Nucleation and growth of calcium-phosphate on Ca-implanted titanium surface

Calcium phosphate formation on Ca-implanted titanium surfaces is studied. Experimental results show that octacalcium phosphate (OCP) is the more energetically favorable phase to precipitate on the positively charged Ca-implanted titanium surfaces compared to hydroxylapatite (HA), especially with the existence of a large amount of CO32- ions. A solution-based cluster theory is employed to explain the process of the formation of calcium phosphate on the Ca-implanted titanium surfaces. Thermodynamic and kinetic calculations show that OCP is the kinetically favored phase to precipitate in the SBF solution than HA. The nucleation rate is much higher than that of HA, but HA is more stable thermodynamically. (c) 2005 Elsevier B.V. All rights reserved.