Uso de prótesis parcial removible con resina acrílica termoplástica: una revisión de literatura

La prótesis parcial removible (PPR) es una alternativa de tratamiento en pacientes que perdieron algunos elementos dentarios, debido al costo relativamente bajo y a la generación de una función masticatoria satisfactoria. Además, es una buena opción cuando hay pérdida de los tejidos óseos, dado que impide la instalación de implantes dentarios. La PPR convencional presenta una estructura metálica que ofrece retención y resistencia a la prótesis, convirtiéndola en poco agradable a los pacientes, por el hecho de dejar a la vista el metal en la cavidad oral. A partir de investigadores que decidieron ir más allá del simple estudio de la función y la estética de las PPR para adentrase en sus diversas formas de presentación, surgió la prótesis parcial flexible (PFlex). La PFlex es una prótesis parcial confeccionada con resina termoplástica, sin metal y con flexibilidad. Si bien, muchos profesionales la emplean como prótesis temporal, otros tantos la han usado como alternativa a la PPR convencional. Así, uno de los frecuentes interrogantes de los clínicos es si realmente es posible utilizar la PFlex como alternativa protética definitiva. Por tanto, el propósito de este trabajo fue realizar una revisión de la literatura para evaluar si el uso de prótesis parciales removibles con resina termoplástica puede ser una alternativa a las prótesis parciales convencionales, exponiendo las ventajas, desventajas, indicaciones, contraindicaciones y las propiedades del material protético.

Removable partial denture (RPP) is an alternative treatment when it comes to patients who have lost some dental elements, as they have the advantages of a relatively low cost and a satisfactory masticatory function. Furthermore, it is a good option when there is bone tissue loss, making dental implants placement unfeasible. Conventional PPR has a metallic frame that provides retention and resistance to the prosthesis, which makes it unpalatable to patients because it leaves the metal in the oral cavity evident. Many researchers, aiming to give back beyond function and aesthetics, are studying forms of presentation of PPR, thus emerging the flexible partial prosthesis (PFlex). PFlex is a partial denture made with thermoplastic, resin metal-free and with flexibility, however its use, for many professionals, is limited only as temporary prostheses, but there are some clinicians who use PFlex as an alternative to conventional PPR. Thus, one of the questions constantly asked by scientists is whether it is possible to use PFlex as a definitive prosthetic alternative. Therefore, the aim of this study was to conduct a literature review to assess whether the use of removable partial dentures with thermoplastic resin can be an alternative to conventional partial dentures, exposing the advantages, disadvantages, indications, contraindications, and the properties of the prosthetic material.

Starch-based orodispersible film for diclofenac release

Abstract The form of drug administration affects the success of treatment, since it can influence adherence of the patient to the therapy. The use of orodispersible films has emerged as a way to overcome some drawbacks of conventional methods of drug delivery, especially for patients experiencing difficulty in swallowing. These films are prepared using a matrix that incorporates the drug and contains other substances that confer the properties of the system. The present work describes the use of thermoplastic starch as a carrier for the model drug diclofenac, including film preparation and testing of its orodispersible potential. Preparation of the film employed a microwave oven to gelatinize and plasticize corn starch, with incorporation of the model drug, followed by solvent-casting. The samples were characterized using mechanical tests, analyses of water uptake and water content, and Fourier transform infrared spectroscopy. The results indicated that the film presented promising properties as an alternative system for oral drug administration, with good incorporation and distribution of the drug in the matrix. The material displayed satisfactory mechanical properties, which are crucial for this type of material, due to the need for oral administration and handling before use.

Advances in 3D printing-based body membrane immobilization technology in radiotherapy / 中华放射医学与防护杂志

The widespread application of 3D printing and computer technologies in the medical field has opened up opportunities for digital and automated fabrication of body immobilization tools for radiotherapy, thus making it possible to get rid of the original complex manual fabrication process. As the most widely used technique for body immobilization, body membrane immobilization has always attracted much attention. This review outlines the development of the body membrane immobilization technology in different radiotherapy stages. Moreover, the advances in the application of 3D-printed body membranes were introduced, as a development direction of body immobilization technology, in the field of radiotherapy. This technology can be utilized as a reference for clinical application and research.

Desempeño Mecánico de Compuestos de Madera Plástica de Matriz Poliolefínica / Mechanical performance of polyolefinic wood plastic composites / Desempenho mecânicos de compostos de Madeira Plástica de Matriz Poliolefina

Resumen Los polímeros termoplásticos, pueden ser mezclados con diferentes tipos de cargas con el propósito de mejorar su rendimiento físico-mecánico, al mismo tiempo que permiten en muchos casos, generar soluciones a problemáticas ambientales como por ejemplo la disposición final de residuos de madera. Los compuestos de madera plástica son productos elaborados mediante la incorporación de fibras o partículas de madera en la matriz polimérica, donde la interacción entre los dos materiales (nula o con acople) es clave para lograr un adecuado desempeño del producto final. En esta revisión se establecen las matrices poliméricas y los tipos de maderas empleadas comúnmente en la elaboración de productos de madera plástica, al mismo tiempo que se definen los tratamientos previos que deben ser realizados tanto en la madera como en el polímero con el propósito de mejorar la compatibilidad de los dos materiales, y de esta manera mejorar propiedades como la absorción de agua, la resistencia a la descomposición, a la intemperie y el desempeño mecánico. En cuanto a las propiedades mecánicas, al adicionar un contenido de madera en el polímero se modifica la rigidez del material polimérico y la resistencia en tensión, flexión e impacto; sin embargo, se establece que es clave el uso de agentes funcionalizantes para que el efecto de la incorporación de la madera en polímero sea positivo. Finalmente se estudian las nuevas tendencias en el uso de diferentes tipos de residuos y matrices poliméricas para la elaboración de maderas plásticas.

Abstract Polymeric materials, especially thermoplastics, can be mixed with different types of fillers to improve their physical-mechanical performance, at the same time they allow, in many cases, to generate solutions to environmental problems such as the final disposal of wood waste. The plastic wood composites are products made by incorporating wood fibers in the polymer matrix, where the interaction between the two materials is key to achieve an adequate performance of the final product. This review establishes the polymer matrices and the types of wood commonly used in the production of plastic wood products, at the same time defining the previous treatments that must be carried out in the wood and in the polymer to improve the compatibility of the two materials, and in this way improve properties such as water absorption, resistance to decomposition, resistance to weathering and mechanical performance. Related to the mechanical properties, adding the wood fibers in the polymer modifies the rigidity of the polymeric material and the resistance in tension, bending and impact; however, it is established that the use of functionalizing agents is a fundamental key to improve the effect of wood incorporation into the polymer matrix. Finally, the new trends in the use of different types of waste and polymeric matrices to produce plastic wood are studied.

Resumo Os materiais poliméricos, principalmente os termoplásticos, podem ser misturados a diferentes tipos de cargas para melhorar seu desempenho físico-mecânico, ao mesmo tempo que, em muitos casos, permitem gerar soluções para problemas ambientais como a destinação final de resíduos. madeira. Os compósitos madeira-plástico são produtos obtidos pela incorporação de fibras de madeira à matriz polimérica, onde a interação entre os dois materiais é fundamental para um desempenho adequado do produto final. Nesta revisão, são estabelecidas as matrizes poliméricas e os tipos de madeira comumente utilizados na produção de produtos plásticos de madeira, ao mesmo tempo em que são definidos os tratamentos anteriores que devem ser realizados na madeira e no polímero para melhorar a compatibilidade dos dois materiais, e desta forma melhorar propriedades como absorção de água, resistência à decomposição, intempéries e desempenho mecânico. Em relação às propriedades mecânicas, ao adicionar as fibras de madeira ao polímero, a rigidez do material polimérico e a resistência à tração, flexão e impacto são modificadas; porém, está estabelecido que o uso de agentes funcionalizantes é fundamental para que o efeito da incorporação da madeira no polímero seja positivo. Por fim, são estudadas as novas tendências no uso de diferentes tipos de resíduos e matrizes poliméricas para a produção de madeira plástica.

Force decay and discoloration of thermoplastic and thermoset orthodontic elastomeric chains / Diminuição de força e descoloração de elásticos corrente termoplásticos e termofixos

Objective: Elastomeric chains are commonly used to apply force for orthodontic dental movements. However, force decay and discoloration are two important weak points of these materials. The present study intended to compare the force decay and color stability of different types of elastomeric chains. Material and Methods: This in vitro study evaluated 6 groups of elastomeric chains, including thermoplastic (TP) and thermoset (TS) chains made by the companies American Orthodontics (AO), Ormco (OR), and G&H Orthodontics (GH). The elastomeric chain forces were measured at the baseline, following 1 hour, 1 day, 1, 2, 3, 4, 5, and 6 weeks of stretching. The elongation required for the chains to exert a force of 250 g was calculated. ΔE of each group was calculated by a spectrophotometer following immersion in black tea solution for 6 days. Data were analyzed using the SPSS 22 software and the statistical methods of repeated measures analysis of variance and two-way analysis of variance (P<0.05). Results: The force decay of the TS chains were significantly lower than the TP chains in the 6-week study duration (P<0.05), and the lowest and highest force decay was observed in the products by AO and GH, respectively. The highest force degradation occurred during the first week in all groups. The elongation rate needed for the TS chains was significantly higher than the TP chains (P<0.05), and the highest elongation rate was observed in the products by OR. TS chains showed significantly higher color stability than TP chains, and products by OR and GH had better color stability than the products by AO. Conclusion: The present study showed that TS chains were superior to TP chains in force decay and color stability in all the brands studied. (AU)

Objetivo: Elásticos corrente são comumente utilizados para aplicar forças para a movimentação ortodôntica. Porém, a diminuição de força e descoloração são duas importantes fraquezas desses materiais. O presente estudo tem o objetivo de comparar a diminuição de força e estabilidade de cor de diferentes tipos de elásticos corrente. Material e Métodos: Este estudo in vitro avaliou 6 grupos de elásticos corrente, incluindo termoplástico (TP) e termofixo (TS) produzidos pelas empresas American Orthodontics (AO), Ormco (OR) e G&H Orthodontics (GH). A força dos elásticos corrente foram mensuradas no início, após 1 hora, 1 dia, 1, 2, 3, 4, 5 e 6 semanas de alongamento. A força de alongamento necessária para aplicação de 250g foi calculada. O ΔE de cada grupo foi calculado por um espectrofotômetro após a imersão em solução de chá preto por 6 dias. Os dados foram analizados utilizando o programa SPSS 22 e a análise estatística foi realizada por análise de variância e análise de variância dois fatores (p<0,05). Resultados: A diminuição da força do grupo TS foi significativamente menor que o grupo TP em 6 semanas de estudo (p<0,05), e o menor e maior valor de diminuição de força foi observado nos produtos da empresa AO e GH, respectivamente. A maior degradação de força ocorreu durante a primeira semana em todos os grupos. A taxa de alongamento necessária para o grupo TS foi significativamente maior que o grupo TP (p<0,05), e a maior taxa de alongamento foi observada nos produtos da empresa OR. Os elásticos TS obtiveram resultados significativamente maiores de estabilidade de cor que os elásticos TP, e os produtos da OR e GH tiveram melhor estabilidade de cor que oa produtos AO. Conclusão: O presente estudo demonstrou que os elásticos TS foram superiores aos elásticos TP em diminuição de força e estabilidade de cor em todas as marcas estudadas.(AU)

The setup errors of thermoplastic head and shoulder molds with or without vacuum pad in HFSRT for brain metastases in the lung cancer / 中华放射肿瘤学杂志

Objective:To retrospectively analyze the setup errors of thermoplastic head and shoulder molds alone or combined with vacuum pad in hypofractionated stereotactic radiotherapy (HFSRT) for non-small cell lung cancer (NSCLC) with brain metastases.Methods:Fifty-four NSCLC patients with brain metastases who received HFSRT from 2017 to 2019 were enrolled in this study. Twenty-four patients were fixed with thermoplastic head and shoulder molds (group A), and 30 patients were fixed with thermoplastic head and shoulder molds plus vacuum pad (group B). The interfraction and intrafraction setup errors were acquired from cone-beam CT online image registration before and after the HFSRT. Optical surface system was applied in monitoring the intrafraction setup errors. The setup errors in each direction between two groups were analyzed by independent samples t-test. Results:For the interfraction setup errors of the whole group, the proportion of the horizontal setup errors of ≥3mm was 7.0% to 15.4% and 7.0% to 12.6% for the rotation setup errors of ≥2°. In group A, the anteroposterior setup error was (1.035±1.180)mm, significantly less than (1.512±0.955)mm in group B ( P=0.009). In group A, the sagittal rotation setup error was 0.665°±0.582°, significantly less than 0.921°±0.682° in group B ( P=0.021). For the intrafraction setup errors of the whole group, the proportion of horizontal setup errors of ≥1mm was 0% to 0.7%, whereas no rotation setup error of ≥1° were observed. In group B, bilateral, anteroposterior and sagittal rotation setup errors were (0.047±0.212)mm, (0.023±0.152)mm and 0.091°±0.090°, significantly less compared with (0.246±0.474)mm, (0.140±0.350)mm and 0.181°±0.210° in group A ( P=0.004, P=0.020, P=0.001), respectively. Optical surface monitoring data were consistent with the obtained results. Conclusions:Thermoplastic head and shoulder molds (with or without vacuum pad) combined with online image registration and six-dimensional robotic couch correction can be applied in HFSRT for brain metastases from NSCLC. The intrafraction setup errors in group B are smaller than those in group A. Optical surface system has certain value in monitoring the intrafractional movement.

Application of individual head-rest combined with thermoplastic fixation mask in position fixation for irradiation with helical tomotherapy for head and neck tumors / 中国基层医药

Objective:To compare the positioning errors of individual head-rest combined with thermoplastic fixation mask versus thermoplastic fixation mask alone in patients with head and neck tumors. Methods:Twenty-eight patients who received irradiation with helical tomotherapy in Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital) between October 2019 and April 2020 were included in this study. They were randomly assigned to receive position fixation with either individual head-rest combined with thermoplastic fixation mask (N1 group, n = 14) or thermoplastic fixation mask alone (N2 group, n = 14). Megavoltage computed tomography (MVCT) scanning registration was used to obtain the positioning errors in translation and rotation (ROLL) in the left-right (X), head-food (Y), and belly-back (Z) directions. There were a total of 841 CT scans, consisting of 425 scans in group N1 and 416 scans in group N2. Results:The positioning errors in X, Y, Z and ROLL directions in the N1 group were (1.37 ± 1.04) mm, (1.38 ± 1.12) mm, (1.47 ± 1.62) mm and (1.47 ± 1.62) ° respectively, and they were (1.57 ± 1.21) mm, (2.10 ± 1.51) mm, (1.61 ± 1.50) mm and (1.40 ± 1.30) ° respectively in the N2 group. There was significant difference in positioning errors in the Y direction between N1 and N2 groups ( P = 0.013). In the N1 group, the outward expansion boundaries in X, Y and Z directions was 4.15 mm, 4.23 mm and 4.81 mm respectively, and it was 4.77, 6.31 and 5.08 mm, respectively in the N2 group. In the X direction, there was significant difference in positioning errors taking 3 mm as the dividing point between N1 and N2 groups ( χ2 = 10.516, P < 0.001). In the Y direction, there was significant difference in positioning errors taking 1, 2 and 3 mm as the dividing points between N1 and N2 groups ( χ2 = 24.889, P < 0.001; χ2 = 42.202, P < 0.001; χ2 = 46.204, P < 0.001). In the Z direction, there was significant difference in positioning errors taking 2 mm as the dividing point between N1 and N2 groups ( χ2 = 7.335, P = 0.007). In the N1 group, the percentage of positioning errors < 3 mm in the X, Y and Z directions was 92%, 90% and 92%, respectively. Conclusion:Compared with thermoplastic fixation mask alone, individual head-rest combined with thermoplastic fixation mask can better effectively improve the positioning stability and reduce positioning errors in patients receiving irradiation with helical tomotherapy for head and neck tumors. The combined method is of certain innovation.

Development Of Mebeverine Hcl Prolonged Release Mini-Tablets By Thermoplastic Granulation Technique

Mebeverine HCl is a BCS class-I drug and thus it possesses high solubility in aqueous media across the biological pH range. The marketed reference product is a multi-unit particulate system (MUPS) containing prolonged release pellets filled in hard gelatin capsule. In conventional manufacturing process, a huge quantity of solvents (aqueous and/or organic) is used to manufacture such dosage form. Additionally, it demands more processing time and efforts. Therefore, a prolonged release capsules dosage form of Mebeverine HCl was formulated using thermoplastic (melt) granulation technique without usage of any solvent. Prolonged release minitablets sized 2 mm in diameter were developed as per quality by design principles. A 23 full-factorial design of experiment was applied to optimize levels of drug release controlling ingredients which includes a hydrophobic meltable binder (hydrogenated castor oil) cum matrixing agent, a hydrophilic meltable binder (polyethylene glycol) which may act as pore former also, and a release controlling polymer (ethyl cellulose). The optimized formulation was found stable. Dissolution profiles of the optimized formulation were found similar to the marketed reference product in different media across the physiological pH range. In conclusion, the explored solvent less process was capable to manufacture the MUPS dosage form of Mebeverine HCl prolonged-release capsules, which is stable and pharmaceutically equivalent with the reference product. The developed process is more beneficial to small and medium scale industry, as it does not require any special and costly equipment, significantly decreases manufacturing cost and increases productivity compared to conventional process, which is mentioned in literature.

Vacuum And Thermoplastic Mould-based Immobilization Systems Used In Patient Undergoing Pelvic Radiation Therapy: A Comparative Study

Introduction: The aim of the present study was to compare two immobilization systems for comparison of setup errors in targeted radiotherapy. Methods: Retrospective analysis was done for the patients undergoing radiotherapy from May 2012 to December 2018 at our institution. Immobilization was performed on 30 patients sessions (Vacuum cushion i.e., Vac-Lok™ = 15; Thermoplastic mould i.e., Pelvicast pelvic masks = 15). A total of 763 cone-beams were analysed. The target lesion location was verified by cone-beam computed tomography (CBCT) prior to each session, with displacements assessed by CBCT simulation prior to each treatment session. Systematic setup errors, random setup errors, isocenter deviations in the Medio-lateral (ML), Supero-inferior (SI), Antero-posterior (AP), Rotation (yaw) directions of the patient position was calculated. Results: On comparing the Vac-Lok™ and Pelvicast pelvic masks group with respect to Systematic and random error in the lateral, longitudinal, vertical and YAW direction, no statistically significant difference was seen except the random error in YAW direction (P=0.037, Unpaired t-test). There was no difference observed in comparing the isocentric deviation. Conclusion: It was inferred and concluded that using a vacuum cushion for pelvic radiotherapy provides no added benefit compared to using a thermoplastic mould. Thermoplastic mould is recommended for patients receiving pelvic radiotherapy to improve overall reproducibility

Comparative study of some mechanical properties of cobalt chromium and polyether ether ketone thermoplastic removable partial denture clasps: an In-vitro Study / Estudo comparativo de algumas propriedades mecânicas dos grampos parciais removíveis termoplásticos removíveis termoplásticos de cobalto cromo e éter cetona: um estudo in vitro

Objective: was to evaluate the retentive force, fatigue resistance and deformity of clasps made from two materials cobalt chromium and poly ether ether ketone (PEEK). Material and Methods: sixteen models were fabricated,each one having lower 1st molar. Models were divided into two groups according to materials,group I (GI) for cobalt chromium (Co-Cr) and group II (GII) for PEEK. Each testing models and its clasps were mounted inside universal testing machine, the retention was measured by applying withdrawal force to it by this machine at 5 mm/min. The Fatigue resistance is measured by the reduction in retention through repeated insertion and removal cycles using robota chewing simulator. Removal and insertion cycling of clasps was carried out for 360, 730, 1080, 1,440, 2,116 and 2,880 cycles (corresponding to 3, 6, 9, 12, 18 and 24 months of simulated clinical use of a RPD) to simulate the fatigue resistance test. Deformity was measured before and after each cycling using a digital micrometer. Statistical analysis was done by 2-way-ANOVA test to detect significance effects of each variable. Results: Retention and fatigue resistance, after 360, 730, 1080, 1,440, 2,116 and 2,880 cycles totally the difference between Co-Cr and PEEK groups was statistically non-significant (P = 0.0980> 0.05) where (Co-Cr > PEEK). Deformation results, regardless to evaluation time, Co-Cr group recorded statistically significant higher deformation mean value than PEEK group (P = 0.008 < 0.05).Regardless to material group, deformation mean value changed nonsignificantly by time (P = 0.2882> 0.05). Conclusion: PEEK clasps (1.0 mm in cross section diameter) engage 0.50 mm undercut provide sufficient retention nearly similar that of Co-Cr clasps.(AU)

Objetivo: o objetivo foi avaliar a força de retenção, a resistência à fadiga e a deformidade dos grampos fabricados com dois materiais diferentes: cromo-cobalto (Co-Cr) e poliéter-éter-étercetona (PEEK). Materiais e métodos: dezesseis modelos foram confeccionados, cada um com 1º molar inferior. Os modelos foram divididos em dois grupos de acordo com o material: grupo I Co-Cr e grupo II para PEEK. Cada modelo de teste universal e seus grampos foram montados em uma máquina de teste universal. A retenção foi medida aplicando força de retirada por esta máquina a 5 mm/min. A resistência à fadiga foi medida pela redução na retenção através de ciclos repetidos de inserção e remoção usando um simulador do ciclo de mastigação. O ciclo de remoção e inserção dos grampos foi realizado por 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos (correspondendo a 3, 6, 9, 12, 18 e 24 meses de uso clínico simulado de um RPD) para simular o teste de resistência à fadiga. A deformidade foi medida antes e após cada ciclo, usando um micrômetro digital. A análise estatística foi realizada pelo teste ANOVA de 2 fatores para detectar os efeitos de significância de cada variável. Resultados: A retenção e a resistência à fadiga após 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos entre os grupos Co-Cr e PEEK não mostrou diferença estatisticamente significativa (p = 0,0980> 0,05), onde (Co-Cr> PEEK). Para os resultados da deformação, independentemente do tempo de avaliação, o grupo Co-Cr registrou um valor médio de deformação maior, com diferença estatística significativa, quando comparado com o grupo PEEK (p= 0,008 < 0,05). Independentemente do grupo de material, o valor médio da deformação foi alterado de forma não significativa pelo tempo (p= 0,2882> 0,05). Conclusão: os grampos PEEK (1,0 mm de diâmetro da seção transversal) engatam 0,50 mm retenção quase semelhante à dos grampos Co-Cr (AU)

Polyisobutylene and its thermoplastic elastomers: How to transform from industry to medical treatment / 中国组织工程研究

BACKGROUND: Polyisobutylene and block copolymer and its crosslinked product are a kind of novel thermoplastic elastomer. They have unique properties and excellent biocompatibility, which is a promising medical biomaterial and applied extensively. OBJECTIVE: To review the research progress and applications of polyisobutylene and its thermoplastic elastomers, and to discuss the application prospect of polyisobutylene-based polymers as medical implant materials. METHODS: A computer-based retrieval of PubMed, Web of Science, CNKI and WanFang databases was conducted for the articles about polyisobutylene published from 1958 to 2019. The key words were “polyisobutylene and block copolymer, polyisobutylene and thermoplastic elastomer, polyisobutylene and biomaterials, polyisobutylene and modification, polyisobutylene and medical application” in English and Chinese, respectively. In accordance with the inclusion and exclusion criteria, 65 eligible articles were included for review. RESULTS AND CONCLUSION: Polyisobutylene and block copolymer and its crosslinked products have favorable biocompatibility and stability. By making full use of polyisobutylene-based materials’ advantages, with the combination of other biomaterials and usage of new technology for surface modification, the copolymer will be more competitive in the field of medical implant in the future, including eye implant materials, soft biomaterials and drug delivery systems.

The Effect of Coloured Beverages on The Colour Stability of a Flexible Denture

@# Colour stability of the material is an essential factor that contributes to the selection of a flexible denture material. Staining effects on the denture may result in unattractive appearance, the dissatisfaction of the wearer, and limited usage period of the denture. This study aims to identify the colour stability of the Valplast flexible denture material using three types of beverages. Methods: A total of 32 disc-shaped flexible resin materials (20 +/- 0.1 mm in diameter and thickness 3 +/- 0.1 mm) were prepared based on the manufacturer instructions. The samples were randomly divided into 4 groups of immersion: distilled water (control), coffee solution, tea solution and red wine. The samples were left in the specified immersion solution for up to 60 days. Colour changes were measured after 1, 3, 7, 14, 21, 30, 45 and 60 days of immersion. Results: The samples immersed in coffee solution changed from S1 to S2, whereas samples in tea solution changed from S1 to S3. Additionally, samples in red wine changed from S1 to S4, as observed using the Valplast colour tone guide. The highest reflection measured using spectroscopy was 65.146 at 385.19 nm of the control samples, whereas the lowest reflection was 1.974 at the wavelength of 385.97 nm on the samples immersed in the red wine. Conclusion: The most significant difference can be observed in the red wine group, followed by samples in tea and coffee solutions. Moreover, increasing the immersion period causes increasing staining effect of the denture.

Factors associated with set-up errors in intensity-modulated radiotherapy after breast conserving surgery / 中华放射医学与防护杂志

Objective To evaluate the difference of set-up errors between thermoplastic mask and breast bracket in patients receiving intensity-modulated radiotherapy after breast conserving surgery,and the impact of clinical factors associated with set-up errors.Methods A total of 34 patients treated with intensity-modulated radiotherapy after breast conserving surgery from January 2016 to June 2018 were reviewed.Eighteen patients were fixed with thermoplastic mask,and sixteen were with breast bracket.Weekly CBCT scan records were used to analyze set-up errors,and group systematic and random errors were computed.The influence of clinical factors on set-up errors was also analyzed.Results The immobilization technique with thermoplastic mask showed great superior in comparison with breast bracket;however,only in the Ty(translation) and Ry(rotation),the differences had significance.Based on group systematic and random errors,PTV margins in Tx,Ty and Tzwere 2.65,4.36 and 2.87 mm in thermoplastic mask group,as well as 5.71,6.07 and 4.20 mm in breast bracket group,respectively.Multi-factor regression analysis showed that BMI was independent factors affecting set-up errors.Conclusions Compared with breast bracket,the immobilization technique with thermoplastic mask has the potential of reducing set-up errors and PTV margins in patients receiving intensity-modulated radiotherapy after breast conserving surgery,especially in patients with high BMI.

Physical properties and color stability of injection-molded thermoplastic denture base resins

PURPOSE: The purpose of this study was to compare mechanical and physical properties of injection-molded thermoplastic denture base resins. MATERIALS AND METHODS: In this study, six commercially available products (VA; Valplast, LC; Lucitone, ST; Smiltone, ES; Estheshot-Bright, AC; Acrytone, WE; Weldenz) were selected from four types of thermoplastic denture base materials (Polyamide, Polyester, Acrylic resin and Polypropylene). The flexural properties and shore D hardness have been investigated and water sorption and solubility, and color stability have evaluated. RESULTS: For the flexural modulus value, ES showed the highest value and WE showed significantly lower value than all other groups (P < .05). Most of experimental groups showed weak color stability beyond the clinically acceptable range. CONCLUSION: Within the limits of this study, thermoplastic denture base resin did not show sufficient modulus to function as a denture base. In addition, all resins showed discoloration with clinical significance, and especially polyamides showed the lowest color stability.

Research progress on rheology in the holt melt extrusion / 中国药学杂志

Hot melt extrusion (HME) is a novel technique to prepare solid dispersions and granules. During the manufacturing process, the drugs and polymers melt and show the complex rheological properties under the heat and forces of shear and extension. Rheology is a potential tool to guide their formulations, manufacturing process and in-line quality control. In this review, we summarized the basic theories of the molten polymer viscoelasticity with temperature and shear rate, and the time-temperature superposition, the widely used rheometries and their applications in the pharmaceutical polymer thermoplasticity, drug solubility and interactions in the molten polymers, manufacturing parameters and the in-line quality control of hot melt extrusion.

Application of combined body position fixation in radiation therapy of lung cancer / 中华放射医学与防护杂志

Objective To explore the CTV to PTV external expansion boundary and the effect of the dose of normal lung tissue under different fixed modes by a comparative analysis of combined body position and thermoplastic film fixed set-up error of radiation therapy for lung cancer. Methods From October 2016 to March 2018, the patients who received chest radiology at the Tangshan people's hospital were enrolled as subjects retrospectively divided into two groups, including 50 patients with lung cancer radiotherapy with combined body position fixation, and 40 patients with lung cancer with thermoplastic film fixation. The two groups of patients drew the target areas in accordance with the unified standard, and the set-up error of left and right, up and down, front and rear ( x, y, z axis) were recorded respectively after 1 time/week cone CT( CBCT) matched with the planned CT image and analyzed by t test. According to the MPTV =2. 5Σ+0. 7δ, CTV to PTV external expansion boundary in the combined body position group were calculated. And the V5、V20 and V30 of two groups of patients were calculated and analyzed by TPS system. Results The set-up error of the combined body position group and thermoplastic film group were respectively (1. 00 ± 0. 58) mm and (3. 28 ± 0. 43) mm on the x axis, (1. 42 ± 0. 28) mm on the y axis and (4. 03 ± 0. 41) mm, (1. 06 ± 0. 44) mm and (3. 18 ± 0. 34) mm on the z axis. The set-up errors of the two groups were statistically significant on x, y and z axis( t= -20. 740, -35. 596, -25. 015,P<0. 05). There was no significant difference in set-up errors between the central and peripheral lung cancer patients and between left and right lung cancer patients(P>0. 05). Through the MPTV =2. 5Σ+0. 7δ, CTV to PTV external expansion boundary in the combined body position fixation group was 2. 906 , 3. 746 and 2. 958 mm on x, y and z axis respectively. The comparison between group A and B showed that the mean values of V5 , V20 and V30 in group B were reduced by 1. 5％, 3. 1％ and 4. 8％ respectively compared with group A. Conclusions The combined body position technique can improve the accuracy of lung cancer patients after radiation therapy,and further reduce the boundary of CTV to PTV, which is of certain value to reduce the occurrence of radiation pneumonitis.

Effects of thermoforming on the physical and mechanical properties of thermoplastic materials for transparent orthodontic aligners / 대한치과교정학회지

OBJECTIVE: The aim of this systematic multiscale analysis was to evaluate the effects of thermoforming on the physical and mechanical properties of thermoplastic materials used to fabricate transparent orthodontic aligners (TOAs). METHODS: Specimens were fabricated using four types of thermoplastic materials with different thicknesses under a thermal vacuum. Transparency, water absorption and solubility, surface hardness, and the results of three-point bending and tensile tests were evaluated before and after thermoforming. Data were analyzed using one-way analysis of variance and Student's t-test. RESULTS: After thermoforming, the transparency of Duran and Essix A+ decreased, while the water absorption ability of all materials; the water solubility of Duran, Essix A+, and Essix ACE; and the surface hardness of Duran and Essix A+ increased. The flexure modulus for the 0.5-mm-thick Duran, Essix A+, and eCligner specimens increased, whereas that for the 0.75-/1.0-mm-thick Duran and eClginer specimens decreased. In addition, the elastic modulus increased for the 0.5-mm-thick Essix A+ specimens and decreased for the 0.75-mm-thick Duran and Essix ACE and the 1.0-mm-thick Essix ACE specimens. CONCLUSIONS: Our findings suggest that the physical and mechanical properties of thermoplastic materials used for the fabrication of TOAs should be evaluated after thermoforming in order to characterize their properties for clinical application.

Nonthermal plasma on the shear bond strength of relining resin to thermoplastic denture base resin / 대한치과보철학회지

PURPOSE: This study evaluated the effect of nonthermal plasma treatment on the bond strength of autopolymerizing relining resin to the injection molded thermoplastic denture base resins (TDBRs) with different surface treatments. MATERIALS AND METHODS: Acrylic Resin (Acrytone), Polyester (Estheshot-Bright), Polyamide (Valplast) and Polypropylene (Weldenz) were subjected to various surface treatments: No treatment, Nonthermal plasma, Sandblasting, Sandblasting and nonthermal plasma. Specimens were bonded using an autopolymerizing relining resin. Shear bond strength was tested using universal testing machine with crosshead speed of 1 mm/min. Statistical analysis by two-way analysis of variance with Tukey's test post hoc was used. RESULTS: Acrytone showed significantly higher shear bond strength value among other TDBR group while Weldenz had the lowest. The sandblasting and nonthermal plasma condition had significantly higher shear bond strength value in all of the resin groups (P < .05). CONCLUSION: The use of nonthermal plasma treatment showed limited effect on the shear bond strength between TDBRs and relining resin, and combination of nonthermal plasma and sandblasting improved the shear bond strength between TDBR and reline material.

Effects of relining materials on the flexural strength of relined thermoplastic denture base resins

PURPOSE: The aim of this study was to evaluate the effects of relining materials on the flexural strength of relined thermoplastic denture base resins (TDBRs). MATERIALS AND METHODS: For shear bond strength testing, 120 specimens were fabricated using four TDBRs (EstheShot-Bright, Acrytone, Valplast, Weldenz) that were bonded with three autopolymerizing denture relining resins (ADRRs: Vertex Self-Curing, Tokuyama Rebase, Ufi Gel Hard) with a bond area of 6.0 mm in diameter and were assigned to each group (n=10). For flexural strength testing, 120 specimens measuring 64.0×10.0×3.3 mm (ISO-1567:1999) were fabricated using four TDBRs and three ADRRs and were assigned to each group (n=10). The thickness of the specimens measured 2.0 mm of TDBR and 1.3 mm of ADRR. Forty specimens using four TDBRs and 30 specimens using ADRRs served as the control. All specimens were tested on a universal testing machine. For statistical analysis, Analysis of variance (ANOVA) with Tukey's test as post hoc and Spearman's correlation coefficient analysis (P=.05) were performed. RESULTS: Acry-Tone showed the highest shear bond strength, while Weldenz demonstrated the lowest bond strength between TDBR and ADRRs compared to other groups. EstheShot-Bright exhibited the highest flexural strength, while Weldenz showed the lowest flexural strength. Relined EstheShot-Bright demonstrated the highest flexural strength and relined Weldenz exhibited the lowest flexural strength (P < .05). Flexural strength of TDBRs (P=.001) and shear bond strength (P=.013) exhibited a positive correlation with the flexural strength of relined TDBRs. CONCLUSION: The flexural strength of relined TDBRs was affected by the flexural strength of the original denture base resins and bond strength between denture base resins and relining materials.

Current situation and prospect for orthodontic thermoplastic materials / 华西口腔医学杂志

Aesthetic and comfortable transparent retainers and clear plastic appliances are becoming increasingly popular, and their components, especially thermoplastic materials, are gradually attracting widespread interest. Orthodontic thermoplastic materials are versatile polymers, and thus their properties, such as force delivery, force relaxation, and aging properties have been comprehensively studied. Meanwhile, blending modification technology has been applied for the acquisition of novel materials with enhanced characteristics. In this paper, we review the types and properties of thermoplastic materials, the development process they undergo, factors that influence their properties, and some development prospects.