated. A total of 1001 teeth that were subjected to endodontic treatment, restored by permanent restoration, were evaluated independently by two experts. According to the predetermined set of radiological criteria, the quality of filling the root canals of the tooth was assessed as good (GE), or poor (PE). In turn, the quality of thetooth crown restoration was also evaluated and recognized as good (GR) or poor (PR). Subsequently, the roots of the teeth and surrounding tissues were investigated, and according to existing or present abnormalities, the outcome of treatment was determined to be either successful or unsuccessful. RESULTS: Results: The successful outcome of endodontic treatment among all the teeth tested was found at 66.4& (n = 1001). The positive result of treatment of teeth with root posts reached 72.7& (n = 527), the success of treatment of teeth without pins was 64.6& (n = 472). The effectiveness of dental treatment, where the technically satisfactory endodontics was found to be the highest. Thus, in combination with technically satisfactory restorations, the success rate reached 82& (GE + GR), and when the restoration was technically unsatisfactory, positive results of treatment were observed in 72& of cases (GE + PR). At the same time, in those groups where endodontics was considered technically unsatisfactory, the positive result of treatment was observed significantly less often, in combination with unsatisfactory restoration, only 55& (PE + GR). If restorations were satisfactory, then somewhat more often, in 57& of the examined teeth (PE + PR). CONCLUSION: Conclusions: Thus, according to the results of the X-ray assessment of non-vital teeth, it became clear that in order to achieve a positive result, technically qualitative endodontics is more important, with the same characteristic of restoration of the crown of the tooth.

[Theory and practice of minimally invasive endodontics].

The primary goal of modern endodontic therapy is to achieve the long-term retention of a functional tooth by preventing or treating pulpitis or apical periodontitis is. The long-term retention of endodontically treated tooth is correlated with the remaining amount of tooth tissue and the quality of the restoration after root canal filling. In recent years, there has been rapid progress and development in the basic research of endodontic biology, instrument and applied materials, making treatment procedures safer, more accurate, and more efficient. Thus, minimally invasive endodontics(MIE)has received increasing attention at present. MIE aims to preserve the maximum of tooth structure during root canal therapy, and the concept covers the whole process of diagnosis and treatment of teeth. This review article focuses on describing the minimally invasive concepts and operating essentials in endodontics, from diagnosis and treatment planning to the access opening, pulp cavity finishing, root canal cleaning and shaping, 3-dimensional root canal filling and restoration after root canal treatment.

Contemporary Cleaning and Shaping of the Root Canal System.

Prevention or treatment of apical periodontitis is aimed at disinfecting the root canal system so that the periradicular tissues are not vulnerable to attack from microbiota within the tooth. This is achieved by a process of cleaning and shaping the root canal space. The fundamental principles underlying this process have not changed in decades. In contrast, the armamentarium available to the clinician continues to evolve rapidly. The use of specially designed nickel titanium (NiTi) files to create a glidepath allows the clinician to manage tight curved canals more predictably in situations which would otherwise have proved too difficult using conventional techniques. Other files, designed to shape the canal, have been developed using metallurgic principles which permit NiTi files to be more flexible and resistant to cyclic fatigue. These newer systems also require fewer instruments to prepare a canal and some, which have adopted a reciprocating (rotational) motion, may only require one file. Progress is also being made in enhancing efficacy of irrigant activity using negative apical pressure systems, sonic and ultrasonic agitation techniques. These contemporary techniques used to clean and shape the root canal system should result in improved confidence and predictability when managing endodontic disease.

Treatment outcomes of single-visit versus multiple-visit non-surgical endodontic therapy: a randomised clinical trial.

BACKGROUND: Clincians have been providing single-visit and multiple-visit endodontic treatments for their patients. This study aims to compare the success rate, prevalence of postoperative pain and chairside time of single-visit and multiple-visit endodontic treatments. METHOD: Patients who required primary endodontic treatment in a university dental clinic were randomly allocated to two general dentists for single-visit or multiple-visit treatments using the same materials and procedures. Ni-Ti rotary files were used to prepare the root canals, which were subsequently obturated with a core-carrier technique. The chairside time was recorded. The treated teeth were followed up every 6 months on clinically signs and symptoms including pain, tenderness to percussion, sinus tract, mobility and abscess. Periapical radiographs were taken to assess periapical pathology. Successful treatments were neither clinical signs/symptoms noted nor radiographic periapical pathology found postoperatively. RESULTS: A total of 220 teeth from patients aged 46.4 ± 14.1 were followed up for at least 18 months. The mean (±SD) follow-up period was 29.4 ± 9.3 months. The success rates of single-visit and multiple-visit treatments were 88.9 and 87.4 %, respectively (p = 0.729, effect size odds ratio = 1.156). Maxillary teeth had odds ratios of 3.16 (95 % CI: 1.33 to 7.46; p = 0.009) and absence of preoperative apical periodontitis had odds ratios of 4.35 (95 % CI: 1.43 to 13.24; p = 0.010) were identified from logistic regression as having a higher success rate. The average chairside times of single-visit and multiple-visit treatments were 62.0 and 92.9 min, respectively (mean difference = -30.9, 95 % CI: -39.4 to -22.4, p < 0.001, effect size odds ratio = -0.996). Single-visit and multiple-visit treatment had no significant difference in the prevalence of postoperative pain within 7 days (21 and 12 %, p = 0.055, effect size odds ratio = 2.061) and after at least 18 months (0.9 and 1.0 %, p > 0.999, effect size odds ratio = 0.879). CONCLUSIONS: The success rate and prevalence of postoperative pain of single-visit or multiple-visit treatment had no significant difference. The chairside time for single-visit treatment was shorter than multiple-visit treatment. TRIAL REGISTRATION: Clinical Trials (WHO) ChiCTR-IOR-15006117 registered on 20 March 2015.

Infection Control in Retreatment Cases: In Vivo Antibacterial Effects of 2 Instrumentation Systems.

INTRODUCTION: This in vivo study compared the antibacterial effects of 2 instrumentation systems in root canal-treated teeth with apical periodontitis. METHODS: Forty-eight teeth with a single root and a single canal showing post-treatment apical periodontitis were selected for this study. For retreatment, teeth were randomly divided into 2 groups according to the instrumentation system used: Self-Adjusting File (SAF; ReDent-Nova, Ra'anana, Israel) and Twisted File Adaptive (TFA; SybronEndo, Orange, CA). In both groups, 2.5% sodium hypochlorite was the irrigant. Bacteriological samples were taken before (S1) and after chemomechanical preparation (S2). In the TFA group, passive ultrasonic irrigation (PUI) was performed after instrumentation, and samples were also taken after this supplementary step (S2b). DNA was extracted from the clinical samples and subjected to quantitative real-time polymerase chain reaction to evaluate the levels of total bacteria, streptococci, and Enterococcus faecalis. Statistical analyses from quantitative real-time polymerase chain reaction data were performed within groups using the Wilcoxon matched pairs test and between groups using the Mann-Whitney U test and the Fisher exact test with the significance level set at P < .05. RESULTS: Bacteria were detected in S1 samples from 43 teeth, which were then included in the antibacterial experiment. Both SAF and TFA instrumentation protocols showed a highly significant intracanal bacterial reduction (P < .001). Intergroup quantitative comparisons disclosed no significant differences between TFA with or without PUI and SAF (P > .05). PUI did not result in significant improvement in disinfection (P > .05). CONCLUSIONS: Both instrumentation systems/treatment protocols were highly effective in significantly reducing the intracanal bacterial counts. No significant difference was observed between the 2 systems in disinfecting the canals of teeth with post-treatment apical periodontitis.

Consequences of crown shortening canine teeth in Greenland sled dogs.

OBJECTIVES: To evaluate the consequences of crown shortening, focusing on the prevalence of pulp exposure and periapical pathology in Greenland sled dogs that had had their canine crowns shortened at an early age. METHODS: Five cadaver heads and 54 sled dogs underwent an oral examination for dental fractures and pulp exposure of canines. All canines were radiographed and evaluated for periapical pathology. RESULTS: The prevalence of canine pulp exposure in 12 (5 heads and 7 dogs) crown shortened dogs was 91 · 7%, and 21 · 3% in 47 not-crown shortened dogs. A significant (P < 0 · 001) risk of pulp exposure of the canines in the crown shortened group compared to the not-crown shortened group was seen with a relative risk of 4 · 3 on a dog basis and a relative risk of 12 · 2 on a tooth basis. In dogs with pulp exposure of canines (n = 51) the prevalence of periapical pathology was 82 · 4%, but only 0 · 8% in dogs without pulp exposure (n = 133) resulting in a significant (relative risk, 109 · 5; P < 0 · 001) risk of periapical pathology in teeth with pulp exposure compared to teeth without pulp exposure. CLINICAL SIGNIFICANCE: The high risk of periapical pathology observed in teeth with pulp exposure confirms that these teeth should not be neglected in affected dogs.

RNA interference-mediated silencing of Atp6i prevents both periapical bone erosion and inflammation in the mouse model of endodontic disease.

Dental caries is one of the most prevalent infectious diseases in the United States, affecting approximately 80% of children and the majority of adults. Dental caries may lead to endodontic disease, where the bacterial infection progresses to the root canal system of the tooth, leading to periapical inflammation, bone erosion, severe pain, and tooth loss. Periapical inflammation may also exacerbate inflammation in other parts of the body. Although conventional clinical therapies for this disease are successful in approximately 80% of cases, there is still an urgent need for increased efficacy of treatment. In this study, we applied a novel gene-therapeutic approach using recombinant adeno-associated virus (AAV)-mediated Atp6i RNA interference (RNAi) knockdown of Atp6i/TIRC7 gene expression to simultaneously target periapical bone resorption and periapical inflammation. We found that Atp6i inhibition impaired osteoclast function in vitro and in vivo and decreased the number of T cells in the periapical lesion. Notably, AAV-mediated Atp6i/TIRC7 knockdown gene therapy reduced bacterial infection-stimulated bone resorption by 80% in the mouse model of endodontic disease. Importantly, Atp6i(+/-) mice with haploinsufficiency of Atp6i exhibited protection similar to that in mice with bacterial infection-stimulated bone erosion and periapical inflammation, which confirms the potential therapeutic effect of AAV-small hairpin RNA (shRNA)-Atp6i/TIRC7. Our results demonstrate that AAV-mediated Atp6i/TIRC7 knockdown in periapical tissues can inhibit endodontic disease development, bone resorption, and inflammation, indicating for the first time that this potential gene therapy may significantly improve the health of those who suffer from endodontic disease.

Effects of the antioxidant agent tempol on periapical lesions in rats with doxorubicin-induced cardiomyopathy.

INTRODUCTION: Cardiovascular diseases have been associated with increased risk of endodontic complications. This study evaluated the effects of the antioxidant agent tempol on periapical lesions in rats with doxorubicin-induced cardiomyopathy in comparison with control animals. METHODS: Forty male Wistar rats were divided into 4 groups: (1) naïve rats orally treated with saline solution (10 mL/kg, during 21 days after periapical lesion induction); (2) naïve rats treated with tempol (30 and 50 mg/kg, during 21 days after periapical lesion induction) by oral pathway; (3) rats with doxorubicin-induced cardiomyopathy treated with saline solution by oral route (10 mL/kg, from day 3 to day 10 after initiating treatment with doxorubicin); and (4) rats with doxorubicin-induced cardiomyopathy orally treated with tempol (30 and 50 mg/kg, from day 3 to day 10 after initiating treatment with doxorubicin). Periapical lesions were induced on the first right mandibular molar tooth. After 21 days of apical periodontitis induction, the animals were killed, and the mandibles were collected for radiographic and histologic analysis. RESULTS: The oral administration of tempol (50 mg/kg) was able to significantly prevent the establishment of periapical lesions in either control animals or rats submitted to the model of doxorubicin-induced cardiomyopathy, according to radiographic and histologic evaluation. Nevertheless, the protective effects of tempol were virtually greater in control animals in comparison with doxorubicin-treated rats, as indicated by histologic inflammatory assessment, which might be related to the increased production of free radicals under cardiomyopathy. CONCLUSIONS: We provide novel evidence on the beneficial systemic effects of the antioxidant tempol on apical periodontitis in both control animals and rats with doxorubicin-elicited cardiomyopathy.

[Microbial decontamination of the root canals of devitalized teeth]. / Mikrobiálna dekontaminácia korenových kanálikov devitálnych zubov.

The primary goal of endodontic therapy is the reduction or elimination of microorganisms and their by-products from the root canal system. Although a number of instrumentation and irrigation techniques exist, debris is often left behind in the root canal system and proper canal cleaning, shaping, and irrigation are needed to reduce significantly or sometimes even eliminate microorganisms from the canals. Residual microbes in the root canal system are the primary cause of post-treatment apical periodontitis that may persist in both poorly and properly treated cases. Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system to the periapical tissue. It results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. When the root canal treatment is carried out properly, healing of the periapical lesion usually follows, with bone regeneration. In certain cases, post-treatment apical periodontitis still persists, the condition being commonly referred to as endodontic failure. It is widely acknowledged that such post-treatment apical periodontitis occurs when root canal treatment has not adequately controlled and eliminated the infection. However, complete elimination of microorganisms is not always achieved in clinical practice due to the anatomical complexities of root canals and consequent limitations in access by instruments and irrigants. The use of antimicrobial medication has been advocated to disinfect the root canal system. The recovery of Candida albicans and Enterococcus faecalis is common after failed root canal treatment. Therefore, when testing different antimicrobial agents for efficacy in endodontic treatment, 100% inhibition of the growth of the two microorganisms is required. The purpose of this article is to assess the antimicrobial action of intracanal medicaments and relevance of the root canal irrigation in endodontic therapy of devitalized teeth.

Use of aminoguanidine, a selective inducible nitric oxide synthase inhibitor, to evaluate the role of nitric oxide in periapical inflammation.

The purpose of this study was to evaluate the effects of aminoguanidine (AG) as a selective inhibitor of inducible nitric oxide synthase (iNOS) on the degree of inflammatory response in periapical lesions in the canine teeth of cats. Root canals from 52 cat canine teeth were exposed to the oral cavity and sealed after 7 days. One day before pulp exposure, cats were administered either AG (experimental group) or normal saline (control group), which was continued on a daily basis until the day of sacrifice. Animals were sacrificed at 28 days after pulp exposure. Inflammatory response in the periapical zones was analyzed histologically. The degree of periapical inflammation in the AG group was significantly lower than that in the control group (P < 0.05). Selective iNOS inhibitors such as AG thus reduce the intensity of inflammatory responses in periapical lesions.