Element provides mechanical and metallurgical testing for porous coating and porous structure medical devices, including resorbable blast media (RBM), titanium plasma spray (TPA), hydroxyapatite (HA), electron beam melting (EBM) and direct metal laser sintering (DMLS).
A porous coating is often applied to medical devices to enhance the fixation of an implant. Newer technologies also allow direct integration of porous structures in the base materials of devices. In order to bring an implant with a porous structure to market, there are a number of tests that must be performed to verify the mechanical and metallurgical properties of the coating. These tests are beneficial in satisfying FDA or regulatory requirements, helping with research and development of new coating processes and technologies, and providing insight to compare or validate coating suppliers.
Mechanical Testing of Porous Structures
Mechanical tests include abrasion along with static and dynamic tension, shear, and bending. These tests are performed on specially-made porous structure test samples, which vary depending upon the test method.
For shear testing, the sample consists of a metallic cylinder that has a 0.75” outer diameter and a 1 to 1.25 inches in length, with the porous coating adhered to one flat side of the metal. The coated specimen is attached to an uncoated specimen and then loaded in shear either statically until failure or dynamically to a predetermined cycle count.
Tensile testing of a porous structure uses a test assembly made up of a disc-shaped sample with one side coated and one uncoated, and bonded between two test fixtures. The test specimen, with a 1” outer diameter, is exposed to a tensile load until failure, meaning the components have separated.
Abrasion testing is critical for porous structures, as poor integrity can have adverse effects in-vivo. The most commonly performed test is Taber abrasion, which consists of a circular porous coating sample which is repeatedly contacted by an abrasive wheel. Results can be used for comparative purposes when evaluating coating types of suppliers or compared to general acceptance criteria set by a regulatory agency
Rotating Beam Fatigue (ASTM F1160)
Rotating beam testing consists of an hourglass-shaped, coated rod which is loaded about its long axis as a beam. During testing, the specimen’s surface material is subject to the greatest amount of stress, making this an ideal test for determining properties of a porous structure.
Coefficient of friction
Coefficient of friction testing consists of measuring both the static and dynamic frictional forces between a porous structure and either polyurethane bone analog, animal tissue, or human donor tissue. Static resistance is the force that is required to initiate motion, while dynamic resistance is the frictional force required to maintain motion. We perform coefficient of friction testing to internal procedures or client protocols.
Metallurgical Testing of Porous Coatings
Element’s metallurgical laboratories perform a variety of evaluations on porous coating samples, including coating thickness, coating surface roughness, volume percent void, and morphology of pores.
Stereological Evaluation (ASTM F1854)
These test methods examine the various porous coatings adhered to nonporous medical implants. Substrates are evaluated using a digital image analysis system and custom software programming to determine the coating thickness, volume and percent void (between tissue interface and substrate interface).
Our metallurgical evaluation tools
- Stereomicroscope - capable of evaluating specimens from 5X - 50X
- Metallographic microscope - capable of evaluating specimens from 50X - 1000X
- Digital microphotography – capable of evaluating specimens from 5X-2500X
- Digital image analysis software for fast and efficient analysis
- Specimen mounting and polishing equipment
- Microetching capability with a variety of chemical etchants
- Low-speed diamond saws for precise, low-stress, low-heat sectioning
- SEM services available for higher magnification analysis
Our trusted medical device testing allows your company to mitigate risk knowing that we are working diligently to help ensure your success and bring a safe product to market. For more information about porous coating testing or to request a quote, contact us today.
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