Effect of light attenuation through veneers on bond strength of adhesives with photoinitiator combinations

Abstract This study aimed to evaluate the effect of light attenuation through ceramic veneers and resin cement on degree of conversion (DC), cohesive strength (CS), and microshear bond strength (μSBS) of experimental adhesive systems. Experimental etch-and-rinse and self-etch adhesives were combined with different ratios of camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiators: CQ-only; 3CQ:1TPO; 1CQ:1TPO; 1CQ:3TPO and TPO-only. Square-shaped ceramic veneer (IPS Empress Esthetic, Ivoclar Vivadent) (n = 10; 10mm long x 10mm wide x 0.5mm thick) and resin cement specimens (Variolink Esthetic LC, Ivoclar Vivadent) (n = 10; 10 mm long x 10 mm wide and 0.3 mm thick) were prepared. Light transmittance of a multiple-peak LED (Bluephase G2, Ivoclar Vivadent) was measured through restorative materials using a spectrometer (n = 5). Adhesive specimens were analyzed for DC, CS, and μSBS by light-curing the adhesive with or without (control) ceramic veneer, and with resin cement fixed to output region of the light-curing tip (n = 10). Data were submitted to ANOVA and Tukey's test (α = 0.05). Total light transmittance through the restorative materials was attenuated, and this attenuation was more evident for the violet spectrum. The DC for the TPO groups in ratios up to 1CQ:1TPO was similar to the control. 1CQ:3TPO showed lower values for CS. μSBS was reduced for all groups with light attenuation, but lower values were observed for 1CQ:3TPO and TPO-only. In conclusion, light transmission was reduced with interposed restorative materials. Adhesives combined with CQ and TPO up to 1CQ:1TPO showed greater cure efficiency and mechanical properties compared with a higher amount of TPO.

Development and characterization of a novel bulk-fill elastomeric temporary restorative composite

Abstract Objectives: This study investigated the physical and mechanical properties, antibacterial effect and biocompatibility of novel elastomeric temporary resin-based filling materials (TFMs) containing zinc methacrylate (ZM). Material and Methods: Experimental TFMs were prepared by mixing the zinc methacrylate with monomer, co-monomer, photoinitiator and fillers. A ZM concentration of 0 (control), 0.5% (Z0.5); 1% (Z1), 2% (Z2), or 5% (ZM5) wt% was added to the TFMs. Fermit-N (F) was used for comparison with the experimental material. Microleakage, water sorption/solubility, degree of conversion, depth of cure, ultimate tensile strength, and hardness were determined and compared. A modified direct contact test (DCT) with Enterococcus faecalis and a Streptococcus mutans' biofilm accumulation assay was carried out to evaluate the antimicrobial effect and cytotoxicity of the assay. Statistical comparisons were performed (α=5%). Results: The results showed that the physical and mechanical properties of the experimental TFMs with ZM are comparable with the properties of the commercial reference and some properties were improved, such as lower microleakage and water sorption, and higher ultimate tensile strength values. TFMs with ZM killed E. faecalis only after 1 h. Biofilm development of S. mutans was not affected by the inclusion of ZM in the experimental TFMs. Conclusions: The present findings suggest that the physical, mechanical and biological properties of the experimental TFMs with ZM are comparable with the properties of the commercial reference. However, some properties were improved, such as lower microleakage and water sorption, and higher ultimate tensile strength values.

Pentaerythritol Tetrasalicylate in the Chemical Composition of Root Canal Sealers

Abstract The aim of this study was to synthesize and evaluate physicochemical properties of a new salicylate derivative in experimental calcium-based root canal sealers. Two salicylate derivatives were synthesized for the transesterification reaction of methyl salicylate with two different alcohols (1,3-butylenoglicol disalicylate-BD and pentaerythritol tetrasalicylate -PT) in molar ratio 1:3 and 1:6, respectively. The products (BD and PT), were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance spectroscopy (RMN). Calcium-based experimental sealers were prepared with the same catalyst paste (60% of MTA, 39% of n-ethyl-o-toluenesulfonamide, and 1% titanium dioxide) and four different concentrations of BD and PT in the base pastes (40/0 - control, 35/5, 30/10 and 20/20) with 60% of bismuth oxide. The experimental sealers were evaluated for setting time, solubility (24 h, 7, 14 and 30 days), diametral tensile strength and Young's Modulus. Data were analyzed by one- or two-way ANOVA with Tukey's test (p<0.05). The addition of PT reduced the materials setting time. After 24 h the sealer 40/0 and 35/5 had higher solubility, and after 14 and 28 days the sealer 20/20 showed the lowest solubility (p<0.05). After 7 days the sealer 20/20 stabilized its solubility. The sealer 40/0 presented the highest values and the 20/20 presented the lowest values of diametral tensile strength and Young's modulus (p<0.05). The addition of PT to calcium-based root canal sealers provides benefits to the setting time and solubility.

Resumo O objetivo neste estudo foi sintetizar e avaliar as propriedades físico-químicas de um novo derivado do salicilato em cimentos endodônticos experimentais à base de cálcio. Dois derivados de salicilato foram sintetizados por meio de uma reação de trans esterificação do salicilato de metila com dois diferentes alcoóis (1,3-butilenoglicol dissalicilato-BD e pentaeritritol tetrassalicilato-PT) na proporção molar de 1: 3 e 1:6, respectivamente. Os produtos (BD e PT), foram caracterizados por espectroscopia infravermelho transformada de Fourier (FTIR) e espectroscopia de ressonância magnética nuclear (RMN). Os cimentos experimentais à base de cálcio foram preparados com a mesma pasta catalisadora (60% de MTA, 39% de N-etil o/p toluenosulfonamida e 1% de dióxido de titânio) e quatro concentrações diferentes de BD e PT nas pastas base (40/0 - controle, 35/5, 30/10 e 20/20) com 60% de óxido de bismuto. Os cimentos foram avaliados quanto ao tempo de endurecimento, à solubilidade (24 h, 7, 14 e 28 dias), resistência à tração diametral e ao módulo de elasticidade. Os dados foram analisados por ANOVA um ou dois fatores e as médias comparadas pelo teste de Tukey (p<0,05). A adição de PT reduziu o tempo de endurecimento dos materiais testados. Após 24 horas os cimentos 40/0 e 35/5 apresentaram maior solubilidade que os demais e após 14 e 28 dias o cimento 20/20 foi o que apresentou menor solubilidade (p<0,05). Após 7 dias o grupo 20/20 estabilizou a sua solubilidade. O cimento 40/0 apresentou os maiores valores e o cimento 20/20 apresentou os menores valores de resistência à tração diametral e módulo de elasticidade (p<0,05). A adição de PT a cimentos à base de cálcio possibilita benefícios ao tempo de presa e solubilidade.

Long-term bonding efficacy of adhesives containing benzodioxioles as alternative co-initiators

Abstract This study evaluated the three-year lifespan of the bond to dentin of experimental self-etch adhesives containing benzodioxole derivatives - 1,3-benzodioxole (BDO) and piperonyl alcohol (PA) - as co-initiator alternative to amines. Adhesive resins were formulated using Bis-GMA, TEGDMA, HEMA, camphorquinone and different co-initiators: BDO, PA or ethyl 4-dimethylamino benzoate (EDAB - amine). An experimental self-etch primer was used to complete the two-step, self-etch adhesive system. Clearfil SE Bond (CSE) was used as commercial reference. Bond strength to human dentin was assessed by microtensile bond strength (µTBS) test, and failure mode was classified. Morphology of the dentin bonding interface was assessed via scanning electron microscopy (SEM). Irrespective of the dental adhesives evaluated, µTBS was higher after 24 hours compared with that after 1.5 and 3 years (p ≤ 0.001). However, adhesives with BDO and PA as co-initiators showed significantly higher bond strength than the bonding resin with EDAB (p ≤ 0.002), independent of the time evaluated. The commercial adhesive CSE showed similar bond strength compared with the other groups (p ≥ 0.05). Mixed failures were mainly observed after 24 hours, while adhesive failures were more frequently observed after 1.5 and 3 years. No notable differences in homogeneity and continuity along the bonded interfaces were detected among the materials in the SEM analysis. In conclusion, benzodioxole derivatives are feasible alternative co-initiators to tertiary amine in camphorquinone-based self-etching dental adhesive formulations.

Evaluation of long-term bond strength and selected properties of self-adhesive resin cements

Abstract This study evaluated the shear bond strength (SBS) of self-adhesive resin cements (SARCs) to dentin and their physical-chemical properties. Five commercial SARCs were evaluated [SmartCem®2 - DENTSPLY (SC2); BisCem® - Bisco (BC); SeT PP® − SDI (SeT); Relyx U100® - 3M ESPE (U100) and YCEM® SA - Yller (YCEM)]. The SARCs were evaluated for SBS to dentin (n = 10) after 24 h, 6 months, and 12 months. The dentin demineralization caused by acidic monomers was observed by SEM, and pH-neutralization of eluate was observed for 24 h. Degree of conversion (DC), rate of polymerization (Rp), flexural strength (FS), and elastic modulus (E) were evaluated. Immediate SBS of SC2, SET, U100, and YCEM were statistically higher than that of BC (p < 0.001). After 12 months, all SARCs showed reduced SBS values and U100 showed values similar to those of SET and YCEM, and higher than those of BC and SC2 (p = 0.001). Demineralization pattern of SARCs was similar. At 24h, all SARCs showed no differences in the pH-value, except BC and U100 (p < 0.001). YCEM showed the highest Rp. U100, YCEM, and SC2 showed statistically higher FS (p<0.001) and E (p < 0.001) when compared with SET and BC. U100 and YCEM showed the best long-term bonding irrespective of the storage period. A significant reduction in SBS was found for all groups after 12 months. SBS was not shown to be correlated with physical-chemical properties, and appeared to be material-dependent. The polymerization profile suggested that an increased time of light activation, longer than that recommended by manufacturers, would be necessary to optimize DC of SARCs.

Characterization of Bis-Acryl Composite Resins for Provisional Restorations

Abstract This study investigated the in vitro performance of the commercial bis-acryl composite resins Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) and ProviPlast (PVP, Biodinamica). Characterization involved optical (color stability, translucency parameter, fluorescence), surface (roughness, morphology and elemental composition), physical-chemical (viscosity, polymerization kinetics) and mechanical analyses (Poisson ratio, biaxial flexural strength, flexural modulus). Most tests were carried out after 24 h, but optical and mechanical analyses were carried out after storage in water at 37 °C for 1, 15, and 30 days. Data were statistically analyzed (a=0.05). Most results were material dependent. SYS and PT4 showed stability in color and translucency over time. All materials had similar or higher fluorescence than human enamel. SC2 and PVP showed rougher surfaces than the other bis-acryl composites. Smaller filler particles were observed on the surface of PT4 and PVP compared with the coarser particles from ST2 and SYS. Viscosity readings indicated a thixotropic behavior for all tested materials. SYS had the lowest and PT4 the highest degree of C=C conversion after 10 min. In the polymerization kinetics, PT4 had the highest maximum polymerization rate and reached earlier the transition between polymerization autoacceleration and autodeceleration. PT4 and SYS had significantly higher flexural strength and modulus than ST2 and PVP for most storage times. Results for Poisson ratio varied between materials. Longer storage periods were generally associated with higher frequency of catastrophic failures in the flexural tests. In conclusion, the performance of bis-acryl composite resins varied largely among materials.

Resumo Este estudo investigou o desempenho in vitro de quatro resinas compostas bisacrílicas comerciais: Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) e ProviPlast (PVP, Biodinamica). A caracterização envolveu análises ópticas (estabilidade de cor, parâmetro de translucidez, fluorescência), de superfície (rugosidade, morfologia e composição elementar), físico-químicas (viscosidade, cinética de polimerização) e mecânicas (razão de Poisson, resistência à flexão biaxial, módulo de elasticidade). A maioria dos testes foram realizados após 24 h, enquanto análises ópticas e mecânicas foram realizadas após armazenamento em água a 37 °C por 1, 15 e 30 dias. Os dados foram analisados estatisticamente (a=0,05). Grande parte dos resultados foi dependente do material. SYS e PT4 mostraram estabilidade de cor e translucidez ao longo do tempo. Todos os materiais apresentaram fluorescência similar ou maior que o esmalte humano. SC2 e PVP apresentaram superfícies mais rugosas que os outros materiais. Menores partículas de carga foram observadas na superfície de PT4 e PVP comparadas às partículas mais irregulares de ST2 e SYS. As leituras de viscosidade indicaram comportamento tixotrópico para todos os materiais testados. SYS teve a menor e PT4 o maior grau de conversão de C=C após 10 min. Na cinética de polimerização, PT4 teve a maior taxa máxima de polimerização e atingiu mais cedo a transição entre autoaceleração e autodesaceleração da polimerização. PT4 e SYS apresentaram resistência à flexão e módulo de elasticidade significativamente maiores que ST2 e PVP na maioria dos períodos de armazenamento. Resultados da razão de Poisson variaram entre os materiais. Períodos mais longos de armazenamento foram em geral associados a maior frequência de falhas catastróficas nos testes de flexão. Em conclusão, o desempenho das resinas compostas bisacrílicas variou amplamente entre os materiais.

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.

Influence of different fillers on the properties of an experimental vinyl polysiloxane

Abstract The aim of the study was to evaluate the effect of the incorporation of different fillers on an experimental vinyl polysiloxane (VPS) at two different concentrations, 20% and 40%. Different fillers were added to an experimental VPS. The study was developed in two stages: (i) incorporation of fillers in different concentrations: (a) 20 wt% fillers, and (b) 40 wt%. The fillers were added to experimental VPS and mixed with a speed mixer; (ii) characterization of experimental VPS; after the base paste and catalyst paste were mixed, the experimental VPS was used to make specimens specifically for each test, which were stored at 23°C for 24 hours. The tests were designed according to the specific standardization for the analysis of tensile strength, detail reproduction, Shore A hardness, and elastic recovery. For analysis of filler size pattern, scanning electron microscopy at 1500× magnification was used. The aerosil OX-50 40% (AE), and pure aluminum hydroxide 40% (PAH) groups presented the highest tensile strength and Shore A hardness values. However, those were the only groups that did not present continuous detail reproduction of an intersection of 20 μm line. The elastic recovery was not statistically significant. The undesirable characteristics of VPS (lowest Shore A hardness and tensile strength) were observed when it was added to the composition of acrylic polymer (AP) and fiberglass (FG) in both concentrations, 20% and 40%. In groups AE and PAH, agglomerates of nanofillers were shown in SEM micrography, while the other groups presented different shapes and fillers sizes.

Influence of addition of 2-[3-(2H-benzotriazol-2-YL)- 4-hydroxyphenyl] ethyl methacrylate to an experimental adhesive system

The aim of this study was to evaluate the addition of 2-[3-(2HBenzotriazol- 2-yl)-4-hydroxyphenyl]ethyl methacrylate (BTAM) to an experimental adhesive resin. An experimental base adhesive resin was formulated with BisGMA, TEGDMA and HEMA, to which BTAM was added at 1, 2.5 and 5%, in weight. One group with no addition was used as control. The experimental adhesives were evaluated for antibacterial potential (against Streptococcus mutans), degree of conversion with FTIR, softening in solvent and microRaman interface analyses. Data were analyzed by Kruskal-Wallis, paired t test and ANOVA and Tukey, considering a 5% level of significance. The results showed antibacterial activity of 5% BTAM against S. mutans (p<0.05), however, no difference was found among BTAM groups (p> 0.05). The results of degree of conversion and softening of solvent showed no statistical difference between BTAM and control groups (p>0.05). The addition of 5% BTAM showed higher antibacterial activity than the negative control, and copolymerization with comonomer blend of adhesive resin and BTAM was detected at the dentin/ adhesive interface.

O objetivo do presente estudo foi avaliar a adicao do 2-[3-(2HBenzotriazol- 2-yl)-4-hidroxifenil]etil metacrilato (BTAM) a um adesivo experimental. Uma resina adesiva base experimental foi formulada com BisGMA, TEGDMA e HEMA e a essa resina foi adicionado o BTAM nas concentracoes de 1, 2,5 e 5%, em peso, alem de um grupo controle sem adicao. Os adesivos experi - mentais foram avaliados quanto ao potencial antimicrobiano contra Streptococos mutans, grau de conversao com FTIR, degradacao em solvente e analise da interface com microespectroscopia Raman. Os dados foram analisados considerando um nivel de significancia de 5%. Os resultados obtidos no teste antimicrobiano contra S. mutans mostrou dife renca estatisticamente significativa do grupo com 5% de BTAM em relacao aos demais grupos e ao controle negativo (p<0,05). Os resultados de grau de conversao e degradacao em solvente dos grupos com BTAM nao apresentaram diferenca quando comparado ao grupo controle (p>0,05). Foi possivel observar a penetracao do BTAM na dentina. A adicao de BTAM na concentracao de 5% mostrou atividade antimicrobiana comparado ao controle negativo, alem de ter sido capaz de copolimerizar e penetrar na dentina.

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.

Effect of Composite Containing an Iodonium Salt on the Bond Strength of Brackets to Bovine Enamel

This study investigated the effect of the incorporation of an iodonium salt in experimental composites, on the bond strength of metallic brackets bonded to bovine teeth. Two hundred and seventy bovine teeth were embedded in self-curing acrylic resin and divided into 18 groups (n=15), according to the experimental composite with an iodonium salt at molar concentrations 0 (control), 0.5, or 1%; the light-activation times (8, 20 and 40 s); and the storage times (10 min or 24 h). Metallic brackets were fixed on the tooth surface using experimental composites. Photoactivation was performed with a quartz-tungsten-halogen light-curing unit curing unit for 8, 20 and 40 s. The specimens were stored in distilled water at 37 °C for 10 min or 24 h and submitted to bond strength test at 0.5 mm/min. The data were subjected to three-way ANOVA and Tukey's test (α=0.05). The Adhesive Remnant Index (ARI) was used to classify the failure modes. The shear bond strengths (MPa) at 10 min for light-activation times of 8, 20 and 40 s were: G1 - 4.6, 6.9 and 7.1; G2 - 8.1, 9.2 and 9.9; G3 - 9.1, 10.4 and 10.7; and at 24 h were: G1 - 10.9, 11.1 and 11.7; G2 - 11.8, 12.7 and 14.2; G3 - 12.1, 14.4 and 15.8. There was a predominance of ARI score 3 for groups with 10 min storage time, and ARI score 2 for groups with 24 h storage time. In conclusion, the addition of iodonium salt (C05 and C1) to the experimental composite may increase the bond strength of brackets to bovine enamel using reduced light exposure times.

Estudo investigou o efeito da incorporação de um sal de iodônio em compósito experimental, na resistência de união de braquetes metálicos fixados em dentes bovinos. Duzentos e setenta dentes bovinos foram embutidos e divididos em 18 grupos (n=15), de acordo com o compósito experimental com sal de iodônio na concentração molar de 0 (controle), 0,5 e 1 %; tempo de fotoativação (8, 20 e 40 s); e, tempo de armazenagem (10 min e 24 h). Braquetes metálicos foram fixados na superfície do dente usando compósitos experimentais. A fotoativação foi efetuada com o aparelho XL 2500 por 8, 20 e 40 s. As amostras foram armazenadas em água destilada a 37º C por 10 min e 24 h e submetidos ao ensaio de resistência de união à velocidade de 0,5 mm/min. Os dados foram submetidos à Análise de variância de 3 fatores e ao teste de Tukey (α=0,05). O Índice de Remanescente do Adesivo (IRA) foi usado para classificar os modos de falhas. Os valores de resistência de união ao cisalhamento (MPa) no período de 10 min para os tempos de fotoativação de 8, 20 e 40 s foram: G1 - 4,6; 6,9 e 7,1; G2 - 8,1; 9,2 e 9,9; G3 - 9,1; 10,4 e 10,7; e no período de 24 h foram: G1 - 10,9; 11,1 e 11,7; G2 - 11,8; 12,7 e 14,2; G3 - 12,1; 14,4 e 15,8. Houve predominância de escore 3 para os grupos armazenados por 10 min e escore 2 para os grupos armazenados por 24 h. Em conclusão, a adição do sal de iondônio (C05 e C1) em compósitos experimentais pode aumentar a resistência de união de braquetes ao esmalte bovino usando reduzidos tempos de fotoativação.

Scholarships for Scientific Initiation Encourage Post-Graduation Degree

This study aimed to evaluate the factors associated with the decision to attend an academic post-graduation program by dental students. A cross-sectional study was conducted in 2012, last-year undergraduate students from Dental Schools of Southern Brazil. A closed questionnaire was applied including questions grouped in three different blocks: pre-graduate, undergraduate period and future perspectives. The outcome was the decision to pursuit an academic post-graduation degree. Associations were tested using chi-squared test and chi-squared test for linear trends when appropriate. Multivariate Poisson regression was also performed. The sample was composed by 671 students (response rate of 69.9%, n=467). In relation to future perspectives, 68% of the interviewed students intended to attend a post-graduation program, but only 17.5% would choose a program with academic and research post-graduation program (Master and PhD programs). In the final model, students from public universities (PR 2.08, 95%CI 1.41-3.08) and students that received scientific initiation scholarship (PR 1.93 95%CI 1.14-3.27) presented a twice greater prevalence to seek academic post-graduate programs. Students with higher family incomes showed a lower prevalence to seek these programs (PR 0.50, 95%IC 0.28-0.90). Scholarships seem to encourage undergraduate students to pursue stricto sensu post-graduation.

Este estudo objetivou avaliar os fatores associados com a decisão de estudantes de Odontologia em participar de um programa de pósgraduação acadêmica. Um estudo transversal foi conduzido em 2012, com estudantes do último ano do curso de Odontologia do Sul do Brasil. Foi aplicado um questionário fechado composto por três diferentes blocos: período prévio à graduação, período da graduação e perspectivas futuras. O desfecho deste trabalho foi definido como a decisão de buscar uma pós-graduação acadêmica. As associações foram testadas com o teste de Qui-quadrado e de Qui-quadrado de tendência linear, quando apropriado. Além disso, foi feita a regressão multivariada de Poisson. A amostra foi composta por 671 estudantes (taxa de resposta de 69,9%, n=467). Em relação às perspectivas futuras, 68% dos estudantes entrevistados pretendem ingressar em um curso de pós-graduação, mas somente 17,5% escolheriam um programa com pós-graduação acadêmica e pesquisa (Programas de Mestrado e Doutorado). No modelo final, estudantes de universidades públicas (RP 2,08, 95% CI 1,41-3,08) e estudantes que receberam bolsa de iniciação científica (RP 1,93 95% CI 1,14-3,27) apresentaram prevalência duas vezes maior na busca de pós-graduação acadêmica. Estudantes de famílias com renda alta mostraram menor prevalência na busca destes cursos (RP 0,50, 95%IC 0,28-0,90). Desta forma, bolsas parecem incentivar os alunos de graduação na busca por pós-graduação stricto sensu.

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.

Novel experimental cements for use on the dentin-pulp complex

This aim of this study was to evaluate the physicochemical and biological properties of novel experimental cements (Hybrid, Paste and Resin) based on synergistic combinations of existing materials, including pH, diametral tensile strength (DTS) and cytotoxicity comparing them with mineral trioxide aggregate (MTA - Angelus®) and a glass ionomer cement (GIC) developed at our laboratory. For the physicochemical and biological tests, specimens with standard dimensions were produced. pH measurements were performed with digital pH meter at the following time intervals: 3, 24, 48 and 72 h. For the DTS test, cylindrical specimens were subjected to compressive load until fracture. The MTT assay was performed for cytotoxicity evaluation. Data were analyzed by ANOVA and Tukey's test (α=0.05). Paste group showed pH values similar to MTA, and Hybrid group presented pH values similar to GIC (p>0.05). The tested materials showed pH values ranging from alkaline to near neutrality at the evaluated times. MTA and GIC showed similar DTS values. The lowest and highest DTS values were seen in the Paste and Resin groups, respectively (p<0.05). Cell viability for MTA and experimental Hybrid, Paste and Resin groups was 49%, 93%, 90% and 86%, respectively, when compared with the control group. The photo-cured experimental resin cement showed similar or superior performance compared with the current commercial or other tested experimental materials.

O objetivo deste estudo foi avaliar propriedades físico-químicas e biológicas de novos cimentos experimentais (Híbrido, Pasta e Resinoso) baseado na combinação sinérgica de materiais existentes, incluindo pH, resistência à tração diametral (RTD) e citotoxidade, comparando-os ao MTA (Angelus®) e a um cimento de ionômero de vidro (CIV) desenvolvido em nosso laboratório. Para a realização dos testes físico-mecânico e biológico, foram confeccionados espécimes com dimensões padrão. O teste de pH foi realizado por meio de pH-metro digital nos tempos: 3, 24, 48 e 72 h. Para o teste de RTD, espécimes cilíndricos foram submetidos a carga compressiva até sua fratura. Para avaliação da citotoxidade, utilizou-se o teste MTT. Os dados foram analisados utilizando ANOVA e teste de Tukey (α=0,05). O grupo Pasta apresentou valores de pH semelhantes ao MTA, assim como o grupo Híbrido seguiu os parâmetros do CIV (p>0,05). Todos os materiais apresentaram valores de pH alcalinos ou próximosà neutralidade nos tempos avaliados. MTA e CIV apresentaram valores de RTD similares. Os menores e maiores valores observados foram do grupo Pasta e Resinoso, respectivamente (p<0,05). A viabilidade celular para os grupos MTA, Híbrido, Pasta, Resinoso, quando comparados ao grupo controle foi de: 49, 93, 90 e 86%, respectivamente. O cimento experimental Resinoso apresentou desempenho similar ou superior aos materiais comerciais e experimentais avaliados.

Influence of OrmocerTM component on the performance of dentin adhesive systems / Influência do componente Ormocer® no desempenho de sistemas adesivos dentinários

OBJECTIVE: Evaluate the influence of Ormocer™ component on the performance of dentin adhesive systems. METHODS: Microtensile bond strength test in adhesion of adhesive and dentin and characterization of the adhesive interface was done. As control, an adhesive system based on a traditional monomeric system was used. The teeth were embedded in acrylic resin and had their vestibular enamel removed in order to expose the dentin surface closer to the enamel. The exposed dentin was polished with 600 SiC sandpaper for 30s in running water to produce a standardized smear layer. Lower bovine incisors were used in this study, divided in two groups, according the adhesive system used: Ormocer™ based adhesive system and Solobond M adhesive system. On the polymerized adhesive two increments of composite resin were placed to cover the dentin surface completely. After storage for 24 hours in distilled water at 37ºC, the samples were cut to produce two sticks for each tooth, with adhesive interface area of approximately 0.5mm². Microtensile bond strength values are shown in MPa and fracture analysis with SEM was classified as adhesive, cohesive or mixed. RESULTS: There were no significant differences between Ormocer™ group: 45.11(±14.24) and Solobond M group: 47.36(±11.51), Student's t test (p>0.05). The predominant failure pattern was mixed for the two groups. CONCLUSION: The incorporation of Ormocer™ into dentin adhesives, in comparison with the conventional adhesive system tested did not influence the immediate bond strength.

OBJETIVO: Avaliar a influência do Ormocer® no desempenho de adesivos dentinários. MÉTODOS: Foi realizado o ensaio de microtração para se obter a resistência de união entre o adesivo e a dentina. A caracterização da interface também foi realizada. Como controle, utilizou-se um método de adesivo baseado em um sistema monomérico tradicional. Os dentes foram embutidos em resina acrílica e tiveram o esmalte vestibular removido para expor a dentina superficial que foi abrasionada com lixa d'água granulação 600 em água corrente, por 30 segundos para padronizar uma camada de lama dentinária. Neste estudo, foram utilizados incisivos inferiores bovinos divididos em dois grupos, de acordo com o sistema adesivo empregado: sistema adesivo com Ormocer® e o sistema adesivo convencional Solobond M. Sobre o adesivo polimerizado foram colocados dois incrementos de resina composta, cobrindo toda a superfície da dentina. Após a polimerização da resina, os dentes foram armazenados em água destilada a 37ºC por 24 horas e então seccionados, produzindo dois palitos por dente, com área adesiva de aproximadamente 0,5mm². Os valores obtidos no ensaio de microtração são mostrados em megapascals e as fraturas analisadas em microscopia eletrônica de varredura são classificadas como adesivas, coesivas ou mistas. RESULTADOS: Não foi encontrada diferença estatisticamente significativa entre os grupos Ormocer® e Solobond M (p>0,05), sendo os valores de 45,11(±14,24) e 47,36(±11,51), respectivamente. O padrão de fratura foi em sua maioria mista. CONCLUSÃO: A adição do componente Ormocer® não influenciou na resistência de união imediata à dentina quando comparado a um sistema adesivo convencional.

Influence of the composition of an experimental adhesive on conversion kinetics, flexural strength and radiodensity / Influência da composição de um adesivo experimental na cinética de conversão, resistência à flexão e radiodensidade

Purpose: To evaluate the effect of the addition of three radiopaque agents to an experimental adhesive on conversion kinetics, flexural strength and radiodensity. Methods: The model adhesive was formulated by mixing 50 wt% Bis-GMA, 25 wt% TEGDMA and 25 wt% HEMA. Barium sulfate, Titanium dioxide and Zirconium in 0.1, 0.2, 0.4, 0.8 and 1.6 wt% were added separately resulting in 15 experimental groups and 1 control group. The conversion kinetics of the model adhesive was evaluated using real time Fourier Transform Infrared Spectroscopy. The flexural tests were performed on 5 specimens (12 × 2 × 2 mm) for each group (total n = 80) in a universal testing machine. The radiodensity was evaluated by using an aluminum step-wedge and VistaScan phosphorous plates radiographs digital system with 0.6 s exposure and focal distance of 40 cm. Results: No statistical difference (P > 0.05) was found in flexural strength among all groups. The values of degree of conversion ranged from 45.51% e 62.46%. All groups showed higher values than 0.54 mm of aluminum for the evaluation of radiopacity. Conclusion: The addition of radiopaquing agents increased the adhesive radiodensity and did not affect its degree of conversion and flexural strength.

Objetivo: Avaliar a influência da adição de três substâncias radiopacificadoras na cinética de conversão, resistência à flexão e radiodensidade de um adesivo experimental. Metodologia: O adesivo foi formulado com 50% de Bis-GMA, 25% TEGDMA e 25% HEMA, em peso. Foram adicionados 0,1%; 0,2%; 0,4%; 0,8%; 1,6%, em peso, de Sulfato de Bário, Óxido de Titânio e Dióxido de Zircônia, totalizando 15 grupos experimentais e um grupo controle. A cinética de polimerização foi avaliada por FTIR em tempo real. O ensaio de miniflexão foi realizado com 5 espécimes (12 × 2 × 2 mm) para cada grupo (n total = 80) em uma máquina de ensaios universal. A radiodensidade foi obtida utilizando um sistema digital com placas de fósforo VistaScan, 0,6 s de exposição e distância focal de 40 cm e os valores foram comparados a uma escala de alumínio. Resultados: Não houve diferença estatisticamente significativa no ensaio de miniflexão entre os grupos (P > 0,05). Os valores de grau de conversão ficaram entre 45,51% e 62,46%, enquanto a radiodensidade foi superior a 0,54 mm de alumínio, sem diferença entre os grupos. Conclusão: O acréscimo das substâncias radiopacificadoras aumentou a radiopacidade do adesivo e não alterou o grau de conversão e a resistência à flexão.

Análise comparativa do desgaste de materiais odontológicos através de tribômetro Callowear: ensaio “in vitro” / Comparative analysis of dental materials wear measurement with Callowear tribometer: an “in vitro” study

The aim of present study was to evaluate the wear coeficient of different dental materials submited to ballcrattering test. Different restorative materials were compared to bovine enamel. The samples were made with nylon matrix stripes and had 7mm diameter and 2mm thickness. The samples were submitted to the ballcratering test in a Calowear tribometer (CSEM Instruments Advanced Mechanical Surface Testing) and maded six measures in each sample with different revolutions of the ball: 10, 20, 30, 40, 50 and 60 revolutions. After the crattering generation the samples were avaliated to a Zeiss Axiotech Vario Microscope with SVGA Cam and all cratters photographed. After, the photos were evaluated at UTHSCSA ImageTool for Windows 3.0 and the meaning of measured radius were inserted at SigmaPlot, that gave the wear coefficients by linear regression. To bovine enamel the coefficient was 3,83 X 10-14 m²/N, to microhybrid resin was 3,6542 x 10-14 m²/N, 2,06 x 10-12 m²/N to amalgam and 2,18 x 10-12 m²/N to acrylic resin. In conclusion, bovine teeth presented higher wear resistance and lower wear coefficient than composite resin, amalgam and acrylic resin.

O objetivo do presente estudo foi avaliar o coeficiente de resistência ao desgaste de diferentes materiais odontológicos submetidos ao ensaio de micro-abrasão através da metodologia de ball-crattering. Para isso foram avaliados diferentes materiais restauradores em comparação com o esmalte bovino. As amostras foram confeccionadas através de matrizes de nylon bipartida, com 7mm de diâmetro e 2mm de espessura em negativo e após, a resistência ao desgaste foi avaliada em um ensaio de micro abrasão (Ball cratering test) realizado em tribômetro modelo Calowear (CSEM Instruments Advanced Mechanical Surface Testing). Em cada corpo de prova foram feitas seis medições com variação no número de voltas realizadas pela esfera: 10, 20, 30, 40, 50 e 60 voltas. Após a realização das crateras o corpo de prova foi levado a um Zeiss Axiotech Vario Microscope com câmera SVGA acoplada onde foram fotografadas todas as crateras geradas e após, foram analisadas em UTHSCSA ImageTool for Windows versão 3.0, os valores de raio médio das marcas foram, então levados ao SigmaPlot versão 8.0 que através da correlação dos dados determinou o coeficiente de desgaste através de uma regressão linear. Para os corpos de esmalte bovino foi encontrado o coeficiente de desgaste de 3,83 X 10-14 m²/N, para resina composta micro híbrida 3,6542 x 10-14 m²/N, para amálgama de prata 2,06 x 10-12 m²/N e para resina acrílica autopolimerizável foi de 2,18 x 10-12 m²/N. Após a execução dos ensaios chega-se a conclusão que o esmalte bovino apresentou maior resistência e menor coeficiente de desgaste, seguido por resina composta, amálgama de prata e resina acrílica autopolimerizável.

Influence of eugenol-containing temporary restorations on the microleakage of total-etch and self-etching adhesive systems / Influência de restaurações temporárias contendo eugenol na microinfiltração de sistemas adesivos convencional e autocondicionante

Purpose: This in vitro study evaluated the influence of zinc oxide-eugenol temporary cement (ZOE-TC) on the sealing ability of composite restorations using two adhesive systems. Methods: Standard Class V cavities were prepared in 20 bovine incisors and restored with either ZOE-TC (IRM®) or eugenol-free cement (Cavit®) (n=10/temporary cement type). After 7 days, five teeth per material group were restored using Single Bond® (SB) and five using Adper Prompt® (AP). The cavities were filled with composite (Filtek Z-250), thermal cycled (500 cycles), immersed in basic fuchsine solution, and longitudinally sectioned. Dye penetration was evaluated using optical-microscopy and scored. Data were analyzed by Kruskal-Wallis test (P = 0.05). Results: Overall, leakage in dentin was similar to that in enamel. In enamel margins, only the group with Cavit® cement associated with AP presented significant higher leakage. In dentin margins, AP exhibited higher leakage than the groups restored with SB; there was no significant difference between eugenol-free cement and ZOE-TC. Conclusion: In general, SB showed better marginal sealing than AP, and ZOE-TC did not increase dye leakage. Eugenol in the temporary cement did not affect the marginal sealing of adhesive restorations.

Objetivo: Este estudo in vitro avaliou a influência de um cimento restaurador temporário à base de óxido de zinco-eugenol (CT-OZE) no selamento marginal de restaurações diretas, utilizando dois sistemas adesivos. Metodologia: Cavidades classe V foram preparadas em 20 incisivos bovinos e restauradas com dois cimentos temporários, CT-OZE (IRM®) ou cimento livre de eugenol (Cavit®) (n=10/cimento temporário). Após sete dias, cinco dentes de cada grupo de cimento temporário foram restaurados utilizando o sistema Single Bond® (SB) e os demais cinco com o sistema Adper Prompt® (AP). As cavidades foram restauradas com resina composta (Filtek Z-250), termocicladas (500 ciclos), imersas em fucsina básica e longitudinalmente seccionadas. A penetração do corante foi avaliada em microscópio ótico. Os dados foram analisados por teste de Kruskal-Wallis (P = 0,05). Resultados: A infiltração em dentina foi similar à do esmalte. Em esmalte, o grupo com Cavit® e AP apresentou infiltração significativamente maior. Em dentina, AP exibiu maior infiltração que SB, e não houve diferença entre CT-OZE e Cavit®. Conclusão: Em geral, SB produziu melhor selamento marginal que AP, e CT-OZE não aumentou a penetração de corante. A presença de eugenol no material restaurador temporário não afetou o selamento marginal de restaurações adesivas.