Studies on New Organically Modified Ceramics Based Dental Restorative Resins

Novel difunctional and tetra functional organically modified ceramics with methacrylate functional groups were developed from liquid precursors using the sol-gel process. These novel inorganic-organic hybrid materials were characterized using various techniques and used for the preparation of visible light cure dental restoratives, which have good mechanical properties and excellent surface hardness. Effect Of Cure time on vickers hardness Of Cured composite was measured, and compared with that of the bisphenol A glycidyl methacrylate (Bis GMA) based composite. Statistical evaluation using analysis of variance (single factor) showed a significant (P < 0.05) difference in diametral tensile strength and hardness with variation in inorganic content. Also a significantly improved hardness was obtained for the new organically modified ceramic composite compared with BisGMA based composite at all exposure time. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 509-517, 201

Studies on Polymerization and Elution Characteristics of Antibiotic Loaded Acrylic Bone Cements

Acrylic bone cements are widely used in orthopedic applications for anchoring the prosthesis to the contiguous bone in cemented arthroplasty. Wide spectrum antibiotics such as ampicillin and tetracycline have been incorporated into bone cement and their effect upon polymerization characteristics such as working and setting times have been monitored using cycloviscograph and properties like diametral tensile strength (DTS) evaluated. Antibiotic elution into phosphate buffered saline at different intervals of time was evaluated and compared for both antibiotics. Working and setting times were found to increase with antibiotic concentration in the bone cement. Presence of ampicillin was found to have no effect upon the strength of the bone cement while tetracycline had a deteriorating effect upon DTS. Rate of antibiotic elution into phosphate buffered saline (PBS) was observed to be higher for ampicillin compared to tetracycline. Cytotoxic evaluation of the virgin bone cement did not elicit any toxic response

Aging Effects of Dental Restorative Materials upon Surface Hardness

This study was conducted to compare the effect of one-year storage of one indigenously developed and seven commercially available dental restorative materials on surface microhardness (VHN) and the use of hardness value as an indirect measure of degree of conversion and degradation in aqueous medium. Four composite pastes (Spectrum- TPH, Z-100, P -60 and indigenously developed Ormo 48, one compomer (F- 2000) and three glass ionomers (Fuji II LC, Fuji II CC and Ketac Molar) were either self or light cured and stored in distilled water at 37 +/- 1 degrees C and Vickers microhardness was measured at intervals of 1 hour, 1 and 7 days, 1, 3, 6, 9 and 12 months. A minimum of 6 measurements was carried out on both surfaces. Mean and standard deviations were calculated. Statistical evaluation was done by means of one-way analysis of variance (ANOVA). Degradation and monomer conversion were correlated with the support of Fourier Transform Raman spectra of cured and uncured paste. A significant difference in hardness was noticed for each material over storage time. Among the materials tested, composites exhibited the highest hardness values throughout the study. The values reached a maximum after 24 hours and showed a significant decline over a period of 1 year. Compomer had the maximum hardness after seven days. However in case of FUJI glass ionomers, no significant change in hardness was noticed even after 1 year whereas Ketac Molar showed a significant increase in hardness with time. FT Raman spectra of photo cured organically modified ceramics composite showed residual unsaturation (1610 cm(-1) peak). The results indicate that composites and compomers show significant decrease in hardness with time whereas glass ionomers tend to show either significant (P< 0.05) increase or no change on storage

Rheological behaviour of polyurethane prepolymers as potting compound for hollow fibre haemodialyzer

The effect of reaction conditions on the rheological behaviour of various polyurethane prepolymer as potting compound for fabrication of hollow fibre haemodialyzer has been studied by means of a Brookfield viscometer. Depending on the monomers used and reaction conditions, dilatant and pseudoplastic behaviour is noticed. Bulk polymerized prepolymers based on HDI/castor oil, SMDI/castor oil and HDI/polypropylene glycol exhibit pseudoplastic character, which are favourable for easy dispensibility, non-wicking and good dispersion in potting of hollow fibre