Qualitative comparison of sonic or laser energisation of 4% sodium hypochlorite on an Enterococcus faecalis biofilm grown in vitro

The effectiveness of sonic activation, laser activation and syringe irrigation of 4% sodium hypochlorite in removing an Enterococcus faecalis biofilm was compared. Biofilms were grown in extracted human single rooted teeth using a flow cell apparatus. After 4 weeks' growth, teeth were subjected to each treatment using 4% sodium hypochlorite and radicular dentinal surfaces of the root canals were analysed by scanning electron microscopy. Results showed that sonic activation and syringe irrigation with sodium hypochlorite showed reduced numbers of bacterial cells on the radicular dentine but were not effective in eliminating E. faecalis in the dentinal tubules. Laser activation of sodium hypochlorite resulted in clean dentine walls and undetectable levels of bacteria within dentinal tubules. Qualitatively, sonic or laser activation of 4% NaOCl resulted in greater bacterial reduction compared with syringe irrigation, with laser activation producing the greatest overall reduction.     

Efficacy of chlorhexidine in disinfecting dentinal tubules in vitro

Abstract Solutions of 0.2% and 2% chlorhexidine, 0.2% and 2% sodium hypochlorite (NaOCl) and normal saline were tested for their efficacy in disinfecting dentinal tubules following root canal irrigation in vitro. Freshly extracted bovine incisor roots were prepared as cylindrical shapes, 4 mm high and 5 mm wide with a lumen 2.1 mm wide. After mechanical removal of the cementum and elimination of the smear layer on the dentine surface with EDTA and NaOCl, the root sections were autoclaved and the dentinal tubules infected with E. faecalis (NCTC 775) by incubating in yeast extract glucose broth for 1 week. The root canals were irrigated with 20 ml of an irrigant solution using a syringe. Each irrigant was used in six specimens. Dentine was removed from the canal wall by sterile burs of increasing diameter to give samples 100, 100–300 and 300–500 μm deep. The dentine samples were then cultured to determine the presence and quantity of remaining micro-organisms. The results indicated that chlorhexidine and NaOCl were equally effective antibacterial agents at similar concentrations against the test microorganism. They significantly reduced the bacterial counts in the first 100 μm of dentinal tubules, however up to 50% of dentine samples remained infected following use of both agents.     

Dentinal tubule invasion and adherence by Enterococcus faecalis

Aim To investigate dentinal tubule invasion and the predilection of Enterococcus faecalis for dentinal tubule walls. Methodology The invasion of dentinal tubules in extracted human teeth by E. faecalis was measured ex vivo after 8 weeks of incubation. The canal walls of 16 root sections were either intact or instrumented with or without smear layer present. Extent and maximum depth of tubule invasion were assessed histologically and compared between groups. In the adherence study, 44 vertically split root samples were prepared to expose longitudinally aligned dentinal tubules and fractured orthodentine (OD). Surfaces were exposed to E. faecalis (erythromycin resistant strain, JH2‐2 carrying plasmid pGh9:ISS1) and incubated aerobically for 2 h. Samples were processed for analysis using scanning electron microscopy. Bacterial adhesion to tubule walls versus fractured OD was calculated as number of cells per 100 μm². Results The strain of E. faecalis used in this study showed moderate to heavy tubule invasion after 8 weeks. In the adhesion studies, significantly more bacteria adhered to fractured OD than to dentinal tubule walls (anova , P < 0.001). With respect to the tubule wall, adherence was greater in inner versus outer dentine (P = 0.02) and greater when bacterial adhesion was tested in chemically defined medium than in phosphate‐buffered saline (anova , P < 0.001). Conclusions Although E. faecalis readily invaded tubules, it did not adhere preferentially to tubule walls. Initial colonization of dentinal tubules by E. faecalis may depend primarily on other factors.     

Microbial analysis of endodontic infections in teeth with post-treatment apical periodontitis before and after medication

This study aimed to determine the intraradicular microbiota of previously root canal-treated teeth with apical periodontitis and to investigate the antibacterial effectiveness of different intracanal medicaments. Sixteen patients with post-treatment apical periodontitis were allocated into two groups according to the intracanal medicament used: calcium hydroxide (CH) and 2% chlorhexidine gluconate gel (CHX) group. Total bacterial loads, as well as the amount of Enterococcus faecalis (E. faecalis) were determined before (S1) and after (S2) chemomechanical preparation and finally, after intracanal medication (S3) by means of ddPCR. The unpaired t test was used to compare parametric. S3-total bacteria copy number of the CH group was lower than the CHX group (p < 0.05). There was no statistical difference between the CHX- and the CH groups in terms of E.faecalis copy number (p > 0.05). But in terms of total bacteria, CH is better than CHX. Consequently, CH can be used to optimise the antibacterial efficiency of chemomechanical preparation in previously root canal-treated teeth with apical periodontitis.     

Disinfection of dentinal tubules with 2% Chlorhexidine gel,Calcium hydroxide and herbal intracanal medicaments against Enterococcus faecalis: An in-vitro study

AimThis in vitro study was conducted to evaluate the disinfection of dentinal tubules using 2% Chlorhexidine gel, Honey, Aloe vera gel, Curcuma longa, Propolis gel and Calcium hydroxide against Enterococcus faecalis.Materials and methodTwo hundred and ten human mandibular first premolars were infected with Enterococcus faecalis for 21 days. Samples were divided into 7 groups. Group I- Saline (negative control), Group II- 2% Chlorhexidine gel(CHX), Group III- honey, Group IV- Aloe vera gel, Group V- 20% Curcuma longa gel, Group VI- Propolis gel and Group VII -Calcium hydroxide (CH). At the end of 1, 3 and 5 days, the antimicrobial efficacy of medicaments against E.faecalis was assessed at the depths of 200 µm and 400 µm.Results2% Chlorhexidine gel was most effective followed by Propolis and Curcuma longa.Conclusion2% Chlorhexidine gel gave the best results. Among the herbal extracts Propolis and Curcuma longa hold a promising future but to implement their use as sole intracanal medicaments clinically, further in vivo and long term studies are warranted.     

Effectiveness of propolis and calcium hydroxide as a short‐term intracanal medicament against Enterococcus faecalis: A laboratory study

The aim of this study was to investigate the antimicrobial activity of propolis‐based intracanal medicament against Enterococcus faecalis using infected dentine models, and to compare its antimicrobial efficacy with that of the non‐setting calcium hydroxide paste when used as a short‐term medication for 1 and 2 days. A total of 50 dentine discs of 7‐mm length was obtained from extracted human teeth. Five dentine discs were kept sterile to serve as a negative control. The remaining 45 were contaminated with E. faecalis and divided into two groups (n = 20) in addition to five discs that served as a positive control. The discs were treated as follow: 20 discs were filled with propolis, while the other 20 discs were filled with non‐setting calcium hydroxide. Microbiological sampling was performed utilising sterile paper point, headstrom file and disc immersion. Results showed that propolis was significantly more effective than non‐setting calcium hydroxide against E. faecalis after short‐term application, which made comparison from this prospect unlevelled. The most effective microbiological sampling technique was abrading the lumen with headstrom file. Propolis is very effective as intracanal medicament in rapidly eliminating E. faecalis ex vivo.     

In vitro evaluation of the antibacterial effect of four root canal sealers on dental biofilms

Objectives

To dynamically evaluate the effect of four root canal sealers on the killing of biofilms within dentinal tubules.

Materials and methods

Dentin blocks were prepared for infection of the dentinal tubules. Enterococcus faecalis VP3-181 and multi-species bacteria from two donors were cultured. After 3 days of incubation, the infected dentin specimens were rinsed with sterile water for 1 min and subjected to treatment. Additionally, multi-species bacteria from donor 1 were incubated for 3 weeks to allow biofilm maturation and then the specimens were subjected to treatment. Gutta-percha-treated dentin specimens comprised the control group. A root canal sealer (bioceramic sealers: EndoSequence BC Sealer, ProRoot Endo Sealer, or GuttaFlow Bioseal; and a traditional silicone-based sealer: Guttaflow 2) was spread onto the canal walls of the dentin. The specimens were examined with confocal laser scanning microscopy at 7, 30, or 60 days.

Results

In the 3-day-old biofilm group, the proportion of killed bacteria decreased significantly from the first 7 days of treatment to 60 days of treatment for all sealers (p?<?0.05). In the 3-week-old biofilm group, 60 days of exposure to bioceramic sealers resulted in more significant dead bacteria than 7-day exposures of the biofilms (p?<?0.05). Bioceramic sealers were more effective in killing bacteria than the GuttaFlow 2 sealer (p?<?0.05).

Conclusions

Calcium silicate–based sealers showed good antimicrobial effects against biofilms within dentinal tubules, especially in the first week in young biofilms. There is no substantive antibacterial activity observed for the examined root canal sealers against young dentinal tubule biofilms.

Clinical relevance

The bioceramic root canal sealers examined demonstrate minimal additional antibacterial effects after long-term exposure to young biofilms.

     

Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals

Objectives

This in vitro study evaluated the effect of fiber insertion depth on antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT) using a photosensitizer (PS; toluidine blue) and a red light-emitting diode (LED) in root canals infected with Enterococcus faecalis.

Materials and methods

Single-rooted extracted teeth were prepared with nickel-titanium-instruments, sterilized, contaminated with E. faecalis, and incubated for 72 h. Roots were randomly divided into four experimental groups: PS only, LED only, aPDT with LED in the apical third, aPDT with LED in the coronal third, as well as into infection and sterile controls (each n = 10). Samples were taken by collecting standardized dentine shavings from the root canal walls. After serial dilution and culturing on blood agar, colony-forming units (CFU) were counted.

Results

Both aPDT groups showed a CFU reduction of 1–2 log₁₀ steps compared with the infection control, whereas the effect of fiber insertion depth was negligible (<0.5 log₁₀ steps). CFU reduction of approximately 0.5 log₁₀ steps for PS alone was detected compared with the infection control, but PS alone was less effective than both aPDT groups. No antibacterial effect was detected for LED alone.

Conclusions

aPDT reduced E. faecalis within the root canal, whereas fiber insertion depth had a negligible influence on antimicrobial effectiveness of aPDT.

Clinical relevance

The insertion depth of the light-emitting diode may not influence the antibacterial efficacy of photodynamic therapy against E. faecalis in straight root canals.

     

Development of endodontic sealers containing antimicrobial-loaded polymer particles with long-term antibacterial effects

ObjectiveThe objective of this study is to prepare new dental resins with a long-lasting antimicrobial activity. Specifically, this study evaluates an approach for controlling infection in root canals using sealers containing polyhydroxyethyl methacrylate trimethylolpropane trimethacrylate (polyHEMA/TMPT) particles loaded with cetylpyridinium chloride (CPC). In addition, the physical properties of sealers containing CPC-loaded polyHEMA/TMPT particles (CLP) are determined.MethodsPolyHEMA/TMPT particles with 10 (10%-CLP) and 25 wt.% CPC (25%-CLP) with different particle sizes were fabricated and incorporated in HEMA-based sealers. CPC-release profiles were evaluated over 14 days of immersion in water, followed by 14 days of storage and 14 days of water immersion. The antibacterial activity of these sealers against Enterococcus faecalis in dentinal tubules was assessed using a root-canal-infection model. Their sealing abilities were evaluated by fluid filtration and physical properties were tested according to the ISO 6876 standard. The long-term antibacterial activity of the cured sealer containing 25%-CLP (∼21 μm particle diameter) was re-assessed after 1 year of storage.ResultsAfter 28 days of immersion, 25%-CLP exhibited a higher and sustained CPC release unlike 10%-CLP. Residual bacteria in root dentinal tubules were eradicated by obturation with 25%-CLP-containing sealers. The incorporation of 25%-CLP (∼21 μm) had no adverse effects on the sealing ability and physical properties of the sealer and resulted in long-term antibacterial activity.SignificanceThe incorporation of CPC-loaded particles in HEMA resins yielded endodontic sealers with long-term bactericidal activity against E. faecalis in root canals. These sealers can potentially be used to prevent recurrent apical periodontitis.     

Antimicrobial Activity of a Sodium Hypochlorite/Etidronic Acid Irrigant Solution

Introduction

The aim of this study was to evaluate the antimicrobial activity of a 2.5% sodium hypochlorite (NaOCl)/9% etidronic acid (HEBP) irrigant solution on Enterococcus faecalis growing in biofilms and a dentinal tubule infection model.

Methods

The antimicrobial activity of the solutions 2.5% NaOCl and 9% HEBP alone and associated was evaluated on E. faecalis biofilms grown in the Calgary biofilm model (minimum biofilm eradication concentration high-throughput device). For the dentinal tubule infection test, the percentage of dead cells in E. faecalis–infected dentinal tubules treated with the solutions for 10 minutes was measured using confocal laser scanning microscopy and the live/dead technique. Available chlorine and pH of the solutions were also measured. Distilled water was used as the control. Nonparametric tests were used to determine statistical differences.

Results

The highest viability was found in the distilled water group and the lowest in the NaOCl-treated dentin (P < .05). Both NaOCl solutions killed 100% of the E. faecalis biofilms and showed the highest antimicrobial activity inside dentinal tubules, without statistical differences between the 2 (P < .05). The HEBP isolated solution killed bacteria inside dentinal tubules but did not present any significant effect against E. faecalis biofilms. The incorporation of HEBP to NaOCl did not cause any loss of available chlorine within 60 minutes.

Conclusions

HEBP did not interfere with the ability of NaOCl to kill E. faecalis grown in biofilms and inside dentinal tubules.     

Effect of irrigation protocol during post space preparation on the dentin adhesive interface: An in vitro study

Statement of problemThe post space must be prepared with techniques that do not interfere with the bond strength. These techniques are related to the availability of opened dentinal tubules and incidence of residue among the dentin, the adhesive, and the cement. Nevertheless, the effect of different irrigants during endodontic instrumentation is unclear.PurposeThe purpose of this in vitro study was to assess the incidence of residue, the number of opened dentinal tubules, and the bond strength of the cementation system to root dentin of post space after 3 different irrigation protocols.Material and methodsThe roots of bovine incisors were obturated, prepared to receive a fiber post, and divided into 3 groups as per the irrigation protocol: without irrigation, with alternating irrigation, and with continuous irrigation. Thirty roots (n=10) were evaluated by using scanning electron microscopy to assess the incidence of residue (×100 magnification) and the number of opened dentinal tubules (×2000 magnification). The fiber posts were cemented, and the remaining specimens (n=10) were subjected to pushout testing and failure mode evaluation.ResultsAll protocols presented a similar incidence of residue, regardless of the post space third (P>.05). The irrigation protocol without irrigation had the lowest number of opened dentinal tubules in the cervical and middle thirds (P<.05). The number of opened dentinal tubules was similar in all protocols in the apical third of the post space (P>.05). The irrigation protocol without irrigation had the lowest bond strength values in the cervical and middle thirds (P<.05). The irrigation protocol with continuous irrigation had the highest bond strength values in the apical third (P<.05).ConclusionsPost space preparation without irrigation negatively affected the bond strength of the resin cementation system to root dentin.     

Invasion of dentinal tubules by root canal bacteria

Bacterial invasion of dentinal tubules and the clinical consequences have been recognized for over a century. However, while many components of the infected dentinal tubule microflora have been identified, it is likely that there are etiological agents involved in endodontic infections that have not yet been recognized. Bacterial invasion of coronal dentinal tubules occurs when the dentine is exposed to the oral environment and of radicular dentinal tubules subsequent to infection of the root canal system or as a consequence of periodontal disease. The content and architecture of a dentinal tubule can influence bacterial invasion, with tubule patency being important. This can account for regional variations in bacterial invasion and is particularly seen with dentinal sclerosis, where more advanced sclerotic changes in apical radicular tubules, especially in elderly individuals, limit bacterial invasion in this area. While several hundred bacterial species are known to inhabit the oral cavity, a relatively small and select group of bacteria are involved in invasion of dentinal tubules. Gram‐positive organisms dominate the tubule microflora in both carious and non‐carious dentine. The relatively high numbers of obligate anaerobes present, such as Eubacterium spp., Propionibacterium spp., Bifidobacterium spp., Peptostreptococcus micros, and Veillonella spp., suggests that the environment favors the growth of these bacteria. Gram‐negative obligate anaerobic rods, e.g. Porphyromonas spp., are less frequently recovered; however, with time, fastidious obligately anaerobic bacteria become established as principal components of the microflora and can be found within the deep dentine layers. In the early stages of infection, Gram‐positive bacteria dominate the microflora. The identification of adhesins that mediate these initial interactions of bacteria with dentine is important for understanding the development of tubule infection and in designing adhesion‐blocking compounds. Recent evidence suggests that streptococci and enterococci may recognize components present within dentinal tubules, such as collagen type I, which stimulate bacterial adhesion and intra‐tubular growth. Specific interactions of other oral bacteria with invading streptococci may then facilitate invasion of dentine by select bacteria. It is important therefore that the mechanisms of invasion and inter‐bacterial adhesion are understood to assist development of novel control strategies.     

Final Endodontic Irrigation with 70% Ethanol Enhanced Calcium Hydroxide Removal from the Apical Third

IntroductionThe purpose of this study was to evaluate the cleanliness of root canal walls and dentinal tubules after attempting to remove the calcium hydroxide dressing with different irrigant solutions and the use of nonactivated irrigation or passive ultrasonic irrigation (PUI).MethodsAfter root canal instrumentation, 80 single-rooted teeth were filled with calcium hydroxide mixed with propylene glycol and 0.1% rhodamine B dye and inserted into canals with a Lentulo spiral. The calcium hydroxide dressing was initially removed with 10 mL saline solution and reinstrumentation with the master apical file. Then, the samples were randomly assigned into 8 experimental groups (n = 10) according to the irrigant solution with or without PUI: 2.5% sodium hypochlorite, 17% ethylenediaminetetraacetic acid + 1.25% sodium lauryl ether sulfate (EDTA-T), 37% phosphoric acid, or 70% ethanol. A final flush with 5 mL saline solution was performed. The percentage of clean root canal walls and the depth of clean dentinal tubules were measured with images of confocal laser scanning microscopy. The groups were compared using the 2-way analysis of variance test with the Bonferroni post hoc test for depth analysis and the Kruskal-Wallis with Dunn post hoc test for the perimeter analysis.ResultsIrrigation with 70% ethanol presented a significantly higher percentage of clean root canal walls and a higher depth of clean dentinal tubules when compared with irrigation with 2.5% sodium hypochlorite and 17% EDTA-T for both irrigation methods (P < .05). No differences were observed between nonactivated irrigation or PUI protocols (P > .05).ConclusionsSeventy percent ethanol enhanced calcium hydroxide removal from the apical root third compared with 2.5% sodium hypochlorite or 17% EDTA-T.     

超声冲洗锉引起牙本质界面微裂的初探

目的 观察超声冲洗锉作用于牙本质界面引起微裂的情况。方法 收集牙体完整的离体牙制作80片牙本质磨片,光镜下观察比较15#冲洗锉尖分别在不同功率（功率5档和10档）以及不同工作时间（30s、1min、2min和3min）所产生的牙本质微裂的情况。结果 在相同功率下,不同工作时间的超声荡洗引起的牙本质微裂差异无统计学意义（P > 0.05）。在相同工作时间下,不同功率的超声荡洗引起的牙本质微裂的差异没有统计学意义（P > 0.05）。结论 在使用冲洗锉行超声荡洗与牙本质面接触时有产生微裂的可能,在3min内、功率10以下超声荡洗的功率大小与工作时间对牙本质界面微裂程度无明显差异。     

Properties of a modified quaternary ammonium silane formulation as a potential root canal irrigant in endodontics

ObjectivesEvaluate a new modified quaternary ammonium silane irrigant solution for its antimicrobial, cytotoxic and mechanical properties of dentine substrate.MethodsRoot canal preparation was performed using stainless steel K-files™ and F4 size protaper with irrigation protocols of 6% NaOCl + 2% CHX; 3.5% QIS; 2% QIS and sterile saline. Biofilms were prepared using E. faecalis adjusted and allowed to grow for 3 days, treated with irrigants, and allowed to grow for 7 days. AFM was performed and surface free energy calculated. MC3T3 cells were infected with endo irrigant treated E. faecalis biofilms. Raman spectroscopy of biofilms were performed after bacterial re-growth on root dentine and exposed to different irrigation protocols and collagen fibers analysed collagen fibers using TEM. Antimicrobial potency against E. faecalis biofilms and cytoxicity against 3T3 NIH cells were also. Resin penetration and MitoTracker green were also evaluated for sealer penetration and mitochondrial viability. Data were analysed using One-way ANOVA, principal component analysis and post-hoc Fisher’s least-significant difference.ResultsElastic moduli were maintained amongst control (5.5 ± 0.9) and 3.5% QIS (4.4 ± 1.1) specimens with surface free energy higher in QIS specimens. MC3T3 cells showed reduced viability in 6%NaOCl+2%CHX specimens compared to QIS specimens. DNA/purine were expressed in increased intensities in control and 6% NaOCl + 2% CHX specimens with bands around 480−490 cm⁻¹ reduced in QIS specimens. 3.5% QIS specimens showed intact collagen fibrillar network and predominantly dead bacterial cells in confocal microscopy. 3.5% QIS irrigant formed a thin crust-type surface layer with cytoplasmic extensions of 3T3NIH spread over root dentine. Experiments confirmed MitoTracker accumulation in 3.5% treated cells.SignificanceNovel QIS root canal irrigant achieved optimum antimicrobial protection inside the root canals facilitating a toxic effect against the Enterococcus faecalis biofilm. Root dentine substrates exhibited optimum mechanical properties and there was viability of fibroblastic mitochondria.     

Effectiveness of calcium hydroxide-based intracanal medication on infectious/inflammatory contents in teeth with post-treatment apical periodontitis

Objective

The objective of this work was to investigate in vivo the effects of calcium hydroxide-based intracanal medication (ICM) on the levels of bacteria, pro-inflammatory cytokines (PICs), and matrix metalloproteinases (MMPs) in root canals and periradicular tissues of teeth with failure of the root canal treatment and apical periodontitis.

Materials and methods

Twenty infected root canals of single-rooted teeth were randomly assigned into two groups according to the irrigant used for chemomechanical preparation (CMP) (n = 10 per group): G1 – 2% chlorhexidine (CHX) gel and G2 – 6% sodium hypochlorite (NaOCl). Root canal contents were taken by using paper points before CMP (S1) and after 30 days of calcium hydroxide-based ICM (S2). Microbial reduction was calculated by means of colony-forming unit count (CFU/mL), with PICs and MMPs (pg/mL) being measured by using enzyme-linked immunosorbent assay (ELISA).

Results

Culturable bacteria (101.2 ± 79.2), PICs (IL-1β 1.2 ± 0.4 and TNF-α 8.8 ± 4.7), MMP-2 (803.7 ± 96.4), MMP-3 (453.9 ± 229.3), MMP-8 (245.9 ± 122.4), MMP-9 (129.4 ± 29.6), and MMP-13 (70.8 ± 12.8) were present in all S1 samples. After 30 days of ICM (S2), a 99.5% microbial reduction was observed, together with a significant reduction of PICs in all groups. Overall, it was observed a decrease in the levels of MMPs (S2), except MMP-13, which was found in increased levels after ICM (P < .05), independently of the groups.

Conclusions

Calcium hydroxide-based intracanal medications have had a positive effect on the microbial reduction by decreasing the levels of PICs and MMPs. Both auxiliary chemical substances (i.e., 2% CHX and 6% NaOCl) presented similar effects when calcium hydroxide was used as intracanal medication.

Clinical relevance

Teeth with failure of the root canal treatment and apical periodontitis, and consequently with high levels of bacteria, PIC, and MMP, may present a better prognosis after a 30 days of a calcium hydroxide-based ICM.

     

Intratubular decontamination ability and physicochemical properties of calcium hydroxide pastes

Objective

This in vitro study compared the penetration, pH, calcium ion release, solubility, and intradentinal decontamination capacity of calcium hydroxide (CH) pastes with different vehicles and additives.

Materials and methods

Infected standard bovine dentine contaminated with Enterococcus faecalis were treated with propolis extract, chlorhexidine, and camphorated paramonochlorophenol (CPMC) loaded in CH paste for the bacterial viability evaluation made by confocal laser scanning microscopy (CLSM) and microbiological culture. Beside this, 50 acrylic teeth were filled with the previously mentioned pastes to evaluate the pH and calcium ion release (pHmeter and atomic absorption spectrophotometer at time intervals of 7, 15, and 30 days) and solubility (micro-computed tomographic imaging before and after 15 days).

Results

After treatment, all samples decreased intra-dentinal contamination, specially, the CH paste with CPMC. There was no statistically significant difference between the groups when evaluating the intra-canal paste penetration. In the pH measurements, CH with distilled water showed the smallest pH values. Regardless the solubility percentage of the pastes, the paste of CH + PG presented the highest values.

Conclusion

The vehicles and additives tested may increase CH antimicrobial effect, but with small differences. In general, all CH pastes tested here were effective in reducing Enterococcus faecalis and were similar in the penetration, pH, calcium ion release, and solubility of calcium hydroxide when compared to distilled water.

Clinical relevance

The use of calcium hydroxide pastes as intracanal medication with an aqueous or viscous vehicle, as propylene glycol, can be useful, since all formulations of the tested pastes resulted in great bacterial reduction inside root canals.

     

Intracanal Metformin Promotes Healing of Apical Periodontitis via Suppressing Inducible Nitric Oxide Synthase Expression and Monocyte Recruitment

IntroductionWe have previously shown that intracanal metformin ameliorates apical periodontitis, partially by modulation of osteoblast apoptosis. The action of metformin on other cell types pertinent to the development of apical periodontitis needs to be examined. In the present study, we aimed to analyze whether its effects on the expression of inducible nitric oxide synthase (iNOS) and monocyte recruitment contribute to the therapeutic effect on apical periodontitis.MethodsLipopolysaccharide (LPS)-induced expression of iNOS in a human monocytic cell line, Mono-Mac-6, was assessed by Western blot. The amount of nitrite in culture medium was assessed to quantify nitric oxide (NO) production. C-C motif chemokine ligand-2 (CCL-2) synthesis was measured by enzyme-linked immunosorbent assay. Experimental apical periodontitis in rats was treated with root canal debridement with or without intracanal metformin medication. Lesion progression was assessed by conventional radiography and micro–computed tomographic imaging. Cellular expression of iNOS and the number of monocytes/macrophages were assessed by immunohistochemistry.ResultsMetformin suppressed LPS-induced iNOS and NO production by monocytes. More importantly, metformin inhibited LPS-enhanced CCL-2 synthesis through modulation of the iNOS/NO pathway. Intracanal metformin reduced bone resorption associated with apical periodontitis and suppressed iNOS expression and monocyte recruitment.ConclusionsOur results confirmed the therapeutic efficacy of intracanal metformin for apical periodontitis. Suppression of monocyte recruitment through modulation of iNOS expression and NO production is an important mechanism underlying the beneficial effect of metformin.     

Adherence of Streptococcus gordonii to smeared and nonsmeared dentine

The purpose of this study was to investigate the adherence of Streptococcus gordonii to smeared and non-smeared dentine and to assess the influence of patent dentinal tubules on bacterial retention. In order to examine bacterial adherence, 10 non-smeared (group 1) and 10 smeared samples (group 2) of outer root dentine were prepared from teeth exhibiting dentine sclerosis. Ten non-smeared samples from inner coronal root dentine that did not exhibit sclerosis were prepared in order to study the influence of patent tubules on bacterial retention (group 3). Cells of the bacterium were radioactively labelled and an adhesion assay was performed. The number of bacteria adhering to the dentine surface was determined by scintillation counting. The results show that the number of bacteria adhering to both smeared and non-smeared outer sclerotic dentine was low (0.3% of inoculum), and there was no significant difference between the groups (P > 0.3). A significantly higher number of bacteria was retained on the inner non-smeared coronal root dentine (P < 0.0001) compared to groups 1 or 2. The results suggest that dentinal smear layers do not enhance or impede bacterial adherence to the dentine matrix. Dentinal surfaces with patent dentinal tubules retain more bacteria than a smeared surface.