Preliminary tribological results of a new total temporary hip joint prosthesis spacer.

Temporary antibiotic-loaded cement spacers are widely used for treating chronic periprosthetic hip infections. The aim of this study is to evaluate the short-term tribological performance of ultra-high-molecular-weight polyethylene (UHMWPE) and (60Co) gamma-irradiated cross-linked UHMWPE (XLPE) self-mated systems as frictional pairs for temporary total hip spacers. A three-axial hip joint simulator, FIME II, was used to test the UHMWPE and XLPE self-mated systems under variable load profiles. A fetal bovine serum solution was used as a lubricant. After simulation tests, wear measurements of damaged coupled surfaces were made with a coordinate measuring machine. Finally, surfaces were characterized with scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and nanoindentation tests. The mass loss test results for UHMWPE were 11.91 ± 3.43 mg for the cups and 4.57 ± 0.92 mg for the heads. Whereas, the results for XLPE showed a significant reduction, with mean mass loss values of 6.59 ± 0.14 mg for the cups and 2.82 ± 0.59 mg for the heads, suggesting the viability of the self-mated XLPE contact pair for a temporary total hip spacer.

The effect of diameter, length and elastic modulus of a dental implant on stress and strain levels in peri-implant bone: A 3D finite element analysis.

This study investigated the effect of three different parameters of a dental implant on stress and strain values in the peri-implant bone by finite element analysis. In this work, the effect of diameter, length and elastic modulus on the biomechanical behavior of a new dental implant was simulated using the finite element method. A three-dimensional model of a mandible segment corresponding to the premolar region and twelve dental implant models were obtained. Loads in three directions were distributed on the surface of the coronal area of the dental implants. The dental implant models were obtained in the FreeCAD 0.16 software and the simulations were made using the Abaqus/CAE software. In all cases, higher stress concentrations were obtained in the peri-implant cortical bone between 40.6 and 62.8 MPa, while the highest levels of strain were observed in the peri-implant trabecular bone between 0.002544 and 0.003873. In general, the highest von Mises equivalent stress values were observed in the peri-implant cortical bone. However, in this bone, both the maximum von Mises equivalent stress values and the von Mises strain are similar or inferior to those reported in different studies by finite element for other models of dental implants under immediate loading. Maximum von Mises strain values were observed in peri-implant trabecular bone. However, in this bone strains levels were obtained that maintain bone density or increase it. The effect of the three simulated variables (implant diameter, length, and elastic modulus) have a statistically significant influence on the von Mises equivalent stress and in von Mises strain values.