Sadia Niazi

Propionibacterium acnes and Staphylococcus epidermidis Isolated from Refractory Endodontic Lesions Are Opportunistic Pathogens

ABSTRACT The predominant cultivable microbiota from 20 refractory endodontic lesions (9 with abscesses and 11 without abscesses) were determined, and Propionibacterium acnes and Staphylococcus epidermidis were among the most predominant organisms. The number of species identified from lesions with abscesses (14.1 ± 2.6) was significantly greater (P < 0.001) than the number from lesions without abscesses (7.4 ± 5.9). Comparison of perioral isolates using repetitive extragenic palindromic PCR of the same species from the same subjects demonstrated that the endodontic and skin populations were significantly different. The P. acnes isolates were typed on the basis of recA gene sequence comparison, and only three types (types I, II, and III) were identified among 125 isolates examined. However, we found that type I (type IA and IB) isolates were primarily isolated from the skin, while types II and III were significantly more likely to be isolated from the endodontic lesions (P < 10−10). We found that the robustness of the recA phylotypes was not strong by comparing the partial gene sequences of six putative virulence determinants, PAmce, PAp60, PA-25957, PA-5541, PA-21293, and PA-4687. The resulting neighbor-joining trees were incongruent, and significant (phi test; P = 2.2 × 10−7) evidence of recombination was demonstrated, with significant phylogenetic heterogeneity being apparent within the clusters. P. acnes and S. epidermidis isolated from refractory endodontic infections, with or without periapical abscesses, are likely to be nosocomial infections.

The effectiveness of passive ultrasonic irrigation on intraradicular Enterococcus faecalis biofilms in extracted single‐rooted human teeth

AIM To compare the efficacy of passive ultrasonic irrigation with 1% sodium hypochlorite, with that of conventional syringe irrigation with 1% sodium hypochlorite, on intraradicular Enterococcus faecalis biofilms in extracted single-rooted human teeth. METHODOLOGY Biofilms of E. faecalis (strain OMGS 3202) were grown on the prepared root canal walls of 48 standardized root halves which had been longitudinally sectioned. Following reapproximation, the roots were divided into four groups of twelve. The two experimental groups were treated with conventional syringe irrigation with 1% sodium hypochlorite solution (experimental group A) and passive ultrasonic irrigation with 1% sodium hypochlorite solution (experimental group B). Of the two control groups, the first was treated with conventional syringe irrigation with sterile saline solution (control group C), whilst the second control group (D) received no irrigation. The root halves were processed for scanning electron microscopy. Three images (x 700), coronal, middle and apical, were taken of the twelve root halves in each of the four groups, using a standardized protocol. The images were randomized and biofilm coverage assessed independently by three calibrated examiners, using a four-point scoring system. RESULTS There were no significant differences in the scores for remaining biofilm coverage between group A (conventional syringe irrigation with 1% sodium hypochlorite) and group B (passive ultrasonic irrigation with 1% sodium hypochlorite) at the three observed levels. There was a significant difference between both experimental groups (groups A and B) and group C (conventional syringe irrigation with sterile saline solution) (P < 0.001) at all three observed levels. CONCLUSIONS Both conventional syringe irrigation and passive ultrasonic irrigation with 1% sodium hypochlorite were effective at completely removing intraradicular E. faecalis biofilms. Conventional syringe irrigation with sterile saline solution was only partially effective at removing the biofilms.

Multiple Apical Radiolucencies and External Cervical Resorption Associated with Varicella Zoster Virus: A Case Report

Varicella zoster virus (VZV) is responsible for the primary infection chickenpox. After the initial infection, it remains latent but can reactivate, resulting in shingles (herpes zoster). Previous reports have implicated VZV in the pathogenesis of apical periodontitis, but the involvement of the virus has not been investigated fully. The present case describes a patient who suffered from a severe episode of shingles and subsequently developed periapical radiolucencies of all the teeth in the affected nerve distribution. Molecular and culture techniques showed the presence of VZV DNA in the root canal system in the absence of bacteria. This confirms that VZV can cause localized pulp necrosis and apical periodontitis. The lesions healed after endodontic treatment, implying chemomechanical debridement using sodium hypochlorite irrigation and a calcium hydroxide interim dressing may be effective against the virus.

Influence of a polymerizable eugenol derivative on the antibacterial activity and wettability of a resin composite for intracanal post cementation and core build-up restoration

OBJECTIVES Eugenol has been used in dentistry due to its ability to inhibit the growth of a range of microorganisms, including facultative anaerobes commonly isolated from infected root canals. The aim of this study was to evaluate the antibacterial activity of the experimental composites containing eugenyl methacrylate monomer (EgMA), a polymeric derivative of eugenol, against a range of oral bacteria, commonly associated with failure of coronal and endodontic restorations. In vitro composite behavior and wettability were also studied in conjunction with their antibacterial activity. METHODS EgMA monomer (5 and 10% by weight) was added into BisGMA/TEGDMA resin based formulations with filler mixtures of hydroxyapatite (HA) and zirconium oxide ZrO2. The antibacterial activity of the experimental composites against Enterococcus faecalis, Streptococcus mutans and Propionibacterium acnes were evaluated by direct contact test and compared with composite formulation without inclusion of EgMA. To clarify the antibacterial mode of action, agar diffusion test (ADT) was also performed. Water sorption, solubility, diffusion coefficient, contact angle and surface free energy as complementary clinically relevant properties were determined. RESULTS Water sorption and wettability studies showed reduction of water uptake and surface free energy values with increasing content of EgMA monomer, resulting in significant increase in the hydrophobicity of the composites. No inhibition zones were detected in any of the composites tested against the three bacteria employed as expected, due to the absence of any leachable antibacterial agent. The covalently anchored EgMA monomer with the composite surface exhibited an effective bacteriostatic activity by reducing the number of CFUs of the three species of bacteria tested with no significant dependence on the concentration of EgMA at 5 and 10% by weight. The surface antibacterial activity R of the experimental composites were different against the three tested species with values in the range 2.7-6.1 following the order E. faecalis

Evaluation of dental adhesive systems incorporating an antibacterial monomer eugenyl methacrylate (EgMA) for endodontic restorations

OBJECTIVE The purpose of this study was to incorporate EgMA, an antibacterial monomer into two commercial dental adhesive systems for their application in endodontic restoration with the aim to disinfect the root canal space before curing and to inhibit bacterial growth on their surfaces after being cured. METHODS EgMA monomer was added at 20%wt. into the formulation of the single-component self-etch, Clearfil Universal Bond™ (CUB) and into the catalyst and the adhesive components of the total-etch Adper Scotchbond-multipurpose™ (SBMP) adhesive systems. The degree of conversion (DC) was calculated from FTIR spectra, glass transition temperature (Tg) determined by DSC, water sorption and solubility were measured gravimetrically, and surface free energy (SFE) via contact angle measurements. The bonding performance to coronal and middle root canal dentin was assessed through push-out bond strength after filling the canals with a composite core material and the surface integrity was observed using SEM and confocal laser scanning microscopy (CLSM). The standard agar diffusion test (ADT) was used to identify the sensitivity of three endodontically pathogenic bacteria, Enterococcus faecalis, Streptococcus mutans and Propionibacterium acnes to uncured EgMA modified adhesives. Multispecies biofilm model from these strains was grown on the disc surface of cured adhesives and investigated using quantitative microbial culture and CLSM with live/dead staining. MTT assay was also used to determine the cytotoxicity of these adhesives. RESULTS The incorporation of EgMA lowered polymerization exotherm and enhanced the hydrophobic character of these adhesives, without changing the DC and Tg in comparison to the controls (without EgMA). The total push-out bond strengths of the EgMA-containing adhesives were not significantly different from those of the controls (p>0.05). The modification of self-etch adhesive system enhanced the bond strength in the middle region of the roots canal. SEM of debonded specimens and CLSM examination showed the integrity of the resin-dentin interfaces. For all three bacteria tested, the sizes of the inhibition zones produced by uncured EgMA modified adhesives were significantly greater (p<0.05) than those of the controls. The results of biofilm inhibition tests showed less CFU for total bacteria on bonding agents with EgMA compared to the control materials (p<0.05). The modification at 20% monomer concentration had no adverse effects on cytocompatibility of both adhesives tested. SIGNIFICANCE The inclusion of EgMA endows dental adhesives with effective antibacterial effects without influencing their curing properties, bonding ability to root canal dentin, and cytotoxicity against human gingival fibroblasts, indicating the usefulness of their application in endodontic restorations.

Bacterial Contamination of Endodontic Materials before and after Clinical Storage

Introduction The aim of this study was to evaluate the bacterial contamination in endodontic consumables (gutta‐percha points, rubber dams, paper mixing pads, caulking agents, and endodontic instrument sponges [EISs]) before and after clinical use and storage. Methods Materials were randomly sampled in triplicates at 3 time points (t0, at package opening; t1, at 7 days; and t2, at 14 days) during their clinical usage. The gutta‐percha points and caulking agent (25 mg) were added to 1 mL phosphate‐buffered saline (PBS). The rubber dam, paper mixing pad, and EIS were added to 25 mL PBS. After vortexing, centrifuging, and removing the supernatant, the pellet was resuspended in 1 mL PBS, plated on fastidious anaerobic agar, and incubated aerobically and anaerobically. The grown colonies were identified by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). The total bacterial load was calculated in the remaining volume (800 &mgr;L) from each sample by quantitative polymerase chain reaction after DNA extraction. Results All tested materials showed a varied number of contaminated samples at the 3 time points (except EIS at t0) using MALDI‐TOF MS. The most isolated genera were Propionibacterium (42%) and Staphylococcus (32%). By using non–culture‐based approaches, all tested materials at the 3 time points (except gutta‐percha at t0 and the caulking agent at t0, t1, and t2) carried bacterial DNA. Conclusions The majority of the tested materials harbored bacteria in their samples before and after clinical storage. Nosocomial infection derived from commonly used consumables could have an impact on the outcome of endodontic treatment. HighlightsConsumables commonly used in endodontics are often in nonsterile packaging.Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy is a valid technique to identify the contaminants of endodontic materials.Clinical storage can induce environmental contamination.The presence of bacteria in endodontic materials may induce nosocomial infection.Nosocomial infections may induce failure in de novo root canal treatments

Rapid Bacterial Detection during Endodontic Treatment

Bacteria present in the root canal (RC) space following an RC treatment (RCT) can lead to persistent infections, resulting in treatment failure and the need for reintervention or extraction. Currently, there are no standardized methods in use to clinically detect bacterial presence within RC spaces. The use of paper point sampling and fluorescence staining was shown to be a rapid method, able to detect residual bacteria following treatment. The study demonstrated that Calcein acetoxymethyl (AM) proved to be a suitable dye for detecting vital bacteria within mature endodontic biofilms, with an improved sensitivity over colony-forming unit counting in a stressed biofilm model. Furthermore, in a clinical trial with primary RCTs, 53 infected teeth were sampled in vivo, and increased detection of vital cells was found when compared with colony-forming unit counting, highlighting the sensitivity of the technique in detecting low cell numbers. By combining fluorescent staining and microspectroscopy with software-based spectral analysis, successful detection of vital cells from RCs was possible after 5 min of Calcein AM incubation. Application of this technology during RCT has the potential to reduce persistent infections through vital cell detection and additional treatment. Furthermore, this technique could be applied to antimicrobial research and disinfection control in clinical settings (ClinicalTrials.gov NCT03055975).

Quantification by SIFT-MS of volatile compounds produced by the action of sodium hypochlorite on a model system of infected root canal content

Root canal irrigation with sodium hypochlorite (NaOCl) is an indispensable part of the chemomechanical preparation of infected root canals in Endodontology. However, there is limited information on the emergence of toxic or hazardous volatile compounds (VOCs) from the interaction of NaOCl with the infected content of tooth biomaterials. The aim of this study was to assess the formation of VOCs and disinfection by-products (DBPs) following the interaction of NaOCl 2.5% v/v with a model system of different sources of natural organic matter (NOM) present in infected root canals, including dentine powder, planktonic multi-microbial suspensions (Propionibacterium acnes, Staphylococcus epidermidis, Actinomyces radicidentis, Streptococcus mitis and Enterococcus faecalis strain OMGS3202), bovine serum albumin 4%w/v and their combination. NaOCl was obtained from a stock solution with iodometric titration. Ultrapure water served as negative control. Samples were stirred at 37°C in aerobic and anaerobic conditions for 30min to approximate a clinically realistic time. Centrifugation was performed and the supernatants were collected and stored at -800 C until analysis. The reaction products were analysed in real time by selected ion flow tube mass spectrometry (SIFT-MS) in triplicates. SIFT-MS analysis showed that the released VOCs included chlorinated hydrocarbons, particularly chloroform, together with unexpected higher levels of some nitrogenous compounds, especially acetonitrile. No difference was observed between aerobic and anaerobic conditions. The chemical interaction of NaOCl with NOM resulted in the formation of toxic chlorinated VOCs and DBPs. SIFT-MS analysis proved to be an effective analytical method. The risks from the rise of toxic compounds require further consideration in dentistry.