The human bone-oxidized titanium implant interface: A light microscopic, scanning electron microscopic, back-scatter scanning electron microscopic, and energy-dispersive X-ray study of clinically retrieved dental implants

Background: Surface modification of titanium implants by anodic oxidation may lead to enhanced bone integration. For instance, in vivo studies have demonstrated formation of more bone contacts in less time than for turned control implants. In addition, oxidized implants have shown a higher resistance to torque forces, indicating a strong interlock between bone and the oxide layer. However, the structure of the oxidized titanium-bone interface in high resolution is not known. Purpose: The aim of the study was to analyze the human bone-oxidized titanium interface at a high-resolution level. Of particular interest was the relationship between bone tissue and the pores of the surface oxide. Materials and Methods: Twelve clinically retrieved implants with an oxidized surface (TiUnite(TM), Nobel Biocare AB, Goteborg, Sweden) were used. Seven were regular dental implants and five were experimental mini-implants and had been subjected to immediate, early, or no loading. They were retrieved after 5 to 9 months of healing and were processed and analyzed using light microscopy, scanning electron microscopy (SEM) in normal and back-scatter (BS-SEM) modes, and energy-dispersive x-ray (EDX) analysis techniques. Results: Bone formation was observed to occur from adjacent bone structures toward the implant surface, and it was evident that bone formation had occurred at the implant surface. SEM, BS-SEM, and EDX revealed that mineralized bone had grown into the pores of the surface oxide layer, including pores with small diameters (< 2 mu m). Conclusions: The clinically retrieved oxidized implants showed evidence of bone growth into the pores of the surface oxide layer. The findings indicate the establishment of a strong interlock between the bone and the oxidized titanium implant, which is suggested to be beneficial for clinical performance.