Characterization of Ivoclar Vivadent Dental Restoration Material for 137CS Retrospective Radiation Dosimetry.

Retrospective dosimetry is the method of using materials on or near a person who is exposed to ionizing radiation to determine the amount of radiation received by the person. A possible candidate material for retrospective dosimetry is Ivoclar Vivadent IPS e.max® CAD ceramic dental restoration material, which exhibits radiation-induced thermoluminescence when exposed to gamma- and x-ray radiation from a Cs source. The purpose of this paper is to characterize the material and study the behavior of the thermoluminescence signal with radiation dose and with delay time between radiation exposure and thermoluminescence measurement. The first glow peak is well-modeled by a first-order glow curve deconvolution formula. The height of the first glow peak is approximately linear with dose. The fading of the signal with time is approximately described by a power law curve with cutoff. The material appears to be suitable for retrospective radiation dosimetry.

The Effect of Postmastectomy Radiation Therapy on Breast Implants: Material Analysis on Silicone and Polyurethane Prosthesis.

INTRODUCTION: The pathogenic mechanism underlying capsular contracture is still unknown. It is certainly a multifactorial process, resulting from human body reaction, biofilm activation, bacteremic seeding, or silicone exposure. The scope of the present article is to investigate the effect of hypofractionated radiotherapy protocol (2.66 Gy × 16 sessions) both on silicone and polyurethane breast implants. METHODS: Silicone implants and polyurethane underwent irradiation according to a hypofractionated radiotherapy protocol for the treatment of breast cancer. After irradiation implant shells underwent mechanical, chemical, and microstructural evaluation by means of tensile testing, infrared spectra in attenuated total reflectance mode, nuclear magnetic resonance, and field emission scanning electron microscopy. RESULTS: At superficial analysis, irradiated silicone samples show several visible secondary and tertiary blebs. Polyurethane implants showed an open cell structure, which closely resembles a sponge. Morphological observation of struts from treated polyurethane sample shows a more compact structure, with significantly shorter and thicker struts compared with untreated sample. The infrared spectra in attenuated total reflectance mode spectra of irradiated and control samples were compared either for silicon and polyurethane samples. In the case of silicone-based membranes, treated and control specimens showed similar bands, with little differences in the treated one. Nuclear magnetic resonance spectra on the fraction soluble in CDCl3 support these observations. Tensile tests on silicone samples showed a softer behavior of the treated ones. Tensile tests on Polyurethane samples showed no significant differences. CONCLUSIONS: Polyurethane implants seem to be more resistant to radiotherapy damage, whereas silicone prosthesis showed more structural, mechanical, and chemical modifications.

Differences in the intensity of light-induced fluorescence emitted by resin composites.

BACKGROUND: The aims of this study were to compare the intensities of fluorescence emitted by different resin composites as detected using quantitative light-induced fluorescence (QLF) technology, and to compare the fluorescence intensity contrast with the color contrast between a restored composite and the adjacent region of the tooth. METHODS: Six brands of light-cured resin composites (shade A2) were investigated. The composites were used to prepare composite discs, and fill holes that had been prepared in extracted human teeth. White-light and fluorescence images of all specimens were obtained using a fluorescence camera based on QLF technology (QLF-D) and converted into 8-bit grayscale images. The fluorescence intensity of the discs as well as the fluorescence intensity contrast and the color contrast between the composite restoration and adjacent tooth region were calculated as grayscale levels. RESULTS: The grayscale levels for the composite discs differed significantly with the brand (p<0.001): DenFil (10.84±0.35, mean±SD), Filtek Z350 (58.28±1.37), Premisa (156.94±1.58), Grandio (177.20±0.81), Charisma (207.05±0.77), and Gradia direct posterior (211.52±1.66). The difference in grayscale levels between a resin restoration and the adjacent tooth was significantly greater in fluorescence images for each brand than in white-light images, except for the Filtek Z350 (p<0.05). However, the Filtek Z350 restoration was distinguishable from the adjacent tooth in a fluorescence image. CONCLUSIONS: The intensities of fluorescence detected from the resin composites varied. The differences between the composite and adjacent tooth were greater for the fluorescence intensity contrast than for the colors observed in the white-light images.

The use of light-cured resin as an alternative method of occlusal splints manufacturing--in vitro study.

BACKGROUND: Temporomandibular disorders are very common nowadays. One of the methods to treat these problems is occlusal splint therapy. Modern materials should be introduced to this treatment. OBJECTIVES: The aim of this paper was to evaluate the properties of light-activated urethane dimethacrylate and the quality of the bonds it creates with thermoforming foils. MATERIAL AND METHODS: Thermoforming foils were covered with light-cured resin. A bond was formed between the materials using an adhesive. A coating lacquer was used on the resin as a final preparatory step. Three laboratory tests were run: dye penetrant inspection, a Vickers microhardness test and a linear polymerization shrinkage test. The materials were layered and then cured with a polymerizing lamp emitting light of a wavelength of 400 Nm, according to the manufacturer's instructions. All the occlusal splints were fitted to upper dental arch. The devices had been made in an articulator on specially prepared gypsum models. The results were analyzed statistically using a one-sided binomial test, Spearman's rank-order correlation coefficient and the Friedman ANOVA (p=0.05). RESULTS: In the dye penetrant inspection, only one sample out of sixty showed the effects of color penetration to the adhesive connection. The dye only penetrated the layer of lacquer coating the resin. The average value of the Vickers microhardness test with a load of F=50 g applied to the material surface for 30 s was HV0.05=7.43 N/mm2. The average linear shrinkage of the resin observed after polymerization was 1.175%. CONCLUSIONS: Light-cured resin and an adhesive connection between the resin and thermoforming foil do not show susceptibility even to strong dye. The maximum polymerization shrinkage occurs immediately after curing. The light-cured resin that was tested seems to be a good alternative method for occlusal splints manufacturing.

Polymerization shrinkage stress of composites photoactivated by different light sources

The purpose of this study was to compare the polymerization shrinkage stress of composite resins (microfilled, microhybrid and hybrid) photoactivated by quartz-tungsten halogen light (QTH) and light-emitting diode (LED). Glass rods (5.0 mm x 5.0 cm) were fabricated and had one of the surfaces air-abraded with aluminum oxide and coated with a layer of an adhesive system, which was photoactivated with the QTH unit. The glass rods were vertically assembled, in pairs, to a universal testing machine and the composites were applied to the lower rod. The upper rod was placed closer, at 2 mm, and an extensometer was attached to the rods. The 20 composites were polymerized by either QTH (n=10) or LED (n=10) curing units. Polymerization was carried out using 2 devices positioned in opposite sides, which were simultaneously activated for 40 s. Shrinkage stress was analyzed twice: shortly after polymerization (t40s) and 10 min later (t10min). Data were analyzed statistically by 2-way ANOVA and Tukey's test (a=5 percent). The shrinkage stress for all composites was higher at t10min than at t40s, regardless of the activation source. Microfilled composite resins showed lower shrinkage stress values compared to the other composite resins. For the hybrid and microhybrid composite resins, the light source had no influence on the shrinkage stress, except for microfilled composite at t10min. It may be concluded that the composition of composite resins is the factor with the strongest influence on shrinkage stress.

Este estudo comparou a contração de polimerização de resinas compostas fotoativadas por luz halógena (QTH) e diodo emissor de luz (LED). Foram confeccionados bastões de vidro (5,0 mm x 5,0 cm), e uma de suas extremidades sofreu jateamento com óxido de alumínio, sobre a qual foi aplicado um adesivo e fotoativado com luz halógena. Os bastões de vidro foram acoplados verticalmente, em pares, em uma máquina universal de ensaios (EMIC DL-2000) e as resinas compostas aplicadas no bastão inferior. A distância entre os bastões foi padronizada em 2 mm e um extensômetro foi acoplado a eles. As resinas foram fotoativadas (n=20), sendo 10 por QTH e 10 por LED utilizando dois aparelhos posicionados em lados opostos, acionados simultaneamente por 40 s. A tensão de contração foi analisada em dois momentos: logo após a polimerização (t40s) e 10 min após (t10min). A tensão de contração apresentada por todas as resinas foi maior em t10min do que em t40s, independente da fonte ativadora. A resina de micropartículas apresentou menores valores de tensão de contração com valores estatisticamente significantes em relação às demais resinas. Para as resinas híbrida e microhíbrida não houve influência da unidade ativadora sobre a tensão de contração, com exceção para a resina de micropartículas em t10min. Concluiu-se que a composição da resina composta foi o fator que mais interferiu na tensão de contração da resina composta.

Effect of gamma irradiation on fluoride release and antibacterial activity of resin dental materials

This study evaluated the effect of gamma irradiation on fluoride release and antibacterial activity of FluroShield (FS) and Clearfil Protect Bond (CPB). Four groups were formed: G1-FS + gamma; G2-FS without gamma; G3-CPB + gamma; G4-CPB without gamma. For fluoride release analysis, 12 disks of each material were prepared and covered with nail polish, except for one side (50.4 mm² area). G1 and G3 were sterilized with a 14.5 KGy dose at 27ºC for 24 h, while G2 and G4 (controls) were not sterilized and were maintained under the same time and temperature conditions. Fluoride release measurements were made in duplicate (n=6) by an ion specific electrode. The antibacterial activity of the CPB and FS against Streptococcus mutans after gamma sterilization was evaluated by the agar-disc diffusion method. The diameter of the zones of microbial growth inhibition was recorded after 48 h. Data were analyzed statistically by ANOVA and Tukey's test (α=5 percent). Gamma sterilization decreased the fluoride release of FS by approximately 50 percent, while CPB was not affected. There was no statistically significant difference (p>0.05) in the antibacterial effect of CPB between gamma and non-gamma sterilization groups. FS presented no antibacterial activity. Gamma irradiation decreased the fluoride release of FS, but did not affect the antibacterial activity of the studied materials.

Este estudo avaliou o efeito da esterilização com raios-gama na liberação de flúor e atividade antibacteriana de materiais resinosos, Fluroshield (FS) e Clearfil Protect Bond (CPB). Quatro grupos foram formados: G1-FS e gama; G2-FS sem gama; G3-CPB e gama; G4-CPB sem gama. Doze discos de cada material foram preparados para análise de liberação de flúor, os quais foram cobertos com esmalte de unha, exceto em um lado com 50,4 mm² de área. G1 e G3 foram esterilizados com dose de 14,5 KGy por 24 h/27ºC, enquanto G2 e G4 (controles) não foram esterilizados e foram mantidos sob as mesmas condições de tempo e temperatura. As leituras de liberação de flúor foram feitas em duplicata (n=6) por um eletrodo específico. A atividade antibacteriana foi avaliada pelo teste de difusão em agar. Os halos de inibição foram medidos após 48 h. Os dados foram analisados pelos testes ANOVA e Tukey (α=5 por cento). A esterilização gama diminuiu a liberação de flúor de FS em cerca de 50 por cento, enquanto CPB não foi afetado. Não houve diferença estatisticamente significante entre os grupos esterilizados e controle no efeito antibacteriano do CPB. FS não apresentou atividade antibacteriana. A esterilização gama diminuiu a liberação de flúor de FS, mas não afetou a atividade antibacteriana dos materiais estudados.

Low-level laser use in dentistry.

The use of laser light at power levels below that capable of direct tissue change (protein denaturation, water vaporisation and tissue ablation), has been advocated in diverse branches of medicine and veterinary practice, yet its acceptance in general dental practice remains low. However, the scope for using low-level laser light (LLLT) has emerged through many applications, either directly or indirectly tissue-related, in delivering primary dental care. The purpose of this article is to explain the mechanisms of action and to explore the uses of this group of lasers in general dental practice.

Modulated photoactivation methods--effect on marginal and internal gap formation of restorations using different restorative composites.

UNLABELLED: This study evaluated the effect of modulated photoactivation methods on gap formation of restorations using different composites. METHODS: Sixty human third molars were selected, sectioned (two fragments), and ground to expose a flat enamel area. A cavity (5 mm long x 2 mm wide x 2 mm deep--outer margins in enamel and inner margins in dentin) was prepared on the central area of flattened surface. Single bond adhesive system was applied according to manufacturer's instructions. The specimens were assigned into 12 groups (n = 10), according to the restorative composite (Filtek Z250, Herculite XRV, and Heliomolar) and the photoactivation method [continuous light (CL); soft-start (SS); pulse delay (PD); and intermittent light (IL)]. Outer margins were stained using Caries Detector, observed under stereomicroscope, and images were transferred to a computer measurement program. Then, the specimens were sectioned in slices and the internal gaps were assigned using the same method. The length of gaps was expressed as a percentage of total length of the margins. Data (internal adaptation) were submitted to ANOVA and Tukey's test. RESULTS: All restorations showed perfect seal of the enamel outer margins. Modulated photoactivation methods (SS, PD, and IL) showed a significant reduction on internal gap formation when compared with CL, regardless of the composite. Filtek Z250 showed the best internal adaptation, regardless of the photoactivation method. CONCLUSION: Modulated photoactivation methods decrease the internal gap formation of composite restorations, and should be encouraged on clinical practice.

Color stability of composites subjected to accelerated aging after curing using either a halogen or a light emitting diode source

The purpose of this study was to evaluate, in vitro, the color stability of three composite resins of two different shades (A3 and C3) cured with either a quartz tungsten halogen (QTH) or a light emitting diode (LED) source. Forty specimens (20 x 2 mm) were prepared for each composite (Tetric Ceram®, Heliomolar® and Esthet-X®), being 20 for each shade. In each group, 10 specimens were light-cured using the QTH unit and 10 with the LED source. The shade of the materials was evaluated before and after submitting the specimens to artificial accelerated aging (4 h UV-B/4 h condensing vapor), using a reflection spectrophotometer. deltaE means were calculated and analyzed statistically by 2-way ANOVA and Tukey's test at 5 percent significance level. Both A3 and C3 shades of Esthet-X composite resin showed the lowest color change when cured with the QTH light, while Tetric C3 cured with the QTH light showed the highest color change.

O objetivo deste estudo foi verificar a estabilidade de cor de três compósitos polimerizados com dois tipos de unidades polimerizadoras, luz halógena ou diodo emissor de luz (LED). Quarenta amostras (20 mm de diâmetro por 2 mm de espessura) foram construídas com cada compósito (Tetric Ceram®, Heliomolar® and Esthet-X®), vinte na cor A3 e vinte na cor C3. Dentro de cada grupo, 10 amostras foram polimerizadas com luz halógena e as outras com LED. A cor dos materiais foi verificada antes e depois das amostras serem submetidas ao envelhecimento artificial acelerado (4h UV-B/4h de condensação de vapor), usando um espectrofotômetro de reflexão. As médias deltaE de foram calculadas e analisadas estatisticamente (ANOVA a dois critérios e teste de Tukey, 95 por cento). Os compósitos Esthet-X A3 e C3 demonstraram a menor alteração de cor quando polimerizados com luz halógena enquanto a resina. Tetric C3 apresentou a maior alteração de cor quando polimerizada por essa mesma fonte de luz.

Characterisation of PRESAGE: A new 3-D radiochromic solid polymer dosemeter for ionising radiation.

For the past 50 years there has been interest in developing 3-D dosemeters for ionising radiation. Particular emphasis has been put on those dosemeters that change their optical properties in proportion to the absorbed dose. Many of the dosemeters that have been evaluated have had limitations such as lack of transparency, diffusion of the image of the dose distribution or poor stability of baseline optical density. Many of these performance limitations have been overcome by the development of PRESAGE, an optically clear polyurethane-based radiochromic 3-D dosemeter. The solid PRESAGE dosemeter is formulated with a free radical initiator and a leuco dye and it does not require a container to maintain its shape. The polyurethane matrix is tissue equivalent and prevents the diffusion of the dose distribution image. There is a linear dose-response, which is independent of both photon energy and dose rate. Simple precautions such as preventing long-term exposure to additional ionising radiation including ultraviolet and controlling storage temperatures prevent the bleaching of the radiochromic response field within the irradiated dosemeter.

Residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation.

The purpose of this study was to investigate the amount of residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation. The resin specimens (4 mm in diameter; 2 mm thick) (n=5) were inserted in Plexglass matrixes and light-cured with a halogen lamp, LED and PAC units for 40, 40 and 5 s, respectively. The polymerized specimens were ground and 25 mg of each specimen were immersed in 8 mL 96% ethanol for 24 h to extract the residual monomer. The amount of residual monomer was determined by the standard straight line method. The light spectrum of the different LCUs was shot and processed through researches of the absorbation of the standard solutions at a level of lambda=275 nm and their extracts. Data were analyzed statistically by variational dispersion analysis and Tukey-Kramer test at 5% significance level. It was observed that, the halogen lamp produced the smallest amount of monomer under sufficient light intensity. The spectrum of light radiation of PAC was within the limits of 450- 490 nm and was of extremely high intensity. This imposes the use of short-limited light impulses, but also might lead to deterioration quality of polymerization. The LED unit had the best spectral radiation. An increase of light intensity was proved necessary.

Abrasion resistance of composites polymerized by light-emitting diodes (LED) and halogen light-curing units

O trabalho comparou a perda de massa e a rugosidade superficial de materiais restauradores diretos polimerizados por luz halógena e por diodo emissor de luz (LED). A partir de uma matriz de politetrafluoretileno, foram confeccionados 20 corpos-de-prova (12 mm de diâmetro; 1,0 mm de espessura) para cada material restaurador [TPH (Dentsply); Definite (Degussa); Charisma (Heraus Kulzer)], sendo 10 espécimes polimerizados por LED e 10 polimerizados por luz halógena durante 40 s. Os corpos-de-prova foram polidos, levados ao rugosímetro para análise da rugosidade superficial (Ra inicial - mm) e armazenados em água a 37°C por 15 dias. Os corpos-de-prova foram pesados (M1) e submetidos a escovação simulada com suspensão preparada com dentifrício de alta abrasividade. Após 100 minutos no simulador de escovação, os espécimes foram limpos e tiveram o peso (M2) e rugosidade superficial (Ra final - mm) aferidos novamente. A perda de massa foi calculada pela diferença entre M1 e M2. Os dados foram registrados e analisados por meio de ANOVA a um critério e teste de Tukey para diferenciação das médias com nível de significância de 5%. Os resultados demonstraram que a resina Definite foi o material que apresentou menor resistência à abrasão quando polimerizada com luz LED, apresentando maiores valores de rugosidade superficial e perda de massa (p<0.05). Quando utilizada a lâmpada halógena, os valores não mostraram diferença estatisticamente significante entre si (p>0.05). O LED não mostrou a mesma eficiência que a lâmpada halógena para polimerização desta resina especificamente. Pode-se concluir que a unidade de luz fotopolimerizadora e a composição das resinas compostas interferiram na resistência à abrasão dos materiais restauradores testados.

Residual monomer in a composite resin after light-curing with different sources, light intensities and spectra of radiation

O objetivo deste trabalho foi investigar a quantidade de monômero residual em resinas compostas fotopolimerizadas, empregando diferentes fontes de energia, variadas intensidades e espectros de radiação. As amostras de resina (4 mm de diâmetro e 2 mm de espessura) foram fabricadas em matrizes de Plexglass e polimerizadas com lâmpada halógena, LED e PAC por 40, 40 e 5 s, respectivamente. As amostras foram pulverizadas e 25 mg de cada uma foi imersa em 8 mL de etanol a 96% por 24 h para extração do monômero residual. A quantidade de monômero residual foi determinada pelo método padrão de linha reta. O espectro luminoso das diferentes fontes de energia foi projetado e analisado pelo espectro de absorção de soluções-padrão no comprimento de onda l= 275 nm. Os dados foram analisados estatisticamente pela dispersão de variância e pelo teste de Tukey-Kramer com nível de significância de 5%. Constatou-se que a lâmpada halógena resultou na menor quantidade de monômero residual com luz de intensidade suficiente. O espectro de radiação do PAC esteve entre 450 e 490 nm e foi de intensidade extremamente alta. Este fato impõe que sejam utilizados pulsos de curta duração, mas também pode levar à deterioração da polimerização. O LED apresentou o melhor espectro de radiação. Constatou-se a necessidade de aumentar a intensidade da luz.

Surface modification of a segmented polyetherurethane using a low-powered gas plasma and its influence on the activation of the coagulation system.

A medical grade segmented polyetherurethane (PEU) was treated with a low-powered gas plasma using O(2), Ar, N(2) and NH(3) as the treatment gases. Changes in the surface functional group chemistry were studied using X-ray photoelectron spectroscopy. The wettability of the surfaces was examined using dynamic contact angle measurements and the surface morphology was evaluated using atomic force microscopy. The influence of the surface modification to the polyurethane on the blood response to the polyetherurethane was investigated by measuring changes in the activation of the contact phase activation of the intrinsic coagulation cascade. The data demonstrate that the plasma treatment process caused surface modifications to the PEU that in all cases increased the polar nature of the surfaces. O(2) and Ar plasmas resulted in the incorporation of oxygen-containing groups that remained present following storage in an aqueous environment. N(2) and NH(3) plasmas resulted in the incorporation of nitrogen-containing groups but these were replaced with oxygen-containing groups following storage in the aqueous environment. In all plasma treatments there was a lowering of contact phase activation compared to the untreated surface, the N(2) and NH(3) treatments dramatically so.

Ablation of composite resins using Er:YAG laser--comparison with enamel and dentin.

OBJECTIVES: The purpose of this work is to investigate comparative ablation rate between composite resins and dental hard tissues (enamel and dentin) after Er:YAG laser irradiation to verify possible development of an ultra-conservative dentistry to with minimum effect for the teeth tissue. METHODS: We have used 11 extracted or exfoliated primary anterior and posterior teeth and six extracted permanent molar teeth. Three different types of composite resin were chosen (microfiller, hybrid, and condensable) in terms of chemical and structural composition. Composite tablets and the teeth were irradiated with a Er:YAG laser at different laser beam energy level per pulse (100, 200, 300, and 400 mJ). Diameter and depth of each resulted microcavity were measured and the material removed volumes were calculated. The resulted values were plotted and fitted to allow a comparative observation of the material removed as a function of energy level per pulse. RESULTS: While the idea of ultra-conservative dentistry seems to apply well for enamel of primary and permanent teeth, at the present stage it does not apply well for primary or permanent dentin. For dentin, the composition and content of water makes the Er:YAG laser ablation equal or superior in rate compared with the three used resins. SIGNIFICANCE: This work presents of a comparative study of Er:YAG laser ablation, allowing to analyze the possible selective ablation between composite resin placed and cured and dental hard tissues, with the goal to propose a new clinical technique: differential ablation for composite resin restorations using Er:YAG laser.

Lactic acid based PEU/HA and PEU/BCP composites: Dynamic mechanical characterization of hydrolysis.

Lactic acid based poly(ester-urethane) (PEU-BDI) and its composites with 20 and 40 vol.% bioceramic filler were characterized prior to their use as biocompatible and bioabsorbable artificial bone materials. Morphological, dynamic mechanical properties, and degradation of these either hydroxyapatite or biphasic calcium phosphate containing composites were determined. Addition of particulate bioactive filler increased the composite stiffness and the glass transition temperature, indicating strong interactions between the filler and matrix. Materials were sterilized by gamma-irradiation, which reduced the average molecular weights by 30-40%. However, dynamic mechanical properties were not significantly affected by irradiation. Specimens were immersed in 0.85 w/v saline at 37 degrees C for 5 weeks, and changes in molecular weights, mass, water absorption, and dynamic mechanical properties were recorded. All the composite materials showed promising dynamic mechanical performance over the 5 weeks of hydrolysis. Average molecular weights of PEU-BDI and its composites did not change substantially during the test period. PEU-BDI retained its modulus values relatively well, and although the moduli of the composite materials were much higher, especially at high filler content, they exhibited faster loss of mechanical integrity.

Selective removal of residual composite from dental enamel surfaces using the third harmonic of a Q-switched Nd:YAG laser.

BACKGROUND AND OBJECTIVE: Conventional methods of residual composite removal after the debonding of orthodontic brackets involve the use of abrasives that damage the underlying enamel. The objective of this study was to demonstrate that 355-nm laser pulses with a pulse width of 10 ns are well suited for the removal of composite through selective laser ablation. STUDY DESIGN/MATERIALS AND METHODS: The residual composite remaining on the surface of extracted human third molars and bovine incisors was removed using multiple laser pulses from the third harmonic (355-nm) of a Q-switched Nd:YAG laser. RESULTS: There is selective ablation of composite from the enamel surface without any discernable damage to the underlying enamel. CONCLUSION: This study demonstrates that 355-nm, 10 ns laser pulses can be used for the selective ablation of dental composite without thermal or mechanical damage to the underlying enamel.

Radiation effects of carbon ions and gamma ray on UDMA based dental resin.

The radiation effects on the mechanical and physical properties of photo-polymerized UDMA resin without filler was investigated by various mechanical tests and spectroscopic measurements. The radiation sources were carbon ion (12C ion) and gamma ray (gamma-ray). With 640 Gy of 12C ion radiation, Vickers hardness increased by about 40%, the degree of abrasion decreased by 30%, and the flexural strength increased by 20%. With the same dose of gamma-ray radiation, only Vickers hardness increased by 19%. The spectra taken by the Fourier Transform Infrared Spectrometer (FT-IR), Raman spectroscopy, and Fluorescence spectrophotometer showed little change in the peak configuration and background intensities. The relative degree of conversion (DC) of carbon double bonds by radiation to the state of non-radiated samples were estimated by FT-IR. Spectroscopic results were indicative for the formation of cross-linking between carbon chains. Cross-linking of carbon molecules induced by radiation might be one of the reasons for the improved mechanical properties of UDMA resin.

Nd:YAG laser effects on the microleakage of composite resin restorations.

OBJECTIVE: This study evaluated microleakage of composite restorations submitted to marginal treatment with Nd:YAG laser and surface sealant. BACKGROUND DATA: Previous studies have demonstrated that Nd:YAG-lased enamel melted and became recrystallized with a morphologic appearance similar to lava, and has been used clinically in the sealing of enamel pits and fissures. METHODS: Class V cavities in enamel of human premolars were restored with composite resin (Z100, 3M) and randomly divided in six groups: G1, control; G2, surface sealant marginal treatment; G3 to G6, were treated with pulsed Nd:YAG laser (1.064 microm) marginal treatment, contact fiberoptic (300 microm), air cooling, for 30 seconds, powers of 1.2-2 W, repetition rates of 20-30 Hz, energies of 40-100 mJ. Teeth were impermeabilized, immersed in a rhodamine dye, sectioned, and evaluated under stereomicroscope microscopy with scores. RESULTS: There were significant differences between marginal treatments; there were no differences between groups 1, 2, and 4, and 3,5, and 6; lower values of microleakage were at groups 3, 5, and 6 (Kruskal-Wallis,p = 0.05). CONCLUSION: Nd:YAG laser showed improved marginal sealing and decreased microleakage of composite resins restorations.

Preparation of poly(acrylic acid) modified polyurethane membrane for biomaterial by UV radiation without degassing.

Poly(acrylic acid) modified polyurethane (AA/PU) membranes were prepared by UV radiation without degassing. The chemical composition of the AA/PU membrane was studied by IR spectroscopy. In addition to those absorption peaks associated with pure PU, the absorption peak at 2400 cm-1 of poly(AA) was also found. The morphology of AA/PU membrane was studied by optical polarizing microscopy. We also measured the glass transition temperature and the decomposition temperature of the AA/PU membrane by differential scanning calorimetry and thermogravimetric analysis. A significant domain was found in the AA/PU membrane, which resulted in different glass transition temperature and decomposition temperature between AA/PU and pure PU membrane. The effect of AA content on the contact angle and water absorption of the AA/PU membrane was determined. It was found that the water content of AA/PU membrane increased with increasing AA content, whereas the contact angle decreased. By using Kaeble's equation and the contact angle data, the surface free energy of AA/PU membrane was determined. The increase of surface free energy resulted from the increase of the dispersion (gammad) term and polar (gammap) term. In order to evaluate the biocompatibility of these membranes, a cytotoxicity test and a cell adhesion and proliferation assay were conducted in cell culture. Immortal cells and primary lymphocytes were both used in this study. The results showed that these AA/PU membranes exhibited very low cytotoxicity and could support cell adhesion and growth. An animal primary test was also done in this study. It was found that the AA/PU membrane could possibly be employed in the treatment of bowel defect.