In vitro and in vivo degradation of biomimetic octacalcium phosphate and carbonate apatite coatings on titanium implants

Abstract

Calcium phosphate (Ca-P) coatings have been applied onto titanium alloys prosthesis to combine the srength of metals with the bioactivity of Ca-P. It has been clearly shown in many publications that Ca-P coating accelerates bone formation around the implant. However, longevity of the Ca-P coating for an optimal bone apposition onto the prosthesis remains controversial. Biomimetic bone-like carbonate apatite (BCA) and Octacalcium Phosphate (OCP) coatings were deposited on Ti6Al4V samples to evaluate their in vitro and in vivo dissolution properties. The coated plates were soaked in alpha-MEM for 1, 2, and 4 weeks, and they were analyzed by Back Scattering Electron Microscopy (BSEM) and by Fourier Transform Infra Red spectroscopy (FTIR). Identical coated plates were implanted subcutaneously in Wistar rats for similar periods. BSEM, FTIR, and histomorphometry were performed on the explants. In vitro and in vivo, a carbonate apatite (CA) formed onto OCP and BCA coatings via a dissolution-precipitation process. In vitro, both coatings dissolved overtime, whereas in vivo BCA calcified and OCP partially dissolved after 1 week. Thereafter, OCP remained stable. This different in vivo behavior can be attributed to (1) different organic compounds that might prevent or enhance Ca-P dissolution, (2) a greater reactivity of OCP due to its large open structure, or (3) different thermodynamic stability between OCP and BCA phases. These structural and compositional differences promote either the progressive loss or calcification of the Ca-P coating and might lead to different osseointegration of coated implants.

Clinical Evaluation of Anodized Surface Implants Submitted to a Counter Torque of 25 Ncm After 60 Days of Osseointegration: Study in Humans

“…It influences not only the quality and the quantity of bone formation but also the speed of both bone formation and implant binding [29]. The main factors that allow for faster osseointegration are the nano-topography of the surfaces and the chemical modification resulting from the incorporation of calcium and phosphate ions [3][4][5][12][13][14][15][16][17][18][19].…”

“…To ensure fibrin retention, several texturization techniques may be utilized, such as etching, etching followed by acid texturing, acid texturing associated with fluorine deposition and anodization [7,11]. Further, anodization is another important factor for faster osseointegration because it incorporates Ca and P ions on the implant surface [3][4][5][12][13][14][15][16][17][18][19].…”

The impact of octacalcium phosphate on the dynamics of bone matrix formation in experimental bone defects

“…На остеоиндуктивные свойства ОКФ указывали ряд ав-торов [4,5,7,10,13,18]. Исследования in vivo показали, что синтетический ОКФ в мышечных (S. Ban и соавт., 1992), подкожных [20] тканях и на различных костных участках [10,19,20] превращается в биологический апатит.…”

“…Также было показано, что вслед за резорбцией ОКФ происходит его замещение новой костью [8,10]. Кроме того, было обна-ружено, что покрытие ОКФ на дентальных имплантатах способствует активной остеоинтеграции [4,5], стимулирует пролиферацию остеобластных клеток [6], а в ряде случаев способствует эктопическому остеогенезу [7,21].…”

Concurrent elution of calcium phosphate and macromolecules from alginate/chitosan hydrogel coatings

“…Although the exact mechanisms responsible for their good biocompatibility are still the subject of intense investigation, it has been shown that calcium phosphate ceramics undergo resorption, subsequent remodeling, and biomineralization. [10][11][12][13][14][15] More specifically, it is the increased local concentration of calcium and a͒ Author to whom correspondence should be addressed; Present address: Molecular and Health Technologies, CSIRO, Bag 10, Clayton South MDC, VIC 3169, Australia; electronic mail: ping.peng@csiro.au phosphate ions from the resorbing calcium phosphates that is considered to be conducive to new bone formation. 16 The concurrent release of calcium and phosphate ions as well as bioactive molecules such as growth factors may offer additional possibilities for the control of orthopaedic wound healing.…”