Influence of polymeric matrix on the physical and chemical properties of experimental composites

Nowadays, the main reasons for replacement of resin-based composite restorations are fracture or problems with the integrity of their interface, such as marginal staining, microleakage, or secondary caries. The aim of the present study was to evaluate the influence of the organic matrix on polymerization stress (PS), degree of conversion (DC), elastic modulus (E), flexural strength (FS), Knoop hardness (KHN), sorption (SP), and solubility (SL). In order to obtain a material which combines better mechanical properties with lower PS, seven experimental composites were prepared using BisGMA to TEGDMA molar ratios of 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 and 8:2 and 40% of silica. PS was obtained in a universal testing machine, using acrylic as bonding substrate. DC was determined using Fourier Transform Raman spectroscopy. E and FS were obtained by the three-point bending test. KHN was measured by a microindentation test using a load of 25 g for 30 s. SP and SL were assessed according to ISO 4049. The data were submitted to one-way ANOVA. The increase in BisGMA concentration resulted in the decrease of PS, DC, E, FS and KHN. However, it did not change the SP and SL values. FS, E and KHN showed a strong and direct relationship with the DC of the materials. The composite material with a BisGMA to TEGDMA molar ratio of 1:1 was the one with better mechanical properties and lower PS.

Radiant exposure effects on physical properties of methacrylate - and silorane-composites

AIM: To evaluate the effect of different radiant exposures on the degree of conversion (DC), Knoop hardness number (KHN), plasticization (P), water sorption (WS), and solubility (S) of different monomer resin-based composites. METHODS: Circular specimens (5 x 2 mm) were manufactured from methacrylate and silorane composite resins, and light-cured at 19.8, 27.8, 39.6, and 55.6 J/cm2, using second-generation LED at 1,390 mW/cm2. After 24 h, DC was obtained using a FT-Raman spectrometer equipped with a Nd:YAG laser, KHN was measured with 50-g load for 15 s, and P was evaluated on the top and bottom surfaces by the percentage of hardness reduction after 24 h immersed in absolute alcohol. WS and S were determined according to ISO 4049. Data were subjected to statistical analysis (α=0.05). RESULTS: Methacrylate material presented higher DC, KHN, P, and WS than silorane (p<0.05). There was no difference in the S values (p>0.05). The increased radiant exposures improved only the KHN (p<0.05). In general, top surfaces showed higher DC and KHN than bottom, for both materials (p<0.05). The increase of the radiant exposure did not improve most physical properties of the composites and were monomer-base dependent. CONCLUSIONS: Chemical composition of the composite resins resulted in different physical properties behavior and could affect the clinical longevity of dental restorations, but overall these properties were not influenced by the different radiant exposures evaluated in the study...

Knoop microhardness and FT-Raman evaluation of composite resins: influence of opacity and photoactivation source

The aim of this study was to evaluate the degree of conversion by Knoop microhardness (KHN) and FT-Raman spectroscopy (FTIR) of one nanofilled (Filtek Supreme-3M-ESPE [FS]) and one microhybrid composite (Charisma-Heraeus-Kulzer [CH]), each with different opacities, namely enamel, dentin, and translucent, which were photo-activated by a quartz-tungsten-halogen lamp (QTH) and a light-emitting diode (LED). Resin was bulk inserted into a disc-shaped mold that was 2.0 mm thick and 4 mm in diameter, obtaining 10 samples per group. KHN and FTIR values were analyzed by two-way ANOVA and Tukey's tests (α = 0.05). Nanofilled resin activated by a LED presented higher microhardness values than samples activated by a QTH for dentin opacity (p < 0.05). The microhybrid resin showed no differences in KHN or FTIR values with different activation sources or opacity. The nanofilled dentin and enamel resins showed lower FTIR values than the translucent resin. The KHN values of the translucent resins were not influenced by the light source.

Influência de diferentes opacidades e fontes ativadoras na microdureza e no grau de conversão de resinas compostas diretas / Influence af different apacities and activatian saurce in microhardness and degree af canversian oi direct campasite resin

Objetivos: avaliar o grau de conversão por meio da microdureza (KHN) e espectroscopia FT-Raman (GC) de uma resina composta direta microhíbrida (Opallis-FGM) com opacidades distintas: esmalte, dentina e translúcida fotoativadas com luz halógena (OTH, 700mW/cm2) ou luz emitida por diodo (LED, 1200mW/ em']. Materiais e métodos: sessenta corpos-de-prova foram preparados através da inserção da resina composta em incremento único em matriz de teflon bipartida com orifício central cilíndrico (2mm de altura e 4mm de diâmetro) e foram divididos em seis grupos (n= 10). Para o teste de microdureza Knoop foram realizadas cinco identações no lado oposto da superfície irradiada. O grau de conversão foi mensurado através de espectroscopia FT-Raman no lado oposto da superfície irradiada (n=5). Os dados de KHN e GC foram analisados separadamente por meio da análise de variância two-way e teste de Tukey (a=0,05) e correlacionados pelo teste de Pearson-r. Resultados: independente da opacidade, o LED proporcionou um maior GC do que OTH. Para a opacidade de dentina maiores valores de KHN e GC foram observados após ativação com LED, entretanto a resina translúcida não apresentou diferenças de KHN. A opacidade de esmalte apresentou valores de GC intermediários entre as demais e KHN similar à dentina, quando ativada com LED ou com OTH. Houve uma boa correlação entre KHN e GC r=0,5671 (p=O,OOll). Conclusões: pode- se concluir que o uso do LED pode resultar em valores maiores de KHN e GC para resina composta mais opaca comparadas à fonte halógena, tal diferença não é observada na resina composta translúcida.

Objectives: to evaluate the degree of conversion by Knoop microhardness (KHN) and FT-Raman spectroscopy (DC) of one microhybrid composite resin (Opallis-FGM) with different opacities: enamel, dentin, and translucent; photo-activated by quartz-tungsten-halogen lamp (OTH; 700mW/cm2) or light emitting diode (LED; 1200mW/cm2). Materiais and Methods: sixty samples were prepared by the resin insertion in bulk in a disc-shaped mold (2.0mm-thick and 4mm in dia meter) according to 6 groups of samples (n= 10). To Knoop evaluation five indentations in the center of the opposite surfa- ce to the light irradiated surface of the specimen were performed. The DC of the side opposite to the irradiated surface of the specimens was determined bya FT-Raman spectroscopy (n=5). KHN and DC values were analyzed by two-way ANOVA and Tukey tests (a=0.05) and correlated by Pearson-r test. Results: independent of the composite resin opacity the use of LED resulted in the higher DC than OTH. To dentin opacity higher KHN and DC were observed when activated by LED, in the other hand the translucent resin did not showed differences in KHN. The enamel opacity showed intermediary results of DC amongs others and similar KHN to dentin groups activated by LED or with OTH. There was a good correlation between KHN and DC r=0.5671 (p=O.OOll). Conclusions: it can be concluded that LED use may result in higher KHN and DC to the composite resin more opaque compared to OTH, this difference may not be observed to translucent composite resin.

Spectroscopic and thermal characterization of alternative model biomembranes from shed skins of Bothrops jararaca and Spilotis pullatus / Caracterização espectroscópica e térmica de biomembranas modelo alternativo de peles galpão de Bothrops jararaca e Spilotis pullatus

Recently, there has been an interest in the use of shed snake skin as alternative model biomembrane for human stratum corneum. This research work presented as objective the qualitative characterization of alternative model biomembranes from Bothrops jararaca and Spilotis pullatus by FT-Raman, PAS-FTIR and DSC. The employed biophysical techniques permitted the characterization of the biomembranes from shed snake skin of B. jararaca and S. pullatus by the identification of vibrational frequencies and endothermic transitions that are similar to those of the human stratum corneum.

Existe atualmente interesse no uso da muda de pele de cobra como modelos alternativos de biomembranas da pele humana. O presente trabalho apresentou como objetivo a caracterização qualitativa de modelos alternativos de biomembranas provenientes de mudas de pele de cobra da Bothrops jararaca e Spilotis pullatus por espectroscopia Raman (FT-Raman), espectroscopia fotoacústica no infravermelho (PAS-FTIR) e calorimetria exploratória diferencial (DSC). As técnicas biofísicas FT-Raman, PAS-FTIR e DSC permitiram caracterizar qualitativamente os modelos alternativos de biomembranas provenientes das mudas de pele de cobra da B. jararaca e S. pullatus e identificar freqüências vibracionais e transições endotérmicas similares ao estrato córneo humano.

Estudo sobre a biocompatibilidade da polisulfona sob a forma de partículas e bastöes / Study of biocompatibility of particles and rods of polysulfone

Foi estudada comparativamente a resposta do músculo tríceps sural e reto do abdome de ratos Wistar à implantação da polisulfona (PSU) e do polietileno de ultra alto peso molecular (UHMWPE) sob a forma de bastões e partículas, por um período de até 52 semanas. Ao final, a PSU foi considerada como tendo a mesma biocompatibilidade do UHMWPE, segundo os critérios utilizados.

Resposta da musculatura de ratos e partículas de polisulfona / Muscle response of rats by polysulphone particles

Neste trabalho foi estudada a resposta da musculatura triceps de ratos Wistar a particulas de uma poliétersulfona fabricada pela AMOCO e vendida sob o nome comercial UDELTM P-1800 implantadas na forma de particulas por um período de até 52 semanas. Ao final do período de implante, näo foi observado pelos autores nenhum indício que indicasse toxicidade do material