PubMed · 2606927
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K de Groot. 1989. Hydroxylapatite coated implants.. https://doi.org/10.1002/jbm.820231112
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A mechanical performance test using an Instron Tensile Tester demonstrated the superior handling characteristics of Surgipro suture as compared to Prolene suture that facilitated knot construction without suture breakage. For both granny and square knots, the knot run down forces for the Surgipro sutures were significantly less than those encountered for comparable knots for Prolene sutures. This propensity of the two-throw knots of Surgipro sutures to advance without breakage considerably facilitated knot construction.
Analytical studies of the stresses on and within ultra high molecular weight polyethylene joint components suggest that damage modes associated with polyethylene fatigue failure are caused by a combination of surface and subsurface crack propagation. Fatigue crack propagation tests under mixed mode loading conditions were conducted on center-cracked tension specimens machined from extruded blocks of sterilized polyethylene in an attempt to determine how fatigue cracks change direction in this material. Cyclic testing was performed using a sinusoidal wave form at a frequency of 5 Hz and an R-ratio (minimum load/maximum load) of 0.15. Specimens had the notch oriented perpendicular to the direction of applied load and at angles of 60 degrees and 45 degrees to the loading direction. Numerical analyses were used to interpret the experimental test and to predict the fatigue behavior of polyethylene under mixed mode conditions. It was found that all cracks eventually propagated horizontally, regardless of the initial angle of inclination of the notch to the direction of applied cyclic load. In fact, the extent of the curvilinear crack growth was quite limited. An effective range of cyclic stress intensity factor was calculated for correlation with the rate of crack growth. The results followed a Paris relation, with crack growth rate linearly related to a power of the range of stress intensity, for all three crack orientations. The numerical analyses adequately modeled the experimental fatigue crack growth results.
The manufacture of fixed prostheses by means of the porcelain-fused-to-metal technique is done by sintering a ceramic powder onto the metal frame work. During this process the ceramic is condensed due to fusion of the powder, accompanied by a loss of volume of the whole material. In this study the sintering process of the dental ceramic VMK 68 was investigated by means of scanning electron microscopy and determination of density. The results showed, that the sintering takes place between 680 degrees C and 950 degrees C, while the density increases from 1.56 g/cm3 to 2.54 g/cm3. The volume shrinkage amounts to 36%. Thermomechanical analyses confirmed that the starting temperature of the sintering process depends on the heating rate. The investigations showed that the instructions for use, given by the manufacturer, represent optimal conditions.