RESUMO

It is well known that Hirshfeld surfaces provide an easy and straightforward way of analysing intermolecular interactions in the crystal environment. The use of atomic Hirshfeld surfaces has also demonstrated that such surfaces carry information related to chemical bonds which allow a deeper evaluation of the structures. Here we briefly summarize the approach of atomic Hirshfeld surfaces while further evaluating the kind of information that can be retrieved from them. We show that the analysis of the metal-centre Hirshfeld surfaces from structures refined via Hirshfeld Atom Refinement (HAR) allow accurate evaluation of contacts of type M...H, and that such contacts can be related to the overall shape of the surfaces. The compounds analysed were tetraaquabis(3-carboxypropionato)metal(II), [M(C4H3O4)2(H2O)4], for metal(II)/M = manganese/Mn, cobalt/Co, nickel/Ni and zinc/Zn. We also evaluate the sensitivity of the surfaces by an investigation of seemingly flat surfaces through analysis of the curvature functions in the direction of C-C bonds. The obtained values not only demonstrate variations in curvature but also show a correlation with the hybridization of the C atoms involved in the bond.

RESUMO

Three 2,4-diarylpyrroles were synthesized starting from 4-nitrobutanones and the crystal structures of two derivatives were analysed. These are 4-(4-methoxyphenyl)-2-(thiophen-2-yl)-1H-pyrrole, C15H13NOS, and 3-(4-bromophenyl)-2-nitroso-5-phenyl-1H-pyrrole, C16H11BrN2O. Although pyrroles without substituents at the α-position with respect to the N atom are very air sensitive and tend to polymerize, we succeeded in growing an adequate crystal for X-ray diffraction analysis. Further derivatization using sodium nitrite afforded a nitrosyl pyrrole derivative, which crystallized in the triclinic space group P-1 with Z = 6. Thus, herein we report the first crystal structure of a nitrosyl pyrrole. Interestingly, the co-operative hydrogen bonds in this NO-substituted pyrrole lead to a trimeric structure with bifurcated halogen bonds at the ends, forming a two-dimensional (2D) layer with interstitial voids having a radius of 5 Å, similar to some reported macrocyclic porphyrins.

RESUMO

Density Functional Theory (DFT) is extensively used in theoretical and computational chemistry to study molecular and crystal properties across diverse fields, including quantum chemistry, materials physics, catalysis, biochemistry, and surface science. Despite advances in DFT hardware and software for optimized geometries, achieving consensus in molecular structure comparisons with experimental counterparts remains a challenge. This difficulty is exacerbated by the lack of automated bond length comparison tools, resulting in labor-intensive and error-prone manual processes. To address these challenges, we propose MolGC, a Molecular Geometry Comparator algorithm that automates the comparison of optimized geometries from different theoretical levels. MolGC calculates the mean absolute error (MAE) of bond lengths by integrating data from various DFT software. It provides interactive and customizable visualization of geometries, enabling users to explore different views for enhanced analysis. In addition, it saves MAE computations for further analysis and offers a comprehensive statistical summary of the results. MolGC effectively addresses complex graph labeling challenges, ensuring accurate identification and categorization of bonds in diverse chemical structures. It achieves a 98.91% average rate in correct bond label assignments on an antibiotics dataset, showcasing its effectiveness for comparing molecular bond lengths across geometries of varying complexity and size. The executable file and software resources for running MolGC can be downloaded from https://github.com/AbimaelGP/MolGC/tree/main .

Assuntos

RESUMO

INTRODUCTION: To assess the effect of combinations of two different endodontic sealers used in initial and endodontic retreatment on the bond strength of the secondary obturation and the penetrability of the sealers. METHODS: Forty-eight mandibular premolars were used, receiving standardized endodontic access and biomechanical preparation. Twenty-four teeth received AH Plus sealer (AHP) in primary obturation and the others received Bio-C Sealer (BCS). Retreatment protocol was performed with an R50 instrument. The samples were further subdivided into four groups (n = 12) based on the combination of primary/secondary obturation sealers: AHP/AHP; AHP/BCS; BCS/AHP; and BCS/BCS. Four samples from each subgroup received the addition of fluorophores to the sealer for penetrability analysis using laser scanning confocal fluorescence microscopy. The root portion on the 8 push-out samples was sectioned into 6 slices of 1.0 mm. Bond strength (BS) was assessed using a universal testing machine until displacement of the filling mass. Failure pattern was evaluated under a stereomicroscope (20× magnification). BS data were analyzed using two-way analysis of variance followed by Tukey's test (P < .05), and the association between the failure pattern and BS value was assessed using the chi-square test (P < .05). Penetrability was qualitatively evaluated. RESULTS: The highest BS values were observed in the AHP/AHP (4.54 ± 1.5 MPa) and BCS/AHP (5.00 ± 1.0 MPa) groups (P < .05), with a higher percentage of adhesive failures to the filling material for all groups. Laser scanning confocal fluorescence microscopy images indicated greater penetrability of AHP compared to BCS, both in initial treatment and retreatment. CONCLUSION: AHP sealer exhibited higher BS and greater penetrability compared to BCS sealer.

Assuntos

RESUMO

The objective of this work was to assess the efficacy of different proteolytic agents on the bond strength of pit and fissure sealants to bovine enamel. Eighty-four bovine enamel specimens were randomly assigned in groups according to the pit and fissure sealant applied (HelioSeal F or Dyad Flow). Then, the specimens were subdivided according to the proteolytic agent used (n = 7): Group 1, distilled water (control); Group 2, 10 wt.% Tergazyme®; Group 3, 10 wt.% ZYME®; Group 4, 10% papain gel; Group 5, 10% bromelain gel; and Group 6, 5.25 wt.% sodium hypochlorite. The cell viability of the proteolytic solutions was assessed through the MTT assay. The proteolytic agents were applied on the enamel surface prior to the acid-etching procedure; then, the pit and fissure sealants were placed. The micro-shear bond strength was evaluated after 24 h or 6 months of water storing at 37 °C. Representative SEM images were taken for each experimental group. The bond strength data were statistically analyzed by a three-way ANOVA test using a significance level of α = 0.05. Bromelain and papain proteolytic solutions did not exert any cytotoxic effect on the human dental pulp cells. After 24 h and 6 months of aging, for both pit and fissure sealants, sodium hypochlorite, papain, bromelain, and Tergazyme® achieved statistically significant higher bond strength values (p < 0.05). Irrespective of the deproteinizing agent used, Dyad Flow resulted in a better bond strength after 6 months of aging. The type 1 etching pattern was identified for sodium hypochlorite, papain, and bromelain. Tergazyme®, papain, and bromelain demonstrated efficacy in deproteinizing enamel surfaces prior to acid etching, leading to the improved bond strength of pit and fissure sealants. Clinically, this suggests that these proteolytic agents can be considered viable alternatives to traditional methods for enhancing sealant retention and longevity. Utilizing these agents in dental practice could potentially reduce sealant failures.

RESUMO

CONTEXT: The debate over whether kinetic energy (KE) or potential energy (PE) are the fundamental energy components that contribute to forming covalent bonds has been enduring and stimulating over time. However, the supremacy of these energy components in reactions where multiple bonds are simultaneously formed or broken has yet to be explored. In this study, we use the reaction electronic flux (REF), an effective tool for investigating changes in driving electronic activity when bond formation or dissociation occurs in a chemical reaction, to examine the fluctuations in the KE and PE in a multi-bond reaction. To that end, the activation of CO 2 by low-valent group 14 catalysts through a concerted σ -bond metathesis mechanism is analyzed. The findings of this preliminary study suggest that the REF can be utilized as a tool to rationalize alterations in the KE and PE in a multi-bond reaction. Specifically, analyses across the reaction coordinate reveal that changes in the KE and PE precede activation in the REF, stimulating the electronic activity where bond formation or dissociation processes dominate. METHODS: The activation of CO 2 by the low-valent LEH catalysts (L = N,N'-bis(2,6-diisopropyl phenyl)- ß -diketiminate; E = Si, Ge, Sn, and Pb) was studied along the reaction coordinate at the M06-2X/6-31 G(d,p)-LANL2DZ(E) level of theory. The respective minimum energy path calculations were obtained using the intrinsic reaction coordinate (IRC) procedure. The reaction electronic flux (REF) was calculated through the computation of the electronic chemical potential using the frontier molecular orbital approximation. Mayer bond orders along the reaction coordinate have been determined using the NBO 3.1 program in Gaussian16. Most of the reaction coordinate quantities reported in this study (REF, KE, PE, among others) have been determined using the Kudi program and custom Python scripts.

RESUMO

OBJECTIVE: Assess dog owners' concern levels and veterinary care decisions pertaining to behaviors that might signify pain before and after receiving brief pain-related educational information. Additionally, evaluate dog owners' perceptions of a modified version of the Colorado State University Canine Acute Pain Scale to identify their dog's pain level, determine whether they should take their dog to the veterinarian, and describe their dog's pain to their veterinarian. SAMPLE: 367 survey respondents who resided in the US and were the primary caretaker of at least 1 dog. METHODS: An electronic survey was created in Qualtrics and distributed via Prolific. Data were analyzed. RESULTS: When assessing differences between participants' concern levels before and after educational pain-related information, significant differences were found for 2 of the 3 scenarios. Significant differences were also found between participants' veterinary-related behaviors before and after educational pain-related information for all 3 scenarios. The most common reasons for not seeking immediate veterinary care included elements related to cost, convenience, and dog-related stress during veterinary visits. Most participants reported finding the Canine Acute Pain Scale useful for identifying their dog's pain level (89%), determining whether they should take their dog to the veterinarian (84%), and describing their dog's pain to their veterinarian (89%). CLINICAL RELEVANCE: Owners' interpretations of and subsequent actions (or inactions) to behaviors that might suggest pain carry great implications for companion animals' overall well-being. Following exposure to brief educational material about signs and symptoms of canine pain, owners in our study reported significant increases in stated concern related to their dog's change in behavior and intention to seek veterinary care. These findings suggest that even very brief pain-related educational material can have a positive impact on owners' perceptions of canine behavioral changes and increase the possibility that they will seek veterinary care.

Assuntos

RESUMO

OBJECTIVE: To evaluate the in vitro influence of prior silane application on the microshear bond strength (µSBS) of Scotchbond Universal Plus to glass ceramic. MATERIALS AND METHODS: Thirty blocks of lithium disilicate ceramic were etched with hydrofluoric acid for 20 s and distributed into Group 1 (no silane and no adhesive), Group 2 (adhesive), Group 3 (silane + adhesive). Three cylinders of resin cement were made on each ceramic block. Five blocks (n = 15 cylinders) were subjected to the µSBS test after 24 h, and the other five blocks (n = 15 cylinders) were tested after 6 months of water storage. RESULTS: According to two-way ANOVA, followed by Tukey's test, the means of µSBS (MPa), denoted by different letters, show significant differences (p < 0.05): after 24 h-Group 1 (31.7)B, Group 2 (43.3)A, and Group 3 (31.3)B; after 6 months-Group 1 (14.8)B, Group 2 (33.6)A, and Group 3 (30.3)A. After 6 months of storage, there was a significant decrease in µSBS for Groups 1 and 2, along with an increase in adhesive failures across all groups. CONCLUSIONS: Prior application of silane did not increase the µSBS between Scotchbond Universal Plus and ceramic, and there was degradation at the bond interface over time. CLINICAL SIGNIFICANCE: Prior application of a silane agent is not necessary when using Scotchbond Universal Plus for bonding to glass ceramics. Regardless of the prior application of silane, there is degradation at the bond interface over time.

Assuntos

RESUMO

CONTEXT: Hydrazones have been studied for a myriad of chemical and physiochemical properties, such as sensors, chelators and numerous biological activities. Experimental data indicates that hydrazones are unstable under cathodic potentials irrespective of the solvent. The single electron reduction of hydrazones to produce radical anions result in unstable species that cleaves at the N-N bond in a heterolytic manner. The literature has proposed a mechanism favouring the radical on the imine moiety, however in this study DFT calculations suggest the radical on the amine product is more likely upon bond cleavage. This has implications on electrochemical mechanisms, and the active molecule in biological studies viz the method of delivery to target areas. METHODS: Density functional theory calculations were carried out using the GAMESS software package. The structures were optimized in the gas phase (B3LYP/6-31G(d,p)) as indicated by the absence of imaginary frequencies in the Hessian, and in CH3CN (B3LYP/6-31G(d,p)/SMD) with the Pople polarization functions. As a comparison, selected pathways were fully optimized using PBE0/6-31G(d,p) and PBE0/6-31G(d,p)/SMD for gas phase and CH3CN, respectively with the Pople polarization functions. The values were not significantly different (< 5% difference). As such only the B3LYP is evaluation is discussed.

RESUMO

This study aimed to evaluate the influence of radiotherapy and different endodontic treatment protocols on the bond strength to pulp chamber dentin. Eighty mandibular molars were randomly divided into two groups (n = 40): non-irradiated and irradiated (60 Gy). The pulp chambers were sectioned, and each group was subdivided (n = 8), according to the endodontic treatment protocol: no treatment (Control); Single-visit; Two-visits; Immediate dentin sealing (IDS) + single-visit; and IDS + two-visits. Each endodontic treatment visit was simulated through irrigation with 2.5% NaOCl, 17% EDTA and distilled water. IDS was performed by actively applying two coats of a universal adhesive to the lateral walls of the pulp chamber. After, the pulp chambers were restored with resin composite and four sticks were obtained for microtensile test. In addition, the dentin of the pulp chamber roof was assessed for surface roughness, chemical composition, and topography after each treatment protocol. Two-way ANOVA, Tukey's post hoc, Mann-Whitney, Kruskal-Wallis and Dunn's post hoc were performed (α = 5%). The treatment protocol affected bond strength (p < 0.05), while the irradiation did not (p > 0.05). The control group presented the highest values (p < 0.05). The single-visit group demonstrated better performance compared to the other groups (p < 0.05), which did not differ from each other (p > 0.05) The use of IDS changed the surface roughness (p < 0.05), chemical composition (p < 0.05) and topography of the dentin. In conclusion, the treatment protocol influenced dentin adhesion, while irradiation did not.

RESUMO

OBJECTIVE: This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin. MATERIALS AND METHODS: Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface. RESULTS: Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure). CONCLUSION: Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition. CLINICAL RELEVANCE: Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Assuntos

RESUMO

INTRODUCTION: The purpose of this study was to evaluate whether the mixing method of AH Plus Jet sealer affects its physicochemical and mechanical properties. METHODS: The properties of AH Plus Jet sealer were analyzed when mixed using either the Auto Mix Tip or manual mixing. The evaluated properties included radiopacity (n = 5), initial and final setting times (n = 5), flow (n = 5), and solubility (n = 3), following specifications outlined in ISO 6876/2012 and ADA Nº 57/2000. pH levels were measured at intervals of 3, 24, 72, and 168 hours (n = 10). The push-out bond strength test was conducted using a universal testing machine and using bovine teeth (n = 30). Failure modes were analyzed with stereomicroscopy. Porosity was evaluated under micro-CT (n = 5), and scanning electron microscopy was also performed (n = 5). One-way analysis of variance and Tukey, unpaired t-tests, or Mann-Whitney tests were used with a significance level of 5%. RESULTS: The Auto Mix exhibited a radiopacity value of 12.11 mmAl, whereas manual mixing resulted in 12.55 mmAl (P > .05). For initial and final setting times, Auto Mix showed 901 minutes and 1779 minutes, respectively, while manual mixing recorded values of 631 minutes and 1504 minutes (P < .05). In terms of flow, Auto Mix demonstrated higher values (25.26 mm) than manual mixing (21.71 mm) (P < .05). No statistical differences were observed between the two methods for solubility and pH (P > .05). Manual mixing presented a higher bond strength value (14.52 MPa) than Auto Mix (9.81 MPa) (P < .05). The mixed failure mode was the most frequent outcome for both methods. The highest porosity was observed for Auto Mix (P < .05). Scanning electron microscopy analysis revealed that manual mixing resulted in a smoother surface with fewer pores and smaller, more evenly distributed agglomerates compared to automatic mixing. CONCLUSION: The mixing method employed for AH Plus Jet sealer influences some physicochemical and mechanical properties of the material.

Assuntos

RESUMO

Ligand-protected gold clusters remain potential building blocks for envisaged molecular materials. The archetypal Au38(SR)24 cluster can be viewed as a robust template for the fusion of two Au25(SR)18 - cluster units, retaining a bi-icosahedral Au23 core. Via electrochemical properties, the overall charge state can be selectively tuned, enabling the access of 14 valence electron (ve) species featuring a single intercluster bond and nearby charge from -1 to +3, achieving related species bearing 15- to 11-ve with variable intercluster bond orders. Here, we explore the characteristics of intermediate intercluster bond orders in order to provide insights into the plausible electron communication between the constituent building blocks, with Au38(SR)24, as a representative template. Our results denote a small structural variation along -1 to +3 charge states, provided by the core-protecting ligand interaction, which is enhanced towards more oxidized species. The remaining unpaired electron from intermediate intercluster bond orders of 1.5 for Au38(SR)24 1-, 1.5 for Au38(SR)24 1+, and 2.5 for Au38(SR)24 3+, holds delocalized characteristics between the building block units, favoring electron communication for conductive and cooperative cluster aggregates. Such features are relevant for the formation of molecular electronic device applications, favoring the rationalization prior to engaging in explorative synthesis of larger ligand-protected cluster aggregates.

RESUMO

Objective: This study aimed to evaluate the bond strength of a universal adhesive to dentin (µTBS) using different time periods of airborne particle abrasion (APA) and two types of acid etching. Methods: Seventy-two human third molars were divided into 9 groups (n=8) according to dentin pretreatment: APA duration (0, 5, or 10s) and acid etching (no acid - NA, 37% phosphoric acid - PhoA, or 1% phytic acid - PhyA). APA was performed at a 0.5 cm distance and air pressure of 60 psi using 50 µm aluminum oxide particles. Afterwards, two coats of Single Bond Universal adhesive (3M) were applied to the dentin surface. Composite blocks were built using the incremental technique, sectioned into 1×1 mm slices and subjected to microtensile bond strength (µTBS) testing. Fracture patterns and surface topography of each dentinal pretreatment were evaluated using a Scanning electron microscope (SEM). Bond strength data were analyzed using two-way ANOVA and Bonferroni post-hoc tests. Results: The group that received pretreatment with 5s APA and PhoA presented higher µTBS values among all groups, which was statistically different when compared with the PhoA, 10APA+PhoA, and 5APA+PhyA groups. PhyA did not significantly influence the bond strength of the air-abraded groups. Finally, adhesive failure was considered the predominant failure in all groups. Conclusion: Dentin pretreated by airborne particle abrasion using aluminum oxide demonstrated an increase in bond strength when abraded for 5 seconds and conditioned with phosphoric acid in a universal adhesive system.

RESUMO

The synthesis, crystallization and characterization of a tri-fluoro-methane-sulfonate salt of 5,10,15,20-tetra-kis-(1-benzyl-pyridin-1-ium-4-yl)-21H,23H-por-phy-rin, C68H54N8 4+·4CF3SO3 -·4H2O, 1·OTf, are reported in this work. The reaction between 5,10,15,20-tetra-kis-(pyridin-4-yl)-21H,23H-porphyrin and benzyl bromide in the presence of 0.1 equiv. of Ca(OH)2 in CH3CN under reflux with an N2 atmosphere and subsequent treatment with silver tri-fluoro-methane-sulfonate (AgOTf) salt produced a red-brown solution. This reaction mixture was filtered and the solvent was allowed to evaporate at room temperature for 3 d to give 1·OTf. Crystal structure determination by single-crystal X-ray diffraction (SCXD) revealed that 1·OTf crystallizes in the space group P21/c. The asymmetric unit contains half a porphyrin mol-ecule, two tri-fluoro-methane-sulfonate anions and two water mol-ecules of crystallization. The macrocycle of tetra-pyrrole moieties is planar and unexpectedly it has coordinated CaII ions in occupational disorder. This CaII ion has only 10% occupancy (C72H61.80Ca0.10F12N8O16S4). The pyridinium rings bonded to methyl-ene groups from porphyrin are located in two different arrangements in almost orthogonal positions between the plane formed by the porphyrin and the pyridinium rings. The crystal structure features cation⋯π inter-actions between the CaII atom and the π-system of the phenyl ring of neighboring mol-ecules. Both tri-fluoro-methane-sulfonate anions are found at the periphery of 1, forming hydrogen bonds with water mol-ecules.

RESUMO

This study evaluated the effect on adhesive layer thickness, bond strength, and adhesive failure pattern of the application of universal adhesive (Scotchbond Universal) using either manual or rotary brush in dentin previously impregnated with bioceramic sealer (Sealer Plus BC) using a manual brush, at 24 h and 1 year. Eighty-eight bovine crowns were divided into four groups (n = 22) according to the intervention: (i) use of bioceramic sealer and adhesive application using manual brush, (ii) use of bioceramic sealer and adhesive application using rotary brush, (iii) use of resin sealer and adhesive application using manual brush, and (iv) use of resin sealer and adhesive application using rotary brush. Subsequently, specimens were restored with a composite resin (Filtek Z-250). Adhesive layer thickness was evaluated using confocal microscopy. Bond strength was assessed using the microtensile bond strength test, and adhesive failure pattern was evaluated under a stereomicroscope. Data were analyzed using two-way ANOVA/Tukey tests. Specimens where a rotary brush had been used exhibited lower adhesive layer thickness. Specimens treated with resin sealer and using a manual brush showed lower bond strength values and a higher occurrence of adhesive failures at 24 h and 1 year than specimens treated with bioceramic sealer and using rotary brush for adhesive application.

Assuntos

RESUMO

AIM: The aim of this study was to compare the microtensile bond strength (µTBS) and failure mode of 4 different universal adhesive systems (UAs) on human dentin. MATERIALS AND METHODS: The study sectioned the occlusal thirds of 32 human third molars and divided them into 4 groups based on the adhesive system used. Group A: Palfique Universal Bond, Group B: Single Bond Universal, Group C: All-Bond Universal, and Group D: One Coat 7 Universal. The specimens underwent a 10,000-cycle thermocycling ageing process prior to testing (n = 32). Afterwards, 8 beams were obtained per group and subjected to µTBS testing using a digital universal testing machine at a speed of 1 mm/min. The microtensile bond strength values were analysed in Megapascals (MPa), and the failure mode was evaluated using a stereomicroscope. Welch's parametric ANOVA with robust variance and the Games-Howell post hoc test were used for µTBS comparisons, and Fisher's exact test was used to determine the association between adhesive type and failure mode. The significance level was set at P < .05. RESULTS: Group D showed a significantly higher µTBS than groups A (P < .001) and B (P < .001), but no significant difference was observed with group C (P= .075). Furthermore, groups B and C showed significantly higher µTBS than group A (P< .001 and P < .001, respectively), but there was no significant difference between groups B and C (P = .132). Additionally, group A exhibited a significant association with an adhesive failure mode (P < .05), whereas groups B, C, and D were significantly associated with a mixed failure mode (P < .05). CONCLUSION: The One Coat 7 Universal adhesive system showed higher microtensile bond strength values and higher chemical interaction with dentin compared to Palfique Universal Bond and Single Bond Universal. However, no significant differences were observed compared to All-Bond Universal.

RESUMO

Aims: The objective of the study was to evaluate two translucent resin composite systems for customizing light-polymerized fiber posts with light-emitting diode (LED) curing units regarding adhesion using conventional cement at 24 h and 6 months. Settings and Design: This was an experimental in vitro study. Methods: Forty roots were prepared and divided into four groups (n = 10): ZV-Z350 resin and LED Valo; ZR-Z350 resin and LED Radii-Cal; OV-Opallis resin and LED Valo; and OR-Opallis resin and LED Radii-Cal. The fiber post was customized and cemented with conventional resin cement and was photoactivated by two different sources. Statistical Analysis Used: The data were subjected to two-way ANOVA and Tukey's post hoc tests (P = 0.05). The data regarding the pattern of adhesive failures were described in terms of the frequency of occurrence in each third of the postspace. Results: Both at 24 h and 6 months, bond strength among groups was similar, regardless of the analyzed postspace 3rd (P > 0.05). Adhesive failure Type 4 was the most frequent in all thirds. Conclusions: Customizing the fiber post with Z350 and Opallis has the same effect on bond strength and adhesive failure pattern, regardless of the LED curing units used for photopolymerization.

RESUMO

Aim: This study aimed to evaluate the effects of polywave and monowave light-emitting diode curing units on the microtensile bond strength and failure types of three bulk-fill resin composites. Materials and Methods: This in vitro experimental study was performed on 180 microbars obtained from human third molars and were distributed into 12 groups according to the type of bulk-fill resin composite and the light-curing unit. Third molars were restored using Filtek One Bulk Fill Restorative, Tetric® N-Ceram Bulk Fill, and Opus Bulk Fill resin composites was light-cured with Elipar Deep Cure L and Valo in three modes: standard, high power, and extra power. Subsequently, microtensile analysis was carried out with a universal testing machine and the type of failure with an optical stereomicroscope. For statistical analysis, the Kruskal-Wallis H-test was used, with the Bonferroni post hoc test and Fisher's exact test, considering a significance of p<0.05. Results: There were significant differences in the microtensile bond strength between the Filtek One Bulk Fill restorative and Opus Bulk-Fill (p = 0.042) when light was cured with the polywave unit at standard power. On the other hand, the Filtek One Bulk Fill Restorative and Opus Bulk Fill resins showed significant differences in microtensile bond strength when light was cured with the monowave unit compared with the polywave unit (p<0.05). Conclusion: The presence of alternative photoinitiator systems that are more reactive than camphorquinone produced higher microtensile bond strength in Tetric N-Ceram Bulk Fill and Opus Bulk Fill resins when light-cured with a high and standard polywave unit, respectively, compared to Filtek One Bulk Fill resins. Finally, Tetric N-Ceram Bulk Fill and Opus Bulk Fill resins had the highest percentage of mixed failures, while Filtek One Bulk Fill resin had adhesive failures, which was related to its lower microtensile bond strength.

RESUMO

Introduction: The final step of irrigation has been considered to of increase the bonding strength of filling material to dentin. This study investigated the impact of three final-step irrigation methods on the endodontic sealer bond strength to dentin by using a micro push-out test. Materials and Methods: Palatal roots of human maxillary molars were cleaned and shaped and randomly divided in six groups (n=15) according to the final-step irrigation method and the type of root canal sealer used. The solutions used for the final-step irrigation were 17% ethylenediaminetetraacetic acid and 2.5% sodium hypochlorite, which underwent three methods: 1) syringe-needle irrigation/conventional, 2) passive ultrasonic irrigation, and 3) XP-endo Finisher agitation. The root canal sealers used were: EndoSequence BC Sealer, and AH-Plus sealer. Roots were obturated with the single cone technique and then, cross-sectioned in 2-mm-thick slices (3 slices from each root). Push-out test was performed on the sliced specimens (cervical, middle, and apical thirds) with a universal testing machine. Bond strength values were recorded in megapascal (MPa). Subsequently, each specimen was longitudinally split to verify the type of failure. Data analysis was performed using Johnson transformation, three-way analysis of variance, Tukey's post-hoc tests, and the partial Eta squared test. Results: There were significant differences in bond strength between the sealers [AH: 4.46±2.24 and BC: 3.47±2.19 MPa (P<0.001)]; between final-step irrigation methods [passive ultrasonic irrigation: 4.52±2.25, XP-endo Finisher: 3.93±3.93 and syringe-needle irrigation/conventional: 3.37±2.51 MPa (P<0.001)], and between the root canal thirds represented by the sliced specimens [cervical: 5.45±2.39, middle: 4.14±1.99 and apical: 2.30±1.30 MPa (P<0.001)]. The interaction between the variables had no significance (P>0.05). Conclusion: Agitation of the final irrigating solution may improve the bonding of the sealer to canal walls. AH-Plus sealer had the highest bond strength. The bond strength reduced significantly towards the apical third.