Determination of leachable components from an experimental endodontic sealer by nuclear magnetic resonance (NMR) spectroscopy

Introduction. Studies of experimental composites based on amorphous calcium phosphate (ACP) intended for dental applications as remineralizing pit and fissure sealants, orthodontic adhesives and, most recently, endodontic sealers were mainly focused on improving their mechanical, esthetic and remineralizing capabilities. Similar to the vast majority of commercial composites, these experimental formulations might have clinical drawbacks due to incomplete conversion of monomers and leachability of monomers and degradation products, shrinkage and stress associated with polymerization, and microleakage typically occurring at the tooth/composite interfacial region. The aim of this study was to identify and quantify leachable components from the experimental amorphous calcium phosphate (ACP) endodontic sealer using 1H nuclear magnetic resonance (NMR) spectroscopy. Material and Methods. The light-cure resin [camphorquinone (CQ) + ethyl-4-N,N-dimethylamino benzoate (4EDMAB)] was formulated from urethane dimethacrylate (UDMA), poly(ethylene glycol)- extended urethane dimethacrylate (PEG-U), 2-hydroxyethyl methacrylate (HEMA) and methacryloyloxyethyl phthalate (MEP). The experimental sealer contained 40 mass % ground ACP and 60 mass % resin. The copolymer (unfiled resin) and ACP/UPHM composite specimens, after being dried to a constant mass, were extracted in butylated hydroxyl toluene (BHT; prevents polymerization of eluted components) containing acetone for 7 days at 23ºC with continuous magnetic stirring. Gravimetric changes were recorded for each specimen. After solvent evaporation, 1H NMR spectra were collected on the extractable portion of each specimen. Representative peaks for each component were used to calculate their relative portions in the extracts. By combining the gravimetric and NMR data, the overall loss of each monomer and its concentration in the extract was calculated. Results were statistically analyzed by ANOVA and multiple pair-wise comparisons (t-test). Results. No CQ could be detected in the extracts. However, 33.06 % and 24.66 % of the initially incorporated 4EDMleached from the copolymers and composites, respectively. 0.30-14.29% and 0.12-10.39% of each monomer content leached out from copolymers and composites, respectively. The apparent differences in the concentrations between copolymers and composites became marginal when composite data were normalized with respect to the initial amount of the resin. Conclusion. 1H NMR conveniently provides qualitative and quantitative information on leachables without the elaborate sample preparation and/or data interpretation. Leachability of the unrectaed monomers from the experimental ACP sealer is apparently controlled by the highly cross-linked resin network and unaffected by the incorporation of bioactive ACP into the resin. The maximum levels of leachables from our experimental composite were within or below the concentration ranges reported for the commercial counterparts

Effects of Melt-Processing Conditions on the Quality of Poly(ethylene terephthalate) Montmorillonite Clay Nanocomposites

Organically modified montmorillonite was synthesized with a novel 1,2-dimethyl-3-N-alkyl imidazolium salt or a typical quaternary ammonium salt as a control. Poly(ethylene terephthalate) montmorillonite clay nanocomposites were compounded via melt-blending in a corotating mini twin-screw extruder operating at 285 degreesC. The nanocomposites were characterized with thermal analysis, X-ray diffraction, and transmission electron microscopy to determine the extent of intercalation and/or exfoliation present in the system. Nanocomposites produced with N,N-dimethyl-N,N-dioctadecylammonium treated montmorillonite (DMDODA-MMT), which has a decomposition temperature of 250 degreesC, were black, brittle, and tarlike resulting from DMDODA degradation under the processing conditions. Nanocomposites compounded with 1,2-dimethyl-3-N-hexadecyl imidazolium treated MMT, which has a decomposition temperature of 350 degreesC, showed high levels of dispersion and delamination. (C) 2002 Wiley Periodicals, Inc

Oncological patterns of care and outcome for 952 patients with newly diagnosed glioblastoma in 2004

This report, an audit requested by the French government, describes oncological patterns of care, prognostic factors, and survival for patients with newly diagnosed and histologically confirmed glioblastoma multiforme (GBM) in France. The French Brain Tumor DataBase, which is a national multidisciplinary (neurosurgeons, neuropathologists, radiotherapists, neurooncologists, epidemiologists, and biostatisticians) network, prospectively collected initial data for the cases of GBM in 2004, and a specific data card was used to retrospectively collect data on the management and follow-up care of these patients between January 1, 2004, and December 1, 2006. We recorded 952 cases of GBM (male/female ratio 1.6, median age 63.9 years, mean preoperative Karnofsky performance status [KPS] 79). Surgery consisted of resection (RS; n = 541) and biopsy (n = 411); 180 patients did not have subsequent oncological treatment. After surgery, first-line treatment (n = 772) consisted of radiotherapy (RT) and temozolomide (TMZ) concomitant +/− adjuvant in 314 patients, RT alone in 236 patients, chemotherapy (CT) alone in 157 patients, and other treatment modalities in 65 patients. Median overall survival was 286 days (95% CI, 266–314) and was significantly affected by age, KPS, and tumor location. Median survival (days, 95% CI) associated with these main strategies, when analyzed by a surgical group, were as follows: RS + RT-TMZ(n=224): 476 (441–506), biopsy + RT-TMZ(n=90): 329 (301–413), RS + RT(n=147): 363 (331–431), biopsy + RT(n=89): 178 (153–237), RS + CT(n=61): 245 (190–361), biopsy + CT(n=96): 244 (198–280), and biopsy only(n=118): 55 (46–71). This study illustrates the usefulness of a national brain tumor database. To our knowledge, this work is the largest report of recent GBM management in Europe