Influence of bioceramic sealers on dentinal tubule penetration and antimicrobial effectiveness: a systematic review and meta-analysis of in vitro studies.

The aim of this systematic review and meta-analysis (SRM) was to evaluate whether bioceramic sealers have better penetration capacity in dentinal tubules and antimicrobial activity when compared to AH Plus® sealer. This SRM was recorded in the Open Science Framework database and followed the guidelines of the PRISMA 2020. Five databases were searched by two independent reviewers. Only in vitro studies that evaluated the effects of bioceramic sealers on dentinal tubule penetration and antimicrobial activity outcomes compared to AH Plus® sealer were included. Meta-analysis was conducted using R software, using the effect measure of the standardized mean difference (SMD) and inverse variance method. A modified Joanna Briggs Institute's Checklist was used for the risk of bias assessment. A total of 1486 studies were identified, and only 54 studies that fulfilled our eligibility criteria were included in this review. There was no statistical difference between the sealers evaluated for dentinal tubule penetration, in the thirds evaluated: coronal SMD 0.58 [0.14; 1.31], p = 0.12; middle SMD 0.07 [0.54; 0.39], p = 0.75; and apical SMD 0.08 [0.73; 0.56], p = 0.80. Both sealers demonstrated similar antimicrobial action (SMD [3.42; 5.32], p = 0.67 and SMD 0.67 [1.89; 0.55], p = 0.28). The studies presented a low risk of bias. Based on the in vitro studies included and according to the limitations of the present review, the data suggest that bioceramic and AH Plus® sealers present similar penetration capacity in dentinal tubules and antimicrobial effect, making them suitable materials to be considered in clinical practice.

Cytotoxicity and cell migration evaluation of a strontium silicate-based root canal sealer on stem cells from rat apical papilla: an in vitro study.

BACKGROUND: Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years, many chemical components and new synthesizing methods were used to improve the base formulation of the materials for positively affecting the sealers properties. Recently, a novel biomaterial formulation, grounded in strontium silicate, has been introduced to the market, offering potential advancements in the field. OBJECTIVE: To comparatively analyze the cytotoxicity and cell migration effects of a novel strontium silicate-based bioceramic material (CRoot SP) and those of calcium silicate-based (iRoot SP) and epoxide amine resin (AH Plus) sealers on stem cells derived from rat apical papilla(rSCAPs). METHODS: rSCAPs were isolated and characterized in vitro and subsequently cultured in the presence of various concentrations of CRoot SP, iRoot SP and AH Plus extracts. Cytotoxicity was assessed by CCK-8 assay, and cell-migration capacity was assessed by using wound healing assays . RESULTS: No significant differences in cell viability were observed in the 0.02 mg/mL and 0.2 mg/mL sealer groups. The cell viability of CRoot SP was consistently greater than that of iRoot SP at concentrations of 5 mg/mL and 10 mg/mL across all time points. Maximum cytotoxic effect was noted on day 5 with 10 mg/mL AH Plus.The scratch was partly healed by cell migration in all groups at 24 h, and the 0.02 mg/mL, and 0.2 mg/mL CRoot SP exerted beneficial effects on rSCAPs migration. CONCLUSIONS: CRoot SP exhibited less cytotoxic than the iRoot SP and AH Plus extracts after setting. A lower concentration of CRoot SP thus promotes the cell migration capacity of rSCAPs, and it may achieve better tissue repair during root canal treatment.

Synthesis of silver core-shell nanoparticles and their influence on an experimental resin endodontic sealer: An in vitro analysis.

AIM: To avoid root canal recontamination and endodontic treatment failure, endodontic sealers with antibacterial activity could be an alternative. Silver nanoparticles have antibacterial activity and this study aimed to synthesize Ag@SiO2 nanoparticles, incorporate them into an experimental endodontic resin sealer and evaluate their influence on physicochemical and biological properties. METHODOLOGY: Ag@SiO2 nanoparticles were produced using the sol-gel process, based on the Stöber method. The particles were characterized in terms of their chemical structure by Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-Vis spectral analysis, scanning electron microscopy, and transmission electron microscopy, where the particle morphology and diameter were analysed. A dual-cured experimental endodontic resin sealer was formulated using 70 wt% UDMA, 15 wt% GDMA, and 15 wt% BisEMA. The photoinitiators were added separately in two pastes. The Ag@SiO2 nanoparticles were incorporated into the endodontic sealer at the concentrations of 2.5 wt%, 5 wt%, and 10 wt%, and a control group without nanoparticles was also formulated. The endodontic sealers were evaluated for their flow, film thickness, degree of conversion, softening in solvent, radiopacity, cytotoxicity and antibacterial activity immediately and after 9 months in water storage. RESULTS: Silver was detected in the chemical characterization of Ag@SiO2 that presented a spheric regular shape and average 683.51 nm ± 93.58 diameter. Sealers presented adequate flow and film thickness while radiopacity values were below the ones required by ISO 6876. All groups underwent softening after immersion in a solvent. The 10 wt% groups showed a higher loss of subsurface hardness (∆KHN%). No reduction in cell viability was observed. Enterococcus faecalis viability in biofilm was reduced in 10 wt% groups after 24 h and 9 months. CONCLUSION: The addition of 10 wt% Ag@SiO2 reduced E. faecalis viability at immediate and longitudinal analysis while maintaining the physicochemical properties of developed sealers.

Inflammatory response to epoxy resin and calcium silicate sealers preheated with different temperatures: an in vivo study.

OBJECTIVE: To determine the impact of heat exposure of different sealers on inflammatory cytokine secretions and tissue response in vivo. MATERIALS AND METHODS: Silicone tubes were prefilled with epoxy resin (ER) or calcium silicate (CS) sealers, preheated at 37, 60, or 120 °C, and implanted in rat subcutaneous site. Peri-implant exudate and tissue were analyzed after 1 and 4 weeks for cytokine secretions and tissue organization. RESULTS: At 1 week, 120 °C-preheated CS and ER induced higher secretions of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6), respectively, as compared to sham/empty tube groups. At 4 weeks, whereas TNF-α secretion was reduced in CS, it increased in ER group, particularly for 120 °C. Both sealers revealed high IL-6 after 4 weeks as compared to sham/empty tube, and generally, higher IL-6 secretions were associated with ER. Histology at 1 week revealed lower degree of inflammatory infiltrate in the groups of the highest preheating temperature (120 °C). Nonetheless, at 4 weeks, whereas fibrous capsule area and inflammatory infiltrate remained low in the CS120 group, they were high in ER120. CONCLUSION: Preheating ER sealer to 120 °C induced high and prolonged secretion of proinflammatory cytokines (TNF-α and IL-6), whereas this effect was transient for the CS sealer. This was associated with increased fibrous capsule and inflammatory infiltrate in response to 120 °C-preheated ER. CLINICAL RELEVANCE: Heat-induced changes in sealer properties alter the inflammatory response in vivo, which may affect the clinical outcome. This will not only help appropriate selection of obturation technique for different sealers, but also for optimizing the properties of new generation of sealers.

Evaluation of Antibacterial Effect of New Sealer "Neoseal" and Two Commercially Used Endodontic Sealers against Enterococcus faecalis: An In Vitro Study.

AIM: To evaluate the antibacterial activity of three endodontic sealing materials, Neoseal, CeraSeal, and AH Plus against Enterococcus faecalis bacteria in vitro. MATERIALS AND METHODS: The antibacterial activity of three endodontic sealing materials including two bioceramic sealers; NeoSEALER Flo (group I), CeraSeal (group II), and one epoxy resin sealer; AH Plus (group III) was investigated against E. faecalis bacteria American Type Cell Culture Collection (ATCC) 29212 (ATCC, Rockville, Maryland, USA). Using modified direct contact test (MDCT). The endodontic sealers were tested in contact with bacterial suspension when unset (20 minutes after mixing) and after setting, assessing the antibacterial activity of aged sealers after 1, 3, 7, and 14 days. Analyzing the collected data has been done with version 25.0 of the statistical package for the social sciences (SPSS) IBM software (SPSS, Chicago, Illinois, USA). Descriptive analyses were calculated using standard deviation (SD) and mean. Shapiro-Wilk test was done to detect the normality of the result values. Kruskal-Wallis test was then performed to test the level of significance between groups. RESULTS: After 20 minutes - Group I showed higher bacterial count mean values (5,500 ± 500) and 0 values for groups II and III groups. After 1 day, the highest bacterial count mean values were in group III (54,333.3 ± 4,041.5) and 0 values for groups I and II. After 3 days - group III again recorded the highest bacterial count mean values (45,000 ± 5,000) and 0 values for I and II groups. After 7 days - Group III still recorded the highest bacterial count mean values (53,333.3 ± 1,527.5) and 0 values for groups I and II. After 14 days - Group III recorded the highest bacterial count mean values (56,000 ± 1,000) followed by group II (6,333.3 ± 577.4), and the least was group I (2,000 ± 500). Kruskal-Wallis test showed significant values between groups in all tested durations, p > 0.05. CONCLUSION: The sealing material AH Plus showed a strong bactericidal effect at the beginning but lost its ability after 24 hours. CeraSeal showed strong bactericidal activity from the beginning till the end of the first week but showed bacterial count at 14 days. Neoseal took 24 hours to show bactericidal effect and similar to CeraSeal showed bacterial count at 14 days; CeraSeal recorded the best results within the study. CLINICAL SIGNIFICANCE: Silicate-based (bioceramic) endodontic sealers can be the best available endodontic sealing material that is clinically beneficial in removing residual microbes which had survived irrigation protocols and chemomechanical preparation. How to cite this article: Basta DG, Reslan MR, Rayyan M, et al. Evaluation of Antibacterial Effect of New Sealer "Neoseal" and Two Commercially Used Endodontic Sealers against Enterococcus faecalis: An In Vitro Study. J Contemp Dent Pract 2023;24(11):871-876.

Cytocompatibility and bioactive potential of AH Plus Bioceramic Sealer: An in vitro study.

AIM: To assess the cytocompatibility and bioactive potential of the new calcium silicate cement-based sealer AH Plus Bioceramic Sealer (AHPbcs) on human periodontal ligament stem cells (hPDLSCs) compared with the epoxy resin-based sealer AH Plus (AHP) and the calcium silicate cement-based sealer Endosequence BC Sealer (ESbcs). METHODOLOGY: Standardized sample discs and 1:1, 1:2 and 1:4 eluates of the tested materials were prepared. The following assays were performed: surface element distribution via SEM-EDX, cell attachment and morphology via SEM, cell viability via a MTT assay, cell migration/proliferation via a wound-healing assay, osteo/cemento/odontogenic marker expression via RT-qPCR and cell mineralized nodule formation via Alizarin Red S staining. HPDLSCs were isolated from extracted third molars. Comparisons were made with hPDLSCs cultured in unconditioned (negative control) or osteogenic (positive control) culture media. Statistical significance was established at p < .05. RESULTS: A higher peak of Ca2 + was detected from ESbcs compared with AHPbcs and AHP in SEM-EDX. Both AHPbcs and ESbcs showed significantly positive results in the cytocompatibility assays (cell viability, migration/proliferation, attachment and morphology) compared with a negative control group, whilst AHP showed significant negative results. Both AHPbcs and ESbcs exhibited an upregulation of at least one osteo/odonto/cementogenic marker compared with the negative and positive control groups. Both ESbcs and AHPbcs showed a significantly higher calcified nodule formation than the negative and positive control groups, indicative of their biomineralization potential and were also significantly higher than AHP group. CONCLUSION: AH Plus Bioceramic Sealer exhibited a significantly higher cytocompatibility and bioactive potential than AH Plus and a similar cytocompatibility to that of Endosequence BC Sealer. Endosequence BC Sealer exhibited a significantly higher mineralization potential than the other tested sealers. The results from this in vitro study act as supporting evidence for the use of AH Plus Bioceramic Sealer in root canal treatment.

A comprehensive in vitro comparison of the biological and physicochemical properties of bioactive root canal sealers.

OBJECTIVES: To evaluate the biological and physicochemical features of bioactive root canal sealers. MATERIALS AND METHODS: Human periodontal ligament fibroblasts (hPDLF) and human osteoblasts (hOB) were exposed to eluates of three bioactive root canal sealers, GuttaFlow® bioseal (GF), BioRoot™ RCS (BR), and TotalFill® BC Sealer (TF), and the epoxy resin-based sealer AH plus® (AH). Cytotoxicity and cellular inflammatory response were evaluated. The osteogenic potential was examined using human mesenchymal stem cells (hMSC). Film thickness, flowability, and pH were assessed. Root canal treatment was performed on human extracted teeth to evaluate the sealers' tightness towards bacterial penetration. The antibacterial activity against common pathogens in primary root canal infections was tested. RESULTS: AH was severely cytotoxic to hPDLF and hOB (p < 0.001). The bioactive sealers were generally less cytotoxic. IL-6 levels in hPDLF were elevated in the presence of AH (p < 0.05). AH and GF suppressed IL-6 production in hOB (p < 0.05). AH and BR stimulated the PGE2 production in hPDLF and hOB (p < 0.05). BR was the only sealer that led to calcium deposits in hMSC (p < 0.05). TF and AH showed the lowest film thickness and the highest flowability. Bacterial tightness was best in teeth filled with AH and BR. All sealers showed similar antimicrobial activity, but the overall antimicrobial efficacy was moderate as the bacteria were reduced by just one log scale (p < 0.05). CONCLUSIONS: This study revealed favorable in vitro results regarding the biocompatibility of the bioactive root canal sealers. CLINICAL RELEVANCE: Bioactive root canal sealers may be a useful alternative to epoxy resin-based sealers.

Impact of cleansing protocols to remove endodontic sealer residues on the adhesive interface: Bonding with universal adhesive systems.

OBJECTIVE: The aim of this study was to evaluate the effectiveness of cleansing protocols to remove sealer residues using different cleaning strategies and the effect of bond strength of two universal adhesives to dentin impregnated with epoxy resin-based sealer. MATERIALS AND METHODS: Fifty bovine dentin specimens were impregnated with epoxy resin-based sealer containing calcium hydroxide (Sealer Plus) and submitted to cleansing protocols (n = 10): negative control (NC), positive control (PC), 95% ethanol (ET), xylol (XI), and amyl acetate (AA). Specimens were evaluated by scanning electron microscope (SEM). Other 100 specimens were submitted to the same protocols (n = 20). Each protocol was divided into subgroups (n = 10) according to the universal adhesive system used: Scotchbond Universal (SU); Ambar Universal (AU). Bond strength was evaluated by micro-shear bond test (µSBT). Persistence of residues data were assessed with Kruskal-Wallis and Dunn's tests. µSBT data were analyzed with two-way ANOVA (α = 5%). RESULTS: ET presented higher persistence of residues compared to AA and XI (p < 0.05). AA and XI were similar from each other (p > 0.05). AU and SU presented similar µSBT values, regardless of the cleansing solution (p > 0.05). SU-NC presented the highest µSBT among all conditions (p < 0.05). CONCLUSION: The bond strength of universal adhesives was not affected by different amounts of sealer residues after different cleaning protocols. CLINICAL SIGNIFICANCE: Non-polar substances such as amyl acetate and xylol are effective for removing residues from epoxy resin-based endodontic sealers.

Cleaning and microstructural effects of amyl acetate on pulp chamber dentin impregnated with epoxy resin-based endodontic sealer.

OBJECTIVE: To evaluate the cleaning potential of 95% ethanol, acetone, and amyl acetate solutions used solely or in association, to remove epoxy resin-based sealer residues from pulp chamber dentin and their microstructural effects. MATERIALS AND METHODS: One hundred and eighty bovine incisor specimens were divided into nine groups according to the cleaning protocol: ET (ethanol); AC (acetone); AA (amyl acetate); E1: AA+AC; E2: AA+ET; E3: AC+ET; E4: AA+AC+ET; PC (positive control), and NC (negative control). All groups were impregnated with epoxy resin-sealer, except NC. Ninety specimens were divided into groups (n = 10) for evaluation of persistence of residues and amount of open dentinal tubules by SEM analysis and evaluation of chemical compounds on the dentin surface after cleaning with electron dispersive spectroscopy. The others 90 specimens were submitted to Knoop microhardness evaluation. Persistence of residues data were submitted to the Kruskal Wallis and Dunn tests (α = 0.05). Open dentinal tubules and microhardness data were submitted to one-way ANOVA and Mann Whitney tests (α = 0.05). RESULTS: AA and E4 protocols showed the lowest persistence of residues. E4 group had the highest incidence of open dentinal tubules. E3 and E4 groups showed no changes in the atomic ratio Ca/P, which was similar to NC group. E4 group did not present W, an element presents in all the other groups. ET and E4 protocols showed the smallest reduction in dentin microhardness. CONCLUSIONS: The combination of amyl acetate, acetone and ethanol is the most effective and safe protocol to remove epoxy sealer residues on pulp chamber dentin. Moreover, it has the lowest microhardness reduction. CLINICAL SIGNIFICANCE: The combined use of amyl acetate, acetone, and ethanol enhanced the cleaning of pulp chamber dentin with minimal microstructural damage.

Evaluation of the biocompatibility of root canal sealers on human periodontal ligament cells ex vivo.

The aim of this study was to evaluate the biocompatibility of two comparatively new calcium silicate containing sealers (MTA-Fillapex and BioRoot-RCS) with that of two established sealers (AH-Plus, epoxy resin-based; Pulp-Canal-Sealer, zinc oxide eugenol containing). Human periodontal ligament cells (PDL-cells) were brought in contact with eluates from freshly mixed and set sealer. The sealers were mixed strictly according to the manufacturers' instructions and identically samples were produced. 1:1, 1:2, and 1:10 dilutions of sealers extract were used. Extracts from freshly mixed sealer were added to the PDL-cells on day one to simulate a clinical scenario. Subsequently, at 24 h, 7, 14, and 21 days extracts form set sealers were used for PDL-cell culturing. PDL-cell viability was analyzed by living-cell-count, MTT-assay, and living/dead-staining, cytotoxicity by LDH-assay, and changes by Richardson-staining. All data were statistically evaluated by one way ANOVA and a posthoc analysis with Bonferroni-Holm testing (p < 0.05). In contact with BioRoot-RCS a regeneration of the PDL-cells were observed over time. This sealer showed the lowest toxicity in a freshly mixed and set state (p < 0.05). MTA-Fillapex and Pulp-Canal-Sealer were cytotoxic in a fresh as well as in a set state, whereas AH-Plus was cytotoxic in a freshly mixed state, but not when the sealer was set. BioRoot-RCS is biocompatible and bioactive because it seems to have a positive influence on the PDL-cell metabolism. Pulp Canal Sealer and MTA-Fillapex showed no biocompatibility in contact with PDL-cells at all. Freshly mixed AH Plus is less biocompatible on PDL than in a set state.

Evaluation of Antimicrobial Efficacy of Root Canal Sealers against Enterococcus faecalis: A Comparative Study.

AIM: The study aimed to evaluate the efficacy of root canal sealer's antimicrobial activity against Enterococcus faecalis. MATERIALS AND METHODS: Root canal sealers with the brands Endoflas FS, AH Plus, and Tubli-Seal EWT were selected. Enterococcus faecalis organisms' zone of inhibition was measured. Tukey post hoc tests and one-way analysis of variance (ANOVA) were used to compare the data among study groups and within its group. The data were said to be statistically significant with an established p-value less than 0.05. RESULTS: The maximum zone of inhibition (23.20 ± 1.202 mm) was shown by Endoflas FS sealer; AH Plus and Tubli-Seal showed the inhibition zone of (18.42 ± 1.023) and (16.88 ± 0.962) respectively, following Endoflas FS. The ANOVA test showed p < 0.0001, which is highly statistically significant. AH Plus and Endoflas FS showed a statistically significant difference of 0.04 and 0.001 in between groups, and there was no statistically significant difference in the Tubli-Seal group from Tukey post hoc test. CONCLUSION: The study showed that Endoflas FS sealer has a significant antimicrobial effect against E. faecalis. CLINICAL SIGNIFICANCE: In clinical situation, despite perfect che-momechanical root canal preparation, persistence of microorganisms may reinfect the root canal. Therefore, endodontic root canal sealers play a major role in the eradication of bacteria. The polymicrobial nature of endodontic infection plays a main role during the usage of endodontic sealer with antimicrobial agents, which in turn reduces the failure of endodontic treatment.

[Effect of root canal sealers on biocompatibility of human periodontal ligament cells].

OBJECTIVE: To compare the effects of three root canal sealers with respect to time on biocompatibility of human periodontal ligament cells (hPDLCs).The sealers included zinc oxide and eugenol based sealers (ZOE), epoxy resin sealers (ERS) and silicone based sealers (SBS). METHODS: hPDLCs were primarily cultured,with the method combining of tissue explant and enzymatic digestion. The cells were then exposed to different extract fluids: (1) ZOE extracted for 24 h group ;(2) ZOE extracted for 1 week group;(3)ZOE extracted for 2 weeks group;(4) ERS extracted after 24 h group; (5) ERS extracted after 1 week group; (6) ERS extracted after 2 weeks group; (7) SBS extracted after 24 h group; (8) SBS extracted after 1 week group; (9) SBS extracted after 2 weeks group; (10) Dulbecco modified Eagle's medium/F12 (DMEM/F12) as negative control group. Cell morphology was observed under an inverted microscope.Cell proliferation was measured by methyl-thiazol-diphenyltetrazolium (MTT) assay. ALP assay kit was used for measuring alkaline phosphatase (ALP) activity. Sealers of 2 weeks' setting time were then immersed in an osteogenic medium for examination of mineral nodules and calcium deposits. RESULTS: Considering the relative growth rate(RGR),ZOE was severely to moderately cytotoxic(RGR:13.6%-39.9%), while ERS was slightly or not cytotoxic (RGR: 87.6%-95.3%).Only SBS did not show any cytotoxicity after setting (RGR: 91.8%-106.7%). The setting time influenced the cytotoxicity of ERS which decreased after 1 week. Considering the ALP activity,there was no difference between SBS group and control group (F=3.397,P=0.053). According to the results of calcium deposits, ZOE:D562 nm=0.180±0.050,ERS: D562 nm=2.968±0.201,SBS:D562 nm=3.623±0.039,Control:D562 nm=3.477±0.102,the ranking of ALP activity and calcium deposits was as follows: ZOE

An in vitro Comparison of Antimicrobial Activity of Three Endodontic Sealers with Different Composition.

AIMS: The aim of the study was to compare the antimicrobial property of newly introduced EndoSequence BC sealer with commonly used zinc oxide-eugenol-based sealer (Zical) and epoxy resin-based sealer (MM-Seal) against Candida albicans, Lactobacillus, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. MATERIALS AND METHODS: The agar diffusion test was done to measure the antimicrobial activity of sealers. The sealers were put in the 4 mm wells prepared in the inoculated agar plates. The agar plates were incubated at 37°C for 24 hours and the zones of inhibition that appeared was measured. Chi-square test was done to evaluate intraobserver bias for all study samples. Intergroup comparison was done for all five parameters using Pearson correlation statistical analysis. RESULTS: EndoSequence BC sealer showed maximum mean of diameter of zones of inhibition against all the microorganisms but with no statistically significant difference with other sealers. Zical did not show any zone of inhibition against the P. aeruginosa. MM-Seal did not show any inhibitory activity against the P. aeruginosa and C. albicans. CONCLUSION: EndoSequence BC sealer showed antimicrobial activity against all the microorganisms and proved to be a better choice when compared with other two sealers. CLINICAL SIGNIFICANCE: Antimicrobial properties of endodontic sealers are important to prevent the persistent infection of the complex root canals. EndoSequence BC sealer has been proved to be a better sealer in this aspect.

Mechanical and anticorrosive properties of graphene/epoxy resin composites coating prepared by in-situ method.

The graphene nanosheets-based epoxy resin coating (0, 0.1, 0.4 and 0.7 wt %) was prepared by a situ-synthesis method. The effect of polyvinylpyrrolidone/reduced graphene oxide (PVP-rGO) on mechanical and thermal properties of epoxy resin coating was investigated using nanoindentation technique and thermogravimetric analysis, respectively. A significant enhancement (ca. 213% and 73 °C) in the Young modulus and thermal stability of epoxy resin coating was obtained at a loading of 0.7 wt %, respectively. Furthermore, the erosion resistance of graphene nanosheets-based epoxy resin coating was investigated by electrochemical measurement. The results showed also that the Rrcco (ca. 0.3 mm/year) of graphene nanosheets-based epoxy resin coating was far lower than neat epoxy resin (1.3 mm/year). Thus, this approach provides a novel route for improving erosion resistance and mechanical-thermal stability of polymers coating, which is expected to be used in mechanical-thermal-corrosion coupling environments.

Evaluation of the amount of apically extruded debris during retreatment of root canals filled by different obturation techniques.

OBJECTIVE: To evaluate the amount of apically extruded debris during retreatment (with or without solvent) of root canals filled by two obturation techniques. MATERIALS AND METHODS: Forty-eight root canals were prepared using ProTaper Universal F3 and filled with Gutta-percha and AH 26 sealer using single cone or lateral condensation techniques. The root canal fillings were removed using ProTaper Universal Retreatment system with or without solvent, and the canals were further prepared with ProTaper F4. The operating time was measured. The debris extruded was collected into preweighed Eppendorf tubes. The dry weight of the extruded debris was calculated by subtracting the weight of the empty tube from that of the tube containing debris. Statistical analysis was performed with two-way analysis of variance test, with Bonferroni correction at a 95% confidence level. RESULTS: There was no statistically significant difference in the amount of extruded debris between the two obturation techniques (P=0.332). The mean amount of debris was higher in the nonsolvent groups than the solvent groups, particularly with the single cone technique (P=0.013). There was a significant difference between groups with regard to the retreatment time (P<0.001). Gutta-percha removal took less time in the single cone group than in the lateral condensation group (P<0.001). Gutta-percha removal in the nonsolvent groups took significantly less time than that in the solvent groups (P<0.001). CONCLUSIONS: The amounts of apically extruded debris were similar in both obturation techniques. A greater amount of apically extruded debris was observed in the nonsolvent groups than the solvent groups.

Epoxy resin monomers with reduced skin sensitizing potency.

Epoxy resin monomers (ERMs), especially diglycidyl ethers of bisphenol A and F (DGEBA and DGEBF), are extensively used as building blocks for thermosetting polymers. However, they are known to commonly cause skin allergy. This research describes a number of alternative ERMs, designed with the aim of reducing the skin sensitizing potency while maintaining the ability to form thermosetting polymers. The compounds were designed, synthesized, and assessed for sensitizing potency using the in vivo murine local lymph node assay (LLNA). All six epoxy resin monomers had decreased sensitizing potencies compared to those of DGEBA and DGEBF. With respect to the LLNA EC3 value, the best of the alternative monomers had a value approximately 2.5 times higher than those of DGEBA and DGEBF. The diepoxides were reacted with triethylenetetramine, and the polymers formed were tested for technical applicability using thermogravimetric analysis and differential scanning calorimetry. Four out of the six alternative ERMs gave polymers with a thermal stability comparable to that obtained with DGEBA and DGEBF. The use of improved epoxy resin monomers with less skin sensitizing effects is a direct way to tackle the problem of contact allergy to epoxy resin systems, particularly in occupational settings, resulting in a reduction in the incidence of allergic contact dermatitis.

Defined 2-D microtissues on soft elastomeric silicone rubber using lift-off epoxy-membranes for biomechanical analyses.

Surface patterning with complex molecules has become a valuable tool in cell biology and biotechnology, as it enables one to control cell shape and function in culture. However, this technique for micro-contact printing is normally performed on rigid substrates, e.g. Petri dishes or glass. Despite the fact that these substrates can easily be patterned they are artificially stiff environments for cells affecting their morphology and function. Those artifacts can be avoided on tissue elasticity resembling substrates, leading to a nature like cell morphology and behavior. However, reproducible patterning of very soft elastomeric substrates is challenging. Here, we describe a simple and highly accurate method through cavities of lift-off membranes for protein patterning of silicone rubber substrates in an elasticity range down to 1.5 kPa without altering their mechanical properties. Membranes are made of epoxy resin with feature sizes that can be chosen almost arbitrarily including widths down to 5 µm and aspect ratios of 100 and more. Different feature shapes were used to actively manipulate cell adhesion, cell morphology and the actin cytoskeleton on soft substrates. Manipulation of cytoskeletal organization furthermore allowed the comparison of myofibril alignment and cellular forces of cardiac myocytes. These data could show that cell forces are largely unaffected upon active disordering of overall myofibril alignment on a single cell level while aligned multicellular systems generate cell forces in an additive manner.

In vitro antimicrobial effects of 3 root canal sealers on Actinomyces radicidentis.

OBJECTIVE: To determine the in vitro antimicrobial effects of 3 endodontic sealers--AH Plus, Sealapex, and Tubli-Seal--on Actinomyces radicidentis, a bacterial species commonly found in root canals. METHODS: Prior to the experimental procedures, bacterial identification tests, such as Gram staining, catalase, and API 20A, were performed, and the bacteria were identified as A. radicidentis. The agar diffusion susceptibility test was performed to determine the areas of bacterial growth inhibition and, consequently, the microbial resistance of the 3 sealers against A. radicidentis. Chlorhexidine was used as a positive control, and saline solution was used as a negative control. RESULTS: Tubli-Seal cement had an average diameter of inhibition zones in the 3 panels of 22.73 mm, that of AH Plus was 17.13 mm, and that of Sealapex, 11.99 mm. A one-way ANOVA test showed that there were significant differences between the 3 cements (p < 0.05). CONCLUSION: Tubli-Seal showed the highest levels of antimicrobial activity, which was followed by AH Plus with the next highest levels and, finally, Sealapex with the lowest levels of antimicrobial activity.

Comparative evaluation of antimicrobial activity of two root canal sealers: MTA Fillapex and AH 26.

AIM: Even after a complete root canal therapy, reinfection may occur as a result of incomplete seal and activation of residual bacteria. Thus, antimicrobial activity is an important characteristic of root canal sealers. MTA Fillapex is a newly developed MTA-based sealer. It has been subjected to various studies evaluating its physical and chemical properties. In this study, we aimed to compare the antimicrobial activity of this sealer to the commonly known widely accepted sealer, AH26. METHODS: MTA Fillapex and AH 26 were exposed the bacterial suspension of Enterococcus faecalis, Escherichia coli, Streptococcus mutans, and Candida albicans after setting. After incubation and complete evaporation, BHI was added to microtubes. 24 hours later, the liquid content was placed in agar diffusion plate and bacterial count was performed. ANOVA followed by Tukey test, and t-Test were performed to analyze the data. RESULTS: With regard to all four bacterial groups, the bacterial count was significantly lower in MTAFillapex group comparing to AH 26 group. CONCLUSION: Newly developed MTA Fillapex sealer, has better antimicrobial properties in comparison to the widely accepted AH26 sealer.

Effect of a 10-Methacryloyloxydecyl Dihydrogen Phosphate-treated Bioceramic Sealer on the Bond Strength of an Endodontic Fiber Post: Multilayer Composite Disk Models and Ultra-highspeed Imaging Analysis.

PURPOSE: Multiple materials are found in the root canal after fiber-post cementation. The layer of a bioceramic-based (BC) sealer may affect the bond strength (σBS) of the fiber post in the root canal. The purpose of this study was to employ multilayer composite-disk models in diametral compression to investigate whether the bond strength between a fiber post and root dentin can be increased by the application of a primer on the BC sealer. MATERIALS AND METHODS: The multilayers of materials in the root canal required 3D finite-element (FE) stress analyses (FEA) to provide precise σBS values. First, BC sealer was characterized using x-ray powder diffraction (XRD) to determine when the sealer completely set and the types of crystals formed to select which primer to apply to the sealer. We selected a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-based primer to treat the BC sealer before post cementation. Ultra-highspeed (UHS) imaging was utilized to analyze the crack initiation interface. The obtained failure force was used in FE analysis to calculate σBS. RESULTS: UHS imaging validated the fracture interface at the post-dentin junction as FEA simulations predicted. σBS values of the fiber posts placed with various material combinations in the root canal were 21.1 ± 3.4 (only cement/ post), 22.2 ± 3.4 (BC sealer/cement/post) and 28.6 ± 4.3 MPa (10-MDP primer treated BC sealer/cement/post). The 10-MDP-treated BC sealer exhibited the highest σBS (p < 0.05). CONCLUSION: The multilayer composite disk model proved reliable with diametral compression testing. The presence of BC sealer in the root canal does not reduce σBS of the fiber post. Conditioning the BC sealer layer with 10-MDP primer before fiber-post cemen-tation increases σBS.