Bone is a living tissue. It continuously reproduces its structure and its growth depends partly upon the applied mechanical load. After an implant is inserted, the load equilibrium is disturbed, leading to bone resorption and the stress shielding phenomena. Aseptic loosening is the main contributor for hip prosthesis failure. The purpose of the study is to determine the effect of bone resorption on the stress values and hence obtain a better understanding of the behavior of the stress adaptive bone-remodeling. The bone material used for the analysis was assumed to be isotropic and linearly elastic, and the external loads applied comprised of a femoral head load and an abductor load. A Finite element computer program for evaluating the changes in bone's density and modulus was developed. The values of stress for bone, cement mantle in medial, and lateral positions of Total Hip Replacement (THR) are presented. The failure mechanisms of THR with bone resorption observed the implant loosening since stress is reduced.
This study aim to evaluate the effect of different angle on bone density estimation based on HU on CT and CBCT scanning. A phantom of jaw was scanned using CT and CBCT machine from different angle (0, 15 and 30 degrees). The data were transformed into DICOM format and loaded into MIMICS software for density measurement. The density was measured at 9.55 mm from cemento-enamel junction (CEJ) on every different angle scanning data. Then these data were grouped as Group A1, A2 and A3 for CBCT group (0, 15 and 30 degrees, respectively) and Group B1, B2 and B3 for CT group (0, 15 and 30 degrees, respectively). The differences between the groups and the references (0 degree scanning) are measured statistically using SPSS software. In the CBCT data, the density reading at 15 and 30 degrees are higher than 0 degree scanning (mean difference = -155.63±62.61, p=0.03, mean difference = -33.13±84.24, p=0.206 for 15 and 30 degrees scanning, respectively). In the CT data, the density at 15 and 30 degrees scanning is lower than at 0 degrees scanning (mean different: 84.49±46.76, p=0.09 and 15.09±23.61, p=0.532). The differences are not significant statistically. Compared with CT, the effect of different angle scanning on density estimation on CBCT is stronger. These results showed that different angle scanning produce more error on density estimation based on HU on CBCT compared with CT. This study demonstrated that the uses of a CBCT and CT for density monitoring to evaluate bone density of jaws are affected by angle scanning.
Surface topography and morphological behaviours are the important aspects in the application of surface bearing as it deals with the contact area of objects upon motion. Improved surface bearing will be set as an indicator for tribology behaviour to reduce the possibility of wear rate and reduce the friction of objects, respectively. Thus, in this study, the fundamental of micro bearing concept was imparted as the Ultra High Molecular Weight Polyethylene (UHMWPE), which is a low density filler, will float onto the surface of the composite system to become a solid lubricant upon curing. UHMWPE filler, which is commonly known for its dominant properties of high tendency to resist wear and has low coefficient of friction were fabricated alongside epoxy resin in the composite system to achieve the desired strength and durability to perform over time. However, there are limitations of UHMWPE during processing upon the dispersion of the fillers with the matrix particles due to epoxy resin that has relatively high in viscosity. Therefore, acetone has been selected as a diluent with ratio of 1:1/4, 1:1/3, 1:1/2, 1:1 to dilute the high viscosity epoxy resin. The surface profile measurement were examined using Alicona Infinite Focus and Polarised Optical Microscope. Based on the results observed, EpUPE3 (epoxy and UHMWPE with acetone ratio of 1:1/2) showed better surface distribution and morphology with relatively low value of surface roughness (Ra) which is 1.41 μm and low pseuodocolour value of surface height which is around 6.76-6.77 cm compared to other formulation ratio. In near future, these surface topography and morphological analysis are important to relate with tribological, physical and mechanical properties of the micro bearing layers for bearing applications, specifically.