In vitro assessment of antimicrobial potential of low molecular weight chitosan and its ability to mechanically reinforce and control endogenous proteolytic activity of dentine.

AIMS: Chitosan-based biomaterials exhibit several properties of biological interest for endodontic treatment. Herein, a low molecular weight chitosan (CH) solution was tested for its antimicrobial activity against Enterococcus faecalis (E. faecalis) and effects on dentine structure. METHODOLOGY: The root canal of 27 extracted uniradicular teeth were biomechanically prepared, inoculated with a suspension of E. faecalis and randomly assigned to be irrigated with either 5.25% sodium hypochlorite (NaClO), 0.2% CH or sterile ultrapure water (W). Bacteriologic samples were collected from root canals and quantified for of E. faecalis colony-forming units (CFUs). The effectiveness of CH over E. faecalis biofilms was further measured using the MBEC Assay®. Additionally, dentine beams and dentine powder were obtained, respectively, from crowns and roots of 20 extracted third molars. Dentine samples were treated or not with 17% EDTA and immersed in either CH or W for 1 min. The effects of CH on dentine structure were evaluated by assessment of the modulus of elasticity, endogenous proteolytic activity and biochemical modifications. RESULTS: The number of E. faecalis CFUs was significantly lower for samples irrigated with CH and NaClO. No significant differences were found between CH and NaClO treatments. Higher modulus of elasticity and lower proteolytic activity were reported for dentine CH-treated specimens. Chemical interaction between CH and dentine was observed for samples treated or not with EDTA. CONCLUSIONS: Present findings suggest that CH could be used as an irrigant during root canal treatment with the triple benefit of reducing bacterial activity, mechanically reinforcing dentine and inhibiting dentine proteolytic activity.

Assessment of depth of penetration and antibiofilm properties of Boswellia sacra compared with calcium hydroxide intracanal medicament (in vitro study).

Successful endodontic treatment requires advanced materials to eliminate biofilm This study aims to assess the penetration depth and the effectiveness of Boswellia sacra as a novel intracanal medicament compared with calcium hydroxide against Enterococcus faecalis biofilm. 60 single-rooted teeth were decoronated, prepared and sterilised. Fifty teeth were contaminated with a culture of E. faecalis (ATCC 19433) for 21 days. Two teeth were used to confirm the biofilm using scanning electron microscope. For colony-forming unit (CFU), 40 samples were divided into one control group (calcium hydroxide) and the other experimental group (B. sacra). Each group was divided into two subgroups to be tested at 3 and 7 days. The minimum inhibitory concentration (MIC) of B. sacra was determined, and the B. sacra's ethanolic extract medicament was prepared. Eight discs divided into groups similar to CFU were used to evaluate live/dead bacteria using confocal laser scanning microscopy (CLSM). Ten teeth were selected for penetration depth using CLSM. The intracanal medicaments were mixed with 0.1% rhodamine B. were inserted into the root canals 0.2 slices were dissected and viewed under CLSM. The MIC of B. sacra was 1.25 mg/ml. The CFU evaluation proved that B. sacra are more effective than calcium hydroxide in the 3 days groups. However, it was statistically insignificant compared with calcium hydroxide after 7 days. The depth of penetration of B. sacra exceeds that of calcium hydroxide. B. sacra is an effective intracanal medicament.

Chlorhexidine and Sodium Hypochlorite Provide Similar Antimicrobial Effect in Root Canal Disinfection.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Ruksakiet K, Hanák L, Farkas N, Hegyi P, Sadaeng W, Czumbel LM, Sang-Ngoen T, Garami A, Mikó A, Varga G, Lohinai Z. Antimicrobial Efficacy of Chlorhexidine and Sodium Hypochlorite in Root Canal Disinfection: A Systematic Review and Meta-analysis of Randomized Controlled Trials. J Endod. 2020 Aug;46(8):1032-1041.e7. doi: 10.1016/j.joen.2020.05.002. Epub 2020 May 12. PMID: 32413440. SOURCE OF FUNDING: The Hungarian Human Resources Development Operational Program, the Higher Education Excellence Program of the Hungarian Ministry of Human Capacities to the Therapy Research Module of Semmelweis University, National Research, Development and Innovation Office, Hungarian Scientific Research Fund and the Economic Development and Innovation Operative Programme Grant. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis.

Multiple assessment methodologies in determining the antibiofilm actions of sodium hypochlorite mixed with clodronate or etidronate in endodontic irrigation.

This study aimed to use multiple methodologies, including a novel usage of scanning electron microscopy (SEM), to evaluate the antimicrobial actions of sodium hypochlorite (NaOCl) admixed with clodronate or etidronate in root canal irrigation. The study also examined the usefulness of colony counting as a biofilm assessment methodology. Seven day Enterococcus faecalis biofilms were grown on hydroxyapatite discs. The discs were disinfected with 0.26 M clodronate-5% NaOCl, 0.26 M etidronate-5% NaOCl, 5% NaOCl, or treated with phosphate buffered saline (PBS). Assessments were performed using colony counting, SEM and the XTT reduction assay. The XTT assessment used the same groups but with 2.5% NaOCl. For colony counting, bacteria were removed from the discs by vortex mixing, followed by plating. The discs were subsequently fixed for SEM imagining and evaluators scored the SEM micrographs for remaining bacteria. Antibiofilm actions were assessed with the Kruskal-Wallis and Dunn's multiple comparison tests. SEM micrographs and the XTT assay revealed no differences between the NaOCl controls and the clodronate or etidronate mixtures with NaOCl (P > 0.05). It was concluded that the chelator mixtures with NaOCl had antibiofilm actions comparable to NaOCl. Furthermore, vortex mixing incompletely removed biofilm from HA discs in the PBS controls and hence colony counting using E. faecalis biofilms on hydroxyapatite discs could not be used for intergroup comparisons involving PBS. Additionally, colony counting could not be used for comparisons between the NaOCl treatment groups because the removal of bacteria from the substrate by vortex mixing was affected by the irrigant type.

Assessment of antibacterial activity of 2.5% NaOCl, chitosan nano-particles against Enterococcus faecalis contaminating root canals with and without diode laser irradiation: an in vitro study.

Objective: This study was done to evaluate the antibacterial effect of chitosan nano-particles (CNPs) root canal irrigant as a new alternative to Sodium hypochlorite (NaOCl) for disinfection of root canals inoculated with Enterococcus faecalis, with and without laser activation.Methodology: Sixty single rooted human premolars were decoronated, prepared and had their apical foramina sealed. E. faecalis were incubated in the root canals for 15 days. The teeth were then randomly divided into two experimental groups (n = 30) according to the disinfection protocol used. In Group I: disinfection was performed using the irrigant solutions only (Saline, 2.5% NaOCl, CNPs). Whereas in Group II, disinfection was done using the same irrigants followed by Diode laser at (980-nm) at 2 W output for 5 × 5 s. Intra-canal bacterial samples were taken before and after canal disinfection to determine the CFU count.Results: In group I, 2.5% NaOCl was as effective as CNP in eradication and significantly more effective than Saline (p = 0.008) in eradication of E. faecalis. In Group II, either 2.5% NaOCl or CNP in combination with diode laser irradiation showed a similarly high effect in bacterial eradication.Conclusions: Within the parameters used in this study, a combination therapy consisting of irrigation followed by diode laser irradiation should be utilized as an effective treatment modality for eliminating E. faecalis from root canal systems.

Why Biphasic? Assessment of the Effect on Cell Proliferation and Expression.

INTRODUCTION: Tricalcium silicate (TCS)-based materials are used in endodontics because they are hydraulic and interact with blood, tissue fluids, and phosphate-based root canal irrigants, resulting in biomineralization. Newer-generation materials are biphasic; calcium phosphate is added to the TCS; thus, the material has 2 cementitious phases. The effect of this addition is not known; thus, the aim of this study was to characterize biphasic cements and assess cellular proliferation and expression. METHODS: TCS cement mixed with calcium phosphate monobasic or hydroxyapatite in 1:1 proportion was prepared. The powders and the mixed cements soaked in Hank's balanced salt solution for 28 days were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy, and X-ray diffraction analysis. Ion leaching was investigated using inductively coupled plasma mass spectroscopy. Cellular interaction with material leachate was investigated by exposing human primary osteoblasts to the leachate from the cements. Cell growth and proliferation were determined using methyltetrazolium assay and SEM. RESULTS: The addition of a calcium phosphate phase to tricalcium silicate changed the material hydration with a reduction in pH and calcium ion release in the leachate when calcium phosphate monobasic was added. No crystalline calcium hydroxide was formed for both biphasic materials. The biphasic cements exhibited a reduction in cell growth and proliferation. SEM of the materials showed heavy carbonation of the material surface caused by processing for microscopy. CONCLUSIONS: The addition of a second cementitious phase results in modification of the hydration characteristics of TCS cement with deterioration of material and biocompatibility properties.

Evaluation of methods for removal of filling material in endodontic retreatment and assessment of antimicrobial action of solutions used in final irrigation / Avaliação de métodos de desobturação do canal radicular no retratamento endodôntico e avaliação da ação antimicrobiana de soluções utilizadas na irrigação final

When endodontic treatment fails, an alternative could be root canal retreatment. During this procedure, all filling material should be removed to allow a new root canal preparation and new obturation of the root canal system. Bacteria are the main cause of endodontic treatment failure, and persistent infection may be related to microorganism ability to penetrate into dentinal tubules. Therefore, this requires the use of irrigating solutions with antimicrobial action and low toxicity. The aim of this study was to evaluate the performance of instruments made of different alloys in root canal re-instrumentation during endodontic retreatment of lateral incisors with apical curvature, using computed microtomography and assessment of these samples by scanning electron microscopy after irrigant activation. Furthermore, the antimicrobial action of a root canal irrigant containing silver nanoparticles, 2% chlorhexidine and 2.5% sodium hypochlorite was evaluated against Enterococcus faecalis biofilm and dentin infected with this microorganism. Thirty extracted maxillary lateral incisors with apical curvature were selected. The teeth were instrumented, filled and divided into three different groups according to the protocol for removal of filling material: Group 1: re-instrumentation with Reciproc R25 instruments, Mtwo 40 and ProDesign Logic 50.01; Group 2: re-instrumentation with ProDesign R, ProDesign Logic 40 and ProDesign Logic 50.01; Group 3: re-instrumentation with Gates-Glidden drills and manual instruments K-file and Hedstroem files. For filling material removal analysis, the samples were scanned in a microtomograph device SkyScan 1174, for comparison of images taken before and after removing the root canal filling, and in each sample the volume was calculated at four levels (apical 1, apical 2, middle and cervical). These samples were split and analyzed by scanning electron microscopy to visualize filling material residues before and after irrigant activation with an ultrasonic device and with the EasyClean system used in continuous rotary motion. Statistical analyses were performed using Kruskal-Wallis, Friedman, Wilcoxon and Dunn tests. Furthermore, the minimum inhibitory concentration of an irrigating solution containing silver nanoparticles was determined against strains of Enterococcus faecalis, by using the microdilution method. Additionally, the antimicrobial activity of silver nanoparticle solution, 2% chlorhexidine and 2.5% sodium hypochlorite was tested against Enterococcus faecalis biofilm in vitro. For biofilm formation, bovine dentin blocks were placed in 24-well culture plates and Enterococcus faecalis biofilm was developed for 21 days. The dentin blocks were divided into 9 experimental groups of 5 blocks each, according to the irrigating solution used and the time in contact with the irrigant (5, 15 and 30 minutes). The samples were stained with Live/Dead reagent for analysis by confocal laser scanning microscopy (CLSM). Finally, the antimicrobial action of these solutions was tested after dentinal tubules were contaminated with Enterococcus faecalis. Dentin tubes were made from bovine incisors, taken to a centrifuge and infected with Enterococcus faecalis. The dentin tubes were treated with silver nanoparticle solution, 2% chlorhexidine and 2.5% sodium hypochlorite, and analyzed by CLSM to assess the antimicrobial activity of these solutions against bacteria in the dentinal tubules. The results showed that residues of filling material were found after root canal reinstrumentation in all groups. No significant difference was observed in removal of filling material between the reciprocating instruments Reciproc and ProDesign R and between rotary instruments Mtwo 40 and ProDesign Logic 40. The ProDesign Logic 50/.01 instrument significantly improved the removal of filling material compared with the use of Reciproc and ProDesign R instruments. The apical levels presented greater amount of remnant filling material compared with middle and cervical levels. After canal reinstrumentation, the passive ultrasonic irrigation and irrigant agitation with EasyClean significantly improved the removal of residual filling material in all root canal thirds. There was no significant difference between the performance of ultrasonics and EasyClean regarding the removal of residual filling material, as well no significant difference was observed in the removal of these residues when comparing apical, middle and cervical thirds. Regarding the action of the irrigating solutions against Enterococcus faecalis, the minimum inhibitory concentration of silver nanoparticle solution capable of eliminating this microorganism in broth and agar plates was 94 ppm. After the irrigation of Enterococcus faecalis biofilm, the silver nanoparticle solution was significantly less effective in killing bacteria compared with chlorhexidine when used for time of contact of 5 minutes. The sodium hypochlorite solution presented antimicrobial activity significantly higher compared with the silver nanoparticle solution and chlorhexidine. This solution also presented higher ability to dissolve biofilm in all times tested, whereas the silver nanoparticle solution presented higher ability to dissolve biofilm compared with chlorhexidine in times of 5 and 15 minutes. In infected intratubular dentin with Enterococcus faecalis, the sodium hypochlorite solution presented significant higher effectiveness than the silver nanoparticle solutions and chlorhexidine, especially in middle third and deep areas of the root canal. When comparing the antimicrobial activity of these solutions in biofilm and infected intratubular dentin, it was shown that when the silver nanoparticle solution was used for shorter periods of time, it was more effective in intratubular dentin compared with biofilm. On the other hand, with longer time of 30 minutes, the number of viable bacteria was higher in intratubular dentin than in biofilm, which was also observed when using the sodium hypochlorite solution in this time of action. It was concluded that to increase the rate of success in endodontic retreatment, the combination of the use of reciprocating and rotary instruments in the removal of filling material, the agitation of irrigants and the use of antimicrobial agents could be used in an attempt to eliminate bacteria that resisted to endodontic treatment. (AU)

Em casos de insucesso do tratamento endodôntico, uma alternativa seria o retratamento do canal radicular. Durante este procedimento deve haver remoção de todo o material obturador para que seja realizada novo preparo biomecânico e nova obturação do sistema de canais radiculares. Bactérias são o principal fator etiológico em casos de fracasso da terapia endodôntica, e esta infecção persistente pode estar relacionada à capacidade dos microganismos em penetrar nos túbulos dentinários. Por este motivo é necessário o uso de soluções na irrigação do canal radicular com ação antimicrobiana e com boa tolerância tecidual. O objetivo deste trabalho foi avaliar o desempenho dos instrumentos de diferentes ligas metálicas na desobturação do canal radicular durante o retratamento endodôntico de incisivos laterais superiores com curvatura apical, por meio da microtomografia computadorizada e análise destas amostras no microscópio eletrônico de varredura após a ativação de irrigantes. Posteriormente foi avaliada a capacidade antimicrobiana de um irrigante do canal radicular contendo nanopartículas de prata, clorexidina a 2% e hipoclorito de sódio a 2,5% frente ao biofilme de Enterococcus faecalis e à dentina contaminada com este mesmo microrganismo. Foram selecionados trinta incisivos laterais superiores humanos extraídos que apresentavam curvatura apical. Os dentes foram instrumentados, obturados e divididos em três diferentes grupos de acordo com o protocolo de remoção do material obturador do canal radicular: no Grupo 1: a desobturação foi realizada com os instrumentos Reciproc R25, Mtwo 40 e ProDesign Logic 50.01; no Grupo 2: foram utilizados os instrumentos ProDesign R, ProDesign Logic 40 e ProDesign Logic 50.01; e no Grupo 3: a desobturação foi realizada com brocas de Gates-Glidden e instrumentos manuais tipo K e Hedstroem. Para a análise da remoção do material obturador, as amostras foram escaneadas em micrótomogafo SkyScan 1174 para que fossem comparadas as imagens antes e após a desobturação do canal radicular, e em cada amostra este volume foi calculado nos quatro níveis (apical 1, 2, médio e cervical). Estas amostras posteriormente foram clivadas e analisadas no microscópio eletrônico de varredura, para a visualização de resíduos de material obturador antes e após a ativação de irrigantes com o ultrassom e com o sistema EasyClean utilizado em rotação contínua. Para a análise estatística dos resultados foram utilizados os testes de Kruskal-Wallis, Friedman, Wilcoxon e Dunn. Posteriormente, foi determinada a concentração inibitória mínima de uma solução irrigadora do canal contendo nanopartículas de prata frente a cepas de Enterococcus faecalis, através do método de diluição em caldo. Em seguida, foi testada a atividade antimicrobiana das soluções de nanopartículas de prata, da clorexidina a 2% e do hipoclorito de sódio a 2,5% sobre o biofilme de Enterococcus faecalis in vitro. Para isso, foram utilizados blocos de dentina bovina colocados em placas de 24 poços e biofilme de Enterococcus faecalis foi formado durante 21 dias. Os blocos de dentina foram divididos em 9 grupos experimentais com 5 blocos cada um, em função dos irrigantes avaliados e do tempo de exposição à solução irrigadora (5, 10 e 15 minutos). As amostras foram coradas com corante Live/Dead para posterior análise no microscópio confocal de varredura a laser (MCVL). Por fim, foi testada a atividade antimicrobiana destas soluções irrigadoras após a contaminação de túbulos dentinários com Enterococcus faecalis. Foram confeccionados tubos de dentina a partir de incisivos bovinos que foram levados à centrífuga e contaminados com Enterococcus faecalis. Os tubos de dentina receberam tratamento com a solução de nanopartículas de prata, com clorexidina a 2% e com hipoclorito de sódio a 2,5%, e foram analisados no MCVL para avaliar a atividade antimicrobiana das soluções sobre bactérias presentes nos túbulos dentinários. Os resultados demonstraram que resíduos de material obturador foram encontrados após a desobturação do canal em todos os grupos. Não houve diferença significante na remoção de material obturador entre os instrumentos reciprocantes Reciproc e ProDesign R e entre os instrumentos rotatórios Mtwo 40 e ProDesign Logic 40. O instrumento ProDesign Logic 50/.01 melhorou significantemente a remoção de material obturador comparado com o uso dos instrumentos Reciproc e ProDesign R. Os níveis apicais apresentaram uma maior quantidade de material obturador remanescente comparados com os níveis médio e cervical. Após a desobturação do canal radicular, a irrigação ultrassônica passiva e agitação dos irrigantes com o EasyClean melhoraram significantemente a remoção de resíduos de material obturador em todos os terços do canal radicular. Não houve diferença significante no desempenho do ultrassom e do EasyClean em relação à remoção de resíduos de material obturador, assim como não foi observada diferença significante na remoção destes resíduos quando comparados terços apical, médio e cervical. No que diz respeito à ação das soluções irrigadoras sobre o Enterococcus faecalis, a concentração inibitória mínima da solução de nanopartículas de prata capaz de eliminar este microrganimo em meio de cultura e ágar foi de 94 ppm. Após a irrigação no biofilme de Enterococcus faecalis, a solução de nanopartículas de prata foi significantemente menos efetiva em matar bactérias comparada com a clorexidina quando utilizadas pelo tempo de 5 minutos. A solução de hipoclorito de sódio apresentou atividade antimicrobiana significantemente maior comparada com as soluções de nanopartículas de prata e clorexidina. Essa solução ainda apresentou maior capacidade de dissolução do biofilme em todos os tempos testados, enquanto que a solução de nanopartículas de prata apresentou maior capacidade de dissolver o biofilme comparada à clorexidina nos tempos de 5 e 15 minutos. Na dentina intratubular infectada com Enterococcus faecalis, a solução de hipoclorito de sódio apresentou efetividade significantemente maior que as soluções de nanopartículas de prata e clorexidina, principalmente no terço médio e na região profunda do canal radicular. Quando comparada a atividade antimicrobiana destas soluções no biofilme e na dentina intratubular infectada, verificou-se que quando a solução de nanopartículas de prata foi utilizada por um tempo mais curto, foi mais efetiva na dentina intratubular comparada com o biofilme. De maneira contrária, com tempo maior de 30 minutos, o número e bactérias viáveis foi maior na dentina intratubular do que no biofilme, o que ocorreu também com a solução de hipoclorito de sódio neste tempo de ação. Conclui-se que para se aumentar a chance de sucesso em tratamentos retratamentos endodônticos, a combinação do uso de instrumentos reciprocantes e rotatórios na desobturação do canal, agitação de irrigantes e uso de agentes com capacidade antimicrobiana podem ser utilizados na tentativa de se eliminar bactérias resistente ao tratamento endodôntico. (AU)

Quantitative assessment of root canal roughness with calcium-based hypochlorite irrigants by 3D CLSM.

Chemical solutions play important roles in endodontic treatment and promote ultrastructural changes in dentin surface. The aim of this study was to quantify root canal roughness at different concentrations of calcium hypochlorite (Ca(OCl)2) and sodium hypochlorite (NaOCl) by confocal laser scanning microscopy (CLSM). Fifty-two human mandibular premolars were sectioned and randomly organized into thirteen groups (n=8): saline (control); 1%, 2.5% and 5% NaOCl; 1%, 2.5% and 5% Ca(OCl)2; the hypochlorite groups were further divided into with or without EDTA. The chlorine concentrations of the different solutions were measured by iodine titration (%). The superficial roughness (Sa) was quantified by CLSM. Ca(OCl)2 presented substantial decrease in chlorine concentration that differed from the package indication, but without compromising the dentin ultrastructure changes. There were no significant differences in dentin roughness between Ca(OCl)2 or NaOCl at all studied concentrations. The combination with EDTA provided similar roughness values among the solutions (p>0.05). The 5% Ca(OCl)2 and NaOCl solutions significantly increased dentin roughness and did not differ from the EDTA association (p>0.05). Ca(OCl)2 promoted similar dentin roughness as the NaOCl at the same concentrations and combined with EDTA. It may be concluded that Ca(OCl)2 modified the root canal dentin roughness similarly to NaOCl, at the same concentrations and EDTA combinations used in this study. Ca(OCl)2 and NaOCl, both at 5%, significantly altered dentin roughness, overcoming EDTA association, thus Ca(OCl)2 concentrations ranging from 1% to 2.5% may be suitable solutions for root canal irrigation protocols.

In vitro assessment of tooth color alteration by two different types of endodontic irrigants.

AIM: The purpose of this study was to assess in vitro the tooth color alterations associated with two commonly used endodontic irrigants, the chlorhexidine gluconate (CHX) and the sodium hypochlorite (NaOCl) up to 15 days post-treatment. Additionally, the possible influence of endodontic access preparation on tooth color was investigated. MATERIALS AND METHODS: Thirty intact human anterior teeth were used. Black adhesive tape with a 4 mm diameter window was used to standardize the enamel surface intended for color analysis. After the access cavity, preparation and the initial root canal negotiation with stainless steel hand files, the root canal shaping was completed with rotary nickel-titanium files. The teeth were divided into three groups (n = 10). Conventional syringe irrigation was performed with one irrigant for each group. The enamel surfaces were colorimetrically evaluated before access cavity, after cavity preparation and at 1, 3, 7 and 15 days post-treatment. The CIE color parameters (L*, a*, b*) were recorded and averaged for each material and the corresponding color differences (ΔE) were calculated and statistically analyzed. RESULTS: The most significant factor in tooth color alteration, during the endodontic treatment, was the access preparation. CHX and NaOCl caused tooth color changes comparable with the saline. CHX and NaOCl did not increase the tooth color changes relative to the values induced by the access preparation. CONCLUSION: The two endodontic irrigants were not able to induce tooth color alteration to a greater extent than the access preparation. CLINICAL SIGNIFICANCE: Chlorhexidine and NaOCl cannot be considered as discoloring endodontic materials. The most contributing factor in tooth color alteration during endodontic treatment in the anterior teeth is access preparation.

Physicochemical and pulp tissue dissolution properties of some household bleach brands compared with a dental sodium hypochlorite solution.

INTRODUCTION: Many clinicians use household bleach to irrigate root canals. Sodium hypochlorite solutions are also available from dental suppliers. We compared physicochemical features of these products and investigated their impact on pulp tissue dissolution. METHODS: Six different brands of household bleach were bought from drugstores. These were compared with Chlor-XTRA and technical NaOCl solutions of controlled concentration and alkalinity regarding their chlorine content (wt% NaOCl), pH, alkaline capacity, osmolarity, surface tension (Wilhelmy plate method), and price. Bovine pulp tissue (n = 10 specimens per group) dissolution at 37°C by test and control solutions adjusted to 1.0% NaOCl was assessed. Reduction in tissue weight was compared between groups by one-way analysis of variance, followed by Bonferroni correction (P < .05). RESULTS: The pH of undiluted solutions ranged between 11.1 and 12.7. Batches of the same product differed in NaOCl content. No product contained more than an equivalent of 0.1 mol/L NaOH. One household bleach brand (Safeway Bleach Summit Fresh) was slightly alkalized; the other solutions under investigation were not. Osmolarity was similar between products. The surface tension of Chlor-XTRA and Safeway Bleach Summit Fresh was about half that of the other solutions. Tissue dissolution was statistically similar (P > .05) among all solutions. Price was about 100-fold higher per liter of Chlor-XTRA compared with household bleach. CONCLUSIONS: Other than its price, the Chlor-XTRA solution had no unique features. In contrast to an earlier report, reduced surface tension did not result in greater soft tissue dissolution by NaOCl.

Microbial culture and checkerboard DNA-DNA hybridization assessment of bacteria in root canals of primary teeth pre- and post-endodontic therapy with a calcium hydroxide/chlorhexidine paste.

AIM: To investigate the root canal microbiota of primary teeth with apical periodontitis and the in vivo antimicrobial effects of a calcium hydroxide/chlorhexidine paste used as root canal dressing. DESIGN: Baseline samples were collected from 30 root canals of primary teeth with apical periodontitis. Then, the root canals were filled with a calcium hydroxide paste containing 1% chlorhexidine for 14 days and the second bacteriologic samples were taken prior to root canal filling. Samples were submitted to microbiologic culture procedure to detect root canal bacteria and processed for checkerboard DNA-DNA hybridization. RESULTS: Baseline microbial culture revealed high prevalence and cfu number of anaerobic, black-pigmented bacteroides, Streptococcus, and aerobic microorganisms. Following root canal dressing, the overall number of cfu was dramatically diminished compared to initial contamination (P <0.05), although prevalence did not change (P > 0.05). Of 35 probes used for checkerboard DNA-DNA hybridization, 31 (88.57%) were present at baseline, and following root canal dressing, the number of positive probes reduced to 13 (37.14%). Similarly, the number of bacterial cells diminished folowing application of calcium hydroxide/chlorhexidine root canal dressing (P = 0.006). CONCLUSION: Apical periodontitis is caused by a polymicrobial infection, and a calcium hydroxide/chlorhexidine paste is effective in reducing the number of bacteria inside root canals when applied as a root canal dressing.

Bacterial localization and viability assessment in human ex vivo dentinal tubules by fluorescence confocal laser scanning microscopy.

AIM: To develop a convenient method for the localization and quantification of live and dead bacteria in human ex vivo mineralized dentinal tubules. METHODOLOGY: The roots from human single-rooted teeth (n = 12) were infected with Enterococcus faecalis V583 and either treated with calcium hydroxide paste or left untreated; six control roots were uninoculated and untreated. Following further incubation, roots were stained with fluorescent DNA-binding reagents, washed thoroughly, sectioned and examined by confocal laser scanning microscopy. Computer-assisted determinations of fluorescence (bacterial viability) were compared statistically. RESULTS: Bacteria were distributed in the tubules throughout the length of the roots but tubule penetration distance was slightly reduced in the apical sections. There was no significant difference in bacterial tubule penetration between roots from different teeth and small standard deviations indicated reproducibility appropriate for experimental application. Following treatment with calcium hydroxide paste, live and dead bacteria were readily distinguishable by contrasting green and red fluorescence. Bacterial viability determinations amongst roots treated in the same way were not significantly different, and the small standard deviation is commensurate with experimental application. CONCLUSIONS: Fluorescent viability staining is a convenient, accurate and reproducible method for localizing and quantifying live and dead bacteria in human ex vivo mineralized dentinal tubules.

Strong effect on dentin after the use of high concentrations of citric acid: an assessment with co-site optical microscopy and ESEM.

OBJECTIVES: To perform a longitudinal analysis of the effect of four substances (citric acid at 1%, 5% and 10% concentrations and 17% EDTA) on dentin. METHODS: Sixteen human molars had their crowns removed exposing cervical root dentin. A grinding procedure was used to produce a standardized smear layer and to create a smooth surface for analysis. Environmental scanning electron microscopy (ESEM) was used for qualitative observations while co-site optical microscopy (CSOM) and image analysis (IA) provided a quantitative comparison of the effect of the substances for several experimental times from 15 to 300s. The methods allowed the observation of the same areas after each experimental time. The open tubule area fraction was measured for several CSOM image fields, at each experimental time, for the four substances. Thus, it was possible to follow the phenomenon and quantitatively analyze the effect of the substances. Kolmogorov-Smirnov, Kruskal-Wallis H and Wilcoxon signed-ranks (with Bonferroni correction) tests were used to analyze the data. The level of significance was set at p<0.05. RESULTS: The CA solutions showed the greatest chelating effect, which was proportional to concentration (EDTA: 9.4-32.8% (15-300s); 1% CA: 21.1-32.2% (15-300s); 5% CA: 32.4-43.1% (15-300s); 10% CA: 35.1-39.5% (15-30s). Erosive effects were observed on inter and peritubular dentin for 5% CA and 10% CA after 60s. SIGNIFICANCE: ESEM allowed a detailed qualitative comparison of the effect of the four substances. CSOM and IA provided a quantitative comparison method with good statistical significance. Future studies should focus on the consequences of dentin erosion caused by citric acid.

Dentin demineralization when subjected to BioPure MTAD: a longitudinal and quantitative assessment.

In the present study, the demineralizing ability of BioPure MTAD (Dentsply/Tulsa, Tulsa, OK), 17% EDTA, and 5% citric acid on radicular dentin was quantitatively and longitudinally analyzed. 3 mm thick disks were obtained at the root cervical third from 9 maxillary human molars, and a standardized smear layer was produced. Cosite images of the dentin surface were obtained after several cumulative demineralization times. Sixteen images were obtained in each dentin sample for each experimental time, at 1000x magnification. An image processing and analysis sequence measured sets of images, providing data of area fraction for thousands of tubules over time. Thus, it was possible to follow the demineralization phenomenon and quantitatively analyze the effect of the various substances. The nonparametric Kruskal-Wallis H-test was used to analyze the data. Based on the present results, it can be concluded that the demineralization kinetics promoted by both 5% CA and BioPure MTAD was significantly faster than by 17% EDTA.

A comparative study of smear layer removal using different salts of EDTA.

Three solutions of EDTA--a 15% concentration of the alkaline salt, a 15% concentration of the acid salt, and a 25% concentration of the alkaline salt--were evaluated for smear layer removal in root canal systems. All solutions were adjusted to pH 7.1 using either NaOH or HCl. When the EDTA solutions were alternately used for root canal irrigation with 5.25% NaOCl, they completely removed the smear layer in the middle and coronal thirds of canal preparations, but were less effective in the apical third. None of the EDTA solutions by themselves were effective at completely removing the smear layer at any level. The alkaline tetrasodium salt, pH adjusted with HCl, is more cost effective and performed equally as well as the more commonly used disodium salt.