Nanoneedle-like zinc oxide as a filler particle for an experimental adhesive resin

Aim: The aim of this study was to develop an experimental adhesive resin with nanoneedle-like zinc oxide (N-ZnO), an inorganic filler, that could avoid particle agglomeration and lead to a homogeneous stress distribution within the material and characterize it. Materials and Methods: N-ZnO particles obtained by a thermal evaporation technique were characterized regarding size and surface area and added at 0 (control), 1, 2, 5, and 10 wt%, to an experimental adhesive resin. The following experimental adhesive resins' properties were assessed: radiopacity, contact angle to conditioned enamel and dentin, color, degree of conversion, flexural strength, resistance to degradation, and cytotoxicity. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test and paired Student's t-test. Results: Particles presented a mean particle size of 40 nm and a specific surface area of 16 m2/g. N-ZnO10%showed an increased radiopacity when compared to N-ZnO0%. Contact angles were significantly higher for N-ZnO10%at enamel and N-ZnO2%, N-ZnO5%, and N-ZnO10%at dentin. All groups showed color change when compared to N-ZnO0%. Higher the N-ZnO concentration, lower the degree of conversion. There were no significant differences between the groups for flexural strength and resistance to degradation. The addition of N-ZnO showed no difference in cytotoxicity when compared to positive control, N-ZnO0%, and all groups showed higher values than negative control. Conclusions: N-ZnO possibly exceeded potential limitations due to particles' agglomeration and improved the transference and distribution of stress within the material. It could be effectively used as a filler for adhesive resins.

Effect of immersion in various disinfectant solutions on the properties of a heat-cured acrylic resin / Efeito da imersão em diferentes soluções desinfetantes nas propriedades de uma resina acrílica de termoativação

ABSTRACT Objective: The aim of the present study was to evaluate the influence, of immersion in different disinfectant solutions, on microhardness and surface roughness of a heat-cured acrylic resin. Methods: Specimens were immersed in distilled water, commercial vinegar for domestic use, sodium hypochlorite and hydrogen peroxide, for 150 hours or 300 hours (n=10). After periods of immersion, Knoop microhardness and surface roughness were evaluated using a microhardness tester and a roughness tester, respectively. The data were analyzed using two-way ANOVA and Holm-Sidak, at a level of significance of 5%. Results: The microhardness values ranged from 16.90 ± 0.33 to 17.80 ± 0.51 and roughness values from 0.05 ± 0.01 to 0.08 ± 0.02. There is no difference in microhardness and roughness between groups and times (p>0.05). Conclusion: Within the limitations of this study, it is possible to conclude that vinegar and hydrogen peroxide, as alternative disinfectant solutions for acrylic resin devices, did not promote deleterious effects on microhardness and polishing of a heat-cured acrylic resin used for the fabrication of prostheses, neither in the medium term nor the long term.

RESUMO Objetivo: Avaliar a influência da imersão em diferentes soluções desinfetantes na microdureza e rugosidade de uma resina acrílica de termoativação. Métodos: Corpos de prova de resina acrílica termopolimerizável foram imersos em água destilada, vinagre comercial de uso doméstico, hipoclorito de sódio e peróxido de hidrogênio, por períodos de 150 h ou 300 h (n=10). A microdureza Knoop e a rugosidade superficial dos corpos de prova foram avaliadas com o uso de microduro?metro e rugosímetro, respectivamente. Os dadosforam analisados com o teste análise de variância a dois critérios e Holm-Sidak, com nível de significância de 5%. Resultados: Osvalores de microdureza variaram de 16,90 ± 0,33 a 17,80 ± 0,51 e a rugosidade, de 0,05 ± 0,01a 0,08 ± 0,02. Não houve diferença nos resultados de microdureza e rugosidade entre os grupos e tempos (p>0.05). Conclusão: Dentro das limitações do estudo, é possível concluir que a utilização de vinagre ou de peróxido de hidrogênio, como alternativas para a desinfecção de resina acrílica, não provocam efeitos deletérios na dureza e no polimento da resina acrílica termoativada utilizada para confecção de próteses, nem a médio nem a longo prazo.

Evaluation of an antibacterial orthodontic adhesive incorporated with niobium-based bioglass: an in situ study

Abstract This in situ study aimed to evaluate the antibacterial and anti-demineralization effects of an experimental orthodontic adhesive containing triazine and niobium phosphate bioglass (TAT) around brackets bonded to enamel surfaces. Sixteen volunteers were selected to use intra-oral devices with six metallic brackets bonded to enamel blocks. The experimental orthodontic adhesives were composed by 75% BisGMA and 25% TEGDMA containing 0% TAT and 20% TAT. Transbond XT adhesive (TXT) was used as a control group. Ten volunteers, mean age of 29 years, were included in the study. The six blocks of each volunteer were detached from the appliance after 7 and 14 days to evaluate mineral loss and bacterial growth including total bacteria, total Streptococci, Streptococci mutans, and Lactobacilli. Statistical analysis was performed using GLM model - univariate analysis of variance for microhardness and 2-way ANOVA for bacterial growth (p<0.05). The 20% TAT adhesive caused no difference between distances from bracket and the sound zone at 10-µm deep after 7 and 14 days. After 14 days, higher mineral loss was shown around brackets at 10- to 30-µm deep for TXT and 0% TAT adhesives compared to 20% TAT. S. mutans growth was inhibited by 20% TAT adhesive at 14 days. Adhesive with 20% TAT showed lower S. mutans and total Streptococci growth than 0% TAT and TXT adhesives. The findings of this study show that the adhesive incorporated by triazine and niobium phosphate bioglass had an anti-demineralization effect while inhibiting S. mutans and total Streptococci growth. The use of this product may inhibit mineral loss of enamel, preventing the formation of white spot lesions.

Performance of progressive and constant tapered instruments rotary systems at canal preparation / Desempenho de sistemas endodônticos rotatórios constante e progressivo no preparo do canal radicular

ABSTRACT Objective: The aim of this study was to compare the performance of two nickel-titanium rotary systems regarding the preparation time, final shape of canal, incidence of aberration, transportation, and fracture of instrument. Methods: A total of 40 simulated canals in resin blocks with 30o curves and a length of 17 mm were divided randomly into two groups: preparation with ProTaper and BioRaCe systems up to F5 and BR5 respectively. Pre- and post-operative canal images were taken and superimposed in order to identify aberrations, transportation, and to take measurements of the canal width. In addition, the preparation time and instrument fractures were recorded. The data were analyzed using Student's t test. Results: There is no difference (p>.05) comparing the systems regarding preparation time, canal aberration, and instrument fracture rates. The progressive tapered instruments of ProTaper prepared significantly larger canal widths in the apical third (p<.05). Conclusion: Overall, both systems provided safe canal preparation, associated with few canal aberrations and instrument fractures.

RESUMO Objetivo: Comparar o desempenho de dois sistemas rotatórios em relação ao tempo de preparo, formato final e alterações do canal, desvio e fratura de instrumento. Métodos: Um total de 40 canais simulados em blocos de resina com curvatura de 30o e comprimento de 17 mm foram divididos randomicamente nos sistemas ProTaper e BioRaCe preparados até F5 e BR5 respectivamente. Imagens pré e após o preparo dos canais foram obtidas e superpostas para identificação de alterações de forma, desvios e largura. O tempo de preparo e fratura de instrumentos também foram avaliados. Os dados foram analisados por teste t de Student. Resultados: O tempo de preparo, alterações de forma e taxa de fratura de instrumentos não teve diferença entre os dois sistemas avaliados (p>0,05). Os instrumentos progressivos do ProTaper resultou em canais significativamente mais largos no terço apical (p<0,05). Conclusão: Os dois sistemas rotatórios avaliados resultaram em preparo endodôntico seguro, com poucas alterações e fratura de instrumento.

Effect on adhesion of a nanocapsules-loaded adhesive system

Abstract This study aimed to evaluate the in situ degree of conversion, contact angle, and immediate and long-term bond strengths of a commercial primer and an experimental adhesive containing indomethacin- and triclosan-loaded nanocapsules (NCs). The indomethacin- and triclosan-loaded NCs, which promote anti-inflammatory and antibacterial effects through controlled release, were incorporated into the primer at a concentration of 2% and in the adhesive at concentrations of 1, 2, 5, and 10%. The in situ degree of conversion (DC, n=3) was evaluated by micro-Raman spectroscopy. The contact angle of the primer and adhesive on the dentin surface (n = 3) was determined by an optical tensiometer. For the microtensile bond strength µTBS test (12 teeth per group), stick-shaped specimens were tested under tensile stress immediately after preparation and after storage in water for 1 year. The data were analyzed using two-way ANOVA, three-way ANOVA and Tukey's post hoc tests with α=0.05. The use of the NC-loaded adhesive resulted in a higher in situ degree of conversion. The DC values varied from 75.07 ± 8.83% to 96.18 ± 0.87%. The use of NCs in only the adhesive up to a concentration of 5% had no influence on the bond strength. The contact angle of the primer remained the same with and without NCs. The use of both the primer and adhesive with NCs (for all concentrations) resulted in a higher contact angle of the adhesive. The longitudinal μTBS was inversely proportional to the concentration of NCs in the adhesive system, exhibiting decreasing values for the groups with primer containing NCs and adhesives with increasing concentrations of NCs. Adhesives containing up to 5% of nanocapsules and primer with no NCs maintained the in situ degree of conversion, contact angle, and immediate and long-term bond strengths. Therefore, the NC-loaded adhesive can be an alternative method for combining the bond performance and therapeutic effects. The use of an adhesive with up to 5% nanocapsules containing indomethacin and triclosan and a primer with no nanocapsules maintained the long-term bond performance.

Effect of beverages on surface properties of resin-based sealants

Aim: The aim of this study was to determine degree of conversion of resin-based sealants and the effect of beverages on surface roughness and color change of materials. Methods: Two commercial resin-based sealants were evaluated (Defense Chroma® and BioSeal®). Degree of conversion (DC) was initially measured using Fourier-transformed infrared (FTIR). Specimens of each sealant were maintained in distilled water and immersed one hour daily in grape juice and cola drink for 30 days. One group was maintained only in distilled water, as a control. Surface roughness and color change were measured before immersion, after seven days of immersion and after 30 days of immersion. Results were analyzed using t-test, paired t-test, one-way repeated measures ANOVA, one-way ANOVA and post-hoc tests (0.05 level of significance). Results: There was no significant difference regarding degree of conversion and initial surface roughness comparing both commercial sealants. Surface roughness increased for BioSeal® immersed in cola drink for 30 days. After 30 days, all groups presented significant color change. Conclusions: The effect of beverages on color stability and surface roughness of resin-based sealants depended on exposure time and kind of beverage (AU)

Triazine Compound as Copolymerized Antibacterial Agent in Adhesive Resins

Abstract The aim of this study was to formulate and evaluate an experimental adhesive resin with the addition of 1,3,5-triacryloylhexahydro-1,3,5-triazine at different concentrations. Experimental adhesive resins were obtained by mixing 50% wt bisphenol A glycol dimethacrylate (BisGMA), 25% wt triethylene glycol dimethacrylate (TEGDMA), 25% wt 2-hydroxyethyl methacrylate (HEMA) and photoinitiator system. The triazine compound was added in 1, 2.5 and 5% wt to a base adhesive resin and one group remained with no triazine as control group. The experimental adhesive resins were analyzed for antibacterial activity (n=3), degree of conversion (n=3) and softening in solvent (n=3). Data distribution was evaluated by Kolmogorov-Smirnov test, paired t test, one-way ANOVA and Tukey’s with a 0.05 level of significance. All groups with added triazine compound showed antibacterial activity against Streptococcus mutans (p<0.05). All groups achieved more than 70% degree of conversion, but there was no difference in this chemical property (p>0.05). The initial Knoop hardness was higher in 2.5 and 5% wt groups (p<0.05) and both groups present lower percentage variation of Knoop hardness after solvent degradation. The present study formulated an antibacterial adhesive resin with a non-releasing agent able to copolymerize with the comonomeric blend, improving the restorative material’s properties.

Resumo O objetivo desse estudo foi desenvolver e avaliar a adição de 1,3,5-triacryloylhexahydro-1,3,5-triazine a uma resina adesiva experimental em diferentes concentrações. Resinas adesivas experimentais foram obtidas a partir da mistura de 50% em peso de bisphenol A glycol dimethacrylate (BisGMA), 25% em peso de triethylene glycol dimethacrylate (TEGDMA), 25% em peso de hidroxietil metacrilato (HEMA) e sistema fotoiniciador. O composto de triazina foi adicionado em proporções de 1; 2,5 e 5% em peso a resina adesiva base e um grupo permaneceu sem a adição do composto de triazina como grupo controle. As resinas adesivas experimentais foram analisadas por atividade antibacteriana (n=3), grau de conversão (n=3) e degradação em solvente (n=3). A distribuição dos dados foi avaliada por teste de Kolmogorov-Smirnov, teste t pareado, ANOVA de uma via e Tukey, considerando nível de significância de 5%. Todos os grupos com adição de composto de triazina demonstraram atividade antibacteriana contra Streptococcus mutans (p<0,05). Todos os grupos atingiram mais de 70% de grau de conversão, mas não houve diferença estatística para essa propriedade química (p>0,05). A dureza Knoop inicial foi maior para os grupos com 2,5 e 5% de triazina (p<0,05) e ambos os grupos apresentaram menor variação percentual de dureza Knoop após degradação em solvente. No presente estudo, foi produzida uma resina adesiva antibacteriana com agente sem liberação para o meio, capaz de copolimerizar com a blenda comonomérica, melhorando as propriedades do material restaurador.

Influence of addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride to an experimental adhesive

Abstract The aim of this study was to develop an experimental adhesive with addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) and to evaluate its mechanical and biological properties and its in vitro antibacterial activity. An experimental adhesive resin was formulated with Bis-GMA, TEGDMA, and HEMA. The antibacterial monomer was added at concentrations of 1%, 2.5%, and 5% (METAC groups). A group without METAC addition was used as control. The experimental adhesives were evaluated as to their antibacterial potential against Streptococcus mutans, degree of conversion, and softening in ethanol for 2 hours. The data were analyzed by one-way ANOVA, Tukey’s post-hoc test, and the paired Student’s t-test (significance level of 0.05). METAC showed antibacterial activity against S. mutans at all concentrations (p < 0.05). There was no statistical difference across METAC groups (p > 0.05). The 1%, 2.5%, and 5% groups yielded the highest mean values for degree of conversion (p < 0.05). The 1% group did not differ from the control group (p > 0.05). There was no statistical difference in baseline microhardness values (p > 0.05) and microhardness values after immersion in ethanol were lower than at baseline for all groups (p < 0.05). There was no statistical difference in the reduction of Knoop hardness number (KHN) after immersion in ethanol for any of the groups (p > 0.05). The results of the present study indicate that METAC is a promising antibacterial agent when added to an adhesive system.

One-year aging effects on microtensile bond strengths of composite and repairs with different surface treatments

Abstract The present study aimed to evaluate effects of different surface treatments and aging of composite cylinders on bond strength of composite resin repair. Thirty-two composite cylinders were produced and divided into four groups according to type of surface treatment and storage time of composite cylinder and repair. Cylinder surface of control group (Gcontrol) received no treatment before composite repair. Other groups were sandblasted with aluminum oxide (GAl2O3), followed by silane (GAl2O3sil) or adhesive (GAl2O3ad). Composite cylinders were stored in artificial saliva for either 24 hours or 1 year. Repairs were performed and stored in artificial saliva for 24 hours or 1 year and repair strength was evaluated using microtensile bond strength test. Data were submitted to Student’s t test, two-way ANOVA, and post hoc test for storage time and treatment (α = 0.05). Gcontrol group showed lower values of aging of composite cylinder and storage time of repair (24 hours or 1 year for both) compared with other groups (p < 0.05). GAl2O3ad and GAl2O3sil groups did not exhibit decreased microtensile bond strength with aged repairs (1 year; p > 0.05). Polymer degradation was significant for composite cylinders during the first year of storage in Gcontrol, GAl2O3, and GAl2O3ad groups (p < 0.05). In GAl2O3sil group, storage time of composite cylinders was not significant (p > 0.05). Aging of composite resin influenced bond strength of restoration repair for up to 1 year. Sandblasting with Al2O3, followed by application of silane layer, produced high bond strength after composite or repair aging.

In vitro analysis of shear bond strength and adhesive remnant index of different metal brackets

ABSTRACT Introduction: There is a great variety of orthodontic brackets in the Brazilian market, and constantly evaluating them is critical for professionals to know their properties, so as to be able to choose which product best suits their clinical practice. Objectives: To evaluate the bond strength and the adhesive remnant index (ARI) of different brands of metal brackets. Material and Methods: A total of 105 bovine incisors were used, and brackets of different brands were bonded to teeth. Seven different bracket brands were tested (MorelliTM, American OrthodonticsTM, TP OrthodonticsTM, Abzil-3MTM, OrthometricTM, TecnidentTM and UNIDENTM). Twenty-four hours after bonding, shear bond strength test was performed; and after debonding, the ARI was determined by using an optical microscope at a 10-fold increase. Results: Mean shear bond strength values ranged from 3.845 ± 3.997 (MorelliTM) to 9.871 ± 5.106 MPa (TecnidentTM). The majority of the ARI index scores was 0 and 1. Conclusion: Among the evaluated brackets, the one with the lowest mean shear bond strength values was MorelliTM. General evaluation of groups indicated that a greater number of bond failure occurred at the enamel/adhesive interface.

RESUMO Introdução: atualmente, há uma grande diversidade de braquetes ortodônticos no mercado brasileiro, e a avaliação desses é fundamental para que os profissionais conheçam suas propriedades e possam qualificar a sua escolha. Objetivo: avaliar o desempenho de diferentes braquetes metálicos - com diferentes características de base -, por meio da resistência de união e do Índice de Adesivo Remanescente (IAR). Material e Métodos: braquetes de sete marcas distintas foram testados (Morelli®, American Orthodontics®, TP Orthodontics®, Abzil-3M®, Orthometric®, Tecnident® e UNIDEN®). Os braquetes foram colados em incisivos bovinos totalizando 105 corpos de prova. O teste de resistência ao cisalhamento foi realizado 24h após a colagem e, em seguida, foi avaliado o IAR, por meio do uso de um microscópio óptico, em aumento de 10 vezes. Resultados: a média dos valores de resistência de união variou entre 3,845 ± 3,997 MPa (Morelli®) e 9,871 ± 5,106 MPa (Tecnident®). A maioria dos escores do IAR foi de 0 e 1. Conclusão: entre os braquetes avaliados, o que obteve a menor média de resistência de união foi o Morelli®. A avaliação geral dos grupos indicou maior número de falhas de colagem na interface esmalte/adesivo.

Efeito do ácido peracético sobre a adesão microbiana e as propriedades de tubos endotraqueais

Objetivo: avaliar a influência do número de imersões em ácido peracético na colonização bacteriana, na composição química, na rugosidade e na capacidade de recuperação após a deformação de tubos endotraqueais. Materiais e método: quatro tubos foram sub-metidos a sucessivas imersões em ácido peracético, constituindo quatro grupos: um controle (esterilizado pelo fabricante) e outros submetidos a uma, duas ou três imersões, de forma a simular o reprocessamento dos tubos. Os ensaios realizados foram: espectroscopia de infravermelho, rugosidade superficial, deformação da luz do tubo após compressão e colonização por Staphylococcus aureus. Resultados: o número de imersões (reprocessamento) não influenciou a colonização dos tubos por Staphylococcus aureus (p = 0,235), nem a composição química, nem a rugosidade (p = 0,621). Além disso, não houve diferença na capacidade do tubo em recuperar-se após deformação (p = 0,633). Conclusão: o reprocessamento por até três vezes não traz prejuízo às propriedades do material e não aumenta a colonização bacteriana na superfície dos tubos.

Effect of silver nanoparticles on the physicochemical and antimicrobial properties of an orthodontic adhesive

ABSTRACT Orthodontic treatment with fixed brackets plays a major role on the formation of white spot lesions. Objective This study aimed to incorporate silver nanoparticle solutions (AgNP) in an orthodontic adhesive and evaluate its physicochemical and antimicrobial properties. Material and Methods Silver nanoparticle solutions were added to a commercial adhesive in different concentrations (w/w): 0%, 0.11%, 0.18%, and 0.33%. Shear bond strength (SBS) test was performed after bonding metal brackets to enamel. Raman spectroscopy was used to analyze in situ the degree of conversion (DC) of the adhesive layer. The surface free energy (SFE) was evaluated after the measurement of contact angles. Growth inhibition of Streptococcus mutans in liquid and solid media was determined by colony-forming unit count and inhibition halo, respectively. One-way ANOVA was performed for SBS, DC, SFE, and growth inhibition. Results The incorporation of AgNP solution decreased the SBS (p<0.001) and DC in situ (p<0.001) values. SFE decreased after addition of 0.18% and 0.33% AgNP. Growth inhibition of S. mutans in liquid media was obtained after silver addition (p<0.05). Conclusions The addition of AgNP solutions to Transbond™ XT adhesive primer inhibited S. mutans growth. SBS, DC, and SFE values decreased after incorporation up to 0.33% AgNP solution without compromising the chemical and physical properties of the adhesive.

Influence of adhesive system on quartz fiber post dislocation resistance in endodontically treated teeth

Aim: To evaluate the dislocation resistance of the quartz fiber post/cement/dentin interface afterdifferent adhesion strategies. Methods: Forty bovine lower central incisors were selected andprepared with K-files using the step-back technique, and irrigated with 3 mL of distilled waterpreceding the use of each instrument. Prepared teeth were stored at 37ºC and 100% humidity for 7days. The roots were prepared and randomized into 4 groups. The quartz fiber post was cementedwith an adhesion strategy according to the following groups: GBisCem- BISCEM; GOneStep±C&B- OneStep ± C&B; GAllBond±C&B- AllBond3 ± C&B; GAllBondSE±C&B- AllBondSE ±C&B with a quartz fiberpost. Cross-sectional root slices of 0.7 mm were produced and stored for 24 h at 37° C beforebeing submitted to push-out bond strength. Results: The mean and standard deviation values ofdislocation resistance were GBisCem: 1.12 (± 0.23) MPa, GOneStep±C&B: 0.81 (± 0.31) MPa, GAllBond±C&B:0.98 (± 0.14) MPa, and GAllBondSE±C&B: 1.57 (± 0.04) MPa. GAllBondSE±C&B showed significantly highervalues of dislocation resistance than the other groups. Conclusions: Based on this study design,it may be concluded that adhesion strategies showed different results of quartz post dislocationresistance. Simplified adhesive system with sodium benzene sulphinate incorporation providedsuperior dislocation resistance.

Swelling of self-adhesive resin cement increases long-term push-out bond strength of fiber post to dentin

Abstract Aim: To evaluate the long-term post push-out bond strength to dentin, water sorption, solubility and swelling of conventional and self-adhesive dual-cure resin cements. Methods: Forty-eight bovine roots were prepared for fiber post cementation with RelyX ARC and RelyX U100. According to resin cement and storage time (24 h and 6 months), 4 groups were assessed using the push-out test. Water sorption and solubility were performed according to ISO 4049:2009. The swelling coefficient was obtained using cement disks of each material immersed in distilled water until the swelling equilibrium was reached. The mass of dry and swelled polymer and solvent density were used to calculate the coefficient. Statistical data analysis was performed using Student's t-test for water sorption, solubility and swelling coefficient and the Kruskal-Wallis and Dunn multiple comparison tests for push-out analysis with a significance level of 0.05. Results: The immediate bond strength was not significantly different between RelyX ARC (3.09 MPa) and RelyX U100 (3.78 MPa) (p>0.05). RelyX U100 showed higher (p<0.05) bond strength after six months of storage (9.60 MPa) than RelyX ARC (6.65 MPa). The water sorption and solubility values were not significantly different (p>0.05) between groups. The swelling coefficient of the RelyX U100 group was significantly higher than that of the RelyX ARC group (p<0.05). Conclusions: RelyX U100 resin cement showed a higher swelling coefficient than RelyX ARC, and the longitudinal push-out bond strength increased after six months. Clinical significance: The clinical longevity of restorative treatment in root-filled teeth is dependent on the long-term properties and behavior of the cement used for post luting. Results of this study suggest that the selfadhesive resin cement may be a reliable alternative.

Glycerol Salicylate-based Pulp-Capping Material Containing Portland Cement

The purpose of this study was to evaluate the water sorption, solubility, pH and ability to diffuse into dentin of a glycerol salicylate-based, pulp-capping cement in comparison to a conventional calcium hydroxide-based pulp capping material (Hydcal). An experimental cement was developed containing 60% glycerol salicylate resin, 10% methyl salicylate, 25% calcium hydroxide and 5% Portland cement. Water sorption and solubility were determined based on mass changes in the samples before and after the immersion in distilled water for 7 days. Material discs were stored in distilled water for 24 h, 7 days and 28 days, and a digital pHmeter was used to measure the pH of water. The cement's ability to diffuse into bovine dentin was assessed by Raman spectroscopy. The glycerol salicylate-based cement presented higher water sorption and lower solubility than Hydcal. The pH of water used to store the samples increased for both cements, reaching 12.59±0.06 and 12.54±0.05 after 7 days, for Hydcal and glycerol salicylate-based cements, respectively. Both cements were able to turn alkaline the medium at 24 h and sustain its alkalinity after 28 days. Hydcal exhibited an intense diffusion into dentin up to 40 µm deep, and the glycerol salicylate-based cement penetrated 20 µm. The experimental glycerol salicylate-based cement presents good sorption, solubility, ability to alkalize the surrounding tissues and diffusion into dentin to be used as pulp capping material.

O objetivo deste estudo foi avaliar a sorção e solubilidade em água, pH e habilidade de difusão na dentina de um cimento para capeamento pulpar à base de glicerol salicilato e compará-lo a um cimento comercial para capeamento pulpar à base de hidróxido de cálcio (Hydcal). Um cimento experimental contendo 60% de resina de glicerol salicilato, 10% de salicilato de metila, 25% de hidróxido de cálcio e 5% de cimento Portland foi formulado. Sorção e solubilidade em água foram determinadas a partir da alteração na massa de espécimes antes e após a imersão em água destilada por 7 dias. Discos dos cimentos foram armazenados em água destilada por 24h, 7 dias e 28 dias e o pH da água foi aferido após cada período. A habilidade de difundir-se no interior de dentina bovina foi avaliada por espectroscopia Raman. O cimento à base de glicerol salicilato apresentou maior sorção e menor solubilidade em comparação com o Hydcal. O pH da água de armazenamento dos espécimes aumentou para ambos os cimentos, chegando a 12,59±0,06 e 12,54±0,05 após 7 dias, para o Hydcal e o cimento à base de glicerol salicilato, respectivamente. Os cimentos foram capazes de promover a alcalinização do meio após 24h e sustentaram a alcalinidade após 28 dias. Hydcal exibiu intensa difusão na dentina até 40 μm de profundidade e o cimento à base de glicerol salicilato penetrou 20 μm. O cimento experimental à base de glicerol salicilato apresentou adequada sorção, solubilidade, habilidade de alcalinizar o meio e difundir-se no interior da dentina para uso como um material para capeamento pulpar.

Long-term bond strength, degree of conversion and resistance to degradation of a HEMA-free model adhesive

Aim: To evaluate the long-term bond strength, degree of conversion and resistance to degradation in ethanol of HEMA-containing and HEMA-free model adhesive resins of a three-step etch-and-rinse adhesive system. Methods: The superficial dentin of 16 bovine incisor teeth was exposed, and the teeth were divided in two groups according to the HEMA concentration in the experimental adhesive (0% and 15%). In each tooth were made 6 cylindrical composite restorations. Half of the tooth restorations were submitted to microshear bond strength test after 24 h and the other half after 6 months. Degree of conversion of experimental resins was determined by Fourier transform infrared spectroscopy. Crosslink density was indirectly determined by the Knoop hardness of five specimens per group before and after immersion in ethanol for 6 h. Results: The group with 0% HEMA showed no difference in bond strength as compared to the group with 15% HEMA after 24 h or 6 months. There was no difference in degree of conversion and crosslink density between groups. Conclusions: HEMA content of the adhesive resin did not influence the bond strength to dentin, degree of conversion or resistance to degradation in ethanol.

Influence of mouthwashes on the physical properties of orthodontic acrylic resin

AIM: The aim of this study was to evaluate the influence of acrylic resin immersion in different mouthwashes on hardness, roughness and color. METHODS: Specimens of an orthodontic self-cured acrylic resin (Orto Clas(r)) were produced and immersed in five mouthwashes: Plax(r) Classic (Colgate(r)); Plax(r) alcohol-free (Colgate(r)); Listerine(r) (Johnson & Johnson(r)); Periogard(r) (Colgate(r)) and Periogard(r) alcohol-free (Colgate(r)). Nine different immersion times were studied: 1, 2, 4, 6, 8, 10, 12, 24 h and 7 days, totalizing 45 groups. The specimens were evaluated before and after immersion by Knoop microhardness (n=5), roughness in Ra parameter (n=5), and colorimetric analysis, CIElab (n=3). RESULTS: All mouthwashes softened the acrylic resins after 7 days of immersion. PlaxÒ alcohol-free showed no statistically significant difference of softening between the immersion times. Listerine(r) showed softening after immersion at all times. Plax(r) alcohol-free and Listerine(r) showed significantly increased values of roughness after 12 h of immersion (p<0.05). Listerine(r) presented a significant increase in color variation after 12 h of immersion. CONCLUSIONS: Immersion in mouthwashes could influence acrylic resin hardness, roughness and color...

Discrepancies in degree of conversion measurements by FTIR

The purpose of this study was to evaluate the influence of the internal standard peak on the measured degree of conversion (DC) for methacrylate-based resins analyzed by Fourier-transform infrared spectroscopy (FTIR). The influence of different baseline measurement methods was also determined. Different blends were prepared, mixing BisGMA/BisEMA and BisGMA/TEGDMA at proportions of 0% to 100%, in weight. Camphoroquinone and ethyl-4-dimethylamino-benzoate were used to permit the light activation of blends. Degree of conversion was evaluated using FTIR equipped with an attenuated total reflectance (ATR) device. Samples were dispensed onto ATR crystal and light activated for 40 s. The DC was calculated by relating the height of the peak 1637 cm-1 to the intensity of different internal standard peaks (1715, 1608, or 1582 cm-1), measured using two different baseline methods, before and after polymerization. Data were compared by ANOVA at 5% significance. The relationship between DC and monomer ratio was obtained by regression analysis. Double-bond conversion ranged from 32.75% to 78.50% for BisGMA/BisEMA blends, and from 32.75% to 76.22% for BisGMA/TEGDMA blends. For the BisGMA/BisEMA blends, the DC showed a linear association with the composition of the comonomer blends, independent of the internal standard peak and baseline method used. In contrast, the trends in DC for BisGMA/TEGDMA blends were different for each method of measurement. The internal standard peaks and measurement baseline should be taken into account when using FTIR to calculate the DC of methacrylate-based resins, especially comonomer blends containing a high degree of monomers that lack aromatic rings.

Influence of radiopaque fillers on physicochemical properties of a model epoxy resin-based root canal sealer

Objective: To verify the influence of radiopaque fillers on an epoxy resin-based sealer. Material and Methods: Experimental sealers were formulated by adding 20%, 40%, 60%, 80%, 100% and 120% of calcium tungstate, ytterbium trifluoride or barium sulphate by weight to an epoxy-resin-base. Setting time, flow, film thickness, radiopacity, sorption, solubility, pH and push-out bond strength were evaluated. Results: The setting time ranged from 373 to 612.66 min, the flow varied from 13.81±0.49 to 22.49±0.37 mm, and the film thickness ranged from 16.67±5.77 to 33.33±11.54 µm. The lowest pH was 5.47±0.53, and the highest was 6.99±0.03. Radiopacity varied from 0.38±0.04 to 2.57±0.21 mmAl and increased with the amount of filler. Calcium tungstate sealers had a higher sorption and solubility than other sealers. There was no significant difference in the push-out bond strength among the fillers at the 120% concentration. CONCLUSION: The inorganic fillers evaluated and their concentrations affect the physicochemical properties of an epoxy resin-based root canal sealer. .

Bismuth subsalicylate as filler particle for an experimental epoxy-based root canal sealer

AIM: To evaluate the influence of bismuth subsalicylate addition in different concentrations on theproperties ofan experimental epoxy-based root canal sealer. METHODS: Bismuth subsalicylate in 20%, 40%, 60%, 80%, 100% and 120 wt% was added tothe sealer. Flow, film thickness, working time, setting time, dimensional change, sorption, solubility and cytotoxicity were evaluated according to ISO standard. Data were statistically analyzed by one-way ANOVA and Tukey'stest with a significance level of 5% for all tests. RESULTS:The flow, working and setting times significantly decreased withincreasing particle concentration. The film thickness, dimensional change, water sorption and solubility values significantly increased with higher particle amount. The results for cytotoxicity showed no statistically significant differences among the particle proportions. CONCLUSIONS: The results suggest that the addition up to 80% wt of bismuth subsalicylate appears to be a promising filler particle to root canal sealer development.