This study evaluated a porous tantalum biomaterial (Hedrocel) designed to function as a scaffold for osseous ingrowth. Samples were characterized for structure, Vickers microhardness, compressive cantilever bending, and tensile properties, as well as compressive and cantilever bending fatigue. The structure consisted of regularly arranged cells having struts with a vitreous carbon core with layers of CVI deposited crystalline tantalum. Microhardness values ranged from 240-393, compressive strength was 60 +/- 18 MPa, tensile strength was 63 +/- 6 MPa, and bending strength was 110 +/- 14 MPa. The compressive fatigue endurance limit was 23 MPa at 5 x 10(6) cycles with samples exhibiting significant plastic deformation. SEM examination showed cracking at strut junctions 45 degrees to the axis of the applied load. The cantilever bending fatigue endurance limit was 35 MPa at 5 x 10(6) cycles, and SEM examination showed failure due to cracking of the struts on the tension side of the sample. While properties were variable due to morphology, results indicate that the material provides structural support while bone ingrowth is occurring. These findings, coupled with the superior biocompatibility of tantalum, makes the material a candidate for a number of clinical applications and warrants further and continued laboratory and clinical investigation.
The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFTTM), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFTTM material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFTTM had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFTTM. The final conclusion is that in this model, grafting with COLLAGRAFTTM provided torsional properties at one year postoperatively at least equivalent to autogenous bone.
This research was designed to compare the in vitro fatigue performance of posterior teeth restored with Ketac-Silver, Amalgam, and 2-100, and an experimental reinforced glass ionomer (EXL-292, 3M) core buildbuildups and gold crowns subjected to compressive fatigue forces 45" to the occlusal surface. Fatigue was utilized to simulate the intra-oral function on a gold crown placed over a pin-retained core buildup. Microleakage at all interfaces was evaluated and the structural integrity of the fatigued material, the build-up/tooth interface and buildup/cement/gold crown system was evaluated by light microscopy.Analysis of the microleakage using the Mann-Whitney Utest, revealed no statistically significant difference (p < -05)between the Amalgam and the 2-100 groups, between the EXL-292 and the Ketac Silver groups, or between the Amalgam and EXL-292 groups. A significant difference existed between the following groups: (1) Amalgam and Ketac Silver, (2) Ketac Silver and 2-100 and (3) EXL-292 and 2-100. These results indicate that the EXL-292 material is equal to or better than three other commonly used materials in maintaining an adhesive seal preventing the influx of materials with a radius greater than Ca4' after 1 x lo6 cycles. Results of examination using light microscopy showed interfaces between the gold crowns, buildup material, and dentin, and porosity and cracking in the EXL-292 probably caused by air incorporation during mixing.
Two Synthes cervical spine plate designs were evaluated in single cycle bending and fatigue. The Synthes CP titanium anterior cervical vertebrae plate commonly referred to as CSLP was evaluated with three different screw types while the Synthes 316L stainless cervical vertebrae plate commonly referred to as OROZCO was evaluated in the same manner with one screw design. Single cycle bending was performed on three plates of each type using one screw type design. Fatigue testing was performed at 5 Hz in ambient air on each of the constructs and corresponding screw types.Bending strength and bending rigidity were calculated from the load vs. deflection plots of the single cycle testing. The general shape of the S/N curve was defined based upon number of cycles to failure at incremental load values.Examination of the data and plots revealed a difference between the stainless plate and the titanium plate. The CP titanium plate with each screw type proved superior to the stainless plate under the conditions tested.Scanning Electron Microscopy was performed to ascertain the mode of fracture.
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