Exuberant Biofilm infection in a lateral canal as the cause of short-term endodontic treatment failure: report of a case

Three-dimensional assessment of obturation volume in lateral canals after three obturation techniques with bioceramic sealer: an in vitro comparative study

OBJECTIVE

This study aimed to evaluate the obturation ability of simulated lateral canal in mandibular premolars at three levels (3, 5, and 7 mm) from the apex using gutta-percha and BC Sealer HiFlow (BCHiF) with different obturation techniques, including continuous wave compaction (CWC), cold lateral condensation (CLC), and single cone (SC) techniques, by a 3D assessment method of the obturation volume with cone beam computed tomography (CBCT) and MIMICS software analysis.

METHODS

Thirty intact human mandibular premolars were decoronated, instrumented up to #30 taper 4%, and uniformly irrigated with 5.25% NaOCl and 17% EDTA. Six simulated lateral canals (3 pairs) were prepared at 3, 5, and 7 mm from the apex in each root, using #10 modified C-file. CBCT images were obtained, and lateral canal volumes were calculated using MIMICS software. The samples were divided into three groups: CWC (n = 10), CLC (n = 10), and SC (n = 10). All groups were obturated with BCHiF and gutta-percha. Another CBCT image was taken post-obturation, and 3D lateral canal obturation volume percentages were calculated using MIMICS software. Data were analyzed using SPSS software with One-way ANOVA and Sidak tests (α = 0.05).

RESULTS

Significant differences were observed in the 3D lateral canal obturation volume percentage at all three levels (P < 0.05). Both CWC and CLC techniques demonstrated higher 3D lateral canal obturation volume percentages (x ¯  = 89.64% andx ¯   =  73.28%; respectively) compared to the SC group)x ¯   =  43.10%).

CONCLUSION

BCHiF combined with the CWC technique has a higher ability to achieve preferable 3D obturation volume in the simulated lateral canal at 3, 5, and 7 mm.

CLINICAL RELEVANCE

In cases requiring endodontic treatment with lateral canals, the CWC obturation technique using BCHiF with gutta-percha may offer better outcomes compared to other obturation techniques.

Improving the Antimicrobial Potency of Berberine for Endodontic Canal Irrigation Using Polymeric Nanoparticles

To address the challenges posed by biofilm presence and achieve a substantial reduction in bacterial load within root canals during endodontic treatment, various irrigants, including nanoparticle suspensions, have been recommended. Berberine (BBR), a natural alkaloid derived from various plants, has demonstrated potential applications in dentistry treatments due to its prominent antimicrobial, anti-inflammatory, and antioxidant properties. This study aimed to produce and characterize a novel polymeric nanoparticle of poly (lactic-co-glycolic acid) (PLGA) loaded with berberine and evaluate its antimicrobial activity against relevant endodontic pathogens, Enterococcus faecalis, and Candida albicans. Additionally, its cytocompatibility using gingival fibroblasts was assessed. The polymeric nanoparticle was prepared by the nanoprecipitation method. Physicochemical characterization revealed spheric nanoparticles around 140 nm with ca, -6 mV of surface charge, which was unaffected by the presence of BBR. The alkaloid was successfully incorporated at an encapsulation efficiency of 77% and the designed nanoparticles were stable upon 20 weeks of storage at 4 °C and 25 °C. Free BBR reduced planktonic growth at ≥125 μg/mL. Upon incorporation into PLGA nanoparticles, 20 μg/mL of [BBR]-loaded nanoparticles lead to a significant reduction, after 1 h of contact, of both planktonic bacteria and yeast. Sessile cells within biofilms were also considered. At 30 and 40 μg/mL, [BBR]-loaded PLGA nanoparticles reduced the viability of the sessile endodontic bacteria, upon 24 h of exposure. The cytotoxicity of BBR-loaded nanoparticles to oral fibroblasts was negligible. The novel berberine-loaded polymeric nanoparticles hold potential as a promising supplementary approach in the treatment of endodontic infections.

Nanomaterial-based drug-delivery system as an aid to antimicrobial photodynamic therapy in treating oral biofilm

Diverse microorganisms live as biofilm in the mouth accounts for oral diseases and treatment failure. For decades, the prevention and treatment of oral biofilm is a global challenge. Antimicrobial photodynamic therapy (aPDT) holds promise for oral biofilm elimination due to its several traits, including broad-spectrum antimicrobial capacity, lower possibility of resistance and low cytotoxicity. However, the physicochemical properties of photosensitizers and the biological barrier of oral biofilm have limited the efficiency of aPDT. Nanomaterials has been used to fabricate nanocarriers to improve photosensitizer properties and thus enhance antimicrobial effect. In this review, we have discussed the challenges of aPDT used in dentistry, categorized the nanomaterial-delivery system and listed the possible mechanisms involved in nanomaterials when enhancing aPDT effect.

Failed Regenerative Endodontic Case Treated by Modified Aspiration-irrigation Technique and Apexification

AIM

This report addresses the management of a large persistent discharging lesion in an 11-year-old boy. The report describes the use of aspiration-irrigation technique for the management of immature necrotic tooth with persistent discharge after a failed regenerative procedure.

BACKGROUND

Regenerative endodontics aim to provide an increase in root canal width, length, and in apical closure. Alternative procedures, such as apexification, should be attempted when regeneration fails. If the canal cannot be dried to persistent discharge, the aspiration-irrigation technique can be used. The technique relies on using aspiration along with irrigation to remove pus from the periapical area.

CASE DESCRIPTION

This is a case for an 11-year-old patient who had trauma to tooth #11, which resulted in the complicated crown fracture. He had an emergency management that included pulpectomy and intracanal medication at another clinic. Two years later, the patient was presented to our clinic. Upon examination, the diagnosis was previously initiated therapy with asymptomatic apical periodontitis in immature tooth #11. Regeneration was attempted first but failed. The mineral trioxide aggregate (MTA) plug was removed, and the canal had persistent pus discharge. The canal was filled with intracanal medication, and then 2 weeks later, the canal was filled with triple antibiotic paste (TAP). Next visit, and due to continuous discharge, tooth #11 was treated conservatively with an intracanal aspiration-irrigation technique. An IrriFlex needle attached to a high-volume suction was used to aspirate the cystic fluid. Mineral trioxide aggregate plug apexification was performed in a later visit and the tooth was restored.

CONCLUSION

During the 3-month and 16-month follow-up, there was resolution of the symptoms, a decrease in the periapical lesion size, and soft tissues appeared within normal limits.

CLINICAL SIGNIFICANCE

Regenerative procedures are a good option for immature necrotic teeth. These procedures may fail due to persistent pus discharge from the root canals. The aspiration-irrigation technique is a good treatment option in cases of consciously discharging canals. How to cite this article: Alsofi L, Almarzouki S. Failed Regenerative Endodontic Case Treated by Modified Aspiration-irrigation Technique and Apexification. J Contemp Dent Pract 2024;25(1):92-97.

Combined effect of electrical energy and graphene oxide on Enterococcus faecalis biofilms

This study aimed to investigate the effects of electrical energy and its synergistic activity with graphene oxide (GO) in Enterococcus faecalis (E. faecalis) biofilms. The viability of E. faecalis biofilms was analyzed by colony-forming units, crystal violet staining, and confocal laser scanning microscopy. The morphologies of the biofilms and the bacterial organelles were observed by scanning electron microscopy and transmission emission microscopy (TEM), respectively. Application of electrical energy combined with 0.2% sodium hypochlorite (NaOCl) on E. faecalis in biofilms significantly decreased the bacterial viability and biofilm biomass compared to the 0.2% NaOCl-only-treated group. Furthermore, additional application of GO showed similar antibacterial effects to 0.5% NaOCl. Notably, TEM observation revealed that the bacteria treated with electric energy and GO showed damaged cell membranes. The results suggest that combination of electrical energy and GO enhances antibacterial activity of NaOCl and has the potential to be applied to root canal irrigation protocols.

Effect of silver diamine fluoride activation on bond strength to root dentin

BACKGROUND

To investigate the effect of silver diamine fluoride (SDF) application and activation on the bond strength of gutta-percha to dentin and resin bonded post to dentin.

METHODS

Thirty-six human premolar teeth were used. The coronal part tooth was removed, and endodontic mechanical preparation was performed for all the teeth. The teeth were divided according to final rinse protocol (n = 9) as follows: Control group; no SDF application, SDF/NA; 38% SDF as a final rinse with no activation, SDF/MDA; 38% SDF as a final rinse with manual dynamic activation and SDF/US; 38% SDF as a final rinse with ultrasonic activation. Root canal obturation using lateral condensation technique followed by fiber post insertion after 48 h in the root canal after corresponding preparations. The roots were cut with a low-speed precision saw creating 2 mm thickness sections. A total of 4 sections were obtained from each tooth, 2 coronal specimens (with post) and 2 apical specimens (with Gutta percha). Each specimen was subjected to push-out bond strength test with a universal testing machine. Data were analyzed using two-way ANOVA.

RESULTS

The Push-out bond strength at the apical root section was significantly higher in SDF/MDA and SDF/US groups compared to control group. While for the coronal part, all SDF treated specimen showed reduced Push-out bond strength.

CONCLUSION

SDF application as final rinse may reduce the bonding performance between fiber post and dentine. Activation with manual and ultrasonic methods improved the bond strength at the apical root section.

Outcome of selective root canal retreatment-A retrospective study

AIM

Selective root canal retreatment is when the treatment is limited to root(s) with radiographic evidence of periapical pathosis. The goals of this retrospective study were as follows: (i) evaluate the clinical and radiographic (periapical radiographs [PR] or cone-beam computerized tomographs [CBCT]) outcome of selective root canal retreatment after ≥12 months follow-up; (ii) evaluate the periapical status of the unretreated roots; and (iii) assess tooth survival.

METHODOLOGY

A retrospective study (January 2018 to April 2021) was conducted to identify permanent multirooted teeth that underwent selective root canal retreatment. Clinical records, PR and CBCT were examined to ascertain variables of interest. Outcomes (per root and per tooth) were classified into 'favourable' or 'unfavourable' using well-established clinical and radiographic healing criteria. Treatment outcomes for the whole tooth and per root were compared as well as bivariate associations between the treatment outcome of the retreated roots and the treatment-related parameters (quality of root filling, sealer extrusion, iatrogenic mishaps and type of restoration) were analysed using Fisher's exact test (α = .05). Survival was recorded in months.

RESULTS

A total of 75 teeth (195 roots) in 75 subjects were available for outcome analysis. The favourable outcome per tooth was 86.7%. At follow-up, 92.6% of the retreated roots had a favourable outcome. From the unretreated roots, 3.5% showed radiographic signs of an emerging periapical lesion. No statistical difference was shown between the outcomes per root and per tooth between both groups. None of the treatment-related parameters had a direct influence on the outcome of the retreated roots. The survival rate at 12-48 months after retreatment was 91.5%.

CONCLUSIONS

Selective root canal retreatment is associated with a favourable outcome in a majority of cases. Unretreated roots rarely developed radiographic signs of a new periapical lesion at follow-up. Future high-quality clinical trials with larger sample sizes and longer follow-up periods are required to confirm these findings.

Effectiveness of various irrigant activation techniques on the penetration of sodium hypochlorite into lateral canals of mature permanent teeth: A systematic review and meta-analysis

Objective

This review aimed to systematically review the effectiveness of various irrigant activation techniques (IATs) on the penetration of sodium hypochlorite (NaOCl) into the lateral canals of mature permanent teeth.

Methods

Electronic databases including MEDLINE (via PubMed), Scopus, ProQuest, and Cochrane Library were searched to identify laboratory studies evaluating the penetration of NaOCl into lateral canals following the use of apical negative pressure irrigation (ANP), passive ultrasonic irrigation (PUI), sonic irrigation (SI), and/or manual dynamic activation (MDA) techniques. Meta-analysis was performed for individual IATs in comparison with CNI into the lateral canals of both straight and curved root canals. On the basis of the previous literature and parameters, the risk of bias of the selected studies was evaluated with the help of a customized tool.

Results

Of the 983 records screened, 12 studies were selected to include in the systematic review, and 10 studies were selected for the meta-analysis. The total quality assessment across the included studies indicated a high quality (83.3%). Overall, the meta-analysis demonstrated IATs had significant improvement in the penetration of NaOCl into the lateral canals of straight canals (34.3%) over CNI. The subgroup analysis of individual IATs demonstrated PUI (60.9%) to be superior in the penetration into lateral canals of straight canals.

Conclusions

IATs improved the irrigant penetration into lateral canals and therefore their use during routine endodontic practice is recommended. In straight canals, PUI is the most effective IAT followed by ANP, SI, and MDA techniques.

Penetration of Three Endodontic Sealers in Simulated Lateral Canals during the Lateral Condensation Technique: An In Vitro Study

Objective

This study aimed to compare the penetration depths of AH Plus, BioRoot RCS, and GuttaFlow 2 into simulated lateral canals when used with the cold gutta-percha lateral compaction technique.

Materials and Methods

Twelve resin training blocks (4 canals perch each resin block) were used. Each primary artificial canal had two lateral canals (apical and coronal). The main canals were instrumented with WaveOne Gold and irrigated with distilled water. The resin blocks were divided into three groups (N = 4 each/16 artificial canals), according to the type of root canal sealer; Group I: AH Plus, Group II: BioRoot RCS, and Group III: GuttaFlow 2. All canals were obturated with the cold lateral condensation technique. The linear extension of each endodontic sealer into the apical and coronal lateral canals was measured using a digital stereomicroscope and measuring software. Data were statistically analyzed using a one-way analysis of variance. The percentages of filling of the lateral canals were calculated and statistically compared using the Mann–Whitney test.

Results

The experimental sealers exhibited variable penetration depths into the lateral canals. All sealers showed significantly better penetration ability into the apical lateral canals than the coronal lateral canals (P < 0.05). AH Plus (3.184 ± 0.012 mm/99.5%) and GuttaFlow 2 (3.176 ± 0.017 mm/99.25%) were significantly better than BioRoot RCS (3.096 ± 0.026 mm/96.75%) in filling the apical lateral canals (P < 0.05). BioRoot RCS was the best sealer to fill coronal lateral canals (3.322 ± 0.085 mm/83.05%).

Conclusion

During the lateral condensation technique, the filling of the lateral canals is affected by the type of root canal sealer and the location of the lateral canals All the sealers tested have a good ability to fill the apical lateral, while BioRoot RCS was effective in filling both the coronal and apical lateral canals.

The Understanding of Vital Pulp Therapy in Permanent Teeth: A New Perspective

The indications of vital pulp therapy (VPT) are expanding, which cases are suitable for VPT, and how to improve the success rate of VPT is a problem that often bothers us. The main purpose of VPT is to eliminate pulpitis by promoting the formation of reparative dentin or calcium bridge, so that it can continue to perform various physiological functions, and finally achieve the purpose of preserving pulp vitality and long-term preservation of affected teeth. Pulp capping and pulpotomy are the most common methods for VPT. The research field of VPT has attracted the attention of many scholars, who have studied it from many aspects (such as indications, material selection, operation requirements, and long-term prognosis). This article reviews the recent advances in the techniques of VPT in permanent teeth.

In Vitro Evaluation of Five Newly Isolated Bacteriophages against E. faecalis Biofilm for Their Potential Use against Post-Treatment Apical Periodontitis

State-of-the-art treatment of root canal infection includes the use of mechanical debridement and chemical agents. This disinfection method is limited, and microorganisms can remain in the canal system. Enterococcus faecalis appears with a high prevalence in secondary and persistent root canal infections and can be linked to endodontic treatment failure due to its various resistance mechanisms. Here, we evaluated the activity of newly isolated bacteriophages against clinical isolates of E. faecalis (including one vancomycin- and gentamicin-resistant strain) as a single treatment or in combination with gentamicin and vancomycin. For the resistant strain, daptomycin and fosfomycin were tested. Sixteen E. faecalis strains were used to screen for the presence of bacteriophages in sewage. Five different bacteriophages were characterized in terms of virion morphology, host range and killing-kinetics against each E. faecalis host strain. To investigate the antibiofilm effect of antibiotic and phages, E. faecalis biofilm was grown on porous glass beads and treated with different antibiotic concentrations and with isolated bacteriophages alone or in staggered combinations. A strong biofilm reduction was observed when phages were combined with antibiotic, where combinations with gentamicin showed a better outcome compared to vancomycin. Regarding the resistant strain, daptomycin had a superior antibiofilm effect than fosfomycin.

Surgical management of a lateral lesion refractory to root canal retreatment caused by an extraradicular calculus. A case report

This article describes the management of a root canal-treated maxillary central incisor displaying a radiographic lateral radiolucency and a sinus tract that persisted irrespective of root canal retreatment following high standards. Endodontic microsurgery was indicated and curettage of the pathologic tissue revealed a calculus-like material attached to the outer root surface around the exit of a large lateral canal. A non-conventional approach was chosen: No root-end resection was conducted. Instead, the calculus was removed and the apical surface was scaled and smoothed, conserving the apical structure. Retrocavities were prepared in both lateral and apical foramens and filled with a bioceramic material. Follow-up examination showed optimal soft tissue healing. One-year follow-up of radiographs revealed healing of the lateral lesion. The lesion was diagnosed as a cyst, with an infected lumen. An exuberant calculus-like material attached to the external root surface was the most likely cause of the recalcitrant lateral periradicular lesion.

Incidence of fracture of ProDesign Logic system instruments: A cross-sectional retrospective study

The aim of the present study was to analyze the incidence of fracture of ProDesign Logic system instruments in endodontic treatments performed by a specialist, in addition to identifying the dental group, arch, and the root canal thirds in which the fractures occurred more frequently. Digital radiographs and medical records were initially analyzed and resulted in the selection of 561 teeth (1302 canals) treated between 2018 and 2020, using the ProDesign Logic system instruments. These data were reassessed to determine the occurrence of fractures and identify the dental group and root canal thirds in which they occurred. Then, the data were statistically analyzed using the Fisher's Exact Test (p < 0.05). The general fracture rates were 8.5 and 3.69%, considering the number of teeth and canals treated, respectively. Mandibular first molars were the teeth most associated with the occurrence of fractures (19.1%). When the arches were compared, there was no statistical difference regarding the number of fractures in the different root canal thirds (p = 0.307). However, they were more frequent in the apical third in both arches (p = 0.000). The incidence of fracture of ProDesign Logic system instruments was relatively high and occurred more frequently in the apical third of molars.

Influence of working length and anatomical complexities on the apical root canal filling: a nano-CT study

The present study aimed to compare the filled volume by gutta-percha and sealer in the apical region of the main canal and ramifications, after instrumentation at two different working lengths using nano-computed tomography (nano-CT). Twenty-two premolars with apical ramifications were selected after micro-computed tomography evaluation and were randomly divided into groups for further endodontic instrumentation at two different working lengths: G1 - Root canals shaped 1 mm short of the apical foramen (n=11), and G2 - Root canals shaped at the apical foramen (n=11). After completing root treatment, nano-CT images were acquired, and the filled volume by gutta-percha and sealer in the main canal apical 0-4 mm and 0-1 mm ranges, and apical ramifications were objectively measured by an operator specialized in both radiology and endodontics, blinded for both groups. The Mann-Whitney test was applied to compare both groups regarding the filling of the main canal apical ranges and apical ramifications with a significance level of 5% (α ≤ 0.05). It was observed that root canals shaped at the apical foramen had a larger volume of the main canal filled than root canals shaped 1 mm short of the apical foramen, at both apical ranges (0-4 and 0-1 mm) (p<0.05). Regarding the filling of the apical ramifications, there was no significant difference between groups (p>0.05). In conclusion, the root canals shaped at apical foramen exhibited increased filling volume of the main canal in the apical region. However, neither of both working lengths influenced filling of the apical ramifications.

Present status and future directions - irrigants and irrigation methods

Irrigation is considered the primary means of cleaning and disinfection of the root canal system. The purpose of this review was to set the framework for the obstacles that irrigation needs to overcome, to critically appraise currently used irrigants and irrigation methods, to highlight knowledge gaps and methodological limitations in the available studies and to provide directions for future developments. Organization of bacteria in biofilms located in anatomic intricacies of the root canal system and the difficulty to eliminate them is the main challenge for irrigants. Sodium hypochlorite remains the primary irrigant of choice, but it needs to be supplemented by a chelator. Delivery of the irrigants using a syringe and needle and activation by an ultrasonic file are the most popular irrigation methods. There is no evidence that any adjunct irrigation method, including ultrasonic activation, can improve the long‐term outcome of root canal treatment beyond what can be achieved by instrumentation and syringe irrigation. It is necessary to redefine the research priorities in this field and investigate in greater depth the penetration of the irrigants, their effect on the biofilm and the long‐term treatment outcome. New studies must also focus on clinically relevant comparisons, avoid methodological flaws and have sufficiently large sample sizes to reach reliable conclusions. Future multidisciplinary efforts combining the knowledge from basic sciences such as Chemistry, Microbiology and Fluid Dynamics may lead to more effective antimicrobials and improved activation methods to bring them closer to the residual biofilm in the root canal system.

Present status and future directions - microbiology of endodontic infections

Apical periodontitis has a microbial aetiology and is one of the most common inflammatory diseases that affect humans. Fungi, archaea and viruses have been found in association with apical periodontitis, but bacteria are by far the most prevalent and dominant microorganisms in endodontic infections. Bacterial infection of the root canal system only occurs when the pulp is necrotic or was removed for previous treatment. In some specific cases, including acute and chronic abscesses, the bacterial infection may reach the periradicular tissues. Intracanal bacteria are usually observed as sessile multispecies communities (biofilms) attached to the dentinal root canal walls. Infection in the main root canal lumen can spread to other areas of the root canal system. Although more than 500 bacterial species have been detected in endodontic infections, a selected group of 20 to 30 species are most frequently detected and may be considered as the core microbiome. There is a high interindividual variability in the endodontic microbiome in terms of species composition and relative abundance. Obligate anaerobic species are more abundant in the intraradicular bacterial communities of teeth with primary apical periodontitis, while both anaerobes and facultatives dominate the communities in post-treatment apical periodontitis. Bacterial interactions play an essential role in determining the overall virulence of the community, which has been regarded as the unit of pathogenicity of apical periodontitis. This article reviews the microbiologic aspects of endodontic infections and provides perspectives for future research and directions in the field.

Antimicrobial Activity of Phytic Acid: An Emerging Agent in Endodontics

Background

Phytic acid (IP6) is a promising and emerging agent, and because of its unique structure and distinctive properties, it lends itself to several applications in dentistry. Recently, IP6 was proposed as a potential chelating agent in endodontics. However, there is limited knowledge regarding its antimicrobial and antibiofilm effectiveness. The aims of this study, were therefore to evaluate the antimicrobial and antibiofilm activities of IP6 against a range of microbial species and compare these with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl). The contact time required for IP6 to exert its bactericidal effect on Enterococcus faecalis was also determined.

Methods

The inhibitory and biocidal activities of IP6, EDTA and NaOCl were assessed using a broth microdilution assay against 11 clinical and reference strains of bacteria and a reference strain of Candida albicans. The contact time required for various IP6 concentrations to eliminate planktonic cultures of E. faecalis was determined using a membrane filtration method according to BS-EN-1040:2005. IP6 bactericidal activity was also evaluated using fluorescent microscopy, and the antibiofilm activity of the test agents was also determined.

Results

IP6 was biocidal against all tested microorganisms. At concentrations of 0.5%, 1% and 2%, IP6 required 5 min to exert a bactericidal effect on E. faecalis, while 5% IP6 was bactericidal after 30 s. IP6 also eradicated biofilms of the tested microorganisms. In conclusion, IP6 had notable antimicrobial effects on planktonic and biofilm cultures and exhibited rapid bactericidal effects on E. faecalis. This research highlighted, for the first time the antimicrobial and antibiofilm properties of IP6, which could be exploited, not only in dental applications, but also other fields where novel strategies to counter antimicrobial resistance are required.

Effectiveness of 1-Visit and 2-Visit Endodontic Retreatment of Teeth with Persistent/Secondary Endodontic Infection: A Randomized Clinical Trial with 18 Months of Follow-up

INTRODUCTION

This randomized clinical trial aimed to compare the effectiveness of endodontic retreatment of teeth with posttreatment apical periodontitis (PTAP) performed in 1 visit versus 2 visits on the reduction of cultivable bacteria (colony-forming units [CFUs]), lipopolysaccharides (LPSs), lipoteichoic acid (LTA), and the periapical lesion volume (mm³) after 18 months of follow-up.

METHODS

Forty patients diagnosed with PTAP were selected and randomly divided into the following 2 groups: 1-visit retreatment and 2-visit retreatment with the placement of calcium hydroxide medication for 14 days. Cone-beam computed tomographic scans were performed at 2 stages: preoperatively and after 18 months of follow-up. Samples were collected before and after root canal procedures. A chromogenic limulus amebocyte lysate assay test was used to quantify endotoxins (EU/mL). LTA levels were measured using the enzyme-linked immunosorbent assay (pg/mL). Culture techniques were used to determine cultivable bacteria by counting the CFU (CFU/mL). The volume of the periapical lesions at the onset of the trial and at the 18-month posttreatment follow-up was obtained by the ITK-SNAP program (Cognitica, Philadelphia, PA).

RESULTS

All samples showed baseline values greater than those collected after the retreatment protocol for all investigated parameters. A higher bacterial load and lower LTA level were found in the 2-visit group after the retreatment protocol (P < .05), with no statistical differences between the groups regarding endotoxin levels and periapical lesion volume (mm³) at the 18-month follow-up analyzed by cone-beam computed tomographic imaging (P > .05).

CONCLUSIONS

Endodontic retreatment in 1 or 2 visits exhibited equally favorable periapical healing at 18 months, with no statistically significant differences between groups.

Effect of Irrigating Agitation after Root End Preparation on the Wall Cleaning and Bond Strength of Calcium Silicate Material in Retrograde Obturation

Objective This study aimed to evaluate the cleaning efficacy of irrigant activation with a new ultrasonic tip in root-end preparations and to determine its influence on the bond strength of calcium silicate-based material.

Materials and Methods Maxillary canines were prepared and filled, and their root ends resected. Root-end cavities were ultrasonically prepared and randomly distributed into four groups according to the final irrigation protocols: G1 (ultrasonic irrigation [UI] + saline solution [SS]), G2 (syringe irrigation [SI] + SS), G3 (UI + ethylenediaminetetraacetic acid [EDTA]), and G4 (SI + EDTA). Cleaning efficacy analysis employed 72 specimens ( n = 18) split longitudinally for imaging of the same areas by scanning electron microscopy (SEM). The percentage of dentinal tubules opened before and after irrigation was used as evaluation parameter. Push-out testing employed 40 specimens ( n = 10) sectioned apical region perpendicularly, which slice was placed on a testing machine for the bond strength measurement and failure mode was assessed by SEM. The data were statistically analyzed (α ≤ 0.05).

Results G3 (UI + EDTA) removed the smear layer more effectively, showed the best tubule opening ( p < 0.05), and presented the highest mean bond strength values ( p < 0.05). Failure modes were predominantly adhesive, except for the G3 (UI + EDTA) group, in which they were mainly mixed (80%).

Conclusion The results of this study suggest that EDTA 17% agitation promoted better cleaning and smear layer removal, improving the push-out bond strength of calcium silicate material in retrograde obturation.

d-Alanine metabolic pathway, a potential target for antibacterial drug designing in Enterococcus faecalis

Enterococcus faecalis (E. faecalis) is associated with persistent root canal infection because of its biofilm and various virulence factors. However, E. faecalis exhibits extensive drug resistance. d-Alanine (D-Ala) metabolism is essential for bacterial peptidoglycan biosynthesis. d-cycloserine (DCS), a second line drug used in the treatment of Mycobacterium tuberculosis infection, can inhibit two key enzymes in D-Ala metabolism: alanine racemase and d-alanine-d-alanine ligase. The aim of this study was to evaluate the effect of D-Ala metabolism on E. faecalis growth, cell wall integrity, biofilm formation and virulence gene expression by additional DCS with or without D-Ala. The results showed that DCS inhibited the planktonic growth and biofilm formation of E. faecalis in a dose-dependent manner. Both the minimum inhibitory concentration (MIC) and minimum biofilm inhibition concentration (MBIC) of DCS against E. faecalis were 200 μg/ml, whereas 50 μg/ml of DCS could inhibit planktonic growth and biofilm formation effectively. The addition of DCS also resulted in bacterial cell wall damage, biofilm surface roughness increase and biofilm adhesion force reduction. Moreover, the treatment of DCS downregulated the expression of asa1, esp, efaA, gelE, sprE, fsrB and ace genes. However, all of these inhibitory effects of DCS could be rescued by the addition of exogenous D-Ala. Meanwhile, DCS exhibited no toxicity to HGEs and HOKs. Therefore, D-Ala metabolic pathway in E. faecalis is a potential target for drug designing.

Patterns of Oral Microbiota in Patients with Apical Periodontitis

In this study, microbial diversity of the root canal microbiota related to different endodontic infections was investigated. In total, 45 patients with endo–perio lesions (8 patients), chronic periapical periodontitis (29 patients) and pulp necrosis (8 patients) were recruited. In 19 (42.2%) patients there was secondary infection of root canals. Microbial specimens were collected from root canals of non-vital teeth with or without changes in periapical area visible in X-ray. Then, oral microbiota were detected and identified using the culture method and real-time PCR amplification primers and hydrolysis-probe detection with the 16S rRNA gene as the target. Overall, 1434 species/genes from 41 different genera of 90 various microbial species were retrieved. Of the major reported phyla, Firmicutes (62.9%), Actinobacteria (14.0%), Bacteroidetes (12.1%), Proteobacteria (9.1%) and Fusobacteria (4.2%) were detected. Of the bacterial species, 54.6% were strict anaerobes. Corynebacterium matruchotii (p = 0.039) was present significantly more frequently in chronic periapical periodontitis. Moreover, the higher values of Decayed, Missing and Filled Permanent Teeth index were positively correlated with relative abundance of Actinomyces spp. (p = 0.042), Lactobacillus spp. (p = 0.006), Propionibacterium spp. (p = 0.024) and Rothia spp. (p = 0.002). The multivariate analyses revealed differences in total root canal samples, where components that affected grouping of root samples into four main categories were identified. Anaerobic Gram-negative bacteria predominated in root canals of teeth with pulp necrosis and periapical lesions. Facultative anaerobic Gram-positive bacteria predominated in canals with secondary infections. All detected members of mixed population groups that might serve as keystone species contributed to the entire community in its clinical relevance.

Recovery of Oral In Vitro Biofilms after Exposure to Peptides and Chlorhexidine

INTRODUCTION

This study aimed to examine the dynamic recovery of established multispecies biofilms of oral bacteria after an initial treatment by D-enantiomeric peptide DJK-5, L-enantiomeric peptide 1018, or chlorhexidine digluconate (CHX).

METHODS

Oral biofilms from 2 donors were grown on collagen-coated hydroxyapatite disks for 3 weeks and exposed to DJK-5, 1018, and 2% CHX for 3 minutes. Immediately after treatment and 1, 2, 3, 5, 7, 8, and 12 weeks after exposure, the biofilm volume and the volume ratio of dead and live bacteria in biofilms were assessed by confocal laser scanning microscopy using a live/dead viability stain. Results were examined by 1-way analysis of variance and post hoc multiple comparisons to determine significance at a P < .05 significance level.

RESULTS

DJK-5 killed almost 80% of biofilms in 3 minutes and maintained this high level of dead bacteria for 1 week. The proportion of viable bacteria in DJK-5-treated biofilms returned to the pretreatment level after 12 weeks. The biovolume of DJK-5-treated biofilm remained significantly lower than that of biofilms after CHX and no treatment throughout the 12-week follow-up period (P < .001). The proportion of dead bacteria was higher in biofilms exposed to DJK-5 than with 1018 or CHX for 8 weeks after the exposure (P < .001). The proportion of dead bacteria almost doubled to 46%-52% during the first 7 days after the 3-minute exposure to CHX and peptide 1018. The timeline of biofilm recovery was slow but similar after exposure to CHX and the 2 peptides.

CONCLUSIONS

ecovery time after exposure to DJK-5 was longer than that after exposure to 1018 and CHX. Peptide 1018 showed a delayed, continued antibacterial effect similar to that of 2% CHX against the biofilm microbes.

An in vitro endodontic model to quantify the accessory canal filling potential of the vertical and lateral condensation techniques

The purpose of this study was to determine the accessory canal filling potential of vertical and lateral condensation techniques in simulated root canals. A total of 130 prepared transparent, straight-simulated root canals with nine accessory canals (0.02 mm), prepared at different levels from the apical, were obturated with vertical (n = 100) and 30 lateral condensation (n = 30) techniques. 50.33% of the accessory canals obturated with vertical condensation were completely filled with gutta-percha; 37.78% completely filled with gutta-percha and sealer. 61.11% of the accessory canals were completely filled with sealer only using the lateral condensation technique. The vertical condensation technique filled the accessory canals more frequently than the lateral condensation techniques. The lateral condensation technique was not capable of delivering gutta-percha to any of the accessory canals. The apical third showed the lowest accessory canal filling frequency with both techniques.

Chemical and mechanical influence of root canal irrigation on biofilm removal from lateral morphological features of simulated root canals, dentine discs and dentinal tubules

Aim

To investigate the anti‐biofilm efficacy of irrigation using a simulated root canal model, the chemical effect of irrigants against biofilms grown on dentine discs and their impact on biofilm viscoelasticity, the efficacy of the irrigants in decontaminating infected dentinal tubules and the capacity of bacteria to regrow.

Methodology

Biofilm removal, viscoelastic analysis of remaining biofilms and bacterial viability were evaluated using a simulated root canal model with lateral morphological features, dentine discs and a dentinal tubule model, respectively. Experiments were conducted using a two‐phase irrigation protocol. Phase 1: a modified salt solution (RISA) and sodium hypochlorite (NaOCl) were used at a low flow rate to evaluate the chemical action of the irrigants. Ultrasonic activation (US) of a chemically inert solution (buffer) was used to evaluate the mechanical efficacy of irrigation. Phase 2: a final irrigation with buffer at a high flow rate was performed for all groups. Optical coherence tomography (OCT), low load compression testing (LLCT) and confocal scanning laser microscopy analysis were used in the different models. One‐way analysis of variance (anova) was performed for the OCT and LLCT analysis, whilst Kruskal–Wallis and Wilcoxon ranked tests for the dentinal tubule model.

Results

US and high flow rate removed significantly more biofilm from the artificial lateral canal. For biofilm removal from the artificial isthmus, no significant differences were found between the groups. Within‐group analysis revealed significant differences between the steps of the experiment, with the exception of NaOCl. For the dentine discs, no significant differences regarding biofilm removal and viscoelasticity were detected. In the dentinal tubule model, NaOCl exhibited the greatest anti‐biofilm efficacy.

Conclusions

The mechanical effect of irrigation is important for biofilm removal. An extra high flow irrigation rate resulted in greater biofilm removal than US in the artificial isthmus. The mechanical effect of US seemed to be more effective when the surface contact biofilm–irrigant was small. After the irrigation procedures, the remaining biofilm could survive after a 5‐day period. RISA and NaOCl seemed to alter post‐treatment remaining biofilms.

Biofilm removal from a simulated isthmus and lateral canal during syringe irrigation at various flow rates: a combined experimental and Computational Fluid Dynamics approach

Aim

(i) To quantify biofilm removal from a simulated isthmus and a lateral canal in an artificial root canal system during syringe irrigation with NaOCl at different concentrations and delivered at various flow rates (ii) to examine whether biofilm removal is further improved by a final high‐flow‐rate rinse with an inert irrigant following irrigation with NaOCl. (iii) to simulate the irrigant flow in these areas using a computer model (iv) to examine whether the irrigant velocity calculated by the computer model is correlated to biofilm removal.

Methodology

Ninety‐six artificial root canals with either a simulated isthmus or lateral canal were used. A dual‐species in vitro biofilm was formed in these areas using a Constant Depth Film Fermenter. NaOCl at various concentrations (2, 5 and 10%) or adhesion buffer (control) was delivered for 30 s by a syringe and an open‐ended needle at 0.033, 0.083, or 0.166 mL s⁻¹ or passively deposited in the main root canal (phase 1). All specimens were subsequently rinsed for 30 s with adhesion buffer at 0.166 mL s⁻¹ (phase 2). The biofilm was scanned by Optical Coherence Tomography to determine the percentage of the remaining biofilm. Results were analysed by two 3‐way mixed‐design ANOVAs (α = 0.05). A Computational Fluid Dynamics model was used to simulate the irrigant flow inside the artificial root canal system.

Results

The flow rate during phase 1 and additional irrigation during phase 2 had a significant effect on the percentage of the remaining biofilm in the isthmus (P = 0.004 and P < 0.001). Additional irrigation during phase 2 also affected the remaining biofilm in the lateral canal significantly (P ≤ 0.007) but only when preceded by irrigation at medium or high flow rate during phase 1. The effect of NaOCl concentration was not significant (P > 0.05). Irrigant velocity in the isthmus and lateral canal increased with increasing flow rate and it was substantially correlated to biofilm removal from those areas.

Conclusions

The irrigant flow rate affected biofilm removal in vitro more than NaOCl concentration. Irrigant velocity predicted by the computer model corresponded with the pattern of biofilm removal from the simulated isthmus and lateral canal.

The benefit of culture-independent methods to detect bacteria and fungi in re-infected root filled teeth: a pilot study

AIM

To identify dominant microorganisms in root filled teeth with apical periodontitis by Pan-PCRs in comparison with a culture-dependent approach, focusing on fungal species profiling.

METHODOLOGY

The root filling material (gutta-percha) removed from 42 teeth with periapical radiolucencies undergoing root canal retreatments was analysed by molecular genetics techniques. Real-Time Pan-PCRs were conducted for the diagnosis of predominant bacteria (targeting 16S rDNA) and fungi (targeting ITS1-2 region). Identification of microorganisms was performed by Sanger sequencing of the PCR products and BLAST analysis. Additionally, subgingival plaque samples were collected and cultured to review the composition of the microbial flora. The McNemar test and the repeated measures anova were used for statistical analyses (significance level was set at P < 0.05).

RESULTS

Overall, 42/42 plaque samples had bacterial growth, whereas 32/42 gutta-percha samples had bacterial growth with a dominance of Streptococcus spp. (12/42) and Enterococcus faecalis (9/42). The mean number of bacterial taxa per gutta-percha sample was 1.6 cultivatable taxa, significantly lower than in the plaque sample that had six taxa/sample (P < 0.001). Fungus-specific cultures were negative for gutta-percha samples, and only one plaque sample had growth of a fungus. In total, 36/42 plaque samples were positive in bacterial Pan-PCRs. In bacterial Pan-PCRs of 31/42 gutta-percha samples, dominant microorganisms were identified including Streptococcus spp. (5/42) and E. faecalis (4/42). Moreover, in 7/42 gutta-percha samples, DNA of bacteria which are difficult-to-cultivate in microbiology routine culture (Acinetobacter,Pyramidobacter,Bacteroidetes,Synergistes,Atopobium and Pseudoramibacter) was found. DNA of Candida spp. was detected in 5/42 root canals by fungal Pan-PCR (1/5) and genus-specific Candida-PCR (5/5).

CONCLUSIONS

Pan-PCR assays remain appropriate as a broad-range approach for the detection of a dominant pathogen in gutta-percha samples which have less diverse microbial composition. The molecular genetic Pan-PCR approach has the advantage of detecting microorganisms that are as-yet-uncultivable or difficult-to-cultivate and should be therefore complement conventional microbiological diagnostics.

Antibacterial efficacy and discolouration potential of antibiotic pastes with macrogol for regenerative endodontic therapy

This study aimed to evaluate the antibacterial efficacy and discolouration potential of antibiotic pastes containing macrogol. Seventy single-rooted teeth were contaminated with a culture of Enterococcus faecalis for 30 days. Double (DAP) and triple antibiotic pastes (TAP) containing propylene glycol or macrogol as vehicles were applied. After 15 days, bacterial viability was compared. Change in teeth coronal colour was measured by a spectrophotometer. Statistical analysis was performed using anova and Tukey's test (P < 0.05). TAP containing clindamycin and propylene glycol was the only medicament that led to the presence of contamination, while the same combination of antibiotics containing macrogol did not result in bacterial growth (P < 0.05). Only the pastes containing minocycline in formulation resulted in coronal discolouration (P < 0.05). Both DAPs evaluated and the TAP containing clindamycin and macrogol showed to be the preferable options for regenerative endodontic therapy, as they were effective against E. faecalis biofilm and did not promote tooth discolouration.

Characteristics of the Irrigant Flow in a Simulated Lateral Canal Under Two Typical Laser-Activated Irrigation Regimens

BACKGROUND AND OBJECTIVES

Photon-induced photoacoustic streaming (PIPS) and shockwave-enhanced emission photoacoustic streaming (SWEEPS) are two promising laser-activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (μPIV) measurement and will be compared with that of ultrasonic-activated irrigation (UAI).

STUDY DESIGN/MATERIALS AND METHODS

A μPIV system with 7 μm fluorescent tracer particles was adopted to measure two-dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non-cutting insert) operating at 40% unit power, was also measured for a direct comparison.

RESULTS

It was found that both SWEEPS and PIPS can activate a so-called "breath mode" during the irrigation. Namely, the induced irrigant flush presented a back-and-forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 μm and lower than LAI (P < 0.05).

CONCLUSION

Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back-and-forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Cone-beam Computed Tomographic and Micro-computed Tomographic Evaluations of the Root Apexes of Teeth with Posttreatment Apical Periodontitis

INTRODUCTION

This study evaluated the association of different variables that may influence the outcome of root canal treatment through cone-beam computed tomographic (CBCT) and micro-computed tomography (micro-CT) assessments of root apexes obtained by endodontic microsurgery of teeth with posttreatment apical periodontitis (AP), the agreement between CBCT and micro-CT findings, and the association of these variables with symptoms or lesion size.

METHODS

Clinical and CBCT records and root apexes obtained by endodontic microsurgery from 11 cases of symptomatic AP and 22 cases of asymptomatic AP were available. Apical root specimens were further scanned using micro-CT imaging. CBCT parameters included periapical radiolucency size, apical extent/density of root canal filling, and occurrence of procedural errors. Micro-CT images evaluated the same parameters plus the presence of filling material in lateral canals and ramifications, the volume of the filled/nonfilled apical root canal, and the percentage of the nonfilled canal space. The agreement between CBCT/micro-CT observations was evaluated.

RESULTS

Mandibular teeth, a lesion size <5 mm, a nonfilled volume <0.04 mm³, and the decreased percentage of the nonfilled canal volume were significantly associated with symptomatic AP. Maxillary teeth and inadequate apical filling density were significantly associated with larger lesions. Agreement between CBCT/micro-CT scores varied from fair (procedural errors) to satisfactory (extent/density of filling).

CONCLUSIONS

Tooth location, lesion size, the nonfilled apical canal volume, and the percentage of the nonfilled apical canal volume were associated with symptomatic AP. In addition, lesion size was significantly associated with tooth location and apical root canal filling density. CBCT imaging may not provide a reliable evaluation of procedural errors associated with posttreatment disease.

Antimicrobial Activity of Nano-Magnesium Hydroxide Against Oral Bacteria and Application in Root Canal Sealer

BACKGROUND The goal of the present work was to assess the antibacterial activity of nano-magnesium hydroxide (NMH) against Streptococcus mutans (S. mutans) and to explore the antimicrobial function of AH Plus™ sealer incorporating NMH. MATERIAL AND METHODS The antimicrobial behavior of NMH against S. mutans was evaluated with bactericidal tests. A modified direct contact test was used to assess the antimicrobial activity of unset AH Plus containing NMH after 5 minutes, 20 minutes, and 60 minutes of contact with bacteria. The antimicrobial effects and the amount of surface-adhering bacteria of the solidified materials were explored by SEM and confocal laser scanning microscopy, respectively. RESULTS NMH powder presented excellent antimicrobial activity against S. mutans. Mg²⁺ and OH⁻ were not the main factors resulting in bacterial death. Approximately 93.1% and 98% of the S. mutans were killed in the AH Plus+7% NMH group after incubation for 5 minutes and 20 minutes, respectively. AH Plus with 5% or 7% NMH were more potent against S. mutans compared with AH Plus alone (P<0.05). Moreover, the antibacterial function of AH Plus was lost after setting. NMH enabled the solidified AH Plus to still have antibacterial properties on the seventh day. CONCLUSIONS NMH can be used to modify AH Plus sealer to eradicate residual bacteria and prevent reinfection.

Multilayering as a solution to medical device failure

There are three main problems associated with medical device implants: biofilm, wear and corrosion, and bio rejection. A potential solution to these problems is multilayering. Polyelectrolyte multilayered films composed of polyallylamine hydrochloride and poly(4-vinylphenol) have been demonstrated to inhibit Staphylococcus epidermidis growth. Another study examined the wear behavior of polyelectrolyte multilayer coated orthopedic surfaces composed of poly(acrylic acid) and poly(allylamine hydrochloride) and found coated systems resulted in 33 % less wear than uncoated systems. Additionally, a heparin/collagen anti-CD34 antibody ((HEP/COL)₅-CD34) multilayer system provided accelerated adhesion of endothelial cells with a significant number of endothelial cells attaching in the first 5 min. This allowed for re-endothelialization to occur possibly reducing cardiac stent bio rejection. This review explores various ways multilayering has been utilized to prolong medical device use and decrease the number of complications associated with them.

Microbiological aspects of traumatic injuries

After traumatic injuries to teeth, microorganisms may invade the compromised pulp tissue and initiate pulp infection and periapical inflammation. In addition to bone resorption that typically accompanies pulp necrosis, root resorption frequently occurs. Root resorption has several variants that may occur shortly after the trauma or at a later stage. The pathological changes seen after traumatic injuries to teeth are invariably linked to the presence of microbial irritants. The presence of bacterial biofilms in the dental pulp space can be treated with regenerative or therapeutic endodontic procedures. However, necrosis of periodontal ligament is usually terminal for the tooth involved. In this review, the sources of bacteria after traumatic injuries are discussed. The types and role of microorganisms involved in the pathogenesis of endodontic pathosis after traumatic injuries are presented, and contemporary approaches for the management of these conditions are reviewed. Contemporary antimicrobial strategies are discussed. The rationale for the use of systemic and topical antimicrobials is presented. Finally, novel approaches to the use of antimicrobial therapies, particularly in regenerative procedures, are reviewed.

The synthesis of nano silver-graphene oxide system and its efficacy against endodontic biofilms using a novel tooth model

OBJECTIVE

The deleterious caustic effects of sodium hypochlorite (NaOCl) as a root canal irrigant makes it imperative that alternative methods are developed for root canal disinfection. The purpose of this study was to examine the antimicrobial efficacy of silver nanoparticles (AgNPs) synthesized on an aqueous graphene oxide (GO) matrix (Ag-GO), with different irrigant delivery methods to enhance the disinfection regimen, using a novel ex vivo infected tooth model.

METHODS

AgNPs were prepared by reducing AgNO₃ with 0.01M NaBH₄ in presence of GO. Elemental analysis was performed with scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and scanning transmission electron microscopy (STEM) was used for size and morphology analysis of GO and Ag-GO. Nutrient stressed, multi-species biofilms were grown in prepared root canals of single-rooted teeth. The irrigants used were sterile saline, 1% and 2.5% NaOCl, 2% chlorhexidine gluconate (CHX), 17% EDTA and an aqueous suspension of 0.25% Ag-GO. The antimicrobial efficacy of the irrigants were performed with paper point sampling and measurement of microbial counts. The biofilm disruption in dentine tubule surfaces was analysed with confocal laser scanning microscopy (CLSM). The acquisition of total biovolume (μm³/μm²) and biofilm viability was performed using software BioImage_L. Two-way analysis of variance (ANOVA) with post hoc Tukey tests was used for data analysis with level of statistical significance set at P<0.05.

RESULTS

SEM/EDS analysis confirmed impregnation of Ag within the GO matrix. TEM images showed polygonal GO sheets and spherical AgNPs of diameter 20-50nm, forming a network on the surface of GO sheets. The use of ultrasonic activation enhanced the efficacy of Ag-GO compared to 1% NaOCl, 2% CHX, 17% EDTA and sterile saline (P<0.05). The microbial killing efficacy of 2.5% NaOCl was superior compared to the experimental groups. The maximum biofilm disruption, in dentine tubule surfaces, was achieved by 2.5% NaOCl, however Ag-GO caused a significant reduction of total biovolumes compared to the rest of the experimental groups (P<0.05%).

SIGNIFICANCE

The successful documentation of the microbial killing and biofilm disruption capacity of Ag-GO is a promising step forward to explore its unique properties in clinical applications and biomaterials in dentistry.

Antimicrobial and antibiofilm efficacy of a copper/calcium hydroxide-based endodontic paste against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans

Endodontic biofilm is a microbial community, enclosed in a polymeric matrix of polysaccharide origin where are found pathogens, like bacteria and opportunistic fungi responsible for various endodontic pathologies. As clinical importance is the fact, that biofilm is extremely resistant to common intracanal irrigants, antimicrobial drugs and host immune responses. The aim of this study was to evaluate the in vitro efficacy of a Cu/CaOH₂-based endodontic paste, against bacteria and fungi, such as Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. We found that such compound significantly reduced microbial replication time and cell growth. Moreover, biofilm formation and persistence were also affected; treated biofilms showed both a reduced number of cells and levels of released pyoverdine. This study provides the first evidence on effectiveness of this endodontic compound against microbial biofilms. Given its wide range of action, its use in prevention and treatment of the main oral biofilm-associated infections will be discussed.

Biofilm model systems for root canal disinfection: a literature review

The aim of this review was to present an overview of laboratory root canal biofilm model systems described in the endodontic literature and to critically appraise the various factors that constitute these models. The electronic databases MEDLINE, Web of Science and EMBASE were searched up to and including December 2016 to identify laboratory studies using endodontic biofilm models. The following search terms were used in various combinations: biofilm, root canal, in vitro, endodontic, bacteria, root canal infection model, colony-forming unit. Only English papers from journals with an impact factor were selected. The records were screened by two reviewers, and full-text articles were assessed according to pre-defined criteria. The following data were extracted from the included studies: the microbial composition of the biofilm, the substrate, growth conditions, validation and quantification. Seventy-seven articles met the inclusion criteria. In the majority (86%) of the studies, a monospecies biofilm was cultured. In two studies, a dual-species biofilm was grown; others cultivated a multispecies biofilm, containing at least three species. Enterococcus faecalis was the most frequently used test species (in 79% of all studies, 92% of the monospecies studies). Four studies used an inoculum derived directly from the oral cavity. Human dentine was the most frequently used substratum (88% of the studies). Incubation times differed considerably, ranging from one to seventy days. The most common quantification method (in 87% of the studies) was bacterial culturing, followed by microscopy techniques. The variation in laboratory root canal biofilm model systems is notable. Because of substantial variation in experimental parameters, it is difficult to compare results between studies. This demonstrates the need for a more standardized approach and a validated endodontic biofilm model.

Unprepared root canal surface areas: causes, clinical implications, and therapeutic strategies

Chemomechanical preparation is intended to clean, disinfect, and shape the root canal. This step is of utmost importance during treatment of infected teeth with apical periodontitis, because treatment outcome depends on how effectively the clinician eliminates bacteria, their products, and necrotic tissue that would serve as substrate for bacterial regrowth. Nonetheless, curvatures and complex internal anatomical variations of the root canal system can pose a high degree of difficulty in reaching these goals. In infected teeth, bacteria may persist not only in difficult-to-reach areas such as isthmuses, ramifications, dentinal tubules, and recesses from C-shaped or oval/flattened canals, but also in areas of the main canal wall that remain untouched by instruments. If bacteria withstand chemomechanical procedures, there is an augmented risk for post-treatment apical periodontitis. This article discloses the reasons why some areas remain unprepared by instruments and discusses strategies to circumvent this issue and enhance infection control during endodontic treatment/retreatment of teeth with apical periodontitis.

Comparison of final disinfection protocols using antimicrobial photodynamic therapy and different irrigants after single-file reciprocating instrumentation against intracanal bacterial biofilm - An in vitro study

BACKGROUND

The aim of the study was to compare the efficacy of antimicrobial photodynamic therapy (aPDT) with irrigation protocols that include sodium hypochlorite (NaOCl), ethylenediaminotetraacetic acid (EDTA) or QMiX (combined irrigant: EDTA, chlorhexidine, detergent) solution after single-file reciprocating root canal instrumentation.

METHODS

The study sample included 68 extracted mandibular human single canal teeth. The canals were inoculated with bacterial suspension made of wild strain of Enterococcus faecalis. After 17 days of incubation, the samples were assigned to experimental groups according to the final disinfection protocol and a control group. The root canals in all groups were, firstly, instrumented with Wave One Gold reciprocating system. Then the canals were disinfected as follows: Group 1. 2.5% NaOCl and EDTA followed by the application of the aPDT; Group 2. 2.5% NaOCl, EDTA and 2.5% NaOCl; Group 3. 2.5% NaOCl and QMIX solution; Group 4. 2.5% NaOCl and EDTA. In the control group, the canals were irrigated with saline solution. Microbiological samples were collected at baseline, after single-file instrumentation and after the final disinfection protocols. The samples were plated onto Mitis Salivarius agar plates for incubation. The colony forming units (CFUs) were counted, and the final number was determined based on the dilution factor.

RESULTS

Reciprocating single-file instrumentation reduced CFUs significantly in all groups (p<0.05). No significant difference between Group 1 and Group 2 was observed (p=0.178). Irrigation with the QMiX was more efficient than the aPDT (p=0.02).

CONCLUSIONS

The aPDT used after irrigation with NaOCl and EDTA demonstrated similar antimicrobial efficacy as conventional irrigation with NaOCl.

Evaluation of physical-mechanical properties, antibacterial effect, and cytotoxicity of temporary restorative materials

The objective of this study was to compare selective physical-mechanical properties, antibacterial effects and cytotoxicity of seven temporary restorative materials (TRM): five resin-based materials [Bioplic (B), Fill Magic Tempo (FM), Fermit inlay (F), Luxatemp LC (L) and Revotek LC (R)], and zinc oxide-eugenol cement (IRM) and glass ionomer cement (GIC) as the controls. Material and methods The physical-mechanical properties were evaluated by determining microleakage (ML), ultimate tensile strength (UTS) and Shore D hardness (SDH). In addition, the polymerization rate (Pr-1), depth of cure (DC), water sorption and solubility (WS/SL) were evaluated. The antimicrobial effects of the materials were assessed by biofilm accumulation of Streptococcus mutans (BT) and the direct contact test (DCT) by exposure to Enterococcus faecalis for 1 and 24 h, and cytotoxicity by MTT assay. The data were analyzed by ANOVA or Kruskall-Wallis tests, and a complementary post-hoc method (p<0.05). Results Group B, followed by FM and GIC had significantly lower percentages of microleakage in comparison with the other groups; Groups FM and L showed the highest WS, while Groups R and FM showed the significantly lowest SL values (p<0.05). Group R showed the statistically highest UTS mean and the lowest DC mean among all groups. Group F showed the lowest S. mutans biofilm accumulation (p=0.023). Only the Group L showed continued effect against E. faecalis after 1 h and 24 h in DCT. The L showed statistically lower viability cell when compared to the other groups. Conclusions These findings suggest the antibacterial effect of the temporary materials Fill Magic and Bioplic against S. mutans, while Luxatemp showed in vitro inhibition of S. mutans biofilm accumulation and E. faecalis growth. Regarding the cell viability test, Luxatemp was the most cytotoxic and Fill Magic was shown to be the least cytotoxic.

Antibacterial efficacy of an endodontic sonic-powered irrigation system: An in vitro study

OBJECTIVE

To evaluate the efficacy of EDDY, a new sonic-powered irrigation system, in reducing intracanal bacteria load.

METHODS

Thirty-eight instrumented, autoclaved single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days. Two teeth were used as negative control without bacterial contamination. For the bacteria-inoculated teeth, 6 were used as positive control without irrigation. The remaining 30 teeth were randomly divided into 2 groups (N = 15), using 3% NaOCl as irrigant: (A) 30-gauge syringe needle irrigation (SNI), (B) EDDY (VDW, Munich, Germany). Twelve teeth per group and 4 teeth in the positive control were evaluated for bacterial reduction using MTT assay. The remaining teeth were split for BacLight LIVE/DEAD staining to examine the percentages of live/dead bacteria present in the dentinal tubules from different canal locations (coronal, mid-root and apical portions of the canal space) using confocal laser scanning microscopy (CLSM).

RESULTS

MTT assay indicated that both SNI and EDDY significantly reduced overall intracanal bacterial load compared with the positive control, with no significant difference between the two techniques. CLSM indicated that EDDY had better intratubular bacterial killing efficacy than SNI in the coronal and mid-root portions of the canal space only but not in the apical portion. In all canal locations (coronal, mid-root apical), both systems failed to eliminate bacteria that proliferated deep within the dentinal tubules.

CONCLUSION

With the use of 3% NaOCl, sonic-powered irrigant activation with EDDY tips did not provide additional advantage over SNI in killing Enterococcus faecalis from deep intraradicular dentin.

CLINICAL SIGNIFICANCE

Both the sonic-powered root canal irrigant activation system and syringe needle irrigation can reduce intracanal bacteria load but are incapable of completely killing all bacteria that resided deep within the dentinal tubules of root canals infected with Enterococcus faecalis.

Effects of three γ-alkylidene-γ-lactams on the formation of multispecies biofilms

This study evaluated the inhibitory effects of lactams on Streptococcus mutans, Enterococcus faecalis, and Candida glabrata multispecies biofilm formation. γ-Alkylidene-γ-lactams 1, 2, and 3 [solubilized in 3.5% dimethyl sulfoxide (DMSO)] were tested. Glass coverslips were conditioned with either the lactams or 3.5% DMSO (control) for 1 h, inoculated with microbial cultures, and incubated for 48 h. To assess the effect of the lactams on biofilm formation, the following parameters were determined: the biofilm biomass (by both crystal violet staining and protein determination); the amount of insoluble polysaccharides of the extracellular matrix; and the number of viable and total cells [by both colony-forming unit counting and quantitative real-time PCR (qPCR)]. Data were analysed using one-way anova and post-hoc Tukey tests. Lactams 1, 2, and 3 promoted a statistically significant reduction in the amount of biofilm biomass, but only lactam 3 resulted in a statistically significant reduction in the number of attached viable E. faecalis. Both total protein content and the amount of extracellular polysaccharides decreased significantly. The effects of γ-alkylidene-γ-lactams 1, 2, and 3 on the inhibition of multispecies biofilm formation were evident by their ability to reduce the amount of protein and extracellular polysaccharides.

Cleaning lateral morphological features of the root canal: the role of streaming and cavitation

AIM

To investigate the effects of ultrasonic activation file type, lateral canal location and irrigant on the removal of a biofilm-mimicking hydrogel from a fabricated lateral canal. Additionally, the amount of cavitation and streaming was quantified for these parameters.

METHODOLOGY

An intracanal sonochemical dosimetry method was used to quantify the cavitation generated by an IrriSafe 25 mm length, size 25 file inside a root canal model filled with filtered degassed/saturated water or three different concentrations of NaOCl. Removal of a hydrogel, demonstrated previously to be an appropriate biofilm mimic, was recorded to measure the lateral canal cleaning rate from two different instruments (IrriSafe 25 mm length, size 25 and K 21 mm length, size 15) activated with a P5 Suprasson (Satelec) at power P8.5 in degassed/saturated water or NaOCl. Removal rates were compared for significant differences using nonparametric Kruskal-Wallis and/or Mann-Whitney U-tests. Streaming was measured using high-speed particle imaging velocimetry at 250 kfps, analysing both the oscillatory and steady flow inside the lateral canals.

RESULTS

There was no significant difference in amount of cavitation between tap water and oversaturated water (P = 0.538), although more cavitation was observed than in degassed water. The highest cavitation signal was generated with NaOCl solutions (1.0%, 4.5%, 9.0%) (P < 0.007) and increased with concentration (P < 0.014). The IrriSafe file outperformed significantly the K-file in removing hydrogel (P < 0.05). Up to 64% of the total hydrogel volume was removed after 20 s. The IrriSafe file typically outperformed the K-file in generating streaming. The oscillatory velocities were higher inside the lateral canal 3 mm compared to 6 mm from WL and were higher for NaOCl than for saturated water, which in turn was higher than for degassed water.

CONCLUSIONS

Measurements of cavitation and acoustic streaming have provided insight into their contribution to cleaning. Significant differences in cleaning, cavitation and streaming were found depending on the file type and size, lateral canal location and irrigant used. In general, the IrriSafe file outperformed the K-file, and NaOCl performed better than the other irrigants tested. The cavitation and streaming measurements revealed that both contributed to hydrogel removal and both play a significant role in root canal cleaning.