Fully bio-based epoxy resins from lignin and epoxidized soybean oil: Rigid-flexible, tunable properties and high lignin content.

The application of epoxidized soybean oil (ESO) in thermosetting polymers is impeded by its unsatisfactory thermomechanical properties. Here, in order to address the limitation, technical lignin was modified by tung oil anhydride and then used as the hardener to compensate for the inherent flexibility defects of ESO thermosets (TLs). As the lignin content increased, a notable improvement in the activation energy of TLs was observed, attributed to the restraining effect of lignin's rigid structure on segmental relaxation. Concurrently, the tensile strength of TLs increased from 2.8 MPa to 34.0 MPa, concomitant with a decrease in elongation at break from 32.9 % to 8.0 %. Comparative analysis with TL-0 (devoid of lignin) demonstrated substantial enhancements in glass transition temperature, shape fixation ratio, and shape recovery ratio for TL-50 (comprising 50 wt% of lignin), elevating from 16.9 °C, 89.1 %, and 89.5 % to 118.6 °C, 94.0 %, and 99.3 %, respectively. These results unequivocally highlight the favorable dynamic mechanical and shape memory properties conferred upon TLs by lignin addition. While the introduction of lignin adversely affected thermal stability, a notable improvement in char yield (800 °C) was observed. Collectively, these findings underscore the potential of technical lignin as a promising bio-based curing agent for ESO.

Recent advancement in synthesizing bio-epoxy nanocomposites using lignin, plant oils, saccharides, polyphenols, and natural rubbers: A review.

Due to environmental issues, production costs, and the low recycling capability of conventional epoxy polymers and their composites, many science groups have tried to develop a new type of epoxy polymers, which are compatible with the environment. Considering the precursors, these polymers can be produced from plant oils, saccharides, lignin, polyphenol, and natural resins. The appearance of these bio-polymers caused to introduce a new type of composites, namely bio-epoxy nanocomposites, which can be classified according to the synthesized bio-epoxy, the used nanomaterials, or both. Hence, in this work, various bio-epoxy resins, which have the proper potential for application as a matrix, are completely introduced with the synthesis viewpoint, and their characterized chemical structures are drawn. In the next steps, the bio-epoxy nanocomposites are classified based on the used nanomaterials, which are carbon nanoparticles (carbon nanotubes, graphene nanoplatelets, graphene oxide, reduced graphene oxide, etc.), nano-silica (mesoporous and spherical), cellulose (nanofibers and whiskers), nanoclay and so on. Also, the features of these bio-nanocomposites and their applications are introduced. This review study can be a proper guide for developing a new type of green nanocomposites in the near future.

Photodynamic therapy on the extrusion bond strength of gutta-percha to radicular dentin sealed with bioceramic and conventional sealers.

OBJECTIVE: The aim of this study was to evaluate the influence of photodynamic therapy (PDT) on the extrusion bond strength (EBS) of gutta-percha to radicular dentin sealed with bioceramic sealers. MATERIALS AND METHODS: Sixty human-extracted mandibular premolars were used in the present study, being decoronated up to the cementoenamel junction, and secured in heat cure acrylic resin for root canal therapy. The specimens were randomly divided into groups based on conventional [2.25% sodium hypochlorite (NaOCl) + 17% EDTA] and disinfection protocols (2.25% NaOCl + PDT + 17% EDTA) (n = 10). Specimens in groups 1, 3, 5: conventional treatment modality (2.25% NaOCl + 17% EDTA). Samples in groups 2, 4, 6: adjunctive PDT treatment modality (2.25% NaOCl+ PDT+ 17% EDTA). Specimens in groups 1 and 2 were sealed with AH Plus sealer (AH). Specimens in groups 3 and 4 were sealed using Endo Sequence BC sealer, and samples in groups 5 and 6 were sealed with MTA Fillapex. All specimens were cut in the coronal and middle segments and positioned in a universal testing machine (UTM) for assessment of extrusion bond strength (EBS). ANOVA and Post-Hoc Tukey multiple comparison tests were applied for performing statistical analysis (p < 0.05). RESULTS: Coronal root samples in group 1 (2.25% NaOCl + 17% EDTA) sealed with AH Plus sealer demonstrated the highest EBS value (9.21 ± 0.62 MPa) whereas the middle-third of specimens in group 6 (2.25% NaOCl + PDT + 17% EDTA) sealed with MTA Fillapex exhibited the lowest EBS value (5.07 ± 0.17 MPa). Intergroup comparison revealed that group 3 (2.25% NaOCl + 17% EDTA) sealed with Endo Sequence BC Sealer and group 5 (2.25% NaOCl + 17% EDTA) sealed with MTA Fillapex disclosed comparable EBS results to group 1 (p > 0.05) while group 2 (2.25% NaOCl + PDT + 17% EDTA) sealed with AH Plus sealer and group 4 (2.25% NaOCl + PDT + 17% EDTA) sealed with Endo Sequence BC Sealer unveiled analogous EBS values to group 6 (2.25% NaOCl + PDT + 17% EDTA) MTA Fillapex (p > 0.05). The most noticeable failure mode in the coronal and middle thirds of non-PDT subjected groups was cohesive. CONCLUSIONS: Combination of 2.25% NaOCl with PDT  and 17% EDTA for canal disinfection with AH Plus sealer, calcium silicate sealer, and MTA-based bioceramic sealers have an unfavorable effect on the EBS of gutta-percha to the root canal wall.

Effect of three different photosensitizers in photodynamic therapy on bond strength of a calcium silicate-based sealer to radicular dentin.

To evaluate the effect of the photodynamic therapy (PDT) using with different photosensitizers on the bond strength of BioRoot RCS (BR) to radicular dentin by comparing with AH Plus (AH). The shaped root canals of 80 human mandibular premolars were divided into four groups based on the final disinfection protocol: NaOCl/EDTA, PDT with methylene Blue (MB), PDT with curcumin (CUR) and PDT with toluidine blue O (TBO) (n = 20). Each group was randomly divided into two subgroups (n = 10), according to the endodontic sealer used for obturation (n = 10). The test of push-out bond strength (PBS) was performed using an universal test machine. The data were analysed using ANOVA, Tukey post-hoc, and independent sample t-test (α = 0.05). MB-BR group showed the highest PBS at the cervical level (p < 0.05). The selection of the photosensitizer in PDT influenced adhesion of root canal sealers to radicular dentin.

A Phosphorous-Based Bi-Functional Flame Retardant Based on Phosphaphenanthrene and Aluminum Hypophosphite for an Epoxy Thermoset.

A phosphorous-based bi-functional compound HPDAl was used as a reactive-type flame retardant (FR) in an epoxy thermoset (EP) aiming to improve the flame retardant efficiency of phosphorus-based compounds. HPDAl, consisting of two different P-groups of aluminum phosphinate (AHP) and phosphophenanthrene (DOPO) with different phosphorous chemical environments and thus exerting different FR actions, exhibited an intramolecular P-P groups synergy and possessed superior flame-retardant efficiency compared with DOPO or AHP alone or the physical combination of DOPO/AHP in EP. Adding 2 wt.% HPDAl made EP composites acquire a LOI value of 32.3%, pass a UL94 V-0 rating with a blowing-out effect, and exhibit a decrease in the heat/smoke release. The flame retardant modes of action of HPDAl were confirmed by the experiments of the scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetry-Fourier transform infrared spectroscopy-gas chromatograph/mass spectrometer (TG-FTIR-GC/MS). The results indicate that the phosphorous-based FRs show different influences on the flame retardancy of composites, mainly depending on their chemical structures. HPDAl had a flame inhibition effect in the gas phase and a charring effect in the condensed phase, with a well-balanced distribution of P content in the gas/condensed phase. Furthermore, the addition of HPDAl hardly impaired the mechanical properties of the matrix due to the link by chemical bonds between them.

Phosphorus Modified Cardanol: A Greener Route to Reduce VolaTile Organic Compounds and Impart Flame Retardant Properties to Alkyd Resin Coatings.

Novel phosphorylated cardanol molecules based on phosphonate (PO3CR) and phosphate (PO4CR) functions were synthetized. Those molecules have two main actions which are described in this article: the reduction in volatile organic compounds (VOC) and the development of flame retardant (FR) properties conferred on alkyd resins used as coatings for wood specimen. Phosphorylated cardanol compounds have been successfully grafted by covalent bonds to alkyd resins thanks to an auto-oxidative reaction. The impact of the introduction of PO3CR and PO4CR on the film properties such as drying time and flexibility has been studied and the thermal and flame retardant properties through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. These studies underscored an increase in the thermal stability and FR properties of the alkyd resins. In the cone calorimeter test, the lowest pHRR was obtained with 3 wt% P of phosphate-cardanol and exhibited a value of 170 KW.m-2, which represented a decrease of almost 46% compared to the POxCR-free alkyd resins. Moreover, a difference in the mode of action between phosphonate and phosphate compounds has been highlighted. The most effective coating which combined excellent FR properties and good coating properties has been obtained with 2 wt% P of phosphate-cardanol. Indeed, the film properties were closed to the POxCR-free alkyd resin and the pHRR decreased by 41% compared to the reference alkyd resin.

Fabrication of a bi-hydroxyl-bi-DOPO compound with excellent quenching and charring capacities for lignin-based epoxy resin.

In this study, lignin-based epoxy resins (EP) were fabricated using lignin, phenol and glyoxal as crosslinking reagents. For improving the flame retardancy, a bi-DOPO compound with bi-hydroxyl structure was successfully synthesized, containing excellent quenching and charring capacities. Good pyrolysis behaviors of as-synthesized flame retardant resulted in significant quenching effect via structure decomposition to release PO and PO2 free radicals for capturing reactive H and OH radicals produced from epoxy combustion. With addition of 0.18 wt% phosphorus, epoxy composite (10% LPG-ER-4) passed V-0 rating with high limited oxygen index (LOI) value of 35.2%. Cone calorimeter tests showed that heat release (including heat release rate (HRR) and total heat release (THR)) from combustion was reduced with assistance of flame retardant. Char residue analyses illustrated that bi-hydroxyl structure in DOPO-based flame retardant benefited the formation of char layer with higher compactness and integrity to serve as a protective shell of interior epoxy matrix. Furthermore, exterior pore size of char residue was narrowed or blocked to avoid the release of heat and volatiles generated from combustion. This study provided a feasible method to improve flame retardancy of lignin-based EP and proposed flame-retardant mechanism both in gaseous and solid phases.

Production of wheat germ oil containing multilayer hydrogel dressing.

A composite wound dressing has been developed by combining different layers consisting of polymers and textiles. Wheat germ oil (WGO) loaded hydrogels have successfully formed on textile nonwovens by cross-linking sodium alginate (SA) with poly(ethylene glycol) diglycidyl ether (PEGDGE). Following freeze-drying, textile-hydrogel composites have been examined according to their physical properties, pH, fluid handling capacity, water vapour permeability, morphology, chemical structure, and cytotoxicity. Hydrogels containing WGO swelled less than pristine hydrogels. Samples with 1% WGO and no WGO showed swelling of 5.9 and 10.5 g/g after 8 h. WGO inclusion resulted in reduced, but more stable fluid handling properties, with more uniform pore distribution (100-200 µm). Moreover, the proliferation of NIH/3T3 cells significantly improved with 1% WGO contained hydrogels. Also, commercial self-adhesive dressings that secure the hydrogels to the wound area were investigated regarding transfer properties. The proposed product demonstrated 8.05 cm3/cm2/s and 541.37 g/m2/day air and water vapour permeability.

Epoxy Coatings Based on Modified Vegetable Oils for Wood Surface Protection against Fungal Degradation.

The study describes the curing and thermal behavior of a new castor oil maleic anhydride adduct/epoxy oils/5-Bromosalicylic acid coatings and their composites with wood. The epoxidized oils were flax and hemp. The kinetic parameters of the curing and thermal degradation processes were calculated. The resistance of the coated wood surfaces against Cladosporium cladosporioides, Aspergillus brasiliensis, and Penicillium chrysogenum was tested. Color changes, FT-IR and SEM were conducted before and after fungal attack. The decay resistance and color change of raw wood and wood treated samples against fungi was tested. Based on the color changes and according to ASTM D 2017, the decay resistance rating for covered samples was considered as "highly resistant". Chemical resistance and coating performance tests were also undertaken. The obtained results recommend the described materials for applications in wood protective coatings.

Development of long-persistent photoluminescent epoxy resin immobilized with europium (II)-doped strontium aluminate.

A facile approach for possible industrial production of long-persistent phosphorescence, continuing to emitting light for a long time period, smart cobbles were developed toward photoluminescent hard surfaces. The inorganic strontium aluminium oxide pigment doped with rare earth elements was added to a synthetic organic epoxy in the presence of polyamine as a hardener to make a phosphor-loaded viscous fluid that can then be hardened in a few minutes. The transparency of the solid cobbles can be accomplished easily using homogeneous dispersion of the phosphor in the epoxy resin fluid before the addition of a hardener to avoid pigment aggregation. This pigment-epoxy formula can be easily applied industrially onto flagstones surfaces under ambient conditions. The photoluminescent cobblestones demonstrated an optimum excitation wavelength at 366 nm and an emission band at 521 nm with a long-persistent phosphorescence cobble surface. The development of a translucent white colour under normal daylight, bright green under ultraviolet (UV) irradiation, bright white colour after 30 sec in the dark, and phosphorescent green colour after 75 min in the dark was indicated using Commission Internationale de l'Eclairage (CIE) Laboratory coloration measurements. The luminescent hard composite cobble exhibited a highly durable and reversible long-persistent phosphorescence light. Photoluminescence, morphological, and hardness properties as well as the elemental composition of the prepared cobbles were explored.

Flame Retardant Epoxy Composites on the Road of Innovation: An Analysis with Flame Retardancy Index for Future Development.

Nowadays, epoxy composites are elements of engineering materials and systems. Although they are known as versatile materials, epoxy resins suffer from high flammability. In this sense, flame retardancy analysis has been recognized as an undeniable requirement for developing future generations of epoxy-based systems. A considerable proportion of the literature on epoxy composites has been devoted to the use of phosphorus-based additives. Nevertheless, innovative flame retardants have coincidentally been under investigation to meet market requirements. This review paper attempts to give an overview of the research on flame retardant epoxy composites by classification of literature in terms of phosphorus (P), non-phosphorus (NP), and combinations of P/NP additives. A comprehensive set of data on cone calorimetry measurements applied on P-, NP-, and P/NP-incorporated epoxy systems was collected and treated. The performance of epoxy composites was qualitatively discussed as Poor, Good, and Excellent cases identified and distinguished by the use of the universal Flame Retardancy Index (FRI). Moreover, evaluations were rechecked by considering the UL-94 test data in four groups as V0, V1, V2, and nonrated (NR). The dimensionless FRI allowed for comparison between flame retardancy performances of epoxy composites. The results of this survey can pave the way for future innovations in developing flame-retardant additives for epoxy.

Phosphorus-Containing Flame Retardants from Biobased Chemicals and Their Application in Polyesters and Epoxy Resins.

Phosphorus-containing flame retardants synthesized from renewable resources have had a lot of impact in recent years. This article outlines the synthesis, characterization and evaluation of these compounds in polyesters and epoxy resins. The different approaches used in producing biobased flame retardant polyesters and epoxy resins are reported. While for the polyesters biomass derived compounds usually are phosphorylated and melt blended with the polymer, biobased flame retardants for epoxy resins are directly incorporated into the polymer structure by a using a phosphorylated biobased monomer or curing agent. Evaluating the efficiency of the flame retardant composites is done by discussing results obtained from UL94 vertical burning, limiting oxygen index (LOI) and cone calorimetry tests. The review ends with an outlook on future development trends of biobased flame retardant systems for polyesters and epoxy resins.

How to improve root canal filling in teeth subjected to radiation therapy for cancer.

The aim of this study was to evaluate the influence of radiation therapy on root canal sealer push-out bond strength (BS) to dentin and the sealer/dentin interface after different final irrigation solutions (NaOCl, EDTA, and chitosan). Sixty-four maxillary canines were distributed into two groups (n=30): non-irradiated and irradiated with 60 Gy. Canals were prepared with Reciproc-R50 and subdivided (n=10) for final irrigation (NaOCl, EDTA, chitosan) and filled. Three dentin slices were obtained from each root third. The first slice of each third was selected for BS evaluation, and the failure mode was determined by stereomicroscopy. SEM analysis of the sealer-dentin interface was performed in the remaining slices. Two-way ANOVA and Tukey's tests (α=0.05) were used. Lower BS (P<0.0001) was obtained after irradiation (2.07±0.79 MPa), regardless of the final irrigation solution used. The NaOCl group (P<0.001) had the lowest BS in the irradiated (1.68±0.72) and non-irradiated (2.39±0.89) groups, whereas the EDTA (irradiated: 2.14±0.77 and non-irradiated: 3.92±1.54) and chitosan (irradiated: 2.37±0.73 and non-irradiated: 3.51±1.47) groups demonstrated a higher BS (P<0.05). The highest values were observed in the coronal third (3.17±1.38) when compared to the middle (2.74±1.36) and apical ones (2.09±0.97)(P<0.0001). There were more cohesive failures and more gaps in irradiated specimens, regardless of the final solution. The present study showed that radiation was associated with a decrease in BS, regardless of the final solution used, whereas chitosan increased BS in teeth subjected to radiation therapy.

How to improve root canal filling in teeth subjected to radiation therapy for cancer

Abstract The aim of this study was to evaluate the influence of radiation therapy on root canal sealer push-out bond strength (BS) to dentin and the sealer/dentin interface after different final irrigation solutions (NaOCl, EDTA, and chitosan). Sixty-four maxillary canines were distributed into two groups (n=30): non-irradiated and irradiated with 60 Gy. Canals were prepared with Reciproc-R50 and subdivided (n=10) for final irrigation (NaOCl, EDTA, chitosan) and filled. Three dentin slices were obtained from each root third. The first slice of each third was selected for BS evaluation, and the failure mode was determined by stereomicroscopy. SEM analysis of the sealer-dentin interface was performed in the remaining slices. Two-way ANOVA and Tukey's tests (α=0.05) were used. Lower BS (P<0.0001) was obtained after irradiation (2.07±0.79 MPa), regardless of the final irrigation solution used. The NaOCl group (P<0.001) had the lowest BS in the irradiated (1.68±0.72) and non-irradiated (2.39±0.89) groups, whereas the EDTA (irradiated: 2.14±0.77 and non-irradiated: 3.92±1.54) and chitosan (irradiated: 2.37±0.73 and non-irradiated: 3.51±1.47) groups demonstrated a higher BS (P<0.05). The highest values were observed in the coronal third (3.17±1.38) when compared to the middle (2.74±1.36) and apical ones (2.09±0.97)(P<0.0001). There were more cohesive failures and more gaps in irradiated specimens, regardless of the final solution. The present study showed that radiation was associated with a decrease in BS, regardless of the final solution used, whereas chitosan increased BS in teeth subjected to radiation therapy.

Effect of photodynamic therapy and non-thermal plasma on root canal filling: analysis of adhesion and sealer penetration.

OBJECTIVE: The aim of this study was to evaluate the effect of photodynamic therapy (PDT) and non-thermal plasma (NTP) on adhesion and sealer penetration in root canals. MATERIAL AND METHODS: Sixty single-rooted premolars were used. The teeth were prepared using a crown-down technique. NaOCl and EDTA were used for irrigation and smear layer removal, respectively. The root canals were divided into three groups: control, PDT, and NTP. After treatments, the roots were filled using gutta-percha and either AH Plus (AHP) or MTA Fillapex (MTAF) sealers. Samples were sectioned at 4, 8, and 12 mm from the apex (1-mm slices)and analyzed by the push-out bond strength test (adhesion) and confocal laser scanning microscopy (sealer penetration). Data were statistically evaluated using Kruskal-Wallis, Dunn's, and Spearman's tests. RESULTS: Regarding AHP, bond strength was similar in the NTP group and in the control group, but significantly lower in the PDT group. As to MTAF, both therapies showed lower values than the control group. In the confocal analysis of AHP, maximum and mean penetration, and penetrated area were statistically higher in the control group than in the PDT and NTP groups. Penetrated perimeter was similar among groups. Regarding MTAF, all parameters yielded better results in the NTP than in the control group. The PDT and control groups showed similar results except for penetrated area. CONCLUSION: PDT and plasma therapy affected the adhesion and sealer penetration of root canals filled with AH Plus and MTA Fillapex and there is no positive correlation between adhesion and sealer penetration.

Effect of photodynamic therapy and non-thermal plasma on root canal filling: analysis of adhesion and sealer penetration

Abstract Objective The aim of this study was to evaluate the effect of photodynamic therapy (PDT) and non-thermal plasma (NTP) on adhesion and sealer penetration in root canals. Material and Methods Sixty single-rooted premolars were used. The teeth were prepared using a crown-down technique. NaOCl and EDTA were used for irrigation and smear layer removal, respectively. The root canals were divided into three groups: control, PDT, and NTP. After treatments, the roots were filled using gutta-percha and either AH Plus (AHP) or MTA Fillapex (MTAF) sealers. Samples were sectioned at 4, 8, and 12 mm from the apex (1-mm slices)and analyzed by the push-out bond strength test (adhesion) and confocal laser scanning microscopy (sealer penetration). Data were statistically evaluated using Kruskal-Wallis, Dunn's, and Spearman's tests. Results Regarding AHP, bond strength was similar in the NTP group and in the control group, but significantly lower in the PDT group. As to MTAF, both therapies showed lower values than the control group. In the confocal analysis of AHP, maximum and mean penetration, and penetrated area were statistically higher in the control group than in the PDT and NTP groups. Penetrated perimeter was similar among groups. Regarding MTAF, all parameters yielded better results in the NTP than in the control group. The PDT and control groups showed similar results except for penetrated area. Conclusion PDT and plasma therapy affected the adhesion and sealer penetration of root canals filled with AH Plus and MTA Fillapex and there is no positive correlation between adhesion and sealer penetration.

Influence of solvents on the bond strength of resin sealer to intraradicular dentin after retreatment.

This study evaluated the removal of filling material with ProTaper Universal Rotary Retreatment system (PTR) combined with solvents and the influence of solvents on the bond strength (PBS) of sealer to intraradicular dentin after canal reobturation. Roots were endodontically treated and distributed to five groups (n = 12). The control group was not retreated. In the four experimental groups, canals were retreated with PTR alone or in combination with xylol, orange oil, and eucalyptol. After filling material removal, two specimens of each group were analysed by SEM and µCT to verify the presence of filling remnants on root canal walls. The other roots were reobturated and sectioned in 1-mm-thick dentin slices that were subjected to the push-out test. Data were analysed by two-way ANOVA and Tukey's test (α = 0.05). SEM and µCT analysis revealed that all retreatment techniques left filling remnants on canal walls. The control group (3.47 ± 1.21) presented significantly higher (p < 0.05) PBS than the experimental groups. The groups retreated with PTR alone (2.59 ± 0.99) or combined with xylol (2.54 ± 0.77) and orange oil (2.32 ± 0.93) presented similar bond strength (p > 0.05), and differed significantly from the group with eucalyptol (1.89 ± 0.63). The solvents reduced the PBS of the sealer to dentin and no retreatment technique promoted complete removal of filling material.

Double dye technique and fluid filtration test to evaluate early sealing ability of an endodontic sealer.

OBJECTIVES: The aim of the present study is to evaluate the possible correlation between sealer penetration into dentinal tubules and sealing ability both in presence and absence of smear layer. MATERIALS AND METHODS: Fourteen maxillary central incisors were treated with 5.25 % NaOCl +10 % EDTA to remove the smear layer (SL-free group) or 5.25 % NaOCl without EDTA (SL group). Root canals were filled using #25 Thermafil Obturators with Topseal sealer labelled with 0.1 wt% rhodamine B. Sealing ability was measured as fluid filtration rate with a fluid-flow meter using water supplemented with 0.3 % calcein fluorescent dye. Specimens were sectioned, observed under confocal microscope to co-localize the presence of sealer (rhodamine B labelling) into dentinal tubules and gaps (calcein labelling) into the root canal. The depth of sealer penetration into dentinal tubules and the percentage of sealer penetration around the root canal were measured at 3, 5 and 8 mm from the apex. RESULTS: No significant differences between groups were observed in fluid filtration rate nor in depth of calcein penetration. Sealer penetration depth and percentage into dentinal tubules were not significantly different between groups, except at 8-mm level in absence of smear layer. CONCLUSION: Sealer penetration at 3- and 5-mm levels was not influenced by smear layer while it was significantly reduced at 8-mm level. Fluid filtration rate was not correlated either with depth of calcein penetration nor with sealer penetration into dentinal tubules. CLINICAL RELEVANCE: The sealing ability of Topseal sealer is not affected by presence or absence of smear layer.

Influence of solvents on the bond strength of resin sealer to intraradicular dentin after retreatment

Abstract This study evaluated the removal of filling material with ProTaper Universal Rotary Retreatment system (PTR) combined with solvents and the influence of solvents on the bond strength (PBS) of sealer to intraradicular dentin after canal reobturation. Roots were endodontically treated and distributed to five groups (n = 12). The control group was not retreated. In the four experimental groups, canals were retreated with PTR alone or in combination with xylol, orange oil, and eucalyptol. After filling material removal, two specimens of each group were analysed by SEM and µCT to verify the presence of filling remnants on root canal walls. The other roots were reobturated and sectioned in 1-mm-thick dentin slices that were subjected to the push-out test. Data were analysed by two-way ANOVA and Tukey’s test (α = 0.05). SEM and µCT analysis revealed that all retreatment techniques left filling remnants on canal walls. The control group (3.47 ± 1.21) presented significantly higher (p < 0.05) PBS than the experimental groups. The groups retreated with PTR alone (2.59 ± 0.99) or combined with xylol (2.54 ± 0.77) and orange oil (2.32 ± 0.93) presented similar bond strength (p > 0.05), and differed significantly from the group with eucalyptol (1.89 ± 0.63). The solvents reduced the PBS of the sealer to dentin and no retreatment technique promoted complete removal of filling material.

Immunoelectron Microscopy of Cryofixed and Freeze-Substituted Plant Tissues.

Cryofixation and freeze-substitution techniques provide excellent preservation of plant ultrastructure. The advantage of cryofixation is not only in structural preservation, as seen in the smooth plasma membrane, but also in the speed in arresting cell activity. Immunoelectron microscopy reveals the subcellular localization of molecules within cells. Immunolabeling in combination with cryofixation and freeze-substitution techniques provides more detailed information on the immunoelectron-microscopic localization of molecules in the plant cell than can be obtained from chemically fixed tissues. Here, we introduce methods for immunoelectron microscopy of cryofixed and freeze-substituted plant tissues.