Effect of water-bath post-polymerization on the mechanical properties, degree of conversion, and leaching of residual compounds of hard chairside reline resins

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

Transfer of radon and parent nuclides U-238 and U-234 from soils of the Mendip Hills area, England, to the water phase

Laboratory time scale experiments were conducted on soils from the Mendip Hills area, England, with the purpose of evaluating the release of Rn-222 and their parent nuclides U-238 and U-234 to the water phase and to determine the influence of parameters that can affect the geochemical behaviour of these nuclides in natural systems. The specific surface area of the samples ranged from 43.8 to 52.5 cm(2) g(-1), where the particle size for all soil horizons is lognormally distributed, with modal values of the particle radius undersize ranging from 107 up to 203 mu m. The values for the released radon were between 26 and 194 pCi, which allowed to estimate emanation coefficients for these materials between 0.1 and 0.2, within the context of other values reported elsewhere. Soils derived from Carboniferous limestone and characterized by higher pH, exchangeable calcium, and the presence of U, but with a lower U-231/U-238 activity ratio, yielded the highest values for released Rn; however, this trend was not observed for dissolved U and its respective U-234/U-238 activity ratio, when considering the less aggressive etchant. Uranium is mobilized from rock matrix to A and B horizons in the analysed soil profiles, where its enrichment is about 10 times higher in soils derived from Carboniferous limestone. These data also permitted an evaluation of a theoretical model for the generation of Rn in soils and its transfer to water, in order to interpret the radioactivity due to this gas in groundwaters from the Mendip Hills district, England. (C) 1999 Elsevier B.V. B.V. All lights reserved.

Residual monomer of reline acrylic resins - Effect of water-bath and microwave post-polymerization treatments

Objectives. This study compared the residual monomer (RM) in four hard chair-side reline resins (Duraliner II-D, Kooliner-K, Tokuso Rebase Fast-TRF and Ufi Gel hard-UGH) and one heat-polymerized denture base resin (Lucitone 550-L), which was processed using two polymerization cycles (short-LS and long-LL). It was also investigated the effect of two after polymerization treatments on this RM content.Methods. Specimens (n = 18) of each material were produced following the manufacturers' instructions and then divided into three groups. Group I specimens were left untreated (GI-control). Specimens of group II (GII) were given post-polymerization treatment by microwave irradiation. In group III (GIII), specimens were submitted to immersion in water at 55 degrees C (reline resins-10 min; denture base resin L-60min). The RM was analyzed using high performance liquid chromatography (HPLC) and expressed as a percentage of RM. Data were analyzed by two-way ANOVA followed by Tukey's test (alpha = 0.05).Results. Comparing control specimens, statistical differences were found among all materials (p < 0.05), and the results can be arranged as K (1.52%) > D (0.85%) > UGH (0.45%) > LL (0.24%) > TRF (0.14%) > LS (0.08%). Immersion in hot water (GIII) promoted a significant (p < 0.05) reduction in the RM for all materials evaluated compared to control (GI), with the exception of LL specimens. Materials K, UGH and TRF exhibited significantly (p < 0.05) lower values of RM after microwave irradiation (GII) than in the control specimens.Significance. The reduction in RM promoted by water-bath and microwave post-polymerization treatments could improve the mechanical properties and biocompatibility of the relining and denture base materials. (c) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Cytotoxicity of denture base resins: Effect of water bath and microwave postpolymerization heat treatments

Purpose: This study compared the effect of two postpolymerization heat treatments on the cytotoxicity of three denture base resins on L929 cells using 3H-thymidine incorporation and MTT assays. Materials and Methods: Sample disks of Lucitone 550, QC 20, and Acron MC resins were fabricated under aseptic conditions and stored in distilled water at 37°C for 48 hours. Specimens were then divided into three groups: (1) heat treated in microwave oven for 3 minutes at 500 W; (2) heat treated in water bath at 55°C for 60 minutes; and (3) no heat treatment. Eluates were prepared by placing three disks into a sterile glass vial with 9 mL of Eagle's medium and incubating at 37°C for 24 hours. The cytotoxic effect from the eluates was evaluated using the 3H-thymidine incorporation and MTT assays, which reflect DNA synthesis levels and cell metabolism, respectively. Results: The components leached from the resins were cytotoxic to L929 cells when 3H- thymidine incorporation assay was employed. In contrast, eluates from all resins revealed noncytotoxic effects as measured by MTT assay. For both MTT assay and 3H-thymidine incorporation, the heat treatments did not decrease the cytotoxicity of the materials tested. Conclusion: Resins were graded by 3H-thymidine incorporation assay as slightly cytotoxic and by MTT assay as noncytotoxic. Cytotoxicity of the denture base materials was not influenced by microwave or water bath heat treatment.

Mechanism of infection and colonization of Rhipicephalus sanguineus eggs by Mertarhizium anisopliae as revealed by scanning eletron microscopy and histopathology

O presente trabalho teve como objetivo verificar a forma de penetração do fungo Metarhizium anisopliae em ovos do carrapato Rhipicephalus sanguineus, assim como as lesões infringidas no interior do ovo. A aderência e penetração do fungo foram estudadas por meio da microscopia eletrônica de varredura e a ação do fungo nos tecidos internos avaliada em secções histológicas convencionais. Para observação destes eventos, realizaram-se infecções experimentais em 11 grupos de ovos do R. sanguineus contendo 25 mg cada. Os ovos foram banhados durante 3 minutos, sob agitação manual, em suspensão com concentração de 10(8) conídios/mL. Nos grupos controle o banho foi realizado apenas no veículo da suspensão. Os ovos foram processados para análise histopatológica e microscopia eletrônica de varredura nos seguintes tempos após a infecção: 1 e 18h, e um, dois, três, quatro, cinco, seis, sete, nove e onze dias. Observou-se grande germinação de conídios em 67% dos ovos 18h após a inoculação e o fungo penetrou em 92,6% dos ovos 5 dias após a infecção. A extrusão do patógeno ocorreu em 87% dos ovos 7 dias após a infecção, chegando a 100% no 9º dia. Nas análises histopatológicas não foram observadas lesões dignas de nota, porem deve-se ressaltar que houve significativa redução (53,9%) na eclosão a partir dos ovos infectados.

Effect of Flasking and Polymerization Techniques on Tooth Movement in Complete Denture Processing

Purpose: The purpose of this study was to compare the artificial tooth positional changes following the flasking and polymerization of complete dentures by a combination of two flasking methods and two polymerization techniques using computer graphic measurements.Materials and Methods: Four groups of waxed complete dentures (n = 10) were invested and polymerized using the following techniques: (1) adding a second investment layer of gypsum and conventional water bath polymerization (Control), (2) adding a second investment layer of gypsum and polymerization with microwave energy (Gyp-micro), (3) adding a second investment layer of silicone (Zetalabor) and conventional polymerization (Silwater), and (4) adding a second investment layer of silicone and polymerization with microwave energy (Silmicro). For each specimen, six segments of interdental distances (A to F) were measured to determine the artificial tooth positions in the waxed and polymerized stages using software program AutoCad R14. The mean values of the changes were statistically compared by univariate ANOVA with Tukey post-hoc test at 5% significance.Results: There were no significant differences among the four groups, except for segment D of the Silmicro group (-0.004 +/- 0.032 cm) in relation to the Gypwater group (0.044 +/- 0.031 cm) (p < 0.05), which presented, repectively, expansion and shrinkage after polymerization.Conclusions: Within the limitations of this study, it was concluded that although the differences were not statistically significant, the use of a silicone investment layer when flasking complete dentures resulted in the least positional changes of the artificial teeth regardless of the polymerization technique.

Bond strength of denture teeth to acrylic resin: effect of thermocycling and polymerisation methods

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

Epidemiology of fluorosis and dental caries according to different types of water supplies

O objetivo do presente artigo é investigar a relação fluorose/cáries em escolas, de acordo com o nível de fluoreto no abastecimento público de água. A amostra consistiu em 360 alunos de doze anos de idade, de ambos os sexos, que frequentam as escolas próximas da região em que nasceram. As escolas foram classificadas em três grupos de acordo com a presença de fluoreto no abastecimento de água: 1) fluoretação na Estação de Tratamento de Água (ETA); 2) fluoretação direta em poços; e 3) áreas não fluoretadas (ANF). Os testes deχe de Goodman (significância = 5%) foram utilizados para avaliar a associação entre a origem da água e o grau de fluorose. Os resultados mais predominantes foram presença de cáries em toda a amostra (P<0,05); ausência de fluorose em ambos gêneros, para indivíduos brancos e aqueles vivendo em áreas abastecidas com água fluoretada diretamente de poços e não fluoretadas (P<0,05). Não houve diferença no grau de severidade da fluorose entre as fontes de abastecimento de água (P>0,05). As cáries ainda são uma importante questão nessa população, apesar do estabelecimento de medida preventiva. A observação da fluorose em alunos vivendo em áreas não fluoretadas confirma a presença de outras fontes de fluorose.

Methods for determination of hexachlorobenzene and pentachlorophenol in soil samples

The efficiency of methods for the determination of hexachlorobenzene (HCB) and pentachlorophenol (PCP) in soil samples was evaluated. An on-line method was applied for HCB determination. Soil samples were transferred to chromatographic columns prepacked with alumina. The HCB elution was processed with n-hexane. The PCP was extracted from soil samples with n-hexane-acetone in an ultrasonic bath. After re-extraction with K2CO3 solution PCP was acetylated with acetic anhydride. The pentachlorophenyl acetate derivative was then extracted with n-hexane. The HCB and PCP derivative were analyzed by gas chromatography with electron capture detection (GC-ECD). Mean recoveries obtained from soil samples fortified at levels of 0.5; 4 and 20 ng g(-1) ranged from 91 to 100% for HCB, and for PCP, at levels of 10; 40 and 200 ng g(-1), ranged from 88 to 101%. These results demonstrated the efficiency of the proposed methods. (C) 1998 Elsevier B.V. B.V. All rights reserved.

In vitro evaluation of antimicrobial activity of sealers and pastes used in endodontics

The antimicrobial activity of four root canal sealers (AH Plus, Sealapex, Ketac Endo, and Fill Canal), two calcium hydroxide pastes (Calen and Calasept), and a zinc oxide paste was evaluated. Seven bacterial strains were used, six of them standard; Micrococcus luteus ATCC 9341, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 25922, and Enterococcus faecalis ATCC 10541. There was a wild strain of Streptococcus mutans isolated from saliva obtained in an adult dental clinic. Activity was evaluated using the agar diffusion method with Brain Heart Infusion agar and Müller Hinton medium seeded by pour plate. Calcium hydroxide-based sealers and pastes were either placed directly into 4.0 × 4.0 mm wells or by using absorbent paper points. The plates were kept at room temperature for 2 hr for diffusion. After incubation at 37°C for 24 hr, the medium was optimized with 0.05 g% TTC gel and inhibition haloes were measured. All bacterial strains were inhibited by all materials using the well method. However, when the materials were applied with absorbent paper points, Enterococcus faecalis was not inhibited by zinc oxide, and Pseudomonas aeruginosa was not inhibited by AH Plus, Fill Canal, and the zinc oxide-based paste. We conclude that sealers and pastes presented antimicrobial activity in vitro and culture medium optimization with 0.05 g% TTC gel facilitated observation of the inhibition haloes. Copyright © 2000 by The American Association of Endodontists.

Degree of conversion and molecular weight of one denture base and three reline resins submitted post-polymerization treatments

The effect of post-polymerization treatments (MW-microwave irradiatron and WB-water-bath) on the degree of conversion (DC) of three reline resins (Ufi Gel hard-U, Kooliner-K, and Tokuso Rebase Fast-T) and one denture base resin (Lucitone 550-L), submitted to two polymerization cycles (LS-short and LL-long), was evaluated by using FT-Raman spectroscopy (n = 5). The molecular weight (Mw) of the powder of all materials and of K polymerized specimens (control; MW; and WB; n = 3) was analyzed using GPC. DC data were analyzed using Kruskal-Wallis test (α = .05). For control specimens, there were no significant differences between U (68%) and LL (77%) and among LL, K (81%), and T (84%). LS (92%) had the highest DC (P<0.05). Only material K exhibited an increased DC after WB (P<0.05). All powders had Mw from 4.0 × 105 to 6.5 × 105 and narrow Mw distributions (2.1 to 3.6). Polymerization and post-polymerization produced K specimens with Mw similar to that of K powder.

Effect of a post-polymerization treatments on the flexural strength and vickers hardness of reline and acrylic denture base resins

This study evaluated the effect of water-bath and microwave post-polymerization treatments on the flexural strength and Vickers hardness of four autopolymerizing reline resins (Duraliner II-D, Kooliner-K, Tokuso Rebase Fast-TR and Ufi Gel Hard C-UGH) and one heat-polymerized acrylic resin (Lucitone 550-L), processed using two polymerization cycles (short cycle - 90 minutes at 73°C and 100°C for 30 minutes; and long cycle - 9 hours at 71°C). For each material, thirty specimens (64 x 10 x 3.3 mm) were made and divided into 3 groups (n=10). Specimens were tested after: processing (control group); water-bath at 55°C for 10 minutes (reline materials) or 60 minutes (L); and microwave irradiation. Flexural strength tests were performed at a crosshead speed of 5 mm/min using a three-point bending device with a span of 50 mm. The flexural strengths values were calculated in MPa. One fragment of each specimen was submitted to Vickers hardness test. Data were analyzed by 2-way ANOVA followed by Tukey's HSD test (α=0.05). L microwaved specimens (short cycle) exhibited significantly higher flexural strength means than its respective control group (p<0.05). Water-bath promoted a significant increase (p<0.05) in flexural strength of K and L (long cycle). The hardness of the tested materials was not influenced by the post-polymerization treatments. Post-polymerization treatments could be used to improve the flexural strength of some materials tested.

Entre o porão e sótão: espaços de formação em The wives of Bath, de Susan Swan

Pós-graduação em Letras - FCLAS

Influence of Concentration and Activation on Hydrogen Peroxide Diffusion through Dental Tissues In Vitro

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

Relationship between race and clinical characteristics, extent of disease, and response to chemotherapy in patients with low-risk gestational trophoblastic neoplasia

Objective. To evaluate the potential effects of race on clinical characteristics, extent of disease, and response to chemotherapy in women with postmolar low-risk gestational trophoblastic neoplasia (GTN).Methods. This non-concurrent cohort study was undertaken including patients with FIGO-defined postmolar low-risk GTN treated with comparable doses and schedules of chemotherapy at the New England Trophoblastic Disease Center (NETDC) between 1973 and 2012. Racial groups investigated included whites, African American and Asians. Information on patient characteristics and response to chemotherapy (need for second line chemotherapy, reason for changing to an alternative chemotherapy, number of cycles/regimens, need for combination chemotherapy, and time to hCG remission) was obtained.Results. Of 316 women, 274 (86.7%) were white, 19 (6%) African American, and 23 (7.3%) Asian. African Americans were significantly younger than white and Asian women (p = 0.008). Disease presentation, and extent of disease, including antecedent molar histology, median time to persistence, median hCG level at persistence, rate of D&C at persistence, presence of metastatic disease, and FIGO stage and risk score were similar among races. Need for second line chemotherapy (p = 0.023), and median number of regimens (p = 0.035) were greater in Asian women than in other races.Conclusions. Low-risk GTN was more aggressive in Asian women, who were significantly more likely to need second line chemotherapy and a higher number of chemotherapy regimens to achieve complete remission than women of African American and Asian descent. Further studies involving racial differences related to clinical, biological and environmental characteristics are needed. (C) 2015 Published by Elsevier Inc.