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At least 523 records · Page 29Linked to original sources
PubMed2003

In vitro evaluation of novel bioactive composites based on Bioglass-filled polylactide foams for bone tissue engineering scaffolds.

Highly porous poly(DL-lactic acid) (PDLLA) foams and Bioglass-filled PDLLA composite foams were characterized and evaluated in vitro as bone tissue engineering scaffolds. The hypothesis was that the combination of PDLLA with Bioglass in a porous structure would result in a bioresorbable and bioactive composite, capable of supporting osteoblast adhesion, spreading and viability. Composite and unfilled foams were incubated in simulated body fluid (SBF) at 37 degrees C to study the in vitro degradation of the polymer and to detect hydroxyapatite (HA) formation, which is a measure of the materials' in vitro bioactivity. HA was detected on all the composite samples after incubation in SBF for just 3 days. After 28 days immersion the foams filled with 40 wt % Bioglass developed a continuous layer of HA. The formation of HA for the 5 wt % Bioglass-filled foams was localized to the Bioglass particles. Cell culture studies using a commercially available (ECACC) human osteosarcoma cell line (MG-63) were conducted to assess the biocompatibility of the foams and cell attachment to the porous substrates. The osteoblast cell infiltration study showed that the cells were able to migrate through the porous network and colonize the deeper regions within the foam, indicating that the composition of the foams and the pore structures are able to support osteoblast attachment, spreading, and viability. Rapid formation of HA on the composites and the attachment of MG-63 cells within the porous network of the composite foams confirms the high in vitro bioactivity and biocompatibility of these materials and their potential to be used as scaffolds in bone tissue engineering and repair.

Biocompatible Materials↗
PubMed2003

Strengthening effect of aluminum fluoride added to resin composites based on polyacid-containing polymer.

OBJECTIVES: The study investigates the possible strengthening effect of aluminum ions liberated during long-time water storage of experimental resin composites containing a polymer with carboxylic acid groups. METHODS: The organic part of the resin composites was formed by photopolymerization of methacrylate monomers. The monomer mixture was composed of UEDMA, HEMA or TEGDMA, and 0-40 mol% HEMAN (the adduct of HEMA and maleic anhydride). The filler part of the resin composites consisted of a conventional silanated glass filler and 1 or 5 wt% of AlF3 x 3H2O. The rupture strength and bending modulus were measured without water storage and after 1 month, 1 year, and 3 years of water storage at 37 degrees C of the resin composite. RESULTS: The experimental composites that had been stored in water had lower rupture strength and modulus than the composites that were tested without water storage. Specimens containing 30 or 40 mol% HEMAN increased in strength, and specimens containing 20, 30, or 40 mol% HEMAN increased in modulus during the period of water storage. Depending on composition, values for strength and modulus obtained after 3 years of water storage was up to 50% higher than the values obtained after 1 month. SIGNIFICANCE: The strengthening effect of aluminum fluoride may be interpreted as the result of increased crosslinking by aluminum ions and carboxylate groups. The results may serve as a basis for the improvement of the mechanical properties of polyacid-modified resin composites.

Aluminum Compounds↗
PubMed2002

Retention of posts luted with phosphate monomer-based composite cement in canals obturated using a eugenol sealer.

PURPOSE: To examine the effect post-obturation sequencing had on retention of endodontic posts luted with a phosphate monomer-based resin cement into canals previously obturated using a eugenol-based sealer. MATERIALS AND METHODS: 64 single-rooted teeth were decoronated, and root canals were filed, cleaned, and shaped with a size 5 Gates Glidden drill and 0.12 taper rotary instrumentation. Teeth were then divided into 4 groups of 16 specimens each. Group 1 was not obturated, and served as a control. The other three groups were obturated with gutta percha and a eugenol-based sealer. Post space preparation and post cementation were completed at three different post-obturation intervals - immediate (Group 2), 1 week (Group 3), and 4 weeks (Group 4). Ten-mm deep post spaces were prepared with a size 6 Gates Glidden drill, and size 5 Paraposts were cemented with Panavia 21 OP. Following 48-hour of storage, specimens were mounted in PVC pipe with acrylic, and the posts were removed in tensile mode using a universal testing machine at 1 mm min(-1), with data recorded in kilograms. RESULTS: Group 1 (controls) mean = 61.80, SD = 16.21; Group 2 (immediate) mean = 38.70, SD = 12.97; Group 3 (1 week) mean = 43.15, SD = 14.66; Group 4 (4 weeks) mean = 18.82, SD = 8.00. Using ANOVA and Bonferroni tests, Group 1 demonstrated significantly greater mean retention strength values than Groups 2 and 3 (P < 0.05), which in turn had significantly greater mean retention strength values than Group 4 (P < 0.05).

Analysis of Variance↗
PubMed1977

Deoxyribonucleic acid base composition of Simonsiellaceae.

The molar percentages of guanine plus cytosine in the DNA of 51 strains of Simonsiellaceae were determined by buoyant density ultracentrifugation of cell lysates in CsCl. The DNA base ratios ranged from 41-55 mole-% guanine plus cytosine. These values fall within the range known for the Order Cytophagales, the non-fruiting gliding bacteria, and are outside the range of the Order Myxobacterales, the fruiting myxobacteria. Among the strains of the genus Simonsiella, four distinct group can be delineated on the basis of source of origin (sheep, dog, cat, human) and GC content. The neotype of Alysiella filiformis has a GC content of 45.4 mole-%.

Animals↗
PubMedDate not supplied

Dental composites based on hybrid and surface-modified amorphous calcium phosphates.

The objectives of this study were to prepare hybrid and surface-modified amorphous calcium phosphates (ACPs) as fillers for mineral-releasing dental composites, and determine whether the mechanical strength of the composites could be improved without decreasing their remineralization potential. ACP was hybridized with tetraethoxysilane or zirconyl chloride and surface-treated with 3-methacryloxypropoxytrimethoxy silane (MPTMS) or zirconyl dimethacrylate (ZrDMA). Composites fabricated with unmodified ACP (u-ACP), hybrid or surface-modified ACP filler and photo-activated Bis-GMA, TEGDMA and 2-hydroxyethyl methacrylate (HEMA) (BTH resin), Bis-GMA, TEGDMA, HEMA and MPTMS (BTHS resin) or Bis-GMA, TEGDMA, HEMA and ZrDMA (BTHZ resin) were tested for their remineralizing potential and biaxial flexure strength (BFS). Ion releases from all composites were significantly above the minimum necessary for reprecipitation of apatite. The BFS of unfilled polymers was not adversely affected by immersion in saline solutions. The BFS of BTH and BTHS composites deteriorated upon soaking. However, BTHZ composites were practically unaffected by exposure to saline solutions. Filler hybridization resulted in a modest, but significant, improvement in the BFS (up to 24%) of BTHZ composites. Heterogeneous distribution of the ACP on disk surfaces was detected by the FTIR microspectroscopy analyses. This might have been caused by uncontrolled aggregation of ACP particles that appeared to hinder interfacial filler/resin interactions and diminish the mechanical strength of composites.

Animals↗