Effect of different mechanical surface treatments on flexural strength of repaired denture base / Efecto de diferentes tratamientos superficiales mecánicos sobre la resistencia a la flexión de la base de la dentadura reparada

Aim: To assess the effect of different mechanical surface treatments on flexural strength of repaired denture base. Material and Methods: Sixty bar-shaped specimens of heat-polymerized acrylic resin were fabricated, and divided into six groups (n=10). All specimens, except the positive control group (group PC), were sectioned into halves to create a 1-mm clearance. A negative control group with no surface treatment (group NC) was also considered. Other groups underwent different surface treatments: group Laser; treated with erbium: yttrium-aluminum-garnet (Er:YAG) laser, group APA; airborne-particle abrasion (APA), group APA plus Laser; a combination of laser and APA, and group Bur; bur grinding. After measuring surface roughness (Ra) with a profilometer, all sectioned specimens were repaired by auto-polymerizing acrylic resin, and thermocycled afterward. Three-point bending test was performed by a universal testing machine. Data were statistically analyzed (α=0.05). Results: The mean surface roughness of all experimental groups were significantly higher than that of group NC (p<0.05). The mean flexural strength of all groups was significantly lower than that of group PC (p<0.05). Group B had significantly higher flexural strength than the other surface-treated groups (p<0.05). Group Laser had significantly higher flexural strength than groups APA (p=0.043) and APA plus Laser (p=0.023). No significant difference was found between groups APA and APA plus Laser (p=0.684). Conclusion: All surface treatments increased the surface roughness and flexural strength compared with the untreated group. The highest flexural strength was observed in specimens treated by bur grinding and then laser, however, it was still significantly lower than intact specimens.

Objetivo: Evaluar el efecto de diferentes tratamientos superficiales mecánicos sobre la resistencia a la flexión de la base de la prótesis reparada. Material y Métodos: Se fabricaron sesenta especímenes en forma de barra de resina acrílica termo-polimerizada y se dividieron en seis grupos (n=10). Todas las muestras, excepto el grupo de control positivo (grupo PC), se seccionaron en mitades para crear un espacio libre de 1 mm. También se consideró un grupo de control negativo sin tratamiento superficial (grupo NC). Otros grupos se sometieron a diferentes tratamientos superficiales: grupo Láser; tratados con láser de erbio: itrio-aluminio-granate (Er:YAG), grupo APA; abrasión por partículas en el aire (APA), grupo APA más láser; una combinación de láser y APA, y grupo Bur; molienda de fresas. Después de medir la rugosidad de la superficie (Ra) con un perfilómetro, todas las muestras seccionadas se repararon con resina acrílica de autopolimerización y se sometieron a termociclado. La prueba de flexión de tres puntos se realizó con una máquina de prueba universal. Los datos se analizaron estadísticamente (α=0,05). Resultados: La rugosidad superficial media de todos los grupos experimentales fue significativamente mayor que la del grupo NC (p<0,05). La resistencia media a la flexión de todos los grupos fue significativamente menor que la del grupo PC (p<0,05). El grupo B tenía una resistencia a la flexión significativamente mayor que los otros grupos tratados en la superficie (p<0,05). El grupo Láser tuvo una resistencia a la flexión significativamente mayor que los grupos APA (p=0,043) y APA más Láser (p=0,023). No se encontró diferencia significativa entre los grupos APA y APA más Láser (p=0,684). Conclusión: Todos los tratamientos superficiales aumentan la rugosidad de la superficie y la resistencia a la flexión en comparación con el grupo sin tratar. La resistencia a la flexión más alta se observó en las muestras tratadas con fresado y luego con láser; sin embargo, aún era significativamente más baja que las muestras intactas.

Biological and physico-mechanical properties of poly (methyl methacrylate) enriched with graphene oxide as a potential biomaterial / Propiedades físicas-mecánicas-biológicas del poli (metilmetacrilato) enriquecido con óxido de grafeno como potencial biomaterial

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulp-dental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: The GO was characterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical mechanical tests (flexural strength and elastic modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's posthoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 µm. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical mechanical properties of PMMA.

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulpdental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: T he G O w as c haracterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical-mechanical tests (flexural strength and elastic modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's post-hoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 ?m. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical-mechanical properties of PMMA.

Evaluation of the physical and antifungal effects of chlorhexidine diacetate incorporated into polymethyl methacrylate

Abstract This study aimed to evaluate the physical properties and antifungal activities of polymethyl methacrylate (PMMA) acrylic resins after the incorporation of chlorhexidine diacetate salt (CDA). Methodology: First, acrylic resin specimens were fabricated with Vipi Cor® and DuraLay® resins with and without the incorporation of 0.5%, 1.0% or 2.0% CDA. The residual monomer and CDA release were measured at intervals ranging from 2 hours to 28 days using ultraviolet spectrometry combined with high-performance liquid chromatography. The antifungal activity against C. albicans was evaluated with the agar diffusion method. Fourier transform infrared spectroscopy was used to analyze the degree of resin conversion. Finally, the water sorption values of the resins were also measured. Results: The incorporated CDA concentration significantly changed the rate of CDA release (p<0.0001); however, the brand of the material appeared to have no significant influence on drug release. Subsequently, the inhibition zones were compared between the tested groups and within the same brand, and only the comparisons between the CDA 2% and CDA 1% groups and between the CDA 1% and CDA 0.5% groups failed to yield significant differences. Regarding the degrees of conversion, the differences were not significant and were lower only in the CDA 2% groups. Water sorption was significantly increased at the 1.0% and 2.0% concentrations. Conclusions: We concluded that the incorporation of CDA into PMMA-based resins enabled the inhibition of C. albicans growth rate, did not alter the degrees of conversion of the tested resins and did not change the release of residual monomers.

The effect of nanodiamonds on candida albicans adhesion and surface characteristics of PMMA denture base material - an in vitro study

Abstract Candida albicans is the main causative pathogen of denture stomatitis, which affects many complete denture patients. Objective: To evaluate the effect of different concentrations of nanodiamonds (NDs) added to polymethyl methacrylate (PMMA) denture base material on Candida albicans adhesion as well as on surface roughness and contact angle. Methodology: Acrylic resin specimens sized 10×10×3 mm3 were prepared and divided into four groups (n=30) according to ND concentration (0%, 0.5%, 1%, 1.5% by wt). Surface roughness was measured with a profilometer, and the contact angle with a goniometer. The effect of NDs on Candida albicans adhesion was evaluated using two methods: 1) slide count and 2) direct culture test. Analysis of variance (ANOVA) and Tukey's post hoc test were used in the statistical analyses. Results: Addition of NDs decreased the Candida albicans count significantly more than in the control group (p<0.05), with a lowest of 1% NDs. Addition of NDs also significantly decreased the surface roughness (p<0.05), but the contact angle remained the same. Incorporation of NDs into the PMMA denture base material effectively reduced Candida albicans adhesion and decreased surface roughness. Conclusion: PMMA/NDs composites could be valuable in the prevention of denture stomatitis, which is considered one of the most common clinical problems among removable denture wearers.

Doxycycline release and antibacterial activity from PMMA/PEO electrospun fiber mats

Abstract Objective: To investigate the use of polymethyl methacrylate (PMMA) electrospun fiber mats containing different amounts of polyethylene oxide (PEO) as a doxycycline delivery system and to test antibacterial activity against an oral pathogen. Methodology: PMMA powders or PEO (mol wt 200 Kd) (10,20,30% w/w/) were dissolved in N, N-dimethylformamide (DMF) to obtain a final polymer concentration of 15% in DMF (w/v). 2% Doxycycline monohydrate was added to the solutions and submitted to vortex mixing. The solution was transferred to a plastic syringe and fit into a nanofiber electrospinning unit. The parameters applied were: voltage at 17.2 kV; distance of 20 cm between the needle tip and the collector plate; target speed at 2 m/min; and transverse speed at 1cm/min. Syringe pump speed was 0.15 mm/min. The drug release analysis was performed by removing aliquots of the drug-containing solution (in PBS) at specific periods. Doxycycline release was quantified using RP-HPLC. Fiber mats from all groups had their antibacterial action tested against S. mutans based on inhibition halos formed around the specimens. The experiments were performed in triplicate. Gravimetric analysis at specific periods was performed to determine any polymer loss. Morphological characterization of the electrospun fibers was completed under an optical microscope followed by SEM analysis. Results: The addition of PEO to the PMMA fibers did not affect the appearance and diameter of fibers. However, increasing the %PEO caused higher doxycycline release in the first 24 h. Fibers containing 30% PEO showed statistically significant higher release when compared with the other groups. Doxycycline released from the fibers containing 20% or 30% of PEO showed effective against S. mutans. Conclusion: The incorporation of PEO at 20% and 30% into PMMA fiber mat resulted in effective drug release systems, with detected antibacterial activity against S. mutans.

Long-term microwaving of denture base materials: effects on dimensional, color and translucency stability

Abstract While the combined effect of microwave irradiation with cleansing solutions on denture base materials has been investigated, the effects of only using microwave irradiation and, more importantly, in a long-term basis, was not studied yet. Objective The purpose of this study was to evaluate the effect of a long-term repeated microwaving on the dimensional, color and translucency stability of acrylic and polyamide denture base materials. Material and Methods Thirty two specimens (32 mm x 10 mm x 2.5 mm) from polyamide (Valplast) and PMMA (Vertex Rapid Simplified) denture base materials were made. Eight specimens from each material were immersed in distilled water (control) and 8 were subjected to microwave exposure at 450 W for 3 minutes for a period simulating 224 days of daily disinfection. Linear dimension, color change (ΔE*) and translucency parameter (TP) were measured at baseline and after certain intervals up to 224 cycles of immersion, using a digital calliper and a portable colorimeter. The results were analysed using two-way repeated measures ANOVA to estimate possible differences among predetermined cycles and material type. Regression analysis was also performed to estimate the trend of changes with time. Statistical evaluations performed at a significance level of 5%. Results Data analysis showed significant changes in length at baseline with an increasing number of cycles (p<0.05) and a significant interaction of cycle-material (p<0.001). The ΔΕ* parameter was significantly higher with a higher number of cycles (p<0.001), but it did not vary between materials (p>0.05). TP decreased similarly in both materials following microwave action but in a significantly higher level for Valplast (p<0.001). Conclusions The results indicated that long-term repeated microwaving affects linear dimensional, color and translucency changes of both materials. Differences between PMMA and polyamide material were noted only in dimension and translucency changes.

Comparing depth-dependent curing radiant exposure and time of curing of regular and flow bulk-fill composites

Abstract The effect of restoration depth on the curing time of a conventional and two bulk-fill composite resins by measuring microhardness and the respective radiosity of the bottom surface of the specimen was investigated. 1-, 3- and 5-mm thick washers were filled with Surefil SDR Flow-U (SDR), Tetric EvoCeram Bulk Fill-IVA (TEC) or Esthet-X HD-B1 (EHD), and cured with Bluephase® G2 for 40s. Additional 1-mm washers were filled with SDR, TEC or EHD, placed above the light sensor of MARC®, stacked with pre-cured 1-, 3- or 5-mm washer of respective material, and cured for 2.5~60s to mimic 2-, 4- and 6-mm thick composite curing. The sensor measured the radiosity (EB) at the bottom of specimen stacks. Vickers hardness (VH) was measured immediately at 5 locations with triplicate specimens. Nonlinear regression of VH vs EB by VH=α[1-exp(-EB/β)] with all thickness shows that the values of α, maximum hardness, are 21.6±1.0 kg/mm2 for SDR, 38.3±0.6 kg/mm2 for TEC and 45.3±2.6 kg/mm2 for EHD, and the values of β, rate parameter, are 0.40±0.06 J/cm2 for SDR, 0.77±0.04 J/cm2 for TEC and 0.58±0.09 J/cm2 for EHD. The radiosity of the bottom surface was calculated when the bottom surface of each material attained 80% of α of each material. The curing times for each material are in agreement with manufacturer recommendation for thickness. It is possible to estimate time needed to cure composite resin of known depth adequately by the radiosity and microhardness of the bottom surface.

Comparison of the marginal adaptation of direct and indirect composite inlay restorations with optical coherence tomography

ABSTRACT Objective The purpose of the study was to use the photonic imaging modality of optical coherence tomography (OCT) to compare the marginal adaptation of composite inlays fabricated by direct and indirect techniques. Material and Methods Class II cavities were prepared on 34 extracted human molar teeth. The cavities were randomly divided into two groups according to the inlay fabrication technique. The first group was directly restored on cavities with a composite (Esthet X HD, Dentsply, Germany) after isolating. The second group was indirectly restored with the same composite material. Marginal adaptations were scanned before cementation with an invisible infrared light beam of OCT (Thorlabs), allowing measurement in 200 µm intervals. Restorations were cemented with a self-adhesive cement resin (SmartCem2, Dentsply), and then marginal adaptations were again measured with OCT. Mean values were statistically compared by using independent-samples t-test and paired samples t-test (p<0.05), before and after cementation. Results Direct inlays presented statistically smaller marginal discrepancy values than indirect inlays, before (p=0.00001442) and after (p=0.00001466) cementation. Marginal discrepancy values were increased for all restorations after cementation (p=0.00008839, p=0.000000952 for direct and indirect inlays, respectively). The mean marginal discrepancy value of the direct group increased from 56.88±20.04 µm to 91.88±31.7 µm, whereas the indirect group increased from 107.54±35.63 µm to 170.29±54.83 µm. Different techniques are available to detect marginal adaptation of restorations, but the OCT system can give quantitative information about resin cement thickness and its interaction between tooth and restoration in a nondestructive manner. Conclusions Direct inlays presented smaller marginal discrepancy than indirect inlays. The marginal discrepancy values were increased for all restorations that refer to cement thickness after cementation.

Eficacia del uso concomitante de dentífrico con Triclosán a 0.3 por ciento y copolímero PVM/MA a 2.0 por ciento, enjuague bucal a base de cloruro de cetilpiridinio a 0.05 por ciento y terapia de raspado/alisado radicular en pacientes con gingivitis / Efficacy of concomitant use of dentifrice with 0.3 per cent Triclosan and 2.0 per cent PVM/MA copolymer, 0.05 per cent cetylpyridinium chloride mouthrinse and scaling/root planning therapy in patients with gingivitis

Introducción: La placa dentobacteriana es el principal factor etiológico en el desarrollo y progresión de la gingivitis. Comúnmente se han sugerido productos de cuidado oral como cremas dentales y/o enjuagues bucales como adyuvante en la terapia mecánica. Objetivo: Evaluar la eficacia del uso combinado de un dentífrico a base de Triclosán a 0.3 por ciento y copolímero PVM/MA a 2.0 por ciento (Colgate Total 12®) y enjuague bucal a base de cloruro de cetilpiridinio a 0.05 por ciento (Colgate Plax®) en pacientes con gingivitis marginal crónica después de una terapia de raspado y alisado radicular comparado con un grupo control. Material y métodos: Se realizó un ensayo clínico controlado, aleatorizado y doble ciego en 50 pacientes sanos con diagnóstico sistemático de gingivitis marginal crónica. Se dividieron en grupo A experimental y grupo B control. Se evaluó índice gingival de Lõe y Silness e índice de placa de Quigley Hein modifi cado por Turesky al inicio y al fi nal del estudio; el periodo de estudio fue de seis semanas. Al inicio se realizó a cada paciente tratamiento de raspado y alisado radicular y se le instruyó sobre el uso correcto de los productos. Al concluir la sexta semana se tomaron mediciones finales bajo las mismas condiciones que las iniciales...

Introduction:Dental plaque is considered to be the main etiological factor in the development and progression of gingivitis. Oral care products such as toothpaste and mouthwash have commonly been rec-ommended as an adjunct to mechanical periodontal therapy. Objective:To evaluate the effi cacy of using a dentifrice containing 0.3% triclosan and 2.0% PVM/MA copolymer (Colgate Total 12®) in combination with a 0.05% cetylpyridinium chloride mouthwash (Colgate Plax®) in patients with chronic marginal gingivitis following scaling and root-planing therapy compared to a control group. Material and methods:A randomized double-blind controlled clinical study was performed on 50 systemically healthy patients diagnosed with chronic marginal gingivitis. These were divided into two groups: A (experimental) and B (control). The Lõe and Silness gingival index and the Turesky modifi ca-tion of the Quigley-Hein plaque index were recorded at baseline and after 6 weeks (the duration of the study). Patients were treated with scaling and root-planning, and all received instructions on the proper use of the oral care products. Final measurements were taken at the end of the six-week assessment under the same conditions as those at the time of the baseline assessment...

Candida albicans biofilms and MMA surface treatment influence the adhesion of soft denture liners to PMMA resin

The effect of Candida albicans biofilms and methyl methacrylate (MMA) pretreatment on the bond strength between soft denture liners and polymethyl methacrylate (PMMA) resin was analyzed. Specimens were prepared and randomly divided with respect to PMMA pretreatment, soft liner type (silicone-based or PMMA-based), and presence or absence of a C. albicans biofilm. Samples were composed of a soft denture liner bonded between two PMMA bars. Specimens (n = 10) were incubated to produce a C. albicans biofilm or stored in sterile PBS for 12 days. The tensile bond strength test was performed and failure type was determined using a stereomicroscope. Surface roughness (SR) and scanning electron microscopy (SEM) analysis were performed on denture liners (n = 8). Highest bond strength was observed in samples containing a silicone-based soft liner and stored in PBS, regardless of pretreatment (p < 0.01). Silicone-based specimens mostly underwent adhesive failures, while samples containing PMMA-based liners predominantly underwent cohesive failures. The silicone-based specimens SR decreased after 12 days of biofilm accumulation or PBS storage, while the SR of PMMA-based soft liners increased (p < 0.01). The PMMA-based soft liners surfaces presented sharp valleys and depressions, while silicone-based specimens surfaces exhibited more gentle features. In vitro exposure to C. albicans biofilms reduced the adhesion of denture liners to PMMA resin, and MMA pretreatment is recommended during relining procedures.

Reconstrução da parede torácica após a ressecção de extensos tumores / Reconstruction of chest wall after resection of large tumors

INTRODUÇÃO: Nos estágios finais da reconstrução torácica, consequente a exéreses tumorais, são necessários procedimentos complexos e implantes. O que requer cuidados multidisciplinares, com a participação dos cirurgiões torácicos, plástico, radiologista e fisioterapeuta. O objetivo foi descrever as opções de reconstrução torácica após ressecção de neoplasia, realizado no Hospital Sarah Brasília. MÉTODO: Estudo retrospectivo de reconstrução torácica em tempo único, após excisão de tumor, fisioterapia respiratória com ventilação não invasiva e exercícios. RESULTADOS: Entre 2007 a 2012 foram operados 10 pacientes, sete homens e três mulheres; idade 10 a 31 anos; oito apresentavam tumores torácicos metastáticos (osteosarcoma, sinoviosarcoma, Fibrosarcoma epitelioide esclerosante e Rabdomiosarcoma) e dois originários da parede torácica (fibromatose e condrosarcoma). Observou-se boa evolução no pós-operatório imediato, com extubação ao final da cirurgia, retirada do dreno torácico entre 5° e 8° PO. As complicações foram: atelectasia (10%), recorrência tumoral (10%), e óbito em 3 (30%) casos . CONCLUSÃO: Foi possível a reconstrução torácica em tempo único utilizando tela de polipropileno, polimetilmetacrilato e retalhos musculares, com recuperação precoce da função pulmonar e baixo índice de complicações imediatas.

INTRODUCTION: Complex procedures and implants are required in the final stages of chest wall reconstruction after tumor excision. This process requires multidisciplinary care with participation from thoracic and plastic surgeons, a radiologist, and a physical therapist. The goal of this study was to describe the options for chest wall reconstruction after neoplasm resection at Hospital Sarah Brasilia. METHOD: A retrospective study of one-time chest wall reconstruction after tumor excision, respiratory physical therapy with noninvasive ventilation, and exercises was conducted. RESULTS: Between 2007 and 2012, 10 patients underwent surgery (seven men, three women; age range: 10-31 years); eight patients had metastatic thoracic tumors (e.g., osteosarcoma, synovial sarcoma, sclerosing epithelioid fibrosarcoma, and rhabdomyosarcoma) and two had tumors originating from the chest wall (fibromatosis and chondrosarcoma). The outcomes were good after the immediate postoperative period, with extubation occurring at the end of surgery and chest tube removal between the fifth and eighth postoperative day. Three cases (30%) involved complications of atelectasis (10%), tumor recurrence (10%), or death. CONCLUSION: One-time chest wall reconstruction using polypropylene mesh, polymethylmethacrylate, and muscle flaps was possible and was associated with early recovery of pulmonary function and a low rate of immediate complications.

Abrasion of 6 dentifrices measured by vertical scanning interference microscopy

OBJECTIVES: The abrasion of dentifrices is well recognized to eliminate the dental plaque. The aims of this study were to characterize the abrasive powders of 6 dentifrices (3 toothpastes and 3 toothpowders) and to measure the abrasion on a test surface by Vertical Scanning Interference microscopy (VSI). MATERIAL AND METHODS: Bright field and polarization microscopy were used to identify the abrasive particles on the crude dentifrices and after prolonged washes. Scanning electron microscopy and microanalysis characterized the shape and nature of the particles. Standardized and polished blocks of poly(methylmethacrylate) were brushed with a commercial electric toothbrush with the dentifrices. VSI quantified the mean roughness (Ra) and illustrated in 3D the abraded areas. RESULTS: Toothpastes induced a limited abrasion. Toothpowders induced a significantly higher roughness linked to the size of the abrasive particles. One powder (Gencix® produced a high abrasion when used with a standard testing weight. However, the powder is based on pumice particles covered by a plant homogenate that readily dissolves in water. When used in the same volume, or after dispersion in water, Ra was markedly reduced. CONCLUSION: Light and electron microscopy characterize the abrasive particles and VSI is a new tool allowing the analysis of large surface of abraded materials. .

An investigation on the influence of tin foil substitute contamination on bond strength between resin denture teeth and the denture base: An in vitro study.

Statement of Problem: The problem of acrylic resin denture teeth separating from their denture base remains a major problem in prosthodontic practice and is frustrating to the patients as well as the dentists. Purpose: This study investigated the influence of tin foil substitute contamination on bond strength between acrylic resin denture teeth and their denture base. Materials and Methods: A total of 80 modified acrylic resin maxillary left central incisors were processed to their denture base material. The 80 specimens were divided into two groups of 40 specimens each: the experimental group and the control group. The experimental group had the denture tooth ridge lap area contaminated with tin foil substitute.The 40 specimens in the control group were not contaminated. After 7 days of storage at room temperature, the bond strengths of the two groups were tested with a universal testing machine.The nature of failure was noted as adhesive (interface) or cohesive (in tooth or denture base material). The Welch test and z-test were performed to identify significant differences. Results: The uncontaminated specimens (group I) showed superior bond strength as compared to the contaminated specimens (group II); the difference in bond strength between the groups was highly significant (P<0.0001). Also the contaminated specimens exhibited predominantly adhesive failure (89.74%), whereas the uncontaminated specimens exhibited 55% adhesive failure and 45% cohesive failure. Conclusion: Tin foil substitute contamination of the ridge laps of acrylic resin denture teeth greatly reduced the bond strength.

A comparison of the accuracy of patterns processed from an inlay casting wax, an auto-polymerized resin and a light-cured resin pattern material.

Background: Traditionally, inlay casting waxes have been used to fabricate patterns for castings. Newer resin pattern materials offer greater rigidity and strength, allowing easier laboratory and intraoral adjustment without the fear of pattern damage. They also claim to possess a greater dimensional stability when compared to inlay wax. Aims: This study attempted to determine and compare the marginal accuracy of patterns fabricated from an inlay casting wax, an autopolymerized pattern resin and a light polymerized pattern resin on storage off the die for varying time intervals. Materials and Methods: Ten patterns each were fabricated from an inlay casting wax (GC Corp., Tokyo, Japan), an autopolymerized resin pattern material (Pattern resin, GC Corp, Tokyo, Japan) and a light-cured resin pattern material (Palavit GLC, Hereaus Kulzer GmbH, Germany). The completed patterns were stored off the die at room temperature. Marginal gaps were evaluated by reseating the patterns on their respective dies and observing it under a stereomicroscope at 1, 12, and 24 h intervals after pattern fabrication. Results: The results revealed that the inlay wax showed a significantly greater marginal discrepancy at the 12 and 24 h intervals. The autopolymerized resin showed an initial (at 1 h) marginal discrepancy slightly greater than inlay wax, but showed a significantly less marginal gap (as compared to inlay wax) at the other two time intervals. The light-cured resin proved to be significantly more dimensionally stable, and showed minimal change during the storage period. Conclusion: The resin pattern materials studied, undergo a significantly less dimensional change than the inlay waxes on prolonged storage. They would possibly be a better alternative to inlay wax in situations requiring high precision or when delayed investment (more than 1 h) of patterns can be expected.

In vitro comparative evaluation of the effect of two different fiber reinforcements on the fracture toughness of provisional restorative resins.

Background: Fracture of provisional fixed partial denture (FPD) may jeopardize the success of provisional prosthodontic treatment phase and cause patient discomfort. Aim: The aim of this study was to compare the fracture toughness of the Polymethyl Methacrylate (PMMA) resin and Bis-Acryl Composite (BAC) resin reinforced with the Polyethylene and Glass fibers. Materials and Methods: Three groups (N=10) of each of the two materials were prepared for the fracture toughness test. Two groups had the different reinforcements and group without reinforcement served as the control. The mean fracture toughness (MPa.m½ ) was compared by One-way ANOVA, followed by the Scheffe analysis. Fracture toughness between fiber-reinforced PMMA and BAC resin was compared by the independent samples t test. Results: For the controls, the fracture toughness for PMMA resin (0.91) was significantly lower than for the BAC resin (1.19). Glass fiber reinforcement produced significantly higher fracture toughness for both, PMMA (1.48) and BAC (1.82) resin, but the Polyethylene fibers did not (0.95 for PMMA and 1.23 for BAC resin). Among the reinforced groups, Silane impregnated Glass fibers showed highest fracture toughness for the BAC resin (1.82). Conclusion: Of two fiber reinforcement methods evaluated, Glass fiber reinforcement for the PMMA and BAC resin produced highest fracture toughness. Clinical Implications: On the basis of this in--vitro study, the use of Glass and Polyethylene fibers tested may be an effective way to reinforce resins used to fabricate fixed provisional restorations.

Exopolysaccharide matrix of developed candida albicans biofilms after exposure to antifungal agents

This study aimed to evaluate the effects of fluconazole or nystatin exposure on developed Candida albicans biofilms regarding their exopolysaccharide matrix. The minimal inhibitory concentration (MIC) against fluconazole or nystatin was determined for C. albicans reference strain (ATCC 90028). Poly(methlymethacrylate) resin (PMMA) specimens were fabricated according to the manufacturer's instructions and had their surface roughness measured. Biofilms were developed on specimens surfaces for 48 h and after that were exposed during 24 h to fluconazole or nystatin prepared in a medium at MIC, 10 x MIC or 100 x MIC. Metabolic activity was evaluated using an XTT assay. Production of soluble and insoluble exopolysaccharide and intracellular polysaccharides was evaluated by the phenol-sulfuric method. Confocal laser scanning microscope was used to evaluate biofilm architecture and percentage of dead/live cells. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. The presence of fluconazole or nystatin at concentrations higher than MIC results in a great reduction of metabolic activity (p<0.001). At MIC or 10 x MIC, fluconazole showed high amounts of intracellular polysaccharides (p<0.05), but did not affect the exopolysaccharide matrix (p>0.05). The exposure to nystatin also did not alter the exopolysaccharide matrix at all the tested concentrations (p>0.05). Biofilm architecture was not affected by either of the antifungal agents (p>0.05). Nystatin promoted higher proportion of dead cells (p<0.05). It may be concluded that fluconazole and nystatin above the MIC concentration reduced the metabolic activity of C. albicans biofilms; however, they were not able to alter the exopolysaccharide matrix and biofilm architecture.

Este estudo avaliou o efeito da exposição de fluconazol ou nistatina a biofilmes de Candida albicans desenvolvidos, considerando a matriz de polissacarídeos extracelulares. Inicialmente uma cepa referência de C. albicans (ATCC 90028) foi submetida ao teste de concentração inibitória mínima (CIM) utilizando-se o fluconazol ou nistatina como agentes antifúngicos. Após, espécimes foram confeccionados em resina acrílica de polimetilmetacrilato (PMMA) de acordo com as recomendações do fabricante e tiveram sua rugosidade de superfície padronizada. Após, biofilmes de C. albicans foram desenvolvidos na superfície dos espécimes durante 48 h. Em seguida, os biofilmes foram expostos a fluconazol ou nistatina nas concentrações de CIM, 10 x CIM ou 100 x CIM, por 24 h. A atividade metabólica dos biofilmes foi avaliada pelo teste de XTT. A produção de polissacarídeos extracelulares solúveis e insolúveis, bem como dos polissacarídeos intracelulares foi avaliada pelo método fenol-sulfúrico. A arquitetura dos biofilmes e proporção de células vivas e mortas foi investigada utilizando-se microscopia confocal a laser. Os resultados foram analisados por ANOVA seguido do teste de Tukey, utilizando-se o nível de significância de 5%. A presença do fluconazol ou nistatina em concentrações maiores que CIM resultaram em uma redução significativa da atividade metabólica (p<0,001). Nas concentrações de CIM e 10 x CIM, biofilmes expostos ao fluconazol apresentaram quantidades significativas de polissacarídeos intracelulares (p<0,05), enquanto não houve alterações na quantidade de polissacarídeos extracelulares (p>0,05). A presença de nistatina também não alterou a matriz de polissacarídeos extracelulares em todas as concentrações investigadas (p>0,05). A arquitetura dos biofilmes não foi afetada por ambos os agentes antifúngicos, em qualquer concentração testada (p>0,05). A nistatina apresentou maior proporção de células mortas (p<0,05). Conclui-se que tanto para o fluconazol quanto para a nistatina, concentrações maiores que CIM reduziram a atividade metabólica dos biofilmes de C. albicans; no entanto, tais concentrações não alteraram a matriz de polissacarídeos extracelulares nem a arquitetura dos biofilmes.

Poly (Methyl Methacrylate) absorption and releasing of nystatin and fluconazole / Absorção e liberação de nistatina e fluconazol por polimetilmetacrilato

Objectives: The aim of this study was to verify if there are poly (methyl methacrylate) (PMMA) absorptionand releasing of nystatin (NYS) and fluconazole (FLZ) after simulated treatment of oral candidosis. Materialsand methods: Specimens (30 × 25 × 5 mm) prepared with PMMA polymerized by hot water bath or microwaveenergy were immersed into NYS (3.12 μg/mL), FLZ (2.56 μg/mL) or deionized water (control) during14 days at 35 ± 2 °C. After treatment simulation, specimens were immersed into distilled water during 3, 7, 10and 14 days. The immersion liquid was changed after each analysis. Higher performance liquid chromatographywas used in order to detect antifungal compounds. In order to determine if there was surface depositionof drugs on PMMA resin, specimens were analyzed with electronic microscopy (SEM). Results: None of theantifungal agents was released from the PMMA resins. Conclusion: Within the limitations of this study, itcould be concluded that PMMA resins had no drug absorption with posterior release.

Objetivos: O objetivo deste estudo foi verificar se o poli (metil metacrilato) (PMMA) é capaz de absorver e liberar nistatina (NYS) e fluconazol (FLZ) após simular um tratamento para candidose oral. Materiais e métodos:Espécimes (30 × 25 × 5 mm) foram preparados em resina de PMMA por banho de água quente ou energia demicro-ondas e, em seguida, imersos em solução contendo NYS (3.12 μg/mL), FLZ (2.56 μg/mL) ou água deionizada(controle) durante 14 dias a 35 ± 2 °C. Após a simulação de tratamento, os espécimes foram imersos em água destilada durante 3, 7, 10 e 14 dias. O líquido de imersão foi trocado após cada análise. Cromatografia líquida de alta performance foi utilizada para detectar a presença dos agentes antifúngicos. Para determinar se houve deposição dos agentes antifúngicos na superfície de PMMA, os espécimes foram analisados por microscopia eletrônica de varredura(MEV). Resultados: Não houve liberação de agentes antifúngicos dos espécimes. Conclusão: Considerando as limitações deste estudo, pode-se concluir que a resina de PMMA não absorve ou libera agentes antifúngicos.

Efeito do ciclo de polimerização sobre a dureza de resinas acrílicas para base de prótese polimerizadas convencionalmente ou em micro-ondas / Effect of polymerization cycle on hardness of denture base acrylic resins polymerized by conventional water bath or microwave irradiation

Introdução: O tempo de polimerização reduz-se significativamente com a utilização do micro-ondas e esse método pode polimerizar com eficiência as resinas acrílicas para base de prótese. O objetivo deste estudo foi avaliar o efeito de ciclos de polimerização, em banho de água aquecida(B) e em micro-ondas (M), sobre a dureza de resinas acrílicas formuladas para serem processadas convencionalmente (Vipi Cril®-VC) ou por micro-ondas (Vipi Wave®-VW). Material e Métodos- Corpos de prova (n=8) foram confeccionados nas dimensões de 64x10x3,3 mm e armazenados em água destilada em estufa a 37ºC por 48h. Amostras de cada material termopolimerizável convencional(VC) ou para micro-ondas (VW) foram divididas aleatoriamente em dois grupos: ciclos de polimerização recomendados pelo fabricante em banho de água aquecida (VCB e VWB) ou em micro-ondas (VCM e VWM). As mensurações de dureza (VHN) foram realizadas utilizando-se um microdurômetro Vickers com carga de 50g durante 10s. Os resultados foram submetidos à ANOVA2 fatores seguida pelo teste de Tukey (α=0,05). Resultados - Independentemente do ciclo utilizado,não houve diferença estatisticamente significante entre os materiais avaliados (P=0,38). Foram observados valores de dureza maiores (P=0,00003) quando os ciclos de polimerização das resinas acrílicas foram invertidos (VCM=48,2>VCB=32,9; VWB=50,5>VWM=24,1). Conclusões - As resinas acrílicas apresentaram valores de dureza sem diferença significativa quando polimerizadas de acordo com as instruções do fabricante. A polimerização da resina Vipi Cril em micro-ondas e da resina Vipi Wave em banho de água resultou em valores de dureza superiores.

Introduction: The processing time is significantly reduced with using microwave and this method can efficiently polymerize denture base acrylic resins. The aim of this study was to evaluate the effect of water-bath (W) and microwave (M) polymerization cycles on hardness of water-bath (VipiCril®-VC) or microwave-polymerized acrylic resin (Vipi Wave®-VW). Material and Methods -Specimens (n=8) of the heat-polymerized denture base acrylic resins were made (64x10x3.3 mm)and stored in distilled water at 37ºC during 48h. After that, specimens of water-bath polymerized(VC) or microwave processed (VW) materials were randomly divided into two groups according to the polymerization cycles recommended by the manufacturer: water-bath (VCW and VWW)or microwave irradiation (VCM and VWM). Hardness measurements (VHN) were made with ahardness tester operated under a 50-g load and a 10-second dwell time. Results were analyzed with 2-way ANOVA and Tukey’s test (α=0.05). Results - Regardless of polymerization cycle,no significant difference was observed between the evaluated materials (P=0.38). The highest hardness values (P=0.00003) were obtained when the polymerization cycles were inverted(VCM=48.2>VCB=32.9; VWB=50.5>VWM=24.1). Conclusions - Vipi Cril and Vipi Wave acrylic resins showed hardness values without significant difference after being polymerized according to the manufacturer’s instructions. Higher hardness values were obtained in Vipi Cril microwavepolymerized and in Vipi Wave water-bath polymerized specimens.

Flexural strength and hardness of resins for interim fixed partial dentures.

Context: Materials used for the fabrication of interim restorations must satisfy biological, esthetic, and functional needs. Strength and wear resistance are two important physical properties contributing to clinical efficiency. Aim: The objective of this in vitro study was to evaluate and compare the flexural strength and hardness of five resins used for the fabrication of interim fixed partial dentures. Materials and Methods: Five groups containing ten specimens of each material were fabricated in customized brass split molds with dimensions 65×10×2.5 mm. The materials subjected to this study were Revotek LC™ (group RLC), Protemp II™ (group PSC), Acry-lux V™ with regular monomer (group AHC), Acry-lux V™ with self-cure monomer (group ASC), DPI™ self-cure tooth molding powder (group DSC). The specimens were polymerized according to the manufacturers' instructions and were evaluated for flexural strength using a universal testing machine and for hardness using a microhardness tester. Statistical Analysis: The mean of the five groups was compared using one way analysis of variance (ANOVA) and pair-wise comparison was done using Tukeys honesty significance difference (HSD) test. P≤.05 was considered to be statistically significant. Results: Flexural test results showed that group AHC (79.8950 MPa) had the highest flexural strength followed, in descending order, by group PSC (77.9700 MPa), group ASC (63.7150 MPa), group RLC (58.8110 MPa), and group DSC (51.9840 MPa). Statistically, the difference was found to be highly significant among all the groups. The hardness tests showed that group AHC (17.6900 KHN) had the highest hardness value followed, in descending order, by group PSC (15.9400 KHN), group RLC (12.6000 KHN), group ASC (11.2500 KHN), and group DSC (8.7700 KHN). Statistically, the difference was found to be highly significant among all the groups. Conclusion: Group AHC, representing a heat-polymerizing resin, showed the highest flexural strength and hardness values as compared to auto-polymerizing resins and light-polymerizing resin.

Glutaraldehyde release from heat-polymerized acrylic resins after disinfection and chemical and mechanical polishing

This study evaluated the release of glutaraldehyde from heat-polymerized acrylic resins subjected to disinfection followed by chemical and mechanical polishing. Ninety disc-shaped specimens (15 x 4 mm), 30 per resin (Lucitone 550, QC-20 and Classico), were made and assigned to 2 groups according to the type of polishing. One side of each specimen was not polished and the other was either mechanically (n=45) or chemically (n=45) polished, and immersed in water at 50°C for 1 h to allow the release of intrinsic substances and then kept in distilled water for 7 days. The specimens were disinfected by immersion in 2% glutaraldehyde for 10 min. After this period, 3 specimens from each group were immersed in water for 15, 30, 60, 120 and 240 min. For the 15-, 30-, 60-min immersions, 4 water exchanges were done at the end of period. High performance liquid chromatography (HPLC) was used to detect and quantify the glutaraldehyde released after each period. Data were analyzed statistically by two-way ANOVA and multiple comparisons were done by Tukey’s and Scheffé’s tests (α=0.05). No glutaraldehyde release was observed from the specimens with chemical polishing at any of the immersion periods, while the mechanically polished specimens released glutaraldehyde. In the groups with water exchanges, Lucitone released more disinfectant in the 15-min period (0.040 μg/mL), Classico in the 30-min (0.021 μg/mL) and 60-min (0.018 μg/mL) periods, and QC-20 the same amount (-1.760 μg/mL) in all periods. In the groups without water exchanges, Lucitone released the highest amount of disinfectant (-1.370 μg/mL), differing significantly from QC-20 (0022 g/mL) and Classico (0019 g/mL), which were similar. The findings of this showed that chemically polished specimens from the 3 resin brands did not release glutaraldehyde after different periods of immersion, while glutaraldehyde release was observed from the mechanically polished specimens, especially from those made of Lucitone resin.

Este estudo determinou a liberação de glutaraldeído de resinas acrílicas termopolimerizáveis submetidas a polimento químico e mecânico e desinfetadas. Noventa corpos-de-prova circulares (15 x 4 mm), 30 de cada tipo de resina (Lucitone, QC-20 e Clássico), foram confeccionados e divididos em 2 grupos referentes ao tipo de polimento. Um dos lados de cada corpo-de-prova não foi polido e o outro foi polido mecanicamente (n=45) ou quimicamente (n=45), e imersos em água aquecida a 50°C por 1 h para liberação de substâncias intrínsecas e mantidos em água destilada por 7 dias. A seguir era realizada a desinfecção por imersão em solução de glutaraldeído a 2% por 10 min. Decorrido este período, três corpos-de-prova de cada grupo eram imersos em água por 15, 30, 60, 120 e 240 min. Nos períodos de 15, 30 e 60 min foram realizadas até 4 trocas de água após cada período. As amostras eram analisadas por meio de cromatografia líquida de alta eficiência (HPLC) após cada período. Os dados foram analisados estatisticamente pela Análise de Variância e testes complementares de Tukey e Scheffé (α=0,05). Os corpos-de-prova com polimento químico, de todas as marcas comerciais de resina, não liberaram glutaraldeído em qualquer um dos períodos de imersão em água, enquanto os com polimento mecânico liberaram. Nos grupos com trocas de água, a resina Lucitone liberou maior quantidade de desinfetante nas trocas de 15 min (0,040 μg/mL), a resina Clássico nas de 30 (0,021 μg/mL) e 60 min (0,018 μg/mL) e a QC-20 liberou a mesma quantidade (-1,760 μg/mL), em todos os períodos de imersão em água. Nos grupos sem trocas de água, a resina Lucitone liberou maior quantidade de desinfetante (-1,370 μg/mL), sendo diferente estatisticamente das resinas QC-20 (0,022 μg/mL) e Clássico (0,019 μg/mL), que são similares. Pelos resultados conclui-se que corpos-de-prova polidos quimicamente, das três marcas comerciais de resina, não liberaram glutaraldeído após os diferentes períodos de imersão. Contudo, nos corpos-de-prova polidos mecanicamente houve liberação do desinfetante, com Lucitone liberando maior quantidade em relação às demais resinas estudadas.