Titanium-Zirconium: A novel Material for Dental Implants

INTRODUCTION: The choice of implant material has a high impact on the resulting mechanical and biological properties. Pure titanium is known for its biocompatibility and its resistance to corrosion. However, its mechanical properties are limited in the case of small diameter implants. A new material for dental implants with the brand name “Roxolid” was developed to overcome the mechanical limitations of pure titanium. PHYSICAL, CHEMICAL & BIOLOGICAL PROPERTIES: The new material is composed of the two elements titanium and zirconium. This binary TiZr alloy has a significantly increased mechanical stability compared to titanium grade 4 with respect to elongation and fatigue strength. Internal measurements show that the ultimate tensile strength is comparable to Ti-6Al-4V. The TiZr implants are manufactured with the SLActive surface like the titanium SLActive implants: Sand blasted, acid etched and then stored in 0.9% NaCl solution in order to maintain the clean oxide layer with its hydrophilic properties. The TiZr SLActive implants have a water contact angle of 0° like the Ti SLActive implants. The scanning electron micrographs in figure 1 show that the same surface structure is obtained on both materials. In general, the SLActive surface has a significantly improved osseointegration compared to the conventional SLA implants packed and stored under ambient conditions. Many metals are known to strongly inhibit growth of osteoblasts (e.g. V and Nb), whereas Ti and Zr do not [1]. Therefore Ti and Zr have preferred osseointegration capabilities. In a biomechanical and histological study in the mandible of 12 miniature pigs Ti SLActive and TiZr SLActive were compared using specially designed implants for removal torque (RT) measurement and bonechamber implants for histological observations. After 4 weeks of healing, RT evaluation indicated significantly higher values (p = 0.02) for TiZr (230.9 ± 22.4 Ncm) in comparison to Ti (204.7 ± 24 Ncm). Histology (toluidine blue) showed that new bone of woven type with a noticeable area of composite bone was invariably present inside the Ti and TiZr implant chambers. Bone trabeculae originating from the edges of the experimental defect followed the osteoconductive surface of the chamber towards its most centripetal aspect. Early stages of haversian systems formation were noticed driven by the presence of mature vessels. The histomorphometry showed a bone to implant contact (BIC) of 75.4 ± 21.3 % for Ti and 74.6 ± 15.3 % for TiZr and a bone density of 50.4 ± 19.1% for Ti and 47.2 ± 12.3 % for TiZr.