Effect of different solutions on color stability of acrylic resin-based dentures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of polyarylacetylene for use in the monolithic vitreous carbon processing

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hygrotermal effects evaluation using the losipescu shear test for glare laminates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dielectric behaviour of CaCu3Ti4O12-epoxy composites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of polymerization methods and thermal cycling on color stability of acrylic resin denture teeth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of storage times on bond strength of resin cements to root canal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural characterization of Li-MN doped powders prepared by Pechini's method

Pechini's method has been successfully used to prepare Li-doped MgNb2O6(MN) at short time and low temperature. It consists in the preparation of metal citrate solution, which is polymerized at 250°C to form a high viscous resin. This resin was burned in a box type furnace at 400°C/2h and ground in a mortar. Successive steps of calcination up to 900°C were used to form a crystalline precursor. SEM, DTA and XRD were used to characterize the powders. MN precursor powders containing from 0.1 to 5.0 mol% of LiNbO3 additive was prepared aiming better dielectric properties and microstructural characteristics of the PMN prepared from columbite route. SEM analysis showed that particles increased by sintering, forming large agglomerates. The surface area is also substantially reduced with the increase in additive amount above 1.0 mol%. In XRD pattern of the precursor material with 5.0 mol% of additive was observed the LiNbO3 phase of trigonal structure. XRD data were used for Rietveld refinement and a decrease in microstrain and pronounced increase in crystallite size with the increase of LiNbO3 were observed. It is in agreement with the particle morphologies observed by SEM analysis.

A comparison of microhardness of indirect composite restorative materials

The purpose of this study was to compare the microhardness of four indirect composite resins. Forty cylindrical samples were prepared according to the manufacturer s recommendations using a Teflon mold. Ten specimens were produced from each tested material, constituting four groups (n=10) as follows: G1 - Artglass; G2 - Sinfony; G3 - Solidex; G4 - Targis. Microhardness was determined by the Vickers indentation technique with a load of 300g for 10 seconds. Four indentations were made on each sample, determining the mean microhardness values for each specimen. Descriptive statistics data for the experimental conditions were: G1 - Artglass (mean ±standard deviation: 55.26 ± 1.15HVN; median: 52.6); G2 - Sinfony (31.22 ± 0.65HVN; 31.30); G3 - Solidex (52.25 ± 1.55HVN; 52.60); G4 - Targis (72.14 ± 2.82HVN; 73.30). An exploratory data analysis was performed to determine the most appropriate statistical test through: (I) Levene's for homogeneity of variances; (II) ANOVA on ranks (Kruskal-Wallis); (III) Dunn's multiple comparison test (0.05). Targis presented the highest microhardness values while Sinfony presented the lowest. Artglass and Solidex were found as intermediate materials. These results indicate that distinct mechanical properties may be observed at specific materials. The composition of each material as well as variations on polymerization methods are possibly responsibles for the difference found in microhardness. Therefore, indirect composite resin materials that guarantee both good esthetics and adequate mechanical properties may be considered as substitutes of natural teeth.

Composite resin color stability: influence of light sources and immersion media

This study evaluated the influence of light sources and immersion media on the color stability of a nanofilled composite resin. Conventional halogen, high-power-density halogen and high-power-density light-emitting diode (LED) units were used. There were 4 immersion media: coffee, tea, Coke® and artificial saliva. A total of 180 specimens (10 mm x 2 mm) were prepared, immersed in artificial saliva for 24 h at 37±1ºC, and had their initial color measured with a spectrophotometer according to the CIELab system. Then, the specimens were immersed in the 4 media during 60 days. Data from the color change and luminosity were collected and subjected to statistical analysis by the Kruskall-Wallis test (p<0.05). For immersion time, the data were subjected to two-way ANOVA test and Fisher's test (p<0.05). High-power-density LED (ΔE=1.91) promoted similar color stability of the composite resin to that of the tested halogen curing units (Jet Lite 4000 plus--ΔE=2.05; XL 3000--ΔE=2.28). Coffee (ΔE=8.40; ΔL=-5.21) showed the highest influence on color stability of the studied composite resin. There was no significant difference in color stability regardless of the light sources, and coffee was the immersion medium that promoted the highest color changes on the tested composite resin.

Acrylic resin cytotoxicity for denture base - Literature review

Acrylic resin is a widely used material in clinical practice, and a satisfactory biocompatibility is essential. When the resin polymerization reaction is incomplete, residual monomers are released into the oral cavity. The aim of this study was to evaluate, through a literature review, the cytotoxicity caused by the denture base acrylic resin used, and its components. The selection of published studies was performed on the Pubmed database from January 2008 to July 2013. The keywords used were: cytotoxicity and acrylic resins, cytotoxicity and denture base resins and cytotoxicity and oral prosthesis. Inclusion criteria were: in vitro studies and literature reviews published in English that evaluated the acrylic resin cytotoxicity for denture base and its components. Studies with no reference to the search strategy were excluded. A total of 182 articles were found. Among these, only 13 were included for writing this review. The MTT test is the most common test used to evaluate acrylic resin cytotoxicity. Auto-polymerized resin is more cytotoxic than heat-polymerized resin because of its higher quantity of residual monomers which cause cell and tissue changes in the oral mucosa. However, more studies are necessary for the development of biocompatible materials.

Color stability of the artificial iris button in an ocular prosthesis before and after acrylic resin polymerization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Polymerization kinetics and polymerization stress in resin composites after accelerated aging as a function of the expiration date

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Adesivos multi-uso-avaliação da resistência adesiva a dentina frente a teste de cisalhamento, estereomicroscopia e microscopia eletrônica de varredura

Recent bonding systems have been advocated as multi-purpose bonding agents. The aim of this study was to determine if some of these bonding systems could be associated to composite resins from different manufacturers. This investigation was conducted to test lhe shear bond strength of three bonding systems: Scotchbond Multi-Purpose (3M Dental Products), Optibond Light Cure (Kerr) and Optibond Dual Cure (Kerr), when each of them was associated to lhe composite resins: Z1 00 (3M Dental Products), Prisma - APH (Dentsply) and Herculite XRV (Kerr). Seventy-two flat dentin bonding sites were prepared to 600 grit on human premolars mounted using acrilic resins. The teeth were assigned at random to 9 groups of 8 samples each. A split die with a 3mm diameter was placed over lhe surface of lhe dentin treated with one of lhe adhesive systems, and lhe selected composite resin was inserted and light cured. The split mold was removed and all samples were termocycled and stored in 37ºC water for 24 hours before testing. Shear bond strength was determined using an lnstron Universal testing machine. Some failures were examined under lhe S.E.M. Data was analysed by one-way analysis of variance, that demonstrated a significant difference (p<0,05) in the mean shear bond strength among Optibond Light Cure (15,446 MPa), Scotchbond Multi-Purpose (13,339 MPa) and Optibond Dual Cure (10,019 MPa). These values did not depend on the composite resin used. The association between bonding system/composite resin was statistycally significant (p<0,05) and the best results were obtained when the composite resins Z100 and Herculite were used with the adhesive system Optibond Light Cure, and when the composite resin APH was used with the adhesive system Scotchbond Multi-Purpose

Protese ocular individualizada em resina acrílica com esfera oca

The technique proposed aims at reducing the weight of individualized ample ocular prostheses using acrylic resins as well as simplifying laboratory procedure. For that, prefabricated hollow spheres made of plastic material, were inserted in the sclera. The average weights of the solid conventional sclera (5.30g) and those of the respective prefabricated plastic ones (3.91g) were compared. The weight reduction was significative with a confidence interval of 95% by the Student t test. ln addition, for illustration purpose, the technique was applied to patients in the ward of the Maxillofacial Prostheses Dicipline of the Dentistry School in the Campus of São José dos Campos - UNESP, having each patient received a solid prosthesis and a hollow prefabricated one made of plastic material. It has been concluded that the prostheses material spheres were inserted are lighter than the ones which received solid spheres; furthermore, thr technique is viable for ample anophtalmic cavities and requires few sessions

Contração de polimerização e expansão higroscópica de resinas compostas: análise pela técnica de video-imagem

To evaluate the volumetric changes due to polymerization and thermocycling on different resin-composites. Methods: Thirteen A2 Universal Dentin shade resin-composites (n = 10) from eight manufacturers were evaluated (4Seasons, Grandio, Venus, Amelogen Plus, P90, Z350, Esthet-X, Amaris, Vita-l-escence, Natural-Look, Charisma, Z250 and Opallis). The polymerization shrinkage percentage (PS) was calculated using an image measurement device (ACUVOL - Bisco Dental). Equal volumes of material, standardized by a semisphere polyurethane matrix (d = 3mm) were used and, after 5 minutes of relaxation, the baseline volume measurements were obtained with 18 J of energy dose from the LED light-curing unit. Measurements were obtained after 5 minutes and PS values calculated. Specimens were stored in a drydark environment for 24 hours and re-measured. Specimens were then thermocycled in distilled water between 5oC and 55oC for 20,000 cycles, subjected to another volume measurement at 5,000 cycle intervals. Specimens were gently dried prior to each measurement. Results: Repeated measurements were made using ANOVA (α = 0.05) showed that all resin-composite volumes were influenced by the number of cycles. Volumes at 5 minutes post-polymerization (12.47 ± 0.08) were significantly lower than those at baseline (12.80 ± 0.09). Volumes at 24 hours (12.43 ± 0.19) were insignificantly lower than those at 5 minutes postpolymerization. With regards to the impact of thermocycling, all specimens showed statistically significant increases in volume after 5,000 cycles (13.04 ± 0.22). Although statistically different from those after 5,000 cycles, there was no statistically significant difference between volumes measured at 10,000 (12.87±0.21), 15,000 (12.92±0.24), and 20,000 (12.84±0.23) cycles. Conclusion: According to the video-imaging analysis, thermocycling caused a significant expansion in resin-composites tested, the volume increase was not able to...