Bio-Medical Materials and Engineering - Volume 14, issue 1

Authors: Chu, K.T. | Oshida, Y. | Hancock, E.B. | Kowolik, M.J. | Barco, T. | Zunt, S.L.

Article Type: Research Article

Abstract: Currently PMMA is the polymer most commonly used as a bone cement for the fixation of total hip prostheses. Ideally, a bone cement material should be easy to handle, biologically compatible, nonsupporting of oral microbial growth, available in the particulate and molded forms, easy to obtain, nonallergenic, adaptable to a broad range of dental and medical applications, in possession of high compressive strength, and effective in guided tissue regenerative procedures. One of the problems associated with the conventional types of bone cement used is their unsatisfactory mechanical and exothermic reaction properties. The purpose of this in vitro study was …to investigate and compare the mechanical properties (three‐point bending strength, energy‐to‐break, and modulus of elasticity) and physical properties (setting time, water sorption, and exothermic heat) of HA/PMMA (HA group) and bovine‐bone originated HA/PMMA (BB group) composites. Composites samples were fabricated by admixing method. It was found that the addition of HA and BB particles increased the water sorption. Generally 10 v/o 20 v/o HA and 0 v/o to 10 v/o BB ratio combinations had significant beneficial effects on the mechanical properties. The heat generated during polymerization was influenced by the different admixtures. More than 40 v/o HA and 40 v/o BB should be mixed into PMMA to reduce the peak temperature. Overall evaluation indicated that the BB group had better properties than the HA group. Show more

Keywords: Hydroxyapatite, bone cement, PMMA, composites, mechanical strength, temperature raise, bovine‐bone‐originated hydroxyapatite

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 1, pp. 87-105, 2004

Authors: Hernandez, E.P. | Oshida, Y. | Platt, J.A. | Andres, C.J. | Barco, M.T. | Brown, D.T.

Article Type: Research Article

Abstract: The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat‐processed and reinforced methacrylate‐based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior …mechanical properties if manufactured through a dough compression molding process at 130°C. However, there have been no published data that relate with the use of this material for fixed provisional restorations. The objective of this study was to compare four methyl methacrylate‐based resins for provisional crowns and bridges with varying processing cycles, including JET [self‐cure], ACRALON [heat‐cured], titanium dioxide filled PMMA [heat‐cured], and IPN [heat‐cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength. Show more

Keywords: Interpenetrating network crosslink, PMMA, self‐cure, heat‐cure, mechanical properties, provisional restorations

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 1, pp. 107-122, 2004

Authors: Fu, Weihua | Dai, Jianrong | Hu, Yimin

Article Type: Research Article

Abstract: Using higher energy photons can obtain better target dose uniformity and skin sparing for treating deep lesions, but the effect of lacking lateral scattering in the low‐density lung may degrade the target coverage. To analyze the influence of lateral electronic disequilibrium on the radiation treatment planning for lung cancer, three dimension conformal treatment (3D‐CRT) plans of using 6 MV and 18 MV X‐ray respectively for a lung cancer case have been worked out by using pencil beam algorithm and collapsed cone algorithm provided by Helax‐TMS treatment planning system for the same radiation field arrangement for both energies. Dose volume histogram …(DVH) in target and organs at risk (OARs) are used for comparison of different plans. The study shows that using pencil beam algorithm, the target DVH are similar for 6 MV and 18 MV plan. However, using collapsed cone algorithm that can make account of lateral electron scattering, the target is underdosed. The change is even more pronounced for 18 MV plan. The doses for lung and spinal cord are similar for these two energies and two algorithms. Therefore, for lung cancer, dose calculation algorithm should have the ability of handling accurately the effect of the tissue density heterogeneity. It is better to use the lower‐energy photons (6 MV) than to use the higher‐energy photons (18 MV). Show more

Keywords: Lateral electronic disequilibrium, pencil beam algorithm, collapsed cone algorithm

Citation: Bio-Medical Materials and Engineering, vol. 14, no. 1, pp. 123-126, 2004