Dureza de resinas acrílicas para base de prótese e reembasamento imediato

INTRODUCTION: The hardness of denture base materials may undergo changes due to continued polymerization reaction and water uptake. However, the extent to which these processes affect the hardness of materials is still unclear. OBJECTIVE: In this study, the degree of conversion of two hard chair-side reline resins (Duraliner II-D and Kooliner-K) and one heat-cured acrylic resin (Lucitone 550-L) was evaluated indirectly by measuring the surface hardness. The effect of immersion in water on this property was also analyzed. MATERIALS AND METHODS: After processing following the manufacturers' instructions, specimens (5mm diameter and 2mm thickness) were dry stored at room temperature and the Vickers hardness (VHN) was measured with a hardness tester after 0, 2, 7, 30 and 90 days. Specimens were then immersed in water at 37ºC and hardness was evaluated after the same time intervals. Five specimens were prepared for each material. Data were analyzed by Kruskal-Wallis test (P=.01). RESULTS: When dry stored, material L showed an increase in hardness (P;.01). After 2-day water storage, all materials showed a significant reduction in hardness (PINTRODUÇÃO: A dureza das resinas para base de prótese e para reembasamento imediato pode apresentar alterações devido à polimerização continuada e absorção de água. Entretanto, a magnitude do efeito de cada um desses processos ainda não foi definida. OBJETIVO: Neste estudo, o grau de conversão de duas resinas autopolimerizáveis para reembasamento (Duraliner II-D and Kooliner-K) e de uma resina termopolimerizável para base de prótese (Lucitone 550-L) foi avaliado, indiretamente, por meio da mensuração da dureza. O efeito da imersão em água sobre essa propriedade também foi analisado. MATERIAL E MÉTODOS: Após a polimerização, amostras (diâmetro - 5 mm; espessura - 2 mm) foram armazenadas a seco em temperatura ambiente e a dureza Vickers (VHN) foi mensurada após 0, 2, 7, 30 e 90 dias. As amostras foram, então, imersas em água a 37º C e a dureza foi avaliada nos períodos citados. Cinco amostras foram preparadas para cada material. Os resultados foram analisados utilizando-se o teste de Kruskal-Wallis (P=.01). RESULTADOS: Para o armazenamento a seco, o material L apresentou aumento significativo na dureza (P;.01). Após 2 dias de armazenamento em água, todos os materiais apresentaram redução significativa na dureza (

Efeito de tratamentos térmicos após a polimerização sobre a citotoxicidade de duas resinas acrílicas para base de próteses

INTRODUCTION: Most denture base acrylic resins have polymethylmethacrylate in their composition. Several authors have discussed the polymerization process involved in converting monomer into polymer because adequate polymerization is a crucial factor in optimizing the physical properties and biocompatibility of denture base acrylic resins. To ensure the safety of these materials, in vitro cytotoxicity assays have been developed as preliminary screening tests to evaluate material biocompatibility. ³H-thymidine incorporation test, which measures the number of cells synthesizing DNA, is one of the biological assays suggested for cytotoxicity testing. AIM: The purpose of this study was to investigate, using ³H-thymidine incorporation test, the effect of microwave and water-bath post-polymerization heat treatments on the cytotoxicity of two denture base acrylic resins. MATERIALS AND METHODS: Nine disc-shaped specimens (10 x 1 mm) of each denture base resin (Lucitone 550 and QC 20) were prepared according to the manufacturers' recommendations and stored in distilled water at 37ºC for 48 h. The specimens were assigned to 3 groups: 1) post-polymerization in a microwave oven for 3 min at 500 W; 2) post-polymerization in water-bath at 55º C for 60 min; and 3) without post-polymerization. For preparation of eluates, 3 discs were placed into a sterile glass vial with 9 mL of Eagle's medium and incubated at 37ºC for 24 h. The cytotoxic effect of the eluates was evaluated by ³H-thymidine incorporation. RESULTS: The results showed that the components leached from the resins were cytotoxic to L929 cells, except for the specimens heat treated in water bath (pINTRODUÇÃO: A maioria das resinas acrílicas utilizadas para confecção de bases de próteses é composta pelo polimetacilato de metila. Muitos autores têm discutido o processo de polimerização dessas resinas em relação à conversão do monômero em polímero devido a sua importância na melhora da biocompatibilidade e das propriedades físicas. Para assegurar a utilização desses materiais, testes preliminares de citotoxicidade in vitro têm sido desenvolvidos para avaliação da biocompatibilidade. Um dos ensaios biológicos sugeridos para a análise da citotoxicidade é o teste de incorporação de ³H-timidina, o qual mede o número de células por meio da síntese de DNA. OBJETIVO: O objetivo do presente estudo foi avaliar, por meio do teste de incorporação de ³H-timidina, a citotoxicidade de duas resinas acrílicas para base de próteses submetidas aos tratamentos em microondas e em banho de água após a polimerização. MATERIAL E MÉTODO: Nove corpos-de-prova em forma de discos (10 x 1 mm) foram confeccionados com as resinas acrílicas Lucitone 550 e QC 20 de acordo com as instruções dos fabricantes, e foram armazenados em água destilada a 37ºC por 48 h. Os corpos-de-prova foram divididos em três grupos: 1) tratamento em forno de microondas por 3 min a 500 W; 2) tratamento em banho de água a 55ºC por 60 min; e 3) sem tratamento térmico. Extratos foram preparados pela colocação de 3 discos em tubos de ensaio estéreis com 9 mL de meio de cultura Eagle e incubação a 37ºC por 24 h. O efeito citotóxico dos extratos foi avaliado utilizando o teste de incorporação de ³H-timidina. RESULTADOS: Os resultados indicaram que os componentes liberados pelas resinas foram citotóxicos para as células L929 exceto para as amostras tratadas em banho de água (

Changes in roughness of denture base and reline materials by chemical disinfection or microwave irradiation: Surface roughness of denture base and reline materials

OBJECTIVE: The effect of disinfection by immersion in sodium perborate solution and microwave irradiation on surface roughness of one denture base resin (Lucitone 550 -L), 3 hard chairside reline resins (Tokuyama Rebase II-TR, New Truliner-NT, Ufi Gel hard-UH) and 3 resilient reline materials (Trusoft-T; Sofreliner-S, Dentusil-D) was evaluated. MATERIAL AND METHODS: Thirty specimens of each material were made and divided into 3 groups: Control - not disinfected; P - daily disinfection by immersing in sodium perborate solution (3.8%); MW - microwave disinfection (6 min/650 W). Roughness measurements were made after polymerization (baseline) and after 1, 3 and 28 days. Roughness differences relative to the baseline readings were analyzed by Student's t-test (P=0.05). RESULTS: At baseline, Trusoft showed the highest (

Effect of thermal cycling on denture base and autopolymerizing reline resins

Objective This study evaluated the fracture toughness (FT) of denture base and autopolymerizing reline resins, with and without thermocycling (T). Material and Methods Specimens of each material (denture base acrylic resin - Lucitone 550 – L; autopolymerizing reline resins - Ufi Gel Hard–UH, Tokuyama Rebase II-TR, New Truliner–NT and Kooliner-K), were produced, notched and divided into two groups (n=10): CG (control group of autopolymerizing reline resins and L): FT tests were performed after polymerization; TG (thermocycled group): FT tests were performed after T (5°C and 55°C for 5,000 cycles). Results: Results (MPa.m1/2) were analyzed by two-way ANOVA and Tukey's test (p=0.05). L exhibited the highest FT mean values in both groups (CG - 2.33; TG - 2.17). For the CG groups, NT showed the highest FT (1.64) among the autopolymerizing reline resins, and K the lowest (1.04). After T, when the autopolymerizing reline resins were compared, a statistically significant difference in FT was found only between the NT (1.46) and TR (1.00). Conclusions Thermocycling increased the FT of K and did not influence the FT of L, UH, TR and NT

Photocatalytic Activity and Antibacterial Effect of Ag3PO4 Powders Against Methicillin-resistant Staphylococcus aureus

In this study, silver phosphate (Ag3PO4) was successfully prepared through a simple precipitation method, and its structural, optical, and morphological properties were characterized by X-ray diffraction, Rietveld refinement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence measurements, and field emission scanning electron microscopy (FE-SEM). Thereafter, the photocatalytic activity for the degradation of rhodamine B (RhB) dye and the antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) were analyzed. Ag3PO4 was highly photocatalytic, degrading approximately 100% of the RhB after 25 min of visible light exposure. The photocatalytic mechanism was evaluated by trapping experiments indicating that photogenerated holes and superoxide radicals were the principal species present in the photocatalytic system. In addition, Ag3PO4 is a potential bacterial agent as it reduced the MRSA population even at sub-inhibitory concentrations. Morphological changes of the MRSA cells exposed to Ag3PO4 powder were investigated by the FE-SEM analysis, and a possible mechanism involving the release of dissolved Ag+, together with the production of reactive photocatalytic oxygen species is proposed based on the experimental results. DOI: http://dx.doi.org/10.17807/orbital.v13i3.156

Extracellular lipids of Candida albicans biofilm induce lipid droplet formation and decreased response to a topoisomerase I inhibitor in dysplastic and neoplastic oral cells

Objective: Some microorganisms, i.e., Candida albicans, have been associated with cancer onset and development, although whether the fungus promotes cancer or whether cancer facilitates the growth of C. albicans is unclear. In this context, microbial-derived molecules can modulate the growth and resistance of cancer cells. This study isolated extracellular lipids (ECL) from a 36-h Candida albicans biofilm incubated with oral dysplastic (DOK) and neoplastic (SCC 25) cells, which were further challenged with the topoisomerase I inhibitor camptothecin (CPT), a lipophilic anti-tumoral molecule. Methodology: ECL were extracted from a 36-h Candida albicans biofilm with the methanol/chloroform precipitation method and identified with Nuclear Magnetic Resonance (1H-NMR). The MTT tetrazolium assay measured ECL cytotoxicity in DOK and SCC 25 cells, alamarBlue™ assessed cell metabolism, flow cytometry measured cell cycle, and confocal microscopy determined intracellular features. Results: Three major classes of ECL of C. albicans biofilm were found: phosphatidylinositol (PI), phosphatidylcholine (PC), and phosphatidylglycerol (PG). The ECL of C. albicans biofilm had no cytotoxic effect on neither cell after 24 hours, with a tendency to disturb the SCC 25 cell cycle profile (without statistical significance). The ECL-induced intracellular lipid droplet (LD) formation on both cell lines after 72 hours. In this context, ECL enhanced cell metabolism, decreased the response to CPT, and modified intracellular drug distribution. Conclusion:The ECL (PI, PC, and PG) of 36-h Candida albicans biofilm directly interacts with dysplastic and neoplastic oral cells, highlighting the relevance of better understanding C. albicans biofilm signaling in the microenvironment of tumor cells

Biocompatibility and inflammatory response of silver tungstate, silver molybdate, and silver vanadate microcrystals

Silver tungstate (α-Ag2WO4), silver molybdate (β-Ag2MoO4), and silver vanadate (α-AgVO3) microcrystals have shown interesting antimicrobial properties. However, their biocompatibility is not yet fully understood. Cytotoxicity and the inflammatory response of silver-containing microcrystals were analyzed in THP-1 and THP-1 differentiated as macrophage-like cells, with the alamarBlue™ assay, flow cytometry, confocal microscopy, and ELISA. The present investigation also evaluated redox signaling and the production of cytokines (TNFα, IL-1β, IL-6, and IL-8) and matrix metalloproteinases (MMP-8 and -9). The results showed that α-AgVO3 (3.9 μg/mL) did not affect cell viability (p > 0.05). α-Ag2WO4 (7.81 μg/mL), β-Ag2MoO4 (15.62 μg/mL), and α-AgVO3 (15.62 μg/mL) slightly decreased cell viability (p ≤ 0.003). All silver-containing microcrystals induced the production of O2 − and this effect was mitigated by Reactive Oxygen Species (ROS) scavenger and N-acetylcysteine (NAC). TNFα, IL-6 and IL-1β were not detected in THP-1 cells, while their production was either lower (p ≤ 0.0321) or similar to the control group (p ≥ 0.1048) for macrophage-like cells. The production of IL-8 by both cellular phenotypes was similar to the control group (p ≥ 0.3570). The release of MMP-8 was not detected in any condition in THP-1 cells. Although MMP-9 was released by THP-1 cells exposed to α-AgVO3 (3.9 μg/mL), no significant difference was found with control (p = 0.7). Regarding macrophage-like cells, the release of MMP-8 and -9 decreased in the presence of all microcrystals (p ≤ 0.010). Overall, the present work shows a promising biocompatibility profile of, α-Ag2WO4, βAg2MoO4, and α-AgVO3 microcrystals

Comparison of denture microwave disinfection and conventional antifungal therapy in the treatment of denture stomatitis: a randomized clinical study

Objective. the aim of this study was to compare the effectiveness of denture microwave disinfection and antifungal therapy on treatment of denture stomatitis.Study Design. Sixty denture wearers with denture stomatitis (3 groups; n = 20 each), were treated with nystatin or denture microwave disinfection (1 or 3 times/wk) for 14 days. Mycologic samples from palates and dentures were quantified and identified with the use of Chromagar, and clinical photographs of palates were taken. Microbiologic and clinical data were analyzed with the use of a series of statistical tests (alpha = .05).Results. Both treatments similarly reduced clinical signs of denture stomatitis and growth on palates and dentures at days 14 and 30 (P > .05). At sequential appointments, the predominant species (P < .01) isolated was C. albicans (range 98%-53%), followed by C. glabrata (range 22%-12%) and C. tropicalis (range 25%-7%).Conclusions. Microwave disinfection, at once per week for 2 treatments, was as effective as topical antifungal therapy for treating denture stomatitis. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:469-479)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CESMAC Univ Ctr, Sch Dent, Maceio, BrazilUniv Estadual Ponta Grossa, Dept Dent, Ponta Grossa, BrazilUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilUNESP Univ Estadual Paulista, Araraquara Dent Sch, Araraquara, BrazilUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilFAPESP: 2005/03211-6FAPESP: 2005/04695-7Web of Scienc