Effect of power densities and irradiation times on the degree of conversion and temperature increase of a microhybrid dental composite resin

The different parameters used for the photoactivation process provide changes in the degree of conversion (DC%) and temperature rise (TR) of the composite resins. Thus, the purpose of this study was to evaluate the DC (%) and TR of the microhybrid composite resin photoactivated by a new generation LED. For the KBr pellet technique, the composite resin was placed into a metallic mould (1-mm thickness and 4-mm diameter) and photoactivated as follows: continuous LED LCU with different power density values (50-1000 mW/cm(2)). The measurements for the DC (%) were made in a FTIR Spectrometer Bomen (model MB-102, Quebec-Canada). The spectroscopy (FTIR) spectra for both uncured and cured samples were analyzed using an accessory for the diffuse reflectance. The measurements were recorded in the absorbance operating under the following conditions: 32 scans, 4-cm(-1) resolution, and a 300 to 4000-cm(-1) wavelength. The percentage of unreacted carbon-carbon double bonds (% C=C) was determined from the ratio of the absorbance intensities of aliphatic C=C (peak at 1638 cm(-1)) against an internal standard before and after the curing of the specimen: aromatic C-C (peak at 1608 cm-1). For the TR, the samples were made in a metallic mould (2-mm thickness and 4-mm diameter) and photoactivated during 5, 10, and 20 s. The thermocouple was attached to the multimeter to allow the temperature readings. The DC (%) and TR were calculated by the standard technique and submitted to ANOVA and Tukey`s test (p < 0.05). The degree of conversion values varied from 35.0 (+/- 1.3) to 45.0 (+/- 2.4) for 5 s, 45.0 (+/- 1.3) to 55.0 (+/- 2.4) for 10 s, and 47.0 (+/- 1.3) to 52.0 (+/- 2.4) for 20 s. For the TR, the values ranged from 0.3 (+/- 0.01) to 5.4 (+/- 0.11)degrees C for 5 s, from 0.5 (+/- 0.02) to 9.3 (+/- 0.28)degrees C for 10 s, and from 1.0 (+/- 0.06) to 15.0 (+/- 0.95)degrees C for 20 s. The power densities and irradiation times showed a significant effect on the degree of conversion and temperature rise.

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degreesC for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.

Effect of different dental composite resins on the polymerization process

Dental composite resins possess good esthetic properties, and are currently among the most popular dental restorative materials. Both organic and inorganic phases might influence the material behavior, the filler particle features and rate are the most important factors related to improvement of the mechanical properties of resin composites. Thus, the objective of this study was to evaluate the effect of three different composite resins on the polymerization process by Vickers hardness test. The samples were prepared using three different composite resins, as follow: group I-P-60 (3M/ESPE); group II-Herculite XRV (Kerr), and group III-Durafill (Heraeus-Kulzer). The samples were made in a polytetrafluoroethylene mould, with a rectangular cavity measuring 7 mm in length, 4 mm in width, and 3 mm in thickness. The samples were photo-activated by one light-curing unit based on blue LEDs (Ultrablue III-DMC/Brazil) for 20 and 40 s of irradiation times. The Vickers hardness test was performed 24 h after the photo-activation until the standardized depth of 3 mm. The Vickers hardness mean values varied from 158.9 (+/- 0.81) to 81.4 (+/- 1.94) for P-60, from 138.7 (+/- 0.37) to 61.7 (+/- 0.24) for Herculite XRV, and from 107. 5 (+/- 0.81) to 44.5 (+/- 1.36) for Durafill composite resins photo-activated during 20 s for the 1st and 2nd mm, respectively. During 40 s of photo-activation, the Vickers hardness mean values were: from 181.0 (+/- 0.70) to 15.6 (+/- 0.29) for P-60, and from 161.8 (+/- 0.41) to 11.2 (+/- 0.17) for Herculite XRV composite resins, for the 1st and 3th mm, respectively. For Durafill composite resin the mean values varied from 120.1 (+/- 0.66) to 61.7 (+/- 0.20), for the 1st and 2nd mm, respectively. The variation coefficient (CV) was in the most of the groups lower than 1%, then the descriptive statistic analysis was used. The Vickers hardness mean values for Durafill were lower than P-60 and Herculite XRV composite resins for 20 and 40 s of irradiation time. The polymerization process was greatly affected by the composition of the composite resins.

Efeito de material cimentante e do tempo na resistência adesiva de pinos de fibra de vidro

Pós-graduação em Ciências Odontológicas - FOAR

Reabilitação estético-funcional sobre implantes agulhados e endósseos

This report shows the resolution of a case study whose aim was promote the aesthetic and functional rehabilitation of upper left hemi-arch over endosseous and needle implant prostheses. To improve the position of the needle implants, we performed the bucco-palatal bending of needles splinting them with composite resin; we removed the screwed implant prosthesis in the regions of the premolars (24 and 25) and molar (26). The mini-abutments of the last two implants were replaced, and in the first premolar and canine, we used cemented abutments due to implant angulation having planned soldering because of implant size and contact with one needle implant that could interfere with intimate contact bone/implant damaging biomechanics. Pick-up impressions were performed with an open tray, using a retractor cord in the needle implants and respective transfer copings. Therefore, models were related on semi-adjustable articulator after a face-bow recording and interocclusal indexes. After working cast fabrication and try-in of infra-structures, these were adjusted and related into the articulator again. Then, after ceramic build-up, adjustments, finishing, and torque, chemically-activated resin cement was applied on units 21 to 24. At the end of the case, we concluded that a good aesthetic and functional rehabilitation depends on thorough knowledge of techniques for each clinical situation.

Influência do comprimento do pino de fibra de vidro na resistência à fratura de raízes fragilizadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influência do comprimento do pino de fibra de vidro na resistência à fratura de raízes fragilizadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise biomecânica de resistência à fratura em dentes caninos artificiais de cães, com restauração metálica fundida e retentores intrarradiculares retos e curvos com núcleo - Estudo comparativo com análise por elementos finitos

Os cães, por fatores diversos, acabam por apresentar dentes fraturados com ou sem exposição de polpa. Estas fraturas basicamente são identificadas como fraturas recuperáveis não complicadas, recuperáveis complicadas ou irrecuperáveis. As fraturas recuperáveis (localizadas apenas no esmalte e dentina) são tratadas com dentística restauradora. As recuperáveis complicadas (com lesões em esmalte, dentina e exposição do canal radicular) passam por tratamento endodôntico, podendo ser seguidas de restaurações metálicas. Os dentes mais comumente acometidos são os dentes caninos, superiores ou inferiores. Este trabalho em dentes artificiais simulando considerável destruição de sua porção coronal objetivou testar, após a adaptação da restauração metálica fundida, a resistência às fraturas no dente canino. Os dentes artificiais foram padronizados com uma técnica de replicação de raízes artificiais em molde de resina acrílica quimicamente ativada. Oitenta réplicas iguais de resina composta fotopolimerizável, padronizadas em tamanho e forma, foram construídas a partir desta técnica. Antes da reconstrução protética, aplicou-se o tratamento endodôntico, desobturação, preparo do canal radicular e moldagem. Proteticamente, um pino intrarradicular reto e outro curvo, ambos com núcleo para sustentar a coroa metálica fundida foram cimentados na porção coronal de cada raiz-réplica. Os núcleos e coroa metálica foram ambos ferulados ou estojados. Avaliou-se os dois tipos de restauração com pino intrarradicular curvos ou retos cimentados com cimento de fosfato de zinco ou resinoso para identificar o melhor conjunto restaurador. Os testes de resistência biomecânica de 80 raízes-réplicas foram divididos em 4 grupos com 20 corpos de prova para cada um dos grupos. Grupo 1: das raízes-réplicas com pino intrarradicular curvo cimentados com cimento resinoso. Grupo 2: das raízes-réplicas com pino intrarradicular curvo cimentados com cimento de fosfato de zinco. Grupo 3: das raízes-réplicas com pino intrarradicular reto cimentados com cimento resinoso. Grupo 4: das raízes-réplicas com pino intrarradicular reto cimentados com cimento de fosfato de zinco. Estes grupos foram submetidos a teste de força com pré-carga de 1,5 N, com velocidade de avanço constante de 0,05 mm por minuto em ponto pré- determinado (mésio-lateral vestibularizada) até ocorrência de fratura do conjunto ou parte dele em uma Máquina Universal Kratos. Com a avaliação biomecânica e estudo estatístico de Kruskall-Wallis, identificou-se que os dados obtidos não seguiram distribuição normal. Esta diferença mostrou-se com o p<0,05 na interpretação do teste. No caso de dados não paramétricos o post-hoc do Kruskal-Wallis foi o teste de U de Mann-Withney. Paralelamente, um estudo com análise de elementos finitos comparou os resultados obtidos. Não houve diferença significativa sobre o tipo de cimento utilizado ou que favorecesse o uso do pino reto ou do pino curvo, recaindo a escolha para o operador decidir de acordo com a melhor indicação para cada caso clínico

Use of activated charcoal and ion-exchange resin to cleaN up and concentrate enzymes in extracts from biodegraded wood.

Use of activated charcoal and ion-exchange resin to cleaN up and concentrate enzymes in extracts from biodegraded wood. Ceriporiopsis subvermispora was used for the biodegradation of Eucalyptus grandis chips in the presence or absence of co-substrates (glucose and corn steep liquor) during 7, 14 and 28 days. Afterwards, the biodegraded chips were extracted with 50 mM sodium acetate buffer (pH 5.5) supplemented with 0.01% Tween 60. High activities of manganese peroxidases (MnPs) were observed in all the extracts, both in the absence (430, 765 and 896 UI kg(-1) respectively) and in the presence of co-substrates (1,013; 2,066 and 2,323 UI kg(-1) respectively). The extracts presented a high ratio between absorbances at 280 and 405 nm, indicating a strong abundance of aromatic compounds derived from lignin over heme-peroxidases. Adsorption into activated charcoal showed to be an adequate strategy to reduce the absorbance at 280 urn in all the extracts. Moreover, it allowed to maximize the capacity of an anion exchange resin bed (DEAE-Sepharose) used to concentrate the MnPs present in the extracts. It was concluded that the use of activated charcoal followed by adsorption into DEAE Sepharose is a strategy that can be used to concentrate MnPs in extracts obtained during the biodegradation of E. grandis by C. subvermispora.

Color stability of chemically activated reline resin after microwave disinfection: A 1-year clinical trial

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

Effect of sodium bicarbonate on Candida albicans adherence to thermally activated acrylic resin

The purpose of this study was to evaluate the effect of 5% sodium bicarbonate on the adherence of Candida albicans to thermally activated acrylic resin. Fifty 4 mm specimens of acrylic resin were obtained using a metallic matrix. The specimens received chemical polishing, were sterilized and then immersed in Sabouraud broth, inoculated with Candida albicans standardized suspension. After 24 hours of incubation at 37°C, the specimens were divided into four groups according to the substance used for disinfection (5% sodium bicarbonate, 0.12% digluconate chlorhexidine, vinegar and Corega Tabs). A control group was included, in which distilled water was used. The adhered microorganisms were dispersed, diluted and plated onto culture media to determine the number of colony-forming units (cfu/mL). The results were analyzed through the Mann-Whitney statistical test at the 5% level of significance. Only 0.12% digluconate chlorhexidine and 5% sodium bicarbonate presented a statistically significant difference (p = 0.0010 and p = 0.0156, respectively) compared to the control group, decreasing the number of cfu/mL. However, when the different disinfecting solutions were compared with each other, only 0.12% digluconate chlorhexidine presented a statistically significant difference in the reduction of cfu/mL. It was concluded that although 0.12% digluconate chlorhexidine was more effective in the reduction of Candida albicans adherence values to thermally activated acrylic resin, 5% sodium bicarbonate also proved to be a viable alternative.

Effect of polymerization techniques and cleaning solution on flexural resistance of acrylic resin chemically activated

The purpose of this study was to evaluate the impact of different disinfection solutions on flexural resistance of chemically-activated acrylic resin. Test pieces were made of clear acrylic resin using a rectangular mold and employing two techniques: wet polymerization under pressure (n = 20) and dry polymerization under pressure (n = 20). Test pieces were subdivided into four equal groups: distilled water (control), sodium bicarbonate, 1% sodium hypochlorite and effervescent ats. The 30-day cycling technique consisted of immersing the test pieces in 100 ml of solution for 10 min three times a day and placing them in closed containers containing artificial saliva at 37°C. Subsequently, the flexural resistance of samples was tested. Data were analyzed using two-way analysis of variance (ANOVA) with forces serving as the dependent variables and the polymerization technique and cleaning agents as independent variables. Post hoc multiple comparisons were performed using Tukey’s test. There was no statistically significant difference in the flexural strength between the two polymerization techniques. The greatest flexural strength was observed for the effervescent tablets group followed by the control and 1% sodium hypochlorite groups which were statistically similar. Thus, the sodium bicarbonate solution caused the lowest flexural resistance of the test pieces.

Immobilization and stabilization of microbial lipases by multipoint covalent attachment on aldehyde-resin affinity: Application of the biocatalysts in biodiesel synthesis

Microbial lipase preparations from Thermomyces lanuginosus (TLL) and Pseudomonas fluorescens (PFL) were immobilized by multipoint covalent attachment on Toyopearl AF-amino-650M resin and the most active and thermal stable derivatives used to catalyze the transesterificanon reaction of babassu and palm oils with ethanol in solvent-free media For this different activating agents mainly glutaraldehyde glycidol and epichlorohydrin were used and immobilization parameters were estimated based on the hydrolysis of olive oil emulsion and butyl butyrate synthesis ILL immobilized on glyoxyl-resin allowed obtaining derivatives with the highest hydrolytic activity (HA(der)) and thermal stability between 27 and 31 times more stable than the soluble lipase Although PFL derivatives were found to be less active and thermally stables similar formation of butyl butyrate concentrations were found for both ILL and PFL derivatives The highest conversion into biodiesel was found in the transesterification of palm oil catalyzed by both ILL and PFL glyoxyl-derivatives (c) 2010 Elsevier B V All rights reserved

Micromorphology of Resin-Dentin Interfaces Using One-Bottle Etch&Rinse and Self-Etching Adhesive Systems on Laser-Treated Dentin Surfaces: A Confocal Laser Scanning Microscope Analysis

Background and Objectives: This study evaluated the hybrid layer (HL) morphology created by three adhesive systems (AS) on dentin surfaces treated with Er:YAG laser using two irradiation parameters. Study Design: Occlusal flat dentin surfaces of 36 human third molars were assigned into nine groups (n = 4) according to the following ASs: one bottle etch&rinse Single Bond Plus (3M ESPE), two-step Clearfil Protect Bond (Kuraray), and all-in-one S3 Bond (Kuraray) self-etching, which were labeled with rhodamine B or fluorescein isothiocyanate dextran and were applied to dentin surfaces that were irradiated with Er:YAG laser at either 120 (38.7 J/cm(2)) or 200 mJ/pulse (64.5 J/cm(2)), or were applied to untreated dentin surfaces (control group). The ASs were light-activated following MI and the bonded surfaces were restored with resin composite Z250 (3M ESPE). After 24 hours of storage in vegetable oil, the restored teeth were vertically, serially sectioned into 1-mm thick slabs, which had the adhesive interfaces analyzed with confocal laser microscope (CLSM-LSM 510 Meta). CLSM images were recorded in the fluorescent mode from three different regions along each bonded interface. Results: Non-uniform HL was created on laser-irradiated dentin surfaces regardless of laser irradiation protocol for all AS, while regular and uniform HL was observed in the control groups. ""Stretch mark""-like red lines were found within the HL as a result of resin infiltration into dentin microfissures, which were predominantly observed in 200 mJ/pulse groups regardless of AS. Poor resin infiltration into peritubular dentin was observed in most regions of adhesive interfaces created by all ASs on laser-irradiated dentin, resulting in thin resin tags with neither funnel-shaped morphology nor lateral resin projections. Conclusion: Laser irradiation of dentin surfaces at 120 or 200 mJ/pulse resulted in morphological changes in HL and resin tags for all ASs evaluated in the study. Lasers Surg. Med. 42:662-670, 2010. (C) 2010 Wiley-Liss, Inc.

Micro-hardness evaluation of a micro-hybrid composite resin light cured with halogen light, light-emitting diode and argon ion laser

This in vitro study aimed to determine whether the micro-hardness of a composite resin is modified by the light units or by the thickness of the increment. Composite resin disks were divided into 15 groups (n = 5), according to the factors under study: composite resin thickness (0 mm, 1 mm, 2 mm , 3 mm and 4 mm) and light units. The light activation was performed with halogen light (HL) (40 s, 500 mW/cm(2)), argon ion laser (AL) (30 s, 600 mW/cm(2)) or light-emitting diode (LED) (30 s, 400 mW/cm(2)). Vickers micro-hardness tests were performed after 1 week and were carried out on the top surface (0 mm-control) and at different depths of the samples. Analysis of variance (ANOVA) and Tukey tests (P a parts per thousand currency signaEuro parts per thousand 0.05) revealed no statistically significant difference among the light units for the groups of 0 mm and 1 mm thickness. At 2 mm depth, the AL was not statistically different from the HL, but the latter showed higher micro-hardness values than the LED. In groups with 3 mm and 4 mm thickness, the HL also showed higher micro-hardness values than the groups activated by the AL and the LED. Only the HL presented satisfactory polymerization with 3 mm of thickness. With a 4 mm increment no light unit was able to promote satisfactory polymerization.