Abstract
Introduction
Cementless arthroplasty has been widely used for younger patients with osteoarthritis and other joint pathology. Cementless arthroplasty will be required to porous surface which is to similar to the trabecular bone for bone ingrowth. Titanium Plasma Spray (TPS) has been worldwide used for the porous coating method on arthroplasty. However, TPS coating is limited that would not to establish optimal porosity for bone ingrowth due to arbitary position of melted powder by plasma gas on substrate. Therefore, it is reported coating detached from its substrate (i.e. arthroplasty) is induced implant loosening. Thus, a novel Laser-aided Direct Metal Tooling (DMT) based on Additive Manufacturing (AM) was developed to overcome these limitations. In this study, we were done to assess stereological analysis, static tensile, shear, abrasion test, and physical analysis for evaluation of the efficacy of DMT which was newly-developed coating technology. Then, mechanical characteristics of DMT coating were compared to commercial TPS coating's.
Materials and Methods
First, porosity of the DMT coating was evaluated using Microphotography and Scanning Electron Microscopy (SEM), as described in Figure 1. Static tensile and shear test for assessment of mechanical characteristic in relation to the DMT and TPS coating specimens were conducted on the basis of ASTM F1147 and F1044 using universal testing machine (Endolab®, Servohydraulic Test Frame, DE). Maximum tensile strength and maximum shear strength were evaluated for each specimen (n=5). Abrasion test was performed based on ASTM F1978 using Taber® Rotary Platform Abraser Model 5135 (TABER®Industries, USA). Abrasion losses for each specimen (n=6) were measured at 2, 5, 10, and 100 cycles, respectively.
Results
Porosity of the DMT coating was found to be 64 ± 11%. Maximum tensile strength (mean ± SD) of the DMT coating (48.6 ± 4.3 MPa) was lower than TPS's (51.5 ± 11.6 MPa) about 5.6%, but detached position of one of the TPS specimens was observed at coating layer not in adhesive layer. Maximum shear strength of the DMT coating (46.3 ± 1.9 MPa) was 10.2% higher, compared to TPS's (42.0 ± 0.6 MPa). Abrasion losses of the DMT (2 cycles, 1.0 ± 0.5 mg; 5 cycles, 2.5 ± 0.9 mg; 10 cycles, 4.2 ± 0.7 mg; 100 cycles, 20 ± 1.4 mg) were significantly higher (71.9% – 77.8% higher) than that of TPS's (2 cycles, 4.5 ± 1.4 mg; 5 cycles, 9.8 ± 2.8 mg; 10 cycles, 17.0 ± 3.4 mg; 100 cycles, 71.1 ± 4.2 mg), as shown in Figure 2. Roughness of the DMT coating was Ra 62.5 ± 2 μm, Rz 316.1 ± 8.1 μm which were 33.5%, 40.6% (Ra, Rz sequence) higher than that of TPS coating (Ra 46.8 ± 8.9 μm, Rz 224.9 ± 28.8 μm), as shown in Figure 3.
Conclusions
Our results suggested that a novel DMT coating technology was feasible to apply coating method on the surface of the arthroplasty in terms of outstanding mechanical characteristics which were compared to commercial TPS coating.
