Microtomographic and histomorphometric evaluation of a new implant surface covered by nano-hydroxiapatite in a challenging bone model. In vivo study in rabbits

Abstract

Implant surface, among other factors, can influence osseointegration. The literature describes that changes in implant microtopography can optimize biological response and promote a better bone anchorage. Nanostructures applied to biomaterials have been proposed to provide higher values of osseointegration. Recently, a new implant surface with nanometric scale hidroxiapatite coverage (20NM thick) was launched on the market. Then, considering the development of new implant surfaces aiming quantitative and qualitative ossseointegration improvements, and otherwise the challenge in maximizing bone to implant contact in sites where bone is reconstructed/regenerated with biomaterials, the proposal of this in vivo study is to evaluate, in healthy rabbits submitted to sinus lift procedures, a new implant surface modified by the addition of nano-hidroxyapatite particles, by means of histomorphometric and microtomographic analisys. For that, 20 New Zealand adult male rabbits will be ramdonly divided in 2 groups of tem animals each, to be evaluated at 30 and 60 days post-operatively. The study will have split mouth design. After anesthesia and incision, two circular windows 6.5mm in diameter will be prepared in both sides of nasal bone. The sinus membrane of both maxillary sinus will be carefully elevated, and the sites for implant installation will be prepared 3mm anterior to the bone windows. Two mini implants will be installed (with surface treated by double acid etched or nano-hidroxyapatite) in the sinus of healthy rabbits (n=40, 2 implants per animal, 1 of each surface per sinus). The animals will be euthanized 30 and 60 days after surgery (10 animals in each time). The regions of maxillary sinus, containing the bone graft and the implants will be removed and fixated for tridimensional microtomographic evaluation (Bone-Implant contact - IS/TS; Tridimensional bone density - BV/TV; Trabecular separation - Tb.Sp; Trabecular Thickness - Tb.Th; Percentage of Closed Porosity - Po.Cl; Percentage of Open Porosity - Po.Op; Percentage of Total Porosity - Po.Tot) and calcified slides histological processing (histomorphometrical analysis of Bone-implant contact - BIC, and Bone área fraction occupancy - BAFO). Pre-statistical tests will be applied to the data to evaluate normality, and based on the results appropriate statistical tests will be selected to analyse diferences between and intra-groups groups in both time periods (30 and 60 days). For all analysis, p<0.05 will be considered. (AU)