Development of an antibacterial and anti-metalloproteinase dental adhesive for long-lasting resin composite restorations.

Despite all the advances in adhesive dentistry, dental bonds are still fragile due to degradation events that start during application of adhesive agents and the inherent hydrolysis of resin-dentin bonds. Here, we combined two outstanding processing methods (electrospinning and cryomilling) to obtain bioactive (antimicrobial and anti-metalloproteinase) fiber-based fillers containing a potent matrix metalloproteinase (MMP) inhibitor (doxycycline, DOX). Poly(ε)caprolactone solutions containing different DOX amounts (0, 5, 25, and 50 wt%) were processed via electrospinning, resulting in non-toxic submicron fibers with antimicrobial activity against Streptococcus mutans and Lactobacillus. The fibers were embedded in a resin blend, light-cured, and cryomilled for the preparation of fiber-containing fillers, which were investigated with antibacterial and in situ gelatin zymography analyzes. The fillers containing 0, 25, and 50 wt% DOX-releasing fibers were added to aliquots of a two-step, etch-and-rinse dental adhesive system. Mechanical strength, hardness, degree of conversion (DC), water sorption and solubility, bond strength to dentin, and nanoleakage analyses were performed to characterize the physico-mechanical, biological, and bonding properties of the modified adhesives. Statistical analyses (ANOVA; Kruskal-Wallis) were used when appropriate to analyze the data (α = 0.05). DOX-releasing fibers were successfully obtained, showing proper morphological architecture, cytocompatibility, drug release ability, slow degradation profile, and antibacterial activity. Reduced metalloproteinases (MMP-2 and MMP-9) activity was observed only for the DOX-containing fillers, which have also demonstrated antibacterial properties against tested bacteria. Adhesive resins modified with DOX-containing fillers demonstrated greater DC and similar mechanical properties as compared to the fiber-free adhesive (unfilled control). Concerning bonding performance to dentin, the experimental adhesives showed similar immediate bond strengths to the control. After 12 months of water storage, the fiber-modified adhesives (except the group consisting of 50 wt% DOX-loaded fillers) demonstrated stable bonds to dentin. Nanoleakage was similar among all groups investigated. DOX-releasing fibers showed promising application in developing novel dentin adhesives with potential therapeutic properties and MMP inhibition ability; antibacterial activity against relevant oral pathogens, without jeopardizing the physico-mechanical characteristics; and bonding performance of the adhesive.

Efeito de diferentes sistemas de polimento na rugosidade superficial e brilho de resina composta: análise clínica e laboratorial / Effect of different polishing systems on the surface roughness and gloss of resin composite: Clinical and in vitro analysis

Este trabalho foi composto por dois estudos: um in vitro e um clínico randomizado e duplo-cego. O objetivo deste estudo foi compreender o efeito de diferentes sistemas de polimento na rugosidade e brilho superficial da resina composta avaliados em diferentes períodos. Estudo Laboratorial: Cinquenta espécimes de resina composta (Amaris, VOCO) foram confeccionados e divididos em dois grupos variando o sistema de polimento utilizado SFE: Sof-Lex Espiral (3M ESPE) - dois passos e DMT: Dimanto (VOCO) - passo único. Análises de brilho espectral, brilho subjetivo e rugosidade superficial foram realizadas, imediatamente após o polimento, após seis meses e após um ano. O teste de Kolmogorov-Smirnov foi utilizado para verificar a normalidade dos dados. Para o brilho espectral foi utilizada análise de variância de medidas repetidas (ANOVA)(p<0,05) seguida do teste de Tukey (α = 0,05) que demonstraram que o grupo SFE apresentou maior brilho e ainda, ambos os grupos obtiveram valores de brilho menores após seis meses. Como os dados de brilho subjetivo e rugosidade superficial não apresentaram normalidade, foram aplicados os testes Mann-Whitney U e Frideman (α = 0,05). Para o brilho subjetivo, SFE apresentou maiores valores do que DMT quando avaliado após o polimento, porém, em seis e doze meses não houve diferença estatisticamente significante entre eles. Quanto a rugosidade superficial não houve diferenças significantes entre os dois sistemas de polimento nem quanto a fator tempo e nem na interação desses fatores. Estudo Clínico: Cinquenta facetas em resina composta (Amaris, VOCO) foram realizadas em pacientes e divididas em dois grupos, dependendo do sistema de polimento utilizado e avaliadas quanto a brilho subjetivo por pacientes e examinadores, quanto a rugosidade superficial em rugosímetro através de réplicas em resina epoxi e pelo paciente através da Escala Análoga Visual (EAV) e percepção pela língua comparando a um dente natural (controle), após o polimento e após seis meses. Os resultados foram submetidos à análise estatística para verificar a normalidade dos dados. Para a analise com EAV não foi encontrada diferença estatística. Para a percepção da textura da superfície, não houve diferença após o polimento, demonstrado pelos testes Exato de Fischer e Qui-Quadrado. Após seis meses o grupo DMT percebeu diferença de rugosidade, onde os pacientes consideraram o dente da faceta mais liso. Em relação a percepção de brilho pelo paciente, o teste Qui-quadrado demonstrou que não houve diferença entre os grupos. Quanto a avaliação pelo profissional, os testes de Mann-Whiteney e Wilcoxon demonstraram que para o grupo após o polimento, sistema DMT apresentou maiores valores de brilho do que SFE e ambos perderam brilho após seis meses. Quanto a rugosidade os testes de Mann-Whiteney e Wilcoxon demonstraram que o grupo DMT apresentou menores valores enquanto SFE apresentou maiores valores em seis meses. Os resultados da avaliação subjetiva realizada pelos profissionais foram bem próximos a dos pacientes, sendo uma alternativa para avaliação da satisfação do paciente com o tratamento recebido(AU)

This research was composed of two studies: an in vitro and a double-blind randomized clinical study. The aim of the research was to understand the effect of different polishing systems on the surface roughness and gloss of resin composite measured in different periods of time. In vitro study: Fifty specimens of composite resin (Amaris, VOCO) were made and divided into two groups according to the polishing system used SFE: Sof-Lex Spiral (3M ESPE) - two steps and DMT: Dimanto (VOCO) - single step. Spectral and subjective gloss and surface roughness analysis were performed at baseline (right after polishing), after six and twelve months. The Kolmogorov-Smirnov test was used to verify the normality of the data. For spectral gloss analysis repeatedmeasures (ANOVA) followed by Tukey´s test (α = 0.05) demonstrated that SFE presents higher values than DMT and both groups obtained higher values of gloss right after polishing than after six months. As the subjective data of gloss and roughness did not present normal distribution, Mann-Whitney and Friedman tests were applied for statistical analysis (α = 0.05). SFE group presented higher values of subjective gloss than DMT just right after polishing, however for other periods evaluated, there was no statistically significant difference. Regarding the surface roughness, there were no significant differences between the two groups evaluated, neither in terms of time, nor for the interaction time and polishing systems. Clinical Study: Fifty composite veneers (Amaris, VOCO) were made on patients and divided into two groups, according to the polishing systems used and assessed for subjective gloss obtained by patients and by examiners evaluation, surface roughness measured using a profilometer and veneer epoxi resin replicas and by patients with Visual Analogue Guide (VAG) and texture perception by the tongue comparing a natural tooth (control) right after polishing and after six months. The results were submitted to statistical analysis to verify the normal distribution of the data. For the surface roughness evaluated by the patients with the VAG no statistical differences were found. For the surface texture perception, patients were not able to identify differences right after the polishing as demonstrate by Fischer Exact and Chi-Square tests, however, after six months DMT group reported differences where natural teeth were consider rougher than the veneers. Regarding the perception of gloss by the patient, the Chi-Square test showed no difference between the groups. However, some patients of DMT group described the veneers glossier than the natural tooth. For the subjective gloss assessed by the professional, the Mann-Whitney and Wilcoxon tests demonstrated that DMT system showed higher values of gloss than SFE right after polishing and at six-month evaluation both groups demonstrated lower values of gloss. For roughness, the Mann-Whitney and Wilcoxon tests showed that the DMT group had lower values of surface roughness and SFE group showed an increase after six months evaluation. The results of the subjective assessment made by professionals were close to that made by patients and was an alternative to evaluate patient satisfaction with the treatment received(AU)

Synthesis, characterization and application of Ag doped ZnO nanoparticles in a composite resin.

The biofilm accumulation over the composite resin restorations can contribute to the formation of secondary caries. In this way, antibacterial restorative composite resins are highly desired. Then, the purpose of this study was to modify a composite resins using Ag doped ZnO nanoparticles (NPs), evaluate the antibacterial and mechanical properties of the modified composite resin. The ZnO/AgNPs were synthesized by two different routes, polymeric precursor and coprecipitation methods, and characterized by thermal decomposition, X-ray diffraction, specific surface area by N2 desorption/desorption and scanning electron microscopy (SEM). Antibacterial activity of composite resin specimens (4 mm in height and 2 mm in diameter; n = 15) modified by ZnO/Ag nanoparticles was performed against 7-days Streptococcus mutans biofilm. Colony forming units (CFU/mL) were used to evaluate the bacterial activity. Additionally, the morphology and the bacteria adherence area were analyzed by SEM images. Cylindrical specimens (6 mm in height and 4 mm in diameter; n = 20) of the composite resin containing ZnO/Ag NPs were prepared to perform compressive strength in a universal mechanical test machine, and the surface of fractured specimens was analyzed by EDX element mapping to verify NPs homogeneity. The normal distribution was confirmed and the two-way analysis of variance (ANOVA) and Tukey's test for pair comparison were performed. The nanospheres of ZnO/Ag lead to a better biofilm inhibition, than nanoplates. No difference on compressive strength was found for the composite resin modified by ZnO/Ag nanoplates. Based on these results, this material could be a good option as a new restorative material.

Synthesis and application of triclosan methacrylate monomer in resin composites.

OBJECTIVES: To evaluate the antibacterial activity, bacterial viability, cytotoxicity, and mechanical/physical properties of a novel methacrylate triclosan-derivative monomer (TM) incorporated in dental resin composite. METHODS: TM was synthesized by esterification and, after characterization by FT-IR, was added to an experimental composite. Samples were divided into two groups according to TM presence, i.e., C1 (control) and C2 (C1 + 14.4% TM). Microbiological properties: Specimens (C1 and C2) were prepared and placed on bacterial suspensions of Streptococcus mutans. Antibacterial activity, MTT, and live/dead bacterial viability were used to test the resin composites. All assays were performed in triplicates. Mechanical properties: Specimens underwent compression (CS) and flexural strength (FS) tests conducted in an Instron universal testing machine at a crosshead speed of 0.5 mm/min. Physical properties: Specimens were assessed for Knoop hardness (KHN) and crosslink density (CD). Fourier transform infrared spectroscopy allowed the degree of conversion (DC) to be evaluated. Data were subjected to appropriate statistical tests according to data distribution and assay (p < 0.05). RESULTS: Microbiological properties: C2 showed the lowest biofilm accumulation and the highest membrane-compromised bacteria in the biofilm. Mechanical/physical properties: For CS, FS, KHN, and DC, there was no significant difference between groups C1 and C2; however, significant difference was observed for the CD assay. CONCLUSIONS: The triclosan methacrylate reduces bacterial adhesion of S. mutans and decreased the formation of bacterial biofilm without affecting important polymer properties. The triclosan methacrylate incorporated in resin composite could greatly reduce the live bacterial adhesion of S. mutans and decrease the formation of bacterial biofilm without affecting important polymer properties. CLINICAL SIGNIFICANCE: The resin composites containing triclosan methacrylate could greatly reduce the bacterial adhesion and biofilm formation. That might prevent the secondary caries round the margins of the restorations.

Ion-releasing dental restorative composites containing functionalized brushite nanoparticles for improved mechanical strength.

OBJECTIVES: This study describes the synthesis of brushite nanoparticles (CaHPO4·2H2O) functionalized with triethylene glycol dimethacrylate (TEGDMA) and their application in dental restorative composites with remineralizing capabilities. METHODS: Nanoparticles were synthesized, with TEGDMA being added to one of the precursor solutions at three different molar ratios (0:1, 0.5:1 and 1:1, in relation to the ammonium phosphate precursor). Then, they were added (10 vol%) to a photocurable dimethacrylate matrix containing 50 vol% of reinforcing glass particles. The resulting composites were tested for degree of conversion, biaxial flexural strength and elastic modulus (after 24h and 28days in water), and ion release (over a 28-day period). Commercial composites (one microhybrid and one microfilled) were tested as controls. RESULTS: The final TEGDMA content in the functionalizing layer was modulated by the molar ratio added to the precursor solution. Functionalization reduced nanoparticle size, but did not reduce agglomeration. Improved mechanical properties were found for the composite containing nanoparticles with higher TEGDMA level in comparison to the composite containing non-functionalized nanoparticles or those with a low TEGDMA level. All brushite composites presented statistically significant reductions in strength after 28 days in water, but only the material with high-TEGDMA nanoparticles retained strength similar to the microhybrid commercial control. Overall, ion release was not affected by functionalization and presented steady levels for 28 days. SIGNIFICANCE: Though agglomeration was not reduced by functionalization, the improvement in the matrix-nanoparticle interface allowed for a stronger material, without compromising its remineralizing potential.

Physical and chemical properties of model composites containing quaternary ammonium methacrylates.

OBJECTIVE: Investigate physical and chemical properties of model composites formulated with quaternary ammonium salt monomers (QAS) at different concentrations and alkyl chains lengths METHODS: QAS with 12 dimethylaminododecyl methacrylate (DMADDM) and 16 dimethylaminohexadecyl methacrylate (DMAHDM) chains lengths were synthesized and incorporated at 5 and 10% in model composites, resulting in four groups: G12.5 (DMADDM 5%), G12.10 (DMADDM 10%), G16.5 (DMAHDM 5%), G16.10 (DMAHDM 10%). One group was used as control group (CG 0%). Degree of conversion (DC); water sorption (WS) and solubility (SL); hygroscopic expansion (HE); degradation temperature (DT); glass transition temperature (Tg) and polymerization shrinkage (PS) were determined. Knoop hardness (KNH), flexural strength (FS) and elastic modulus (EM) were measured before and after storage Data were submitted to ANOVA and Tukey's test (p≤0.05). RESULTS: DC ranged between 76.1 (G12.10) and 70.7 (G16.5) %; CG had the lowest WS, SL and HE. There was no statistical difference for PS and FS. KHN values ranged between 30.2 (GC) and 25 (G16.10) and after storage the performance was depended on QAS concentration and chain length. For EM, CG had the highest values before and after storage and no difference was observed in the QAS groups before storage. After storage, the results were dependent on QAS concentration (3.5-4.3GPa). SIGNIFICANCE: In general, the addition of QAS increased composite's degradation compared with the CG. In the tested QAS, the addition of DMADDM at 5% concentration resulted in a less degradable material.

Characterization of methacrylate-based composites containing thio-urethane oligomers.

OBJECTIVE: To evaluate the ability of thio-urethane oligomers to improve the properties of restorative composite resins. METHODS: Oligomers were synthesized by combining 1,6-hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 0-20 wt% to BisGMA-TEGDMA (70-30 wt%). Silanated inorganic fillers were added (70 wt%). Materials were photoactivated at 800 mW/cm(2) filtered to 320-500 nm. Near-IR was used to follow degree of methacrylate conversion (DC). Mechanical properties were evaluated in three-point bending with 2 mm × 2 mm × 25 mm bars for flexural strength/modulus and toughness (FS/E, and T) according to ISO 4049, and 2 mm × 5 mm × 25 mm notched specimens for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Results were analyzed with ANOVA/Tukey's test (α=5%). RESULTS: Significant increase in DC was observed in thio-urethane-containing materials especially for the group with 20 wt% of aliphatic version. Materials composed by oligomers also promoted higher FS, E, and KIC in comparison to controls irrespective of thio-urethane type. A significant increase in toughness was detected by ANOVA, but not distinguished in the groups. The PS was significantly reduced by the presence of thio-urethane for almost all groups. CONCLUSIONS: The use of thio-urethane oligomer to compose methacrylate-based restorative composite promote increase in DC, FS, E and KIC while significant reduces PS. SIGNIFICANCE: A simple additive was shown to reduce stress while increasing convrersion and mechanical properties, mainly fracture toughness. This has he potential of increasing the service life of dental composites, without changing current operatory procedures.

Deproteinization technique stabilizes the adhesion of the fiberglass post relined with resin composite to root canal.

To evaluate the effects of pretreatment of root dentin by 5.25% sodium hypochlorite (NaOCl) alone, associated with 2% chlorhexidine in gel base (CHX) and/or ethanol (EtOH), and the air-drying technique (Air) on the bond strength and adhesive durability of fiberglass post relined with resin composite to root dentin. A total of 100 bovine incisor roots were divided into 10 groups: G1 (control), irrigation with physiologic solution; G2, Air; G3, NaOCl; G4, NaOCl + Air; G5, NaOCl + EtOH; G6, NaOCl + EtOH + Air; G7, NaOCl + CHX; G8, NaOCl + CHX + Air; G9, NaOCl + CHX + EtOH; G10, NaOCl + CHX + EtOH + Air. Fiberglass post relined with resin composite was cemented and each group was randomly divided into two subgroups: 24 h of water storage and 12 months of water storage. The push-out test was performed and bond strength values were analyzed by ANOVA and Tukey's test. The use of NaOCl alone or associated with CHX had the highest values of bond strength with or without Air in the immediate and stored groups, being statistically similar to the immediate control group (p > 0.05). The groups using EtOH or Air alone had lower bond strength in the immediate and stored groups (p < 0.05). A significant decrease with the time of the bond strength in the control group was observed after 12 months of storage (p > 0.05). The use of NaOCl or NaOCl associated with CHX preserved the bond strength immediate and for 12 months. The air-drying technique and the other associations decreased the immediate bond strength values.

Nanomechanical properties of biochemically modified dentin bonded interfaces.

The effect of biomodification of dentin matrices using collagen cross-linkers, glutaraldehyde (GD) and grape seed extract (GSE), on the reduced modulus of elasticity (Er) and nanohardness (H) of the hybrid layer and underlying dentin was investigated at the dentin-resin bonded interface. The coronal dentin of nine molars were exposed and divided into groups: 5% GD, 6·5% GSE and control. Control samples were etched, bonded with Adper Single Bond Plus and Premise composite. GD and GSE were applied for 1 h prior to bonding procedures. After 24 h, samples were sectioned, and resin-dentin beams were either kept in distilled water or exposed to collagenase treatment for 24 h. Nano-indentations were performed at the hybrid layer and underlying dentin. GD and GSE treatment increased the Er and H of resin-dentin interface structures when compared to the control group (P<0·05), particularly the hybrid layer, and may be a promising novel approach to strengthen the dentin-resin bonded interface structures when using these adhesive system and resin-based composite.

Avaliação clínica de restaurações reparadas por resina composta à base de silorano: estudo longitudinal randomizado controlado / Repair of dimethacrylate-based composite restorations using a silorane-based composite: a prospective, randomized clinical trial

Objetivo: Este estudo investigou o desempenho clínico de restuarações Classe I e II de resina composta à base de dimetacrilato reparadas por uma resina composta de baixa contração à base de silorano ou por uma resina composta à base de dimetacrilato, em baseline e ao longo de 6 a 12 meses. Materiais e métodos: cem restaurações defeituosas de resina composta à base de dimetacrilato foram reparadas neste estudo. Destas, 93 foram examinadas uma semana após terem sido reparadas - baseline, 91 após 6 meses e 83 após 12 meses. As restaurações foram alocadas aleatoriamente em dois grupos de tratamento - Controle (n=50): Adper SE/ESPF + Filtek P90 3M/ESPE...

Valorization of an industrial organosolv-sugarcane bagasse lignin: Characterization and use as a matrix in biobased composites reinforced with sisal fibers.

In the present study, the main focus was the characterization and application of the by-product lignin isolated through an industrial organosolv acid hydrolysis process from sugarcane bagasse, aiming at the production of bioethanol. The sugarcane lignin was characterized and used to prepare phenolic-type resins. The analysis confirmed that the industrial sugarcane lignin is of HGS type, with a high proportion of the less substituted aromatic ring p-hydroxyphenyl units, which favors further reaction with formaldehyde. The lignin-formaldehyde resins were used to produce biobased composites reinforced with different proportions of randomly distributed sisal fibers. The presence of lignin moieties in both the fiber and matrix increases their mutual affinity, as confirmed by SEM images, which showed good adhesion at the biocomposite fiber/matrix interface. This in turn allowed good load transference from the matrix to the fiber, leading to biobased composites with good impact strength (near 500 J m(-1) for a 40 wt% sisal fiber-reinforced composite). The study demonstrates that sugarcane bagasse lignin obtained from a bioethanol plant can be used without excessive purification in the preparation of lignocellulosic fiber-reinforced biobased composites displaying high mechanical properties.

Influence of BisGMA, TEGDMA, and BisEMA contents on viscosity, conversion, and flexural strength of experimental resins and composites.

Different monomer structures lead to different physical and mechanical properties for both the monomers and the polymers. The objective of this study was to determine the influence of the bisphenylglycidyl dimethacrylate (BisGMA) concentration (33, 50 or 66 mol%) and the co-monomer content [triethylene glycol dimethacrylate (TEGDMA), ethoxylated bisphenol-A dimethacrylate (BisEMA), or both in equal parts] on viscosity (eta), degree of conversion (DC), and flexural strength (FS). Eta was measured using a viscometer, DC was obtained by Fourier transfer Raman (FT-Raman) spectroscopy, and FS was determined by three-point bending. At 50 and 66% BisGMA, increases in eta were observed following the partial and total substitution of TEGDMA by BisEMA. For 33% BisGMA, eta increased significantly only when no TEGDMA was present. The DC was influenced by BisGMA content and co-monomer type. Mixtures containing 66% BisGMA showed a lower DC compared with mixtures containing other concentrations of BisGMA. The BisEMA mixtures had a lower DC compared with the TEGDMA mixtures. The FS was influenced by co-monomer content only. BisEMA mixtures presented a statistically lower FS, followed by TEGDMA + BisEMA mixtures, and then by TEGDMA mixtures. Partial or total replacement of TEGDMA by BisEMA increased eta, which was associated with the observed decreases in DC and FS. Although the BisGMA content influenced the DC, it did not affect the FS results.

Influence of storage solution and curing method on a microhybrid composite microhardness.

AIM: The purpose of this study is to evaluate and compare the Vickers microhardness of one microhybrid composite polymerized with different sources and stored in different solutions for up to 14 days. METHODS: Using a bipartite PTFE mould with 6 mm inner diameter and 3 mm high, 30 samples were manufactured with Charisma B1 shade for each polymerization procedures (halogen light, LED and halogen light and postcure cycles) stored in tree types of storage solution. RESULTS: The postcuring method tended to improve the microhardness, but was not statistically different from halogen or LED curing methods (P>0.05). The storage solutions interfered in surface hardness, with the samples eluted in red wine showing the lowest hardness values (P<0.05). After seven days, the hardness values were higher than the first day, but statistically equal to 14 days (P<0.05). CONCLUSION: On accordance with the findings of this study, different storage solutions can change the surface microhardness of a composite resin. An alcoholic solution seems most harmful to the composite. Samples postcured in autoclave had an improved mean value, however, without differing from those of the LED and halogen photo polymerized specimens.

Effect of the composite surface sealant application moment on marginal sealing of compactable composite resin restoration.

An analysis was carried out to observe whether the application or not of a composite surface sealant (CSS), as well the moment for CSS application were able to reduce marginal microleakage in compactable composite resin restoration. All the preparations were restored with a compactable composite resin. The restored teeth were randomly assessed. G1 (control group): finished and polished; G2: finished, polished, etched and cover with CSS; G3: immediately after the restoration done the CSS was applied, then finished and polished; G4: CSS applied immediately after the restoration was done, the finished and polished, etched, and covered with CSS. The specimens were isolated with nail polish, thermocycled, immersed in aqueous solution of silver nitrate, and followed in a photo developing solution. The microleakage scores obtained from the occlusal and cervical walls were analyzed with the Kruskall-Wallis nonparametric test. No microleakage was found at the enamel margins. Comparing the microleakage scores at dentin/cementum margins (p < 0.05) it was found that G3 (p = 0.0162) and G4 (p = 0.0187) were able to reduce microleakage when compared with group G2. However the results were not statistically different from the control group. The application of CSS was not able to completely eliminate marginal microleakage at the dentin/cementum margins.

Processing, properties, and in vitro bioactivity of polysulfone-bioactive glass composites.

The mismatch between the mechanical properties of bioceramics and natural tissue has restricted in several cases a wider application of ceramics in medical and dental fields. To overcome this problem, polymer matrix composites can be designed to combine bioactive properties of some bioceramics with the superior mechanical properties of some engineering plastics. In this work, polymer particulate composites composed of a high mechanical-property polymer and bioactive glass particles were produced and both the in vitro bioactivity and properties of the system were investigated. Composites with different volume fraction and particle size were prepared. In vitro tests showed that hydroxy-carbonate-apatite can be deposited on the surface of a composite as early as 20 h in a simulated body fluid. Ionic evolution from a composite with 40% volume fraction of particles was demonstrated to be similar to bulk bioactive glasses. The mechanical properties of some of the obtained composites had values comparable with the ones reported for bone. Moreover, a physical model based on dynamical mechanical tests showed evidences that the interface of the composite was aiding in the stress transfer process.

Diametral tensile strength of composite resins submitted to different activation techniques / Resistência à tração diametral de compósitos resinosos submetidos a diferentes técnicas de ativação

The aim of this study was to evaluate the diametral tensile strength (DTS) of composite resins submitted to different curing techniques. Four composite resins were tested in this study: Targis (Ivoclar), Solidex (Shofu), Charisma (Heraeus-Kulzer) and Filtek Z250 (3M Espe). Sixty-four cylindrical specimens were prepared and divided into eight groups according to each polymerization technique (n = 8). The indirect composite resins (Targis and Solidex) were polymerized with their respective curing systems (Targis Power and EDG-lux); Charisma and Filtek Z250 were light-cured with conventional polymerization (halogen light) and additionally, with post-curing systems. Specimens were stored in artificial saliva at 37°C for one week. DTS tests were performed in a Universal Testing Machine (0.5 mm/min). The data were statistically analyzed by ANOVA and Duncan tests. The results were (MPa): Z250/EDG-lux: 69.04ª; Z250/Targis Power: 68.57ª; Z250/conventional polymerization: 60.75b; Charisma/Targis Power: 52.34c; Charisma/conventional polymerization: 49.17c; Charisma/EDG-lux: 47.98c; Solidex: 36.62d; Targis: 32.86d. The results reveal that the post-cured Z250 composite resin showed the highest DTS means. Charisma composite presented no significant differences when activation techniques were compared. Direct composite resins presented higher DTS values than indirect resins.

O objetivo do trabalho foi avaliar a resistência à tração diametral (DTS) de compósitos submetidos a diferentes técnicas de polimerização. Foram testados quatro compósitos neste estudo: Targis (Ivoclar), Solidex (Shofu), Charisma (Heraeus-Kulzer) e Filtek Z250 (3M Espe). Foram confeccionados 64 corpos-de-prova cilíndricos, que foram divididos em 8 grupos de acordo com a técnica de polimerização (n = 8). Os compósitos indiretos (Targis e Solidex) foram polimerizados com seus respectivos sistemas de ativação (Targis Power e EDG-lux); Charisma e Filtek Z250 foram fotoativados com polimerização convencional (luz halógena) e, adicionalmente, com sistemas de polimerização adicional. Os corpos-de-prova foram armazenados em saliva artificial a 37°C por uma semana. Ensaio de DTS foi realizado em Máquina Universal de Ensaios Instron (0,5 mm/min). Os dados foram analisados estatisticamente pelos testes ANOVA e Duncan. Os resultados foram (MPa): Z250/EDG-lux: 69,04ª; Z250/Targis Power: 68,57ª; Z250/polimerização convencional: 60,75b; Charisma/Targis Power: 52,34c; Charisma/polimerização convencional: 49,17c; Charisma/EDG-lux: 47,98c; Solidex: 36,62d; Targis: 32,86d. Os resultados indicaram que o compósito Z250 polimerizado adicionalmente mostrou os maiores valores de DTS. O compósito Charisma não apresentou diferenças significativas quando foram comparadas diferentes técnicas de polimerização. Compósitos diretos apresentaram maiores valores de DTS que os compósitos indiretos.

Influence of the power density on the kinetics of photopolymerization and properties of dental composites.

Polymer shrinkage during photopolymerization of dimethacrylate monomers, used for many years to produce materials for dental restoration, can induce either the formation of tooth-restoration gaps or the production of residual stress depending on the quality of adhesion between tooth and dental composites. In this work, the effect of the power density, used to photopolymerize three commercial dental composites (Fill Magic, Supra Fill, and Z100), on the kinetics of the reaction was investigated to determine processing conditions in which the generation of residual stress would be reduced by allowing polymer chains and macromers to flow before freezing during gelation of the polymer network. The kinetics of photopolymerization of the dental composites was monitored by real-time infrared (FTIR) spectroscopy. Polymer shrinkage and mechanical properties were also investigated by using, respectively, density and microhardness measurements. Results showed that the final conversion (after 200 s), volumetric shrinkage, and microhardness values were not affected by different power densities, mainly because the amount of energy used during photopolymerization was set constant by using different irradiation times. Lower power densities were able to reduce the maximum polymerization rate and delay the formation of a rigid network. Conversion before the formation of the rigid network was also enhanced by using a lower power density. Considering that too premature gelation can lead to residual stress during shrinkage, the results of this work indicated that the use of a lower power density can be effective in terms of delaying the onset of the formation of a rigid network, providing then conditions for macromolecules to flow and relieve stress during shrinkage.

Evaluation of microleakage in human, bovine and swine enamels

A adequação de dentes bovinos e suínos na substituição de dentes humanos extraídos tem sido avaliada em vários estudos. O objetivo deste estudo in vitro foi analisar o padrão de infiltração marginal em esmaltes humano, bovino e suíno. Cavidades cúbicas (2 x 2 x 2 mm3) foram realizadas em blocos de esmalte obtidos de dentes molares humanos, incisivos bovinos e molares suínos. As cavidades foram restauradas com compósito resinoso fotopolimerizável e cimento de ionômero de vidro. Os espécimes foram submetidos à termociclagem por 1.000 ciclos entre 5 ± 2ºC e 55 ± 2ºC e imersos em azul de metileno a 2%, por 12 horas. A concentração de corante infiltrado foi medida, quantitativamente, através de espectrofotometria. Os dados foram transformados em µg/ml e submetidos à análise estatística ANOVA, seguida pelo teste de Tukey. As médias de infiltração marginal (µg/ml ± DP) nos esmaltes bovino e suíno não foram significativamente diferentes (0,0668 ± 0,0246 vs. 0,0674 ± 0,0286), mas foram superiores e estatisticamente diferentes (p < 0,01) das encontradas no esmalte humano (0,0407 ± 0,0195, p < 0,01), e as médias de infiltração marginal foram superiores nas restaurações realizadas com o cimento de iônomero de vidro (0,0695 ± 0,01313 vs. 0,0471 ± 0,0163, p < 0,01). Os resultados permitiram concluir que os substratos bovino e suíno permitem uma maior infiltração marginal que o esmalte humano, indicando que a capacidade de selamento marginal pode ser afetada por diferenças entre esses substratos. Os resultados indicam que se deve ter prudência na substituição do esmalte humano em estudos laboratoriais de microinfiltração.

Effectiveness of composite resin polymerization using light-emitting diodes (LEDs) or halogen-based light-curing units

A longevidade clínica das resinas compostas é grandemente influenciada pela qualidade do aparelho fotopolimerizador utilizado. O objetivo deste trabalho foi comparar a eficácia de um aparelho fotopolimerizador de diodos emissores de luz e a de um de luz halógena através do grau de penetração de um corante em uma resina composta micro-híbrida. A resina composta utilizada (Filtek Z250/3M Dental) foi inserida em matrizes acrílicas e fotopolimerizada por 40 segundos por um aparelho fotopolimerizador de diodos emissores de luz (Ultraled/Dabi Atlante) ou de luz halógena (Degulux/Degussa Hüls). Imediatamente depois, os corpos-de-prova foram imersos em 1 ml de solução de azul de metileno a 2% e mantidos em estufa a 37ºC ± 2ºC. Após 24 horas, foram lavados com água corrente destilada por 1 minuto e armazenados em estufa a 37ºC ± 2ºC em umidade relativa por 24 horas. As resinas compostas foram removidas das matrizes, individualmente trituradas e imersas em 1 ml de álcool absoluto por 24 horas. As soluções foram filtradas e centrifugadas por 3 minutos a 4.000 rpm, e o sobrenadante foi utilizado para determinar a absorbância em um espectrofotômetro a 590 nm. O teste t foi aplicado para verificar as diferenças entre os grupos. Não houve diferenças estatísticas entre os grupos fotopolimerizados por diodos emissores de luz ou luz halógena (p > 0,05). O aparelho fotopolimerizador de diodos emissores de luz apresentou a mesma efetividade em polimerizar uma resina composta micro-híbrida quanto o de luz halógena.

Phenylboronate-chitosan resins for adsorption of beta-amylase from soybean extracts.

Isolation and purification of bioproducts from crude extracts can be obtained by affinity methods based on reversible binding of a specific molecule to ligand immobilized in a porous matrix. In the present work, nicrospheres based on chitosan matrix, which incorporated aminophenylboronic acid as a derivative, were prepared and characterized, aimed at developing a beta-amylase adsorption process. Kinetic curves and adsorption isotheriru of the crude extracts as well as the breakthrough curves for a frontal chromatographic separation method of a commercial sample of beta-amylase from soybean are presented. These results were compared to similar data obtained with a comercial microspheres gel based-on agarose.