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OBJECTIVE. The aim of this study was to investigate the influence of the photoinitiator system on the polymerization kinetics of methacrylamide-based monomers as alternatives to methacrylates in adhesives dental-based materials. METHODS. In total, 16 groups were tested. Monofunctional monomers (2-hydroxyethyl methacrylate) – HEMA; (2-hydroxy-1-ethyl methacrylate) −2EMATE, (2-hydroxyethyl methacrylamide) – HEMAM; and (N-(1-hydroxybutan-2-yl) methacrylamide) −2EM; were combined with bifunctional monomers containing the same polymerizing moieties as the monofunctional counterparts (HEMA-BDI; 2EMATE-BDI; HEMAM-BDI; and 2EM-BDI) at 50/50M ratios. BHT was used as inhibitor (0.1 wt%) and the photoinitiators used were: CQ+EDMAB (0.2/0.8), BAPO (0.2), IVOCERIN (0.2), and DMPA (0.2), in wt%. The polymerization kinetics were monitored using Near-IR spectroscopy (~6165cm(−1)) in real-time while the specimens were photoactivated with a mercury arc lamp (Acticure 2; 320–500nm, 300mW/cm(2)) for 5min, and maximum rate of polymerization (Rp(max), in %.s(−)–(1)), degree of conversion at Rp(max) (DC@Rp(max), in %), and the final degree of conversion (Final DC, in %) were calculated (n = 3). Initial viscosity was measured with an oscillating rheometer (n = 3). Data were analyzed using Two-way ANOVA for the polymerization kinetics and one-way ANOVA for the viscosity. Multiple comparisons were made using the Tukey’s test (α= 0.05). RESULTS. There was statistically significant interaction between monomer and photoinitiator (p < 0.001). For the methacrylates groups, the highest Rp(max) was observed for HEMA + DMPA and 2EMATE + BAPO. For methacrylamides groups, the highest Rp(max) were observed for HEMAM and 2EM, both with DMPA. Final DC was higher for the methacrylate groups, in comparison with methacrylamide groups, independent of the photoinitiators. However, for the methacrylamide groups, the association with BAPO led to the lowest values of DC. In terms of DC@Rp(max), methacrylate-based systems showed significantly higher values than methacrylamide formulations. DMPA and Ivocerin led to higher values than CQ/EDMAB and BAPO in methacrylamide-based compounds. BAPO systems showed de lowest values for both HEMA and HEMAM formulations. For the viscosity (Pa.s), only 2EM had higher values (1.60±0.15) in comparison with all monomers. In conclusion, polymerization kinetics was affected by the photoinitiators for both monomers. Viscosity was significantly increased with the use of secondary methacrylamide.

Objectives Thiourethane oligomers have been shown to increase the fracture toughness and reduce the polymerization stress of methacrylate-based materials. However, network formation has not been elucidated in these materials yet. The aim of this study was to evaluate how the addition of a thiourethane oligomer (TU) influences the sol/gel composition and network structure of methacrylate-based materials using dynamic mechanical analysis and extraction methods. Materials and methods BisGMA/TEGDMA at systematically varied mass ratios (20/80 to 80/20 wt%) were mixed with pre-polymerized thiourethane oligomers at 0 (control) or 20 wt%, synthesized by combining pentaerythritol tetra-3-mercaptopropionate with dicyclohexylmethane 4,4′-Diisocyanate, at 1:2 isocyanate:thiol. 0.1 wt% of 2,2-Dimethoxy-2-phenylacetophenone was added as the photoinitiator and 0.3 wt% of 2,6-di-tert-butyl-4-methylphenol was added as a free radical inhibitor. Disk specimens (0.8 × 10 mm in diameter, n = 3) were photoactivated at 270 mW/ (320–500 nm) for 1 min. The degree of conversion (DC) was measured in near-IR (˜6165 cm−1). Specimens were immersed in two different solvents (water for 7 days or dicholoromethane for 48 h). Water sorption (WS) and solubility (SL) were obtained according to ISO 4049. The leachates for both solutions were analyzed with 1H-NMR (400 MHz, CDCL3). Bar specimens (1 × 3 × 25 mm, photocured and then post-processed at 180 °C for 8 h to DC > 95%) were subjected to dynamic mechanical analysis (−30 to 230 °C) to obtain glass transition temperature (Tg), tan delta curves and crosslinking density (ν). Data was analyzed with two-way ANOVA/Tukey’s test (95%). Results In general, the presence of TU increased the overall conversion. The WS was similar for all groups, but the SL decreased by 2-fold with the addition of the TU oligomer for all compositions, except BisGMA/TEGDMA 80/20. The BisGMA concentration of the leachates increased with increasing BisGMA in the initial mixture, and with the presence of thiourethane. This compositional drift of the gel with the presence of TU was attributed to the preferential dissolution of TEGDMA into the TU network. Tg and ν decreased with the addition of TU, as expected. The addition of TU produced more homogeneous networks, as evidenced by narrower breadth of the tan delta curve. Conclusion The addition of TU affected the composition of the sol/gel in crosslinked networks, which were more homogeneous and presented 2-fold less potentially toxic leachates than the methacrylate controls. Clinical significance The addition of TU may produce less cytotoxic materials based on the increased conversion and reduced amount of unreacted extractables from its network after water storage.

This study investigated the effects of oxygen inhibition and finishing/polishing procedures on the composite resin properties. One bulk-fill and two conventional composite resins (nanoparticle and microhybrid) were evaluated. Specimens were prepared using 4 surface treatments: control, no treatment; Gly, oxygen inhibition with glycerin; FP, finishing and polishing; Gly + FP, glycerin followed by finishing and polishing. The degree of conversion (DC) was measured using Fourier Transformed Infrared Spectroscopy (FTIR) immediately and after 15 days (n=5). Color stability (ΔEab, and ΔE00) and opacity were evaluated using a spectrophotometer after 15 days of immersion in coffee, using the CIELAB system (n=5). Data were analyzed by two-way ANOVA and Tukey tests (α=0.05) and opacity by two-way repeated-measures ANOVA. Glycerin usage increased significantly the DC however had no influence on the ΔEab, ΔE00 and, opacity values. Finishing and polishing reduced ΔEab and ΔE00 values, regardless of composite resins. Microhybrid showed higher opacity, followed by the nanoparticle and bulk fill, regardless of surface treatment. Post-polymerization polishing procedures resulted in lower conversion than using an oxygen inhibitor agent (Gly condition), but similar staining caused by coffee. Resumo Este estudo investigou os efeitos da inibição de oxigênio e dos procedimentos de acabamento/polimento nas propriedades das resinas compostas. Foram avaliadas uma resina composta bulk fill e duas resinas convencionais (nanoparticulada e microhíbrida). Os espécimes foram confeccionados, variando o tratamento de superfície: controle, sem tratamento; glicerina (inibidor de oxigênio); acabamento e polimento; glicerina + acabamento e polimento. O grau de conversão (GC) foi medido pela Espectroscopia de Infravermelho Transformada de Fourier (FTIR) imediatamente e após 15 dias da confecção dos espécimes (n=5). Os índices de alteração de cor ΔEab, ΔE00 e opacidade foram avaliados por meio de espectrofotômetro, após 15 dias de imersão no café, utilizando o sistema CIELAB (n=5). Os dados da alteração da cor foram analisados pelos testes ANOVA de dois fatores e Tukey (α=0,05) e a opacidade por ANOVA de medidas repetidas. O uso de glicerina aumentou significativamente o GC, no entanto, não teve influência sobre os valores ΔEab e ΔE00. O acabamento e o polimento reduziram os valores de ΔEab e ΔE00, independentemente da resina composta. A resina microhíbrida apresentou maior opacidade, seguida pela nanoparticula e bulk-fill, independentemente do tratamento de superfície. O acabamento e polimento resultou em menor grau de conversão das resinas compostas se comparado ao uso de um agente inibidor de oxigênio (glicerina), porém apresenta resultados similares para a pigmentação pelo café.

O objetivo geral desse estudo foi investigar a composição química, o desafio bacteriano, o acabamento/polimento e os protocolos de cimentação de diferentes materiais restauradores. Este estudo foi dividido em 4 capítulos, de acordo com cada objetivo específico: capítulo 1) avaliar como a adição de tiouretano influencia a composição do método de síntese sol-gel e a estrutura da rede polimérica de metacrilatos; capítulo 2) avaliar o efeito do desafio bacteriano na resistência de união de resinas compostas reparadas com silano modificado com tiouretano; capítulo 3) avaliar os efeitos da inibição de oxigênio e dos procedimentos de acabamento/polimento nas propriedades de resinas compostas convencionais e de incremento único; capítulo 4) avaliar os protocolos de cimentação e o momento para a realização do preparo protético na resistência de união e padrões de falha de pinos de fibra de vidro à dentina do canal radicular de incisivos bovinos. Os métodos experimentais utilizados foram grau de conversão, sorção e solubilidade, análise dinâmico-mecânica e de extração, ensaio mecânico de microcisalhamento, alteração de cor, opacidade, ensaio mecânico de micro push-out e microscopia óptica. Após a análise estatística dos dados, conclui-se que a adição de tiouretano nos metacrilatos afetou a composição no método de síntese sol-gel nas redes de ligações cruzadas, as quais apresentaram ser mais homogêneas, com menor quantidade de lixiviados potencialmente tóxicos; após o desafio bacteriano, o silano modificado com tiouretano foi capaz de manter a resistência de união das interfaces entre a resina composta original e reparada; o acabamento e polimento resultou em menor grau de conversão das resinas compostas se comparado ao uso de um agente inibidor de oxigênio (glicerina), porém apresentou resultados similares para o manchamento com café; o protocolo de cimentação dos pinos de fibra de vidro e o momento para a realização do preparo protético não influenciaram a resistência da união do pino à dentina radicular, mas a interação entre estes fatores foi significante; nenhuma falha coesiva foi observada e duas falhas adesivas na interface de união entre pino e dentina radicular foram detectadas. The general objective of this study was to investigate the chemical composition, finishing and polishing and luting protocols of different restorative materials. This study was divided into 4 chapters, according to the specific objectives: chapter 1) to evaluate how the addition of thiourethane influences the composition of the sol-gel composition and network structure of methacrylate-based materials; chapter 2) to evaluate the effect of bacterial challenge on the bond strength of composite resins repaired with silane modified with thiourethane; chapter 3) to evaluate the effects of oxygen inhibition and finishing/polishing procedures on the surface of conventional and bulk-fill composite resins; chapter 4) to evaluate luting protocols and the time to prosthetic preparation, in the bond strength and failure modes of fiber post to the root dentin of bovine incisors. The experimental methods used were degree of conversion, water sorption and solubility, dynamic mechanical analysis, extraction methods, micro-shear bond strength, color stability, opacity, micro push-out bond strength and optical microscopy. After statistical analysis of the data, it was concluded that the addition of thiouretane in methacrylates affected the composition in the sol-gel synthesis method in cross-link networks, which presented to be more homogeneous, with a lower amount of leached potentially toxic; after bacterial challenge, the use of TU silanes was able to maintain the bond strength of repaired interfaces of composites; post-polymerization polishing procedures resulted in lower conversion than using an oxygen inhibitor agent (Gly condition), but similar staining caused by coffee; both time to prosthetic preparation and luting protocol influenced the bond strength of the fiber post to the root dentin with combined effect; no cohesive failures were observed, and two adhesive failures in the interface between the post and root dentin were found. Tese (Doutorado) 2022-03-11

Despite several advantages associated with pre-fabricated glass-fiber posts, the coronal portion of these posts must be cut to allow their use in various clinical situations. However, cutting the cemented post can generate stress on the bonding interface and affect the bond strength. The aim of this study was to investigate the effect the of fiber post cutting on the bond strength of root canals. Sixty bovine incisor roots were included in resin cylinders with simulated periodontal ligaments. Glass-fiber posts were luted using regular resin cement RelyX ARC (3M ESPE) or self-adhesive cement RelyX Unicem (3M ESPE). The posts were cut prior to cementation, immediately after luting or after building up the core (n=10). After storage for 24 h, the samples were cut and subject to push-out testing using a mechanical testing machine (EMIC DL 2000). Data were analyzed using two-way ANOVA (resin cement x moment of post cutting) and Tukey's post hoc test (α=0.05). The moment of fiber post cutting did not affect the bond strength when Unicem was used. However, the bond strength was reduced when ARC was used and when the post was cut immediately. In conclusion, the moment of fiber post cutting may affect the retention of root canal posts when a regular resin cement is used.

Posterior composite restorations may be negatively affected by acidic and colored drinks. Little information is available about the effect of acidic drinks on bulk-fill composite resins.The purpose of this in vitro study was to investigate the effect of acidic drinks on the different properties of conventional and bulk-fill composite resins.A conventional composite resin and 2 representative bulk-fill composite resins were used to prepare disk-shaped specimens. The degree of conversion (DC) was monitored by spectroscopy (n=5). The specimens were divided into 5 groups: control, artificial saliva, acai juice, red wine, and Coca-Cola and were maintained for 30 days of challenge (3 periods of 15 min/d). Surface topography parameters were measured by interferometry (n=5). Elastic modulus (E) and Vickers hardness (VH) were determined by microhardness dynamic indentation (n=5). Diametral tensile strength (DTS) was determined at 0.5 mm/min (n=5). Shade matching was evaluated by using the Vitapan Classic Shade Guide. The DC, Sa, Ssk, Sku, Sdq, and DTS were statistically analyzed using 2-way ANOVA, followed by the Tukey HSD tests. E and VH were statistically analyzed by 3-way ANOVA, followed by Tukey HSD tests (α=.05). Shade matching was analyzed with the Kruskal-Wallis test.DC values were similar for the immediate evaluation and after 24 hours, regardless of the composite resin (P.05). All surface topography parameters increased significantly after the acidic drinks and were greatest for Coca-Cola. The E, VH, and DTS decreased significantly for all composite resins tested (P.05). Acai juice and red wine produced more surface staining than Coca-Cola.Acidic drinks negatively influenced the physical and mechanical properties of conventional and bulk-fill composite resins.

O bom desenvolvimento dos tuberculos de batata requer, entre outras praticas culturais, uma adubacao adequada. A cultura da batata e altamente exigente em nutrientes, sendo responsavel por um elevado consumo de fertilizantes. O fosforo e o nutriente que oferece maior resposta em produtividade de tuberculos nos solos brasileiros. O objetivo deste trabalho foi estudar o efeito de doses de adubacao fosfatada na cultura da batata, cultivar Agata, avaliando-se o teor foliar e a produtividade de tuberculos, em condicoes de campo. O experimento foi conduzido na Estacao Experimental da Cooperativa Agropecuaria do Alto Paranaiba – COOPADAP, localizada no municipio de Rio Paranaiba – MG, durante o ano agricola de 2008/2009. Os tratamentos consistiram de cinco doses de fosforo (P2O5) – 0, 200, 400, 600 e 800 kg ha-1, tendo o superfosfato simples como fonte. O teor de fosforo foliar nas plantas de batata diminui com o aumento das doses de adubacao fosfatada. A cultura apresenta incremento de produtividade com a adicao de doses crescentes de fosforo, atingido a produtividade maxima total estimada de 49,11 t ha-1 com a aplicacao de aproximadamente 700 kg ha-1 de P2O5.

The aim of this study was to evaluate the effect of adhesive protocol on the retention of glass-fiber posts luted into root canals. Thirty bovine incisors were endodontically treated and 9-mm-deep post holes were prepared. Fiber posts were luted using one of following protocols (n = 10): SB – Single Bond (3 M ESPE) with regular resin cement RelyX ARC (3 M ESPE); SBMP – Scotchbond Multipurpose Plus (3 M ESPE) associated with RelyX ARC; or UNI – the self-adhesive resin cement RelyX Unicem (3 M ESPE). After cementation, root/post specimens were transversally sectioned into 1-mm-thick slices, which were submitted to push-out testing in a mechanical testing machine. Bond strength data were analyzed by ANOVA (α = 0.05). There was no statistical difference between the adhesive protocols evaluated. Considering that the adhesive protocols evaluated showed similar bond strength values, simpler protocols must be preferable to lute fiber posts to root canal.