Phylogenic analysis of serotype Asia1 foot-and-mouth disease virus from Sulaimani/Iraq using VP1 protein: heterogeneity with vaccine strain As1/Shamir/89.

Foot-and-mouth disease virus (FMDV) serotypes O, A and Asia1 are responsible for a significant number of disease outbreaks in Iraq. The current study can be considered as the first molecular characterization of serotype Asia1 in Iraq. The present investigation reports the detection of serotype FMDV Asia1 from local farms in Sulaimani districts in 2012 and 2014 outbreaks. Phylogenetic analysis of the complete VP1 gene has shown that FMDV Asia1 field isolates were under genetic novel variant Sindh-08 (group VII) including PAK/iso/11 and TUR/13 strains. The VP1 protein sequence of circulatory FMDV Asia1 genotype showed heterogeneity of nine amino acid substitutions within the G-H loop with the vaccine strain As1/Shamir/89 (JF739177) that is currently used in vaccination program in Iraq. Our result indicated that differences in VP1 protein at G-H loop of the locally circulated FMDV serotype Asia1 strain may be a reason for current vaccination failure.

Optimal specimen geometry in bonded-disk shrinkage-strain measurements on light-cured biomaterials.

OBJECTIVES: The aim was to determine the effect on apparent shrinkage-strain values of varying specimen aspect ratio in the bonded-disk configuration. Thereby one source of possible inter-laboratory variation might be understood and eliminated. METHODS: The bonded-disk procedure was followed and applied to three representative resin-composites. However, specimen sub-groups were examined, each of different diameters (3.5, 5.0, 7.0 and 9.0 mm), corresponding to C-factors in the range 0.45-7.0. RESULTS: For each material, no statistically significant difference was apparent between data obtained with 7 and 9 mm diameter specimens. However, statistically significant reductions (p < 0.05, Scheffé and SNK) were apparent at 5.0 and 3.5 mm diameter, in the range 14-18% of the maximum 'true' value. For each material, the diameter (d)-dependence of apparent shrinkage-strain (epsilon) was given by the curve fit expression: epsilon = A - B/d2. SIGNIFICANCE: For accurate determination of maximum final equilibrium shrinkage-strain values, a high aspect ratio (7-9:1) of the bonded-disk should be utilised. This is important for accurate comparison of data from proposed low-shrinkage amalgam-replacement materials.

Photo-polymerization shrinkage-stress kinetics in resin-composites: methods development.

OBJECTIVES: Studies of free shrinkage-strain kinetics on restoratives have begun to multiply. However, there have been fewer investigations of the more difficult problem of concurrent stress-kinetic measurements. The aim was to outline design parameters for a new methodology for this problem, amenable especially to light-cured materials, and to present illustrative results for a range of restorative composites. METHODS: Absolute values of stress measurable for a given material and geometry are dependent upon the stiffness of the measurement system. In an infinitely stiff system, the measured stress would also tend towards infinity. Real teeth and their cavities are not infinitely stiff; they have elastic and visco-elastic compliance. Consequently, it is important that some minimal, but essentially constant compliance be allowed, whatever the final or time-dependent modulus of the material may be. This goal has been realised by measurement of the time-development, for a disk-geometry specimen (phi=10, h approximately 1.0 mm) of stress (S(r)), with a calibrated cantilever beam-geometry load cell. A novel specimen-holder design was used for this purpose, held in a rigid base assembly. Specimen thicknesses (or gap-widths) of 0.8 and 1.2 mm were specifically investigated on four representative resin-composites. Concurrent measurements were made of the end-displacement of the cantilever load cell, relative to a lower glass plate retaining the specimen. RESULTS: Load-calibration of the cantilever load cell gave an end-displacement per unit stress of circa 6 microm/MPa. This compares with literature values for cuspal compliance or displacement of circa 20 microm. Re-normalisation of the stress-data was implemented. This was accomplished assuming Hooke's law behavior at each instant and equivalent to a stiffer system, with a correction (multiplier) factor of 4 on the raw-stress values. For the materials examined, resultant maximum-stress levels determined were circa 5-8 MPa Stress-levels obtained at 1.2mm thickness were slightly higher (11-15%) than the level of stress obtained at 0.8 mm thickness. This is attributable to the greater mass of material undergoing shrinkage at 1.2 mm, offset slightly by the different C-factors. SIGNIFICANCE: The new device is a practical and self-contained system for rapid and accurate measurement of stress-kinetics in photo-polymerising and also self-cure materials.