Effect of poly(acrylic acid) architecture on setting and mechanical properties of glass ionomer cements.

OBJECTIVE: This work focuses on the influence of poly(acrylic acid) (PAA) architecture (linear or branched) on setting behavior and compressive strength of glass ionomer cements (GICs). METHODS: Branched and linear poly(acrylic acid)s were synthesized according to the Strathclyde methodology or by free radical polymerization. They were characterized by 1H-NMR spectroscopy and size exclusion chromatography to determine their molecular weight and size distribution. GIC setting was characterized by oscillating rheometry and time-dependent FTIR spectroscopy. In addition, compressive strength was tested on cylindrical samples (6 × 4 mm; n = 8/cement composition) after storage in deionized water at 37 °C for one day. RESULTS: We used two different routes to prepare PAA. One direct route in order to provide straightforward access to branched PAA and a two-step approach in order to get more control about the PAA molecular weight using tert-butyl acrylate (tBA) for polymerization with subsequent deprotection. Using the second approach we obtained several linear PAA of which a mixture was used in order to mimic the molecular weight and size distribution of branched PAA. This allowed the direct comparison of properties relying only on the polymer architecture. Comparing linear PAA to branched samples in general led to faster setting but at the same time decreased the compressive strength. Increasing molecular weight of branched PAA resulted in even faster GIC setting while increasing compressive strength and this correlates well with the trends reported for linear PAA in literature. Mixing of branched and linear PAA, however, turned out to be an effective way of tailoring GIC properties. SIGNIFICANCE: our results suggest that both molecular weight and dispersity need to be considered when choosing suitable PAA architecture for obtaining specific GIC properties.

Cefpodoxime: comparative antibacterial activity, influence of growth conditions, and bactericidal activity.

The antimicrobial activity of cefpodoxime, the active metabolite of the new cephalosporin ester cefpodoxime proxetil, in comparison to cefixime, cefotiam, cefuroxime, and cefotaxime was determined against a broad spectrum of freshly isolated gram-positive and gram-negative bacterial strains. Cefpodoxime was demonstrated to be inhibitory at concentrations of less than or equal to 1 mg/l against 90% of strains of Moraxella catarrhalis, Haemophilus influenzae, Escherichia coli (beta-lactamase- negative strains), Klebsiella spp., Serratia spp., Proteus mirabilis, Proteus vulgaris, Providencia spp., and Salmonella spp. This antimicrobial activity of cefpodoxime was generally superior to that of cefuroxime and similar to that of cefixime. Cefpodoxime was active at less than or equal to 1 mg/l against 50% of the members of beta-lactamase-producing Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter spp., and Morganella morganii. Cefpodoxime proved to be highly inhibitory against group A, B, and G streptococci and Streptococcus pneumoniae (MIC90 less than 0.015 mg/l). The MICs of cefpodoxime and those of the other cephalosporins were less than 2 mg/l for greater than or equal to 90% of the strains of Staphylococcus aureus and Staphylococcus epidermidis, with the exception of cefixime which had no activity with MICs below 8 mg/l against these bacteria. Pseudomonas spp., Acinetobacter spp., and Enterococcus spp. were resistant to cefpodoxime. The antibacterial activity of cefpodoxime was only to a minor degree influenced by different growth conditions with the exception of high inoculum sizes against some beta-lactamase producing strains of gram-negative bacilli.(ABSTRACT TRUNCATED AT 250 WORDS)

[Arthroscopic therapy in limited mobility of the elbow joint]. / Die arthroskopische Therapie bei Bewegungseinschränkungen des Ellenbogengelenks.

Limitation of elbow mobility constitutes a grave problem for therapy. Arthroscopy offers a therapeutic option, but in cases of loss of motion poses a considerable challenge to the operative technique. Placement of the portals already carries an increased risk of neurovascular lesions due to the altered anatomy and reduced distension capacity of the joint. Thus, particular significance attaches to the standardized arthroscopic procedure for localization and placement of the cannulas, intra-articular assessment, differentiated evaluation of the dorsal joint regions, and operative tactics for transsection of cicatrization, removal of loose bodies, and excision of osteophytes. If extra-articular factors are involved in the genesis of the limited motion, arthroscopic treatment often does not achieve the desired result. It is therefore considered propitious to differentiate the causes of the loss of motion during clinical examination with imaging diagnostics, in particular to determine those caused by extra-articular elements. If, however, individually localized intra-articular adhesive bands or loose bodies are responsible, the prognosis for arthroscopic management is clearly more favorable. Patients with minor loss of motion (> 15 degrees) profit more from the arthroscopic operation than those with a extension or flexion deficit of more than 30 degrees.