Effects of calcium ions on titanium surfaces for bone regeneration.

The chemistry and topography of implant surfaces are of paramount importance for the successful tissue integration of load-bearing dental and orthopedic implants. Here we evaluate in vitro and in vivo titanium implant surfaces modified with calcium ions (Ca(2+) surfaces). Calcium ions produce a durable chemical and nano-topographical modification of the titanium oxide interface. Time of flight secondary ion mass spectrometry examination of the outermost surface composition, shows that calcium ions in Ca(2+) surfaces effectively prevent adventitious hydrocarbon passivation of the oxide layer. In aqueous solutions Ca(2+) surfaces release within the first minute, 2/3 of the total measured Ca(2+), the rest is released over the following 85 days. Additionally, Ca(2+) surfaces significantly increase human fetal osteoblasts-like cell adhesion, proliferation and differentiation, as measured by the autocrine synthesis of osteopontin. Relevant for clinical application, after 12 weeks of healing in sheep tibia, microcomputer tomography and histomorphometric analysis show that Ca(2+) surfaces develop significantly more bone contacts and higher bone density in the 1mm region around the implant. Consequently, titanium implants modified with calcium ions represent a valuable tool to improve endosseous integration in the clinical practice.