Synergy in IR–Hybrid CT/C-arm in the setting of critical trauma

Emergency Radiology - Access to multi-detector computed tomography (MDCT) scanning for interventional procedures can prove to be logistically challenging as resources are often in different areas...     

Stories of despair: a Kierkegaardian read of suffering and selfhood in survivorship

Medicine, Health Care and Philosophy - A life-threatening illness such as cancer can bring about much existential suffering and a disconnect to self in spite of surviving cancer. In my recent...     

The influence of bracket base design on the strength of the bracket-cement interface

The objectives of the study were to isolate the bracket-cement interface, and to determine the influence of bracket base morphology and orthodontic bonding agent chosen on strength of adhesion. The bracket bases evaluated included 60, 80, and 100 single mesh bases, a double mesh base, and the Dynalock, and Mini Twin bases. The strength of interface provided by each of these bases with Concise, Transbond, Right On, and non-encapsulated Fuji Ortho LC cements, was measured in tension and recorded in Mega Pascals. The single-mesh bases performed well with either Concise or Right On (11*88-22*72 MPa) and, other than the 80-mesh bracket, relatively poorly with Transbond (2*18-5*15 MPa). With Fuji Ortho LC, the single mesh bases performed well (6*05-12*19 MPa). The double mesh base performed well with Right On (13*75 MPa), and reasonably well with Concise, Transbond, and Fuji Ortho LC (6*00-9*20 MPa). The Dynalock and Mini Twin Bases performed fairly well with all cements (8*87-17*16 MPa). It was concluded that the orthodontic bonding agent selected would appear to largely determine the bond strength achieved with a particular bracket base design. A definite trend was difficult to identify in this study, and it appeared that certain combinations of bracket base and bonding agent performed optimally. Particular base designs may allow improved adhesive penetration or improved penetration of curing light. Alternatively, the dimension and distribution of resin/cement tags prescribed by one base could promote a stress distribution that is better resisted by a particular adhesive.     

A comparison of plaster, digital and reconstructed study model accuracy

Objectives: To evaluate the accuracy and reproducibility of a three-dimensional (3D) optical laser-scanning device to record the surface detail of plaster study models. To determine the accuracy of physical model replicas constructed from the 3D digital files. Design and setting: A method comparison study using 30 dental study models held in the Orthodontic Department, School of Dentistry, Cardiff University. Materials and methods: Each model was captured three-dimensionally, using a commercially available Minolta VIVID 900 non-contact 3D surface laser scanner (Konica Minolta Inc., Tokyo, Japan), a rotary stage and Easy3DScan integrating software (TowerGraphics, Lucca, Italy). Linear measurements were recorded between landmarks, directly on each of the plaster models and indirectly on the 3D digital surface models, on two separate occasions by a single examiner. Physical replicas of two digital models were also reconstructed from their scanned data files, using a rapid prototyping (RP) manufacturing process, and directly evaluated for dimensional accuracy. Results: The mean difference between measurements made directly on the plaster models and those made on the 3D digital surface models was 0.14 mm, and was not statistically significant (P = 0.237). The mean difference between measurements made on both the plaster and virtual models and those on the RP models, in the z plane was highly statistically significant (P <0.001). Conclusions: The Minolta VIVID 900 digitizer is a reliable device for capturing the surface detail of plaster study models three-dimensionally in a digital format but physical models of appropriate detail and accuracy cannot be reproduced from scanned data using the RP technique described.     

Studies on the binding of lipoteichoic acid to osseous tissue

Tritium-labelled lipoteichoic acid (³H-LTA) was examined for its interaction with connective tissue components by employing autoradiography. Evidence was obtained for LTA binding to both the calcified matrix and to cells of neonatal rat parietal and long bones in vitro . The interaction of LTA with bone-derived cells was studied in a model system utilizing an osteosarcoma cell line in tissue culture. These tumour cells incorporated ³H-LTA as long as they were actively dividing but deacylated LTA was not incorporated. This suggested that the lipid portion of the molecule was necessary for interaction with the cells. Evidence has also been obtained for an interaction of LTA with components from the culture fluid of osteosarcoma cells.     

Influence of surface hardener on gypsum abrasion resistance and water sorption

STATEMENT OF PROBLEM: Abrasion is a major concern when gypsum products are used for dies, leading to the frequent recommendation that surface hardeners should be used before waxing or scanning. PURPOSE: This study evaluated abrasion resistance and water sorption with 4 commonly used gypsum die materials with and without the application of surface die hardeners. MATERIAL AND METHODS: Three ADA Type IV (Vel-Mix, ResinRock, and Silky-Rock) and 1 Type V die material (Die-Keen) were evaluated for abrasion resistance after application of 2 surface hardeners (Permabond 910 cyanoacrylate and Clear Coat). Thirty specimens of each material were fabricated using an impression of a standard brass die machined with 1-mm high ridges, sloped 45 degrees. Gypsum materials were mixed according to manufacturers' recommendations and allowed to set 1 hour before separating. All replicated dies were allowed to bench set for 14 days before testing. One hour before testing, specimens were arbitrarily assigned to 1 of 3 treatment subgroups (n=10/group): no treatment (control), coated with Permabond 910, or coated with Clear Coat. In the coated groups, die hardener was painted over the grooves and air dried. Abrasion resistance (measured by weight loss) was evaluated using a reciprocal abrasion device in which a stylus applied a 50-g mass perpendicular to the ridges. Mass loss was determined using an analytical balance before and after each test cycle. Five sets of 20 unidirectional passes were made on each specimen. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Water sorption was also evaluated using 2 Type IV (Silky-Rock, ResinRock) and 1 Type III (Microstone) gypsum materials. Specimen dies were separated 1 hour after pouring the impression and allowed to bench set 1 week before testing. Five specimens from each material group received a coating of a surface hardener 1 hour before testing. Specimens were placed in distilled water for 15 minutes and differences in mass were determined using an analytical balance before and after each test. A 2-way analysis of variance was completed followed by a Tukey post hoc test (alpha=.05). RESULTS: The 2-way analysis of variance revealed an interaction between product and surface coating (P=.0459). Given this interaction, the 12 combinations determined by surface treatment and material type were considered individually using the Tukey method. Vel-Mix, control (2.62 +/- 2.64 mg) had the most material loss and Vel-Mix, Clear Coat (0.48 +/- 0.29 mg) had the least material loss. Water sorption results indicated an interaction between the gypsum material and the surface treatment (P<.0001). The control groups of Microstone (299.2 +/- 49.6 mg) and Silky-Rock (159.0 +/- 8.5 mg) showed the most water sorption compared with the other treatment groups. CONCLUSIONS: This study demonstrated that a significant improvement in abrasion resistance occurred only with specific gypsum/surface hardener material combinations. Also, water sorption decreased significantly for Microstone and Silky-Rock gypsum materials when a surface hardener was used.     

Enumeration of oral streptococci on media containing different concentrations of sodium and potassium ions

Laboratory "type" strains of oral streptococci were screened for their ability to grow on mitis-salivarius agar (MSA) in the presence of increasing concentrations of either Na+ or K+ up to 500 mmol/L. Strains were generally better able to withstand increasing concentrations of Na+ than K+, although low numbers of colony-forming units (cfus) were seen with the highest concentration of either cation. Two strains of Streptococcus mutans, Ingbritt 162 and Ingbritt 175, behaved differently when the concentration of cation was increased from 50 to 200 mmol/L; the latter showed a marked increase in the number of cfus when the Na+ concentration was increased from 50 to 200 mmol/L, whereas there was a decrease with strain Ingbritt 162. Strains of oral streptococci from the saliva of adults and children were isolated on modified MSA containing known concentrations of Na+ and K+ and further examined if they showed "mutans-like" colony morphology. The number of cfus generally dropped as the concentration of Na+ or K+ was increased from 200 to 350 or 500 mmol/L. Greater numbers of streptococci were tolerant to Na+ than to K+. Half of the isolates were members of the Streptococcus sanguis group (SSG), either Streptococcus mitis or S. sanguis II, and these were more tolerant to high concentrations of Na+ or K+ than other isolates that were identified as Streptococcus morbillorum, Streptococcus acidominimus, and Streptococcus milleri.