Biomechanical evaluation of different hydroxyapatite coatings on titanium for keratoprosthesis

Stable tissue integration is important to keratoprosthesis (KPro). The aim of this study was to evaluate the tissue bonding ability of hydroxyapatite (HAp)-coated titanium KPro. The samples were divided into three groups: test groups (IBAD group and AD group) and Ti control. The coated samples had a HAp layer created by ion beam assisted deposition (IBAD) or aerosol deposition (AD). The surface characteristics were analyzed with SEM, AFM, and XRD. The samples were surgically inserted into the muscles of rabbits. Eight weeks after healing, the attachment to the tissue was tested with a universal test device. The three samples exhibited distinctive surface morphology. The force to remove the HAp implants from the muscles was significantly greater than that of Ti group (P < 0.01), with the AD samples requiring the greatest force (P < 0.01). After removal, SEM showed that the tissue was firmly attached to the surface of AD samples. Photomicrographs of the peri-implant muscles showed a layer of aligned fibrous tissue without severe inflammation. The AD samples had more fibroblasts. Results indicate that because of enhanced mechanical adhesion of soft tissue to the implants, HAp-coated Ti by AD is a suitable KPro skirt material.