Isolation and identification of a polyester-polyurethane degrading bacterium Bacillus altitudinis YX8-1 / 生物工程学报

Although polyurethane (PUR) plastics play important roles in daily life, its wastes bring serious environmental pollutions. Biological (enzymatic) degradation is considered as an environmentally friendly and low-cost method for PUR waste recycling, in which the efficient PUR-degrading strains or enzymes are crucial. In this work, a polyester PUR-degrading strain YX8-1 was isolated from the surface of PUR waste collected from a landfill. Based on colony morphology and micromorphology observation, phylogenetic analysis of 16S rDNA and gyrA gene, as well as genome sequence comparison, strain YX8-1 was identified as Bacillus altitudinis. The results of high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed that strain YX8-1 was able to depolymerize self-synthesized polyester PUR oligomer (PBA-PU) to produce a monomeric compound 4, 4'-methylene diphenylamine. Furthermore, strain YX8-1 was able to degrade 32% of the commercialized polyester PUR sponges within 30 days. This study thus provides a strain capable of biodegradation of PUR waste, which may facilitate the mining of related degrading enzymes.

Screening and identification of a polyurethane-degrading bacterium G-11 and its plastic degradation characteristics / 生物工程学报

Polyurethane (PUR) plastics is widely used because of its unique physical and chemical properties. However, unreasonable disposal of the vast amount of used PUR plastics has caused serious environmental pollution. The efficient degradation and utilization of used PUR plastics by means of microorganisms has become one of the current research hotspots, and efficient PUR degrading microbes are the key to the biological treatment of PUR plastics. In this study, an Impranil DLN-degrading bacteria G-11 was isolated from used PUR plastic samples collected from landfill, and its PUR-degrading characteristics were studied. Strain G-11 was identified as Amycolatopsis sp. through 16S rRNA gene sequence alignment. PUR degradation experiment showed that the weight loss rate of the commercial PUR plastics upon treatment of strain G-11 was 4.67%. Scanning electron microscope (SEM) showed that the surface structure of G-11-treated PUR plastics was destroyed with an eroded morphology. Contact angle and thermogravimetry analysis (TGA) showed that the hydrophilicity of PUR plastics increased along with decreased thermal stability upon treatment by strain G-11, which were consistent with the weight loss and morphological observation. These results indicated that strain G-11 isolated from landfill has potential application in biodegradation of waste PUR plastics.

Influence of a hydrophobic monomer on the physical and mechanical properties of experimental surface sealants

Abstract This study evaluated the effect of adding the hydrophobic monomer 1,12 dodecanediol dimethacrylate (DDDMA) to experimental sealants with and without thermocycling on degree of conversion (DC), water sorption (WS), water solubility (WSB), color stability (ΔE), and micro-shear bond strength (μSBS). Five experimental and one commercially available sealant (Bisco - BIS) were tested. The experimental sealants were formulated by mixing different percentages of DDDMA monomers and urethane dimethacrylate (UDMA). The photoinitiator system was composed by camphorquinone (CQ) and tertiary amine 4-ethyl benzoate dimetilamiono (EDBA). Ethanol was used as a solvent. The experimental groups were named sequentially according to the monomeric content (DDDMA/UDMA): S40/40 (40/40), S50/30 (50/30), S60/20 (60/20), S70/10 (70/10) and S80/0 (80/0). Data were analyzed separately by one-way ANOVA, followed by Tukey's test (p<0.05). The values of DC ranged from 94.59% (S40/40) to 54.02% (S80/10). BIS showed the highest WS value (p<0.05) and S40/40, S50/30, S60/20 and S80/0 showed the lowest WS values of all tested sealants. WSB values ranged from 7.88 µg/mm3 (BIS) to 13.27 µg/mm3 (S70/10). The highest ΔE value was 11.05±2.88 for BIS and the highest μSBS value was found for S60/20. No significant difference was observed in bond strength between sealants and bovine enamel after thermocycling. Adding DDDMA to the composition of surface sealants can improve its performance, once the monomer increased the degree of conversion and the color stability.

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars

Abstract Objective This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays.

Surface, thermal and hemocompatible properties of novel single stage electrospun nanocomposites comprising polyurethane blended with bio oilTM

ABSTRACT In this work, the physicochemical and blood compatibility properties of prepared PU/Bio oil nanocomposites were investigated. Scanning electron microscope (SEM) studies revealed the reduction of mean fiber diameter (709 ± 211 nm) compared to the pristine PU (969 nm ± 217 nm). Fourier transform infrared spectroscopy (FTIR) analysis exposed the characteristic peaks of pristine PU. Composite peak intensities were decreased insinuating the interaction of the bio oilTM with the PU. Contact angle analysis portrayed the hydrophobic nature of the fabricated patch compared to pristine PU. Thermal gravimetric analysis (TGA) depicted the better thermal stability of the novel nanocomposite patch and its different thermal behavior in contrast with the pristine PU. Atomic force microscopy (AFM) analysis revealed the increase in the surface roughness of the composite patch. Activated partial thromboplastin time (APTT) and prothrombin time (PT) signified the novel nanocomposite patch ability in reducing the thrombogenicity and promoting the anticoagulant nature. Finally the hemolytic percentage of the fabricated composite was in the acceptable range revealing its safety and compatibility with the red blood cells. To reinstate, the fabricated patch renders promising physicochemical and blood compatible nature making it a new putative candidate for wound healing application.

Influence of resin cement shade on the color and translucency of ceramic veneers

ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.

Optimizing light-cured composite through variations in camphorquinone and butylhydroxytoluene concentrations

Abstract The use of a free-radical polymerization inhibitor, butylhydroxytoluene (BHT), and a common photo-initiator, camphorquinone (CQ), to reduce polymerization stress in dental composite was investigated in this study. Samples were prepared by mixing Bis-GMA, UDMA, and TEGDMA at a 1:1:1 ratio (wt%), and silanized borosilicate glass fillers at 70 wt% were added to form the composite. Sixteen groups of resin composite were prepared using combinations of four CQ (0.1%, 0.5%, 1.0%, and 1.5%) and four BHT (0.0%, 0.5%, 1.0%, and 1.5%) concentrations. For each group, six properties were tested, including flexural strength (FS), flexural modulus (FM), degree of conversion (DC), contraction stress (CS), stress rate, and gel point (GP). The effects of CQ and BHT combinations on each of these properties were evaluated using two-way analysis of variance (ANOVA) and Fisher's Protected Least Significant Differences test at the 5% significance level. Groups with low CQ and BHT showed moderate values for FS, FM, and CS with a 70% DC. Increasing the BHT concentration caused a decrease in CS and DC with an increase in GP values. Increasing the CQ content led to a steady increase in values for FS and FM. High CQ and BHT combinations showed the most promising values for mechanical properties with low stress values.

Influence of polyurethane resin dies on the fit and adaptation of full veneer crowns.

Context: Polyurethane resin is a possible alternative to type IV dental stone for fabrication of indirect restorations however its dimensional accuracy is questionable. Aim: The aim was to investigate the dimensional accuracy of silica filled polyurethane resin die material by evaluating the marginal fit and adaptation of indirect gold castings. Settings and Design: Experimental, in vitro study. Materials and Methods: Totally 40 copper plated replicas of a nickel chrome master die analogous to a veneer gold crown preparation were made and impressions recorded using polyvinylsiloxane material. Twenty impressions were poured in type IV dental stone (control group (Vel‑mix, Kerr, UK) and the remaining (n = 20) in silica filled polyurethane die material (test group) (Alpha Die MF, CA, USA). Gold castings were fabricated for each die using standardized techniques. The castings were seated on their respective copper plated dies, embedded in resin and sectioned. The specimens were analyzed by measuring marginal opening and the area beneath the casting at a ×63 magnification and using image analysis software. Statistical Analysis Used: Data were analyzed using a Student’s t‑test. Results: No significant difference was observed between the experimental groups (P > 0.05). The mean marginal opening for type IV, dental stone and polyurethane resin, was 57 ± 22.6 μm and 63.47 ± 27.1 μm, respectively. Stone displayed a smaller area beneath the casting (31581 ± 16297 μm2) as compared to polyurethane resin (35003 ± 23039 μm2). Conclusions: The fit and adaptation of indirect gold castings made on polyurethane and type IV dental stone dies were comparable.

A castor oil-containing dental luting agent: effects of cyclic loading and storage time on flexural strength

Favorable results in the use of castor oil polyurethane (COP) as pulp capping, membrane material, sealer, mouthwash and in bone repair, associated with the fact that Ricinus communis is not derived from petroleum and it is abundant in Brazil, encourage researches in the development of luting agents. Objectives This study compared the flexural strength (FS) of a castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate (COP10) with RelyX ARC (RX) after mechanical cycling (MC) and distilled water storage. Material and Methods Sixty-four specimens (25x2x2 mm) were fabricated and divided into two groups, COP10 and RX (control). Each group was divided into 4 subgroups (n=8) according to the storage time, 24 hours (24 h) or 60 days (60 d), and the performance (MC+FS) or not (only FS) of the mechanical cycling test. The FS (10 kN; 0.5 mm/min) and MC tests (10,000 cycles, 5 Hz, 0.5 mm/min) were carried out using an MTS-810 machine. The data were analyzed using ANOVA (α=0.05). Results The obtained FS (MPa) values were: COP10 24h- 19.04±2.41; COP10 60d- 17.92±3.54; RX 24h- 75.19±3.43; RX 60d- 88.77±6.89. All the RX specimens submitted to MC fractured, while the values for COP10 after MC were as follows: COP10 24h- 17.90±1.87 and COP10 60d- 18.60±1.60. Conclusions A castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate is resistant to mechanical cycling without decreases in flexural strength. However, mean COP10 showed only about 25% of the RelyX ARC mean flexural strength. .

Mastopexia periareolar (circum-areolar) com implante mamário cônico: tratamento de ptose, hipomastia e alterações de posição e tamanho do complexo aréolo-papilar / Periareolar (circumareolar) mastopexy with conical breast implants: treatment of ptosis, hypomastia, and changes in position and size of the nipple-areola complex

INTRODUÇÃO: A cirurgia de mastopexia associada ao aumento mamário vem sendo cada vez mais solicitada. Ao mesmo tempo, pacientes com graus menores de ptose aceitam menos as correções por meio de cicatrizes verticais. Nesse contexto, a mastopexia periareolar (circum-areolar) com implante cônico é uma opção que resulta em cicatriz limitada ao perímetro areolar e possibilita o tratamento das alterações de posição e tamanho do complexo aréolo-papilar. MÉTODO: Foram avaliadas 22 pacientes, submetidas à mastopexia periareolar com utilização de próteses cônicas, revestidas com poliuretano, colocadas em posição subglandular e operadas pelo mesmo cirurgião. RESULTADOS: Dados observados: 45% das pacientes apresentavam ptose grau I; 32%, grau II, e 23%, grau III; 86% das pacientes apresentavam assimetria do complexo aréolo-papilar; 27%, lateralização, e 18%, aréolas grandes, havendo associações na mesma paciente. O volume das próteses variou de 215 mL a 380 ml. Houve dois casos de alargamento da cicatriz, mas não houve casos de alargamento de aréola ou cicatriz hipertrófica. Não houve, no período pesquisado, complicações relacionadas à colocação do implante. No questionário de satisfação, a maioria das pacientes considerou o aspecto da mama natural, conferindo boas notas aos aspectos: formato, simetria e altura das mamas, qualidade da cicatriz e posição, formato e tamanho das aréolas. CONCLUSÕES: A técnica permite resultados satisfatórios nos casos indicados, como ptoses leves a moderadas, aréolas grandes, lateralização e assimetria do complexo aréolo-papilar. São aspectos técnicos importantes: a retirada conservadora de pele periareolar, o uso de implantes de tamanhos moderados e a confecção da sutura de contenção em round-block.

INTRODUCTION: Mastopexy surgery associated with breast augmentation is increasingly being requested. At the same time, patients with lower degrees of ptosis are less receptive to any correction through vertical scars. In this context, periareolar (circumareolar) mastopexy with a conical implant is an option that results in a scar that is limited to the areolar perimeter, and enables the treatment of changes in the position and size of the nipple-areola complex. METHOD: We evaluated 22 patients submitted to periareolar mastopexy with use of conical prostheses coated with polyurethane and placed in a subglandular position. All patients were operated on by the same surgeon. RESULTS: Among the patients, 45% presented with grade I ptosis, 32% grade II, and 23% grade III, and 86% exhibited asymmetry of the nipple-areola complex, 27% lateralization, and 18% large areolas, with some combination in the same patient. The volume of the prostheses ranged from 215 to 380 mL. There were two cases of scar enlargement; however, there were no cases of enlargement of the areola or hypertrophic scar. During the period studied, there were no complications related to the placement of the implant. In the satisfaction questionnaire, most of the patients considered the aspect of the breast to be natural in appearance, giving good grades to the size, symmetry, and height of the breasts; the quality of the scar; and the position, shape, and size of the areolas. CONCLUSIONS: This technique produces satisfactory results in cases of mild to moderate ptoses, large areolas, lateralization, and asymmetry of the nipple-areola complex. Important technical aspects include the conservative removal of periareolar skin, use of implants of moderate sizes, and the use of the round-block containment suture.

Estudo de complicações em próteses mamárias: avaliação de 546 casos em oito anos / A report on complications of breast implantation: evaluation of 546 cases in 8 years

INTRODUÇÃO: O implante de próteses mamárias é uma das cirurgias mais frequentes e desafiadoras da cirurgia plástica, devido às complicações associadas. MÉTODO: Foi realizado um estudo retrospectivo de 546 pacientes operadas em oito anos (maio de 2004 a maio de 2012), sendo estudadas todas as pacientes submetidas à inclusão de próteses mamárias, isoladamente ou associadas à mastopexia ou mamoplastia redutora. RESULTADOS: Foram utilizadas próteses texturizadas em 84,8% e poliuretano, em 15,2%, com plano de implantação subglandular em 91,7% e submuscular, em 8,24%. Foram estudados: contratura (3,3%), seroma (2,7%), ptose (2,7%) e infecção (0,6%). A maioria das contraturas surgiu cinco anos após a cirurgia e apenas nas próteses texturizadas, que tiveram tempo de seguimento maior (4,2 anos, nas próteses texturizadas versus 1,7 ano nas de poliuretano). Houve maior frequencia de ptose nas texturizadas e de infecção, nas de poliuretano. Somente apresentaram contraturas pacientes com próteses texturizadas no período observado. Comparando-se o plano de implantação, o seroma foi mais frequente nas submusculares. Considerando-se a complexidade do procedimento, houve aumento do índice de complicações: nas implantadas com poliuretano, aumentou o índice de infecção; nas texturizadas, de ptose e seroma, mas não houve diferenças quanto à contratura. Todos os casos de infecção ocorreram em mamoplastias redutoras com próteses de poliuretano e foram causados por germes comuns, sem casos de micobactérias. CONCLUSÕES: Contraturas e ptose foram exclusivas em próteses texturizadas, no tempo de seguimento mais curto. Infecção apenas ocorreu em próteses de poliuretano. As mastopexias e mamoplastias redutoras apresentaram um índice progressivamente mais alto de complicações.

INTRODUCTION: Breast augmentation implant surgery is one of the most frequently performed plastic surgery procedures; however, it can be challenging because of its associated complications. METHOD: We conducted a retrospective study of 546 patients operated on in eight years (May 2004 to May 2012). These patients underwent breast augmentation, alone or in association with mastopexy or breast reduction. RESULTS: In this study, 84.8% textured and 15.2% polyurethane prostheses, with 91.7% deployed in the subglandular plane and 8.24% in the submuscular plane, were used. We investigated the occurrence of contracture (3.3%), seroma (2.7%), ptosis (2.7%), and infection (0.6%). Most contractures occurred 5 years after surgery and only in textured prostheses, which had a longer follow-up (4.2 years for textured implants vs. 1.7 years for polyurethane implants). There was a higher frequency of ptosis in textured implants and of infection in polyurethane implants. Only patients with textured prostheses showed contractures in the observed period. Concerning the deployment plane, seroma was more frequently observed in submuscular implants. More complex procedures showed a higher rate of complications. Polyurethane implants were associated with increased infection rates, whereas textured implants resulted in ptosis and seroma; however, there were no differences in contracture rates. All cases of infection occurred in patients who received reduction mammoplasty with polyurethane prostheses and were caused by common germs, with no cases of mycobacterial infection. CONCLUSIONS: Contractures and ptosis uniquely occurred in textured prostheses in the shortest follow-up time. Infection occurred only in polyurethane prostheses. Mastopexies and reduction mammoplasties showed a progressively higher rate of complications.

An in-vitro study to compare the force degradation of pigmented and non-pigmented elastomeric chains.

Aim: The purpose of the study was to compare the force delivery and force decay property of pigmented and non-pigmented elastomeric chains, widely used in orthodontic practice. Materials and Methods: Force delivered by the samples consisting of pigmented and non-pigmented elastomeric chains obtained from 3 manufacturers were tested at 3 time intervals (as received, after 24 hours and 21 days of stretching) to measure the force delivered by the test samples, as well as the force decay over time. Results: The force delivered by the non-pigmented samples was significantly greater than the pigmented ones at all 3 time intervals irrespective of the brand. Force decay was more significant in case of pigmented samples. Force decay was greater noticed in first 24 hours of testing and a gradual decrease in force was observed from 24 hours to 21 days in all test samples irrespective of the brand or color. Conclusion: Non-pigmented elastomeric chains exhibited better force delivery and less force decay percentage when compared to pigmented chains. Though colored elastomeric chains are widely used in present day orthodontic practice to satisfy the younger age group patients, the study ascertains the prudential use of pigmented and non-pigmented chains for efficient and faster orthodontic treatment.

Comparison of Silorane and Methacrylate-Based Composites on the Polymerization Heat Generated with Different Light-Curing Units and Dentin Thicknesses

This study evaluated the temperature variation in the pulp chamber during photoactivation of two restorative composite resins (Filtek P90 silorane-based composite and Heliomolar methacrylate-based composite) with either a quartz-tungsten-halogen (QTH) or light-emitting diodes (LED) light-curing unit (LCU) and using dentin thicknesses (0.5 and 1.0 mm). Standardized cavities (2x2x2 mm) were prepared in 80 bovine incisors, which were randomly assigned to 8 groups according to the photoactivation method and dentin thickness. Filtek P90 and Heliomolar (both in shade A3) were used with their respective adhesive systems (P90 self-etch primer / P90 adhesive bond and Excite adhesive). All experiments were carried out in a controlled environment (37°C). The temperature variations (°C) were recorded using a digital thermometer attached to a K-type thermocouple. The results were analyzed statistically by ANOVA and Tukey's test (α=0.05). For composite/dentin thickness interaction, temperature increase was significantly higher in 0.5 mm dentin thickness (40.07°C) compared with 1.0 mm dentin thickness (39.61°C) for Filtek P90. For composite/LCU interaction, the temperature increase was significantly higher for Filtek P90 (39.21°C - QTH and 40.47°C - LED) compared with Heliomolar (38.40°C - QTH and 39.30°C - LED). The silorane-based composite promoted higher temperature increase in the pulp chamber than the methacrylate-based composite.

Este estudo avaliou a variação de temperatura na câmara pulpar durante a fotoativação de duas resinas compostas (Filtek P90 – compósito à base de silorano e Heliomolar – compósito à base de metacrilato) com as unidades foto-ativadoras (UFs) luz de quartzo-tungstênio-halogênio (QTH) ou diodo emissor de luz (LED) e utilizando espessuras de dentina (0,5 e 1,0 mm). Cavidades padronizadas (2×2×2 mm) foram preparadas em 80 incisivos bovinos, as quais foram aleatoriamente divididas em 8 grupos de acordo com os métodos de fotoativação e espessura da dentina. Filtek P90 e Heliomolar (ambos na cor A3) foram utilizadas com seus respectivos sistemas adesivos (Primer P90 auto-condicionante / adesivo P90 e adesivo Excite). Todos os experimentos foram realizados em um ambiente controlado (37°C). As variações de temperatura (°C) foram mensuradas usando um termômetro digital conectado a um termopar tipo-K. Os resultados foram analisados estatisticamente por ANOVA e teste de Tukey (α=0,05). Para interação compósito/espessura de dentina, o aumento da temperatura foi estatisticamente superior para a espessura de dentina de 0,5 mm (40,07°C) quando comparado com a espessura de dentina de 1,0 mm (39,61°C) para a Filtek P90. Para a interação compósito/UFs, o aumento de temperatura foi estatisticamente superior para o Filtek P90 (39,21°C – QTH e 40,47°C – LED) quando comparado ao Heliomolar (38,40°C – QTH e 39,30°C – LED). Compósitos à base de silorano promovem maior aumento da temperatura na câmara pulpar em relação aos compósitos à base de metacrilato.

Silorane- and high filled-based"low-shrinkage" resin composites: shrinkage, flexural strength and modulus

This study compared the volumetric shrinkage (VS), flexural strength (FS) and flexural modulus (FM) properties of the low-shrinkage resin composite Aelite LS (Bisco) to those of Filtek LS (3M ESPE) and two regular dimethacrylate-based resin composites, the microfilled Heliomolar (Ivoclar Vivadent) and the microhybrid Aelite Universal (Bisco). The composites (n = 5) were placed on the Teflon pedestal of a video-imaging device, and VS was recorded every minute for 5 min after 40 s of light exposure. For the FS and FM tests, resin discs (0.6 mm in thickness and 6.0 mm in diameter) were obtained (n = 12) and submitted to a piston-ring biaxial test in a universal testing machine. VS, FS, and FM data were submitted to two-way repeated measures and one-way ANOVA, respectively, followed by Tukey's post-hoc test (a = 5%). Filtek LS showed lower VS than did Aelite LS, which in turn showed lower shrinkage than did the other composites. Aelite Universal and Filtek LS exhibited higher FS than did Heliomolar and Aelite LS, both of which exhibited the highest FM. No significant difference in FM was noted between Filtek LS and Aelite Universal, while Heliomolar exhibited the lowest values. Aelite LS was not as effective as Filtek LS regarding shrinkage, although both low-shrinkage composites showed lower VS than did the other composites. Only Filtek LS exhibited FS and FM comparable to those of the regular microhybrid dimethacrylate-based resin composite.

In vitro evaluation of force degradation of elastomeric chains used in Orthodontics

OBJECTIVE: To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics. METHODS: The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation force was recorded at the following time intervals: initial, 1, 3, 5, 7 and 9 hours, and 1, 7, 14, 21, 28, and 35 days. RESULTS: There was a statistically significant difference between the groups regarding the force degradation, mainly within the first day, as a force loss of 50-55% was observed during that time in relation to the initial force. The force delivered at 35 days ranged from 122 g to 148 g. CONCLUSION: All groups showed force degradation over time, regardless of their trademarks, a force loss of 59-69% was observed in the first hour compared to baseline. However, because the variation in force degradation depends on the trademark, studies such as the present one are important for guiding the clinical use of these materials.

OBJETIVO: analisar, in vitro, a degradação de força, ao longo do tempo, de elastômeros das marcas comerciais American Orthodontics, Morelli, Ormco e TP Orthodontics. MÉTODOS: a amostra constituiu-se de 80 segmentos de elastômeros em cadeia fechada na cor cinza, divididos em quatro grupos, conforme o fabricante. A distensão foi padronizada em 21mm, com liberação de força inicial variando de 300 a 370g de força. As amostras foram mantidas em saliva artificial em temperatura constante de 37ºC, e a força avaliada nos seguintes intervalos: inicial, 1h, 3h, 5h, 7h, 9h, 1 dia, 7 dias, 14 dias, 21 dias, 28 dias e 35 dias. RESULTADOS: houve diferença estatisticamente significativa na degradação de força entre os grupos avaliados, sendo que no primeiro dia houve perda de 50 a 55% em relação à força inicial. Os valores médios de força em 35 dias variaram de 122 a 148g. CONCLUSÃO: todas as marcas comerciais apresentaram degradação de força ao longo do tempo, sendo que na primeira hora a perda de força esteve entre 59 e 69% da força inicial. Porém, como existe variação dessa degradação dependendo da marca comercial, estudos como esses são importantes para orientação do uso desses elastômeros.

Color agreement between nanofluorapatite ceramic discs associated with try-in pastes and with resin cements

The aim of this study was to evaluate the in vitro color agreement between nanofluorapatite ceramic discs (e.max Ceram / Ivoclar Vivadent / A2) associated with try-in pastes and those bonded with resin cements (Vitique / DMG/ try-in shade A2½ and cement shade A2½, Variolink II / Ivoclar Vivadent / try-in shade A1 and cement shade A1, and Choice 2 / Bisco / try-in shade A2 and cement shade A2), and to evaluate the shade stability of the discs bonded with resin cements. The shades of composite resin discs (Lliss / FGM / A2) and nanofluorapatite ceramic discs with try-in pastes or cements were evaluated according to the Vita Classical shade guide by a digital spectrophotometer (Micro EspectroShade, MHT) immediately after placing the try-in pastes or resin cements between composite resin discs and ceramic discs. Other evaluations were performed at 2, 5, and 6 day intervals after cementation with the resin cements. All ceramic discs that received try-in pastes presented an A2 shade. There was no statistical difference in the shade of the ceramic specimens fixed with different cements at the different intervals, as evaluated by the Friedman test (p > 0.05). Two try-in pastes presented shade compatibility with those recommended by the manufacturers. There was no similarity of shades between the ceramic discs with try-in pastes and those with the respective resin cements. Shade stability was observed in ceramic discs with resin cements within the intervals evaluated.

Castor oil polyurethane containing silica nanoparticles as filling material of bone defect in rats / Poliuretana de mamona contendo nanopartículas de sílica como material de preenchimento de defeito ósseo em ratos

PURPOSE: To evaluate the biologic behavior of the castor polymer containing silica nanoparticles as a bone substitute in diafisary defect. METHODS: Twenty seven male rattus norvegicus albinus wistar lineage were submitted to bone defect filled with castor oil polymer. Three experimental groups had been formed with nine animals each: (1) castor oil polymer containing only calcium carbonate; (2) castor oil polymer with calcium carbonate and doped with 5 percent of silica nanoparticles; (3) castor polymer with calcium carbonate doped with 10 percent of silica nanoparticles; 3 animals of each group were submitted to euthanasia 15, 30 and 60 days after experimental procedure, and their femurs were removed to histological evaluation. RESULTS: there was bone growth in all the studied groups, with a greater tendency of growth in the group 1. After 30 days all the groups presented similar results. After 60 days a greater amount of fibroblasts, osteoblasts, osteocytes and osteoclasts in group 3 was observed, with integrated activity of 3 kinds of cells involved in the bone activation-reabsorption-formation. CONCLUSIONS: The castor polymer associated to the silica nanoparticles is biocompatible and allows osteoconduction. The presence of osteoprogenitors cells suggests silica osteoinduction capacity.

OBJETIVO: Avaliar o comportamento biológico do polímero de mamona contendo nanopartículas de sílica como substituto ósseo. MÉTODOS: Vinte e sete rattus norvergicus albinus, Wistar foram submetidos a defeito ósseo preenchido com polímero de mamona. Foram formados três grupos experimentais, com nove ratos cada: (1) Polímero com carbonato de cálcio; (2) Polímero com carbonato de cálcio dopado com 5 por cento de nanopartículas de sílica; (3) Polímero com carbonato de cálcio dopado com 10 por cento de nanopartículas de sílica; três animais de cada grupo foram submetidos à eutanásia 15, 30 e 60 dias após o procedimento experimental e os fêmures removidos e submetidos à avaliação histológica. RESULTADOS: Houve crescimento ósseo em todos os grupos estudados, com maior tendência de crescimento no grupo contendo polímero de mamona acrescido apenas por carbonato de cálcio. Aos 30 dias, todos os grupos apresentaram resultados semelhantes. Aos 60 dias, notou-se maior presença de fibroblastos, osteoblastos, osteócitos e osteoclastos no grupo 3, com persistência da atividade integrada dos três tipos de células envolvidas no processo de ativação-reabsorção-formação óssea. CONCLUSÕES: O polímero de mamona associado com nanopartículas de sílica é biocompatível e permite a osteocondução. A presença de células osteoprogenitoras nos implantes contendo 10 por cento de sílica indica sua capacidade osteoindutora.

Novel experimental cements for use on the dentin-pulp complex

This aim of this study was to evaluate the physicochemical and biological properties of novel experimental cements (Hybrid, Paste and Resin) based on synergistic combinations of existing materials, including pH, diametral tensile strength (DTS) and cytotoxicity comparing them with mineral trioxide aggregate (MTA - Angelus®) and a glass ionomer cement (GIC) developed at our laboratory. For the physicochemical and biological tests, specimens with standard dimensions were produced. pH measurements were performed with digital pH meter at the following time intervals: 3, 24, 48 and 72 h. For the DTS test, cylindrical specimens were subjected to compressive load until fracture. The MTT assay was performed for cytotoxicity evaluation. Data were analyzed by ANOVA and Tukey's test (α=0.05). Paste group showed pH values similar to MTA, and Hybrid group presented pH values similar to GIC (p>0.05). The tested materials showed pH values ranging from alkaline to near neutrality at the evaluated times. MTA and GIC showed similar DTS values. The lowest and highest DTS values were seen in the Paste and Resin groups, respectively (p<0.05). Cell viability for MTA and experimental Hybrid, Paste and Resin groups was 49%, 93%, 90% and 86%, respectively, when compared with the control group. The photo-cured experimental resin cement showed similar or superior performance compared with the current commercial or other tested experimental materials.

O objetivo deste estudo foi avaliar propriedades físico-químicas e biológicas de novos cimentos experimentais (Híbrido, Pasta e Resinoso) baseado na combinação sinérgica de materiais existentes, incluindo pH, resistência à tração diametral (RTD) e citotoxidade, comparando-os ao MTA (Angelus®) e a um cimento de ionômero de vidro (CIV) desenvolvido em nosso laboratório. Para a realização dos testes físico-mecânico e biológico, foram confeccionados espécimes com dimensões padrão. O teste de pH foi realizado por meio de pH-metro digital nos tempos: 3, 24, 48 e 72 h. Para o teste de RTD, espécimes cilíndricos foram submetidos a carga compressiva até sua fratura. Para avaliação da citotoxidade, utilizou-se o teste MTT. Os dados foram analisados utilizando ANOVA e teste de Tukey (α=0,05). O grupo Pasta apresentou valores de pH semelhantes ao MTA, assim como o grupo Híbrido seguiu os parâmetros do CIV (p>0,05). Todos os materiais apresentaram valores de pH alcalinos ou próximosà neutralidade nos tempos avaliados. MTA e CIV apresentaram valores de RTD similares. Os menores e maiores valores observados foram do grupo Pasta e Resinoso, respectivamente (p<0,05). A viabilidade celular para os grupos MTA, Híbrido, Pasta, Resinoso, quando comparados ao grupo controle foi de: 49, 93, 90 e 86%, respectivamente. O cimento experimental Resinoso apresentou desempenho similar ou superior aos materiais comerciais e experimentais avaliados.

In vitro wear of Ionofil Molar AC quick glass-ionomer cement.

Aim: The aim of this study was to evaluate the three-body wear-resistance of one type of restorative glass-ionomer cement (GIC). Materials and Methods: Specimen including conventional GIC (Ionofil Molar AC Quick: IMACQ), hybrid ionomer (Fuji II LC), and composite resin (Heliomolar) were tested in a wearing machine. In this machine, a 6 kg load was applied via pressable chromium-cobalt bar at 5,000, 10,000, 20,000, 40,000, 80,000, 120,000 cycles. Specimen weight was measured by an electronical weight balance before and after each cycle. Data were analyzed using one-way analysis of variance (ANOVA) followed by a t-test, and a paired t-test at P≤0.05. Results: The highest weight loss has been found in Fuji II LC, then in GIC IMACQ and the least wear rate has been reported in heliomolar composite in all cycles except 120,000 cycles. In 120,000 cycles, the highest weight loss was seen in GIC IMACQ, then Fuji II LC, and finally heliomolar composite. There was a statistically significant difference in weight loss between GIC IMACQ and heliomolar composite (P=0/001). Conclusion: The wear rate of GIC IMACQ was between those of heliomolar composite and Fuji II LC glass ionomer in all cycles except 120,000 cycles. The most important advantage of this new-generation glass ionomer is its good manipulability and also high wear-resistance compared to the hybrid ionomer. Therefore, it is suggested that it can be used as restorative material in class I restorations in primary teeth.

Validation of an experimental polyurethane model for biomechanical studies on implant supported prosthesis - tension tests

OBJECTIVES: The complexity and heterogeneity of human bone, as well as ethical issues, frequently hinder the development of clinical trials. The purpose of this in vitro study was to determine the modulus of elasticity of a polyurethane isotropic experimental model via tension tests, comparing the results to those reported in the literature for mandibular bone, in order to validate the use of such a model in lieu of mandibular bone in biomechanical studies. MATERIAL AND METHODS: Forty-five polyurethane test specimens were divided into 3 groups of 15 specimens each, according to the ratio (A/B) of polyurethane reagents (PU-1: 1/0.5, PU-2: 1/1, PU-3: 1/1.5). RESULTS: Tension tests were performed in each experimental group and the modulus of elasticity values found were 192.98 MPa (SD=57.20) for PU-1, 347.90 MPa (SD=109.54) for PU-2 and 304.64 MPa (SD=25.48) for PU-3. CONCLUSION: The concentration of choice for building the experimental model was 1/1.