Evaluation of Mechanical Properties of Various Nanofibre Reinforced Bis-GMA/TEGDMA Based Dental Composite Resins / Evaluación de las propiedades mecánicas de varias resinas compuestas dentales basadas en Bis-GMA/TEGDMA reforzadas con nanofibras

ABSTRACT Objective: To investigate the mechanical properties of various mass fractions of Nylon 6 (N6), polymethyl-metacrylate (PMMA) and polyvinylidene-difluoride (PVDF) nanofibres reinforced bisphenol A-glycidyl methacrylate (Bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) based dental composite resins and to evaluate the penetration characteristics of the nanofibres into the resin. Methods: Nylon 6, PMMA and PVDF nanofibres were produced using the electrospinning method. The morphologies of the fabricated nanofibres were evaluated with a scanning electron microscope (SEM). The nanofibres were placed into the resin matrix at different mass fractions (3%, 5% and 7%). The three-point bending test was applied to nanofibre-reinforced dental composite resins and neat resin specimens. The flexural strength (Fs), flexural modulus (EY) and work of fracture (WOF) of the groups were found. The analysis of variance was used for the statistical analysis of the acquired data. Tukey 's multiple test was performed to compare the Fs, EY and WOF means. Fractured surfaces of the samples were observed by SEM, and fracture morphologies were evaluated. Results: Polymethyl-metacrylate nanofibres dissolved in the matrix, and a polymer alloy took place in the matrix. Fibre pull-out and fibre bridging mechanisms were observed by SEM images of the N6 and PVDF nanofibre-reinforced dental composites. The produced nanofibres enhanced the mechanical properties of the dental composite resins. Conclusion: Fibre pull-out and fibre bridging mechanisms on the fractured surfaces of samples may play a key role in the reinforcement of dental composite resins. However, polymer alloy of PMMA nanofibres increased the mechanical properties of the resin matrix.

RESUMEN Objetivo: Investigar las propiedades mecánicas de resinas compuestas dentales basadas en bisfenol A-diglicidildimetacrilato (Bis-GMA) y dimetacrilato trietilen-glicol (TEGDMA) reforzadas con nanofibras de fracciones de masa de Nylon 6 (N6), polimetilmetacrilato (PMMA) y fluoruro de polivinilideno (PVDF), y evaluar las características de la penetración de las nanofibras en la resina. Métodos: Se produjeron nanofibras de Nylon 6, PMMA y PVDF utilizando el método de electrohilado (electrospinning). Las morfologías de las nanofibras fabricadas fueron evaluadas con un microscopio electrónico de barrido (MEB). Las nanofibras fueron introducidas en la matriz de resina en diferentes fracciones de masa (3%, 5% y 7%). La prueba de flexión de tres puntos fue aplicada a las resinas compuestas dentales reforzadas por nanofibras y a las muestras de resina pura. La resistencia a la flexión (Rf), el módulo de flexión (EY) y el trabajo de fractura (WOF) de los grupos fueron halladas. El análisis de varianza se usó para el análisis estadístico de los datos adquiridos. Se realizó la prueba de comparaciones múltiples de Tukey con el propósito de comparar las medidas de Rf, EY y WOF. Las superficies fracturadas de las muestras fueron observadas mediante un MEB, y se evaluaron las morfologías de fractura. Resultados: Las nanofibras de polimetilmetacrilato se disolvieron en la matriz, y tuvo lugar una aleación de polímeros en la matriz. Los mecanismos de desprendimiento de fibras y puenteo de fibras fueron observados mediante imágenes de MEB de los compuestos dentales reforzados con nanofibras de N6 y PVDF. Las nanofibras producidas realzaron las propiedades mecánicas de las resinas compuestas dentales. Conclusión: Los mecanismos de desprendimiento de fibras y puenteo de fibras en las superficies fracturadas de las muestras pueden desempeñar un papel clave en el reforzamiento de las resinas de los compuestos dentales. Sin embargo, la aleación polimérica de las nanofibras de PMMA aumentó las propiedades mecánicas de la matriz de resina.

Outcome of avulsion fractures of the ulnar base of the proximal phalanx of the thumb treated nonsurgically.

We report a retrospective study of avulsion fractures of the ulnar collateral ligament of the thumb metacarpophalangeal joint that were treated nonsurgically. The study included 30 patients who answered a questionnaire. None of the patients underwent surgery after treatment. The average follow-up interval was 3.1 years (range, 1-5.2 years). All 30 patients were satisfied with the treatment and outcome. No patient had a permanent job change or inability to participate in recreational activities. Nineteen patients had no pain on motion of the thumb. Of the 20 patients (67%) who agreed to a follow-up examination, key pinch and grip strength were not statistically different between the injured and noninjured sides. Three patients had instability on stress testing. There was a 25% nonunion rate. While not statistically significant, symptomatic patients tended to have slightly larger fragments (5.4 mm x 1.7 mm vs 3.2 mm x 1.4 mm on anterioposterior x-rays) and greater initial rotation (26 degrees vs 24 degrees) of the fracture than asymptomatic patients. Despite the nonunion rate and the patients with clinical instability, all 30 patients were satisfied with their treatment.