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Background Demographic change is leading to an increase in the number of osteoporotic patients, so a rethink is required in implantology in order to be able to guarantee adequate anchoring stability in the bone. The functional modification of conventional standard screw implants using superelastic, structured Ti6Al4V anchoring elements promises great potential for increasing anchoring stability. Methods For this purpose, conventional screw implants were mechanically machined and extended so that structured-superelastic-positionable-Ti6Al4V anchoring elements could be used. The novel implants were investigated with three tests. The setup of the anchoring elements was investigated in CT studies in an artificial bone. In a subsequent simplified handling test, the handling of the functional samples was evaluated under surgical conditions. The anchorage stability compared to standard screw implants was investigated in a final pullout test according to ASTM F543—the international for the standard specification and test methods for metallic medical bone screws. Results The functionalization of conventional screw implants with structured superelastic Ti6Al4V anchoring elements is technically realizable. It was demonstrated that the anchoring elements can be set up in the artificial bone without any problems. The anchorage mechanism is easy to handle under operating conditions. The first simplified handling test showed that at the current point of the investigations, the anchoring elements have no negative influence on the surgical procedure (especially under the focus of screw implantation). Compared to conventional standard screws, more mechanical work is required to remove the functional patterns completely from the bone. Conclusion In summary, it was shown that conventional standard screw implants can be functionalized with Ti6Al4V-structured NiTi anchoring elements and the new type of screws are suitable for orthopedic and neurosurgical use. A first biomechanical test showed that the anchoring stability could be increased by the anchoring elements.

The aim of this 10-year clinical trial was to evaluate the treatment outcome (condition of hard and soft peri-implant tissues, patient satisfaction, surgical and prosthetic aftercare) of mandibular overdentures supported by two or four implants.Sixty edentulous patients with a mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture supported by four IMZ implants (group B). Standardised clinical and radiographic parameters were evaluated 6 weeks after completion of the prosthetic treatment and after 1, 5 and 10 years of functional loading. Prosthetic and surgical aftercare was scored during the evaluation period, as well as patient satisfaction.There were no statistically significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues between the groups. In addition, no differences in satisfaction and aftercare were observed between the groups.There is no difference in the clinical and radiographical state of patients treated with an overdenture on two or four implants during a 10-year evaluation period. Patients of both groups were evenly satisfied with their overdentures and received the same amount of aftercare. For reasons of cost-effectiveness, a two-implant overdenture is advised for patients with a Cawood classes IV-VI resorption of the mandible and complaints concerning retention and stability of the lower denture.To cite this article:Meijer HJA, Raghoebar GM, Batenburg RHK, Visser A, Vissink A. Mandibular overdentures supported by two or four endosseous implants: a 10-year clinical trial.Clin. Oral Impl. Res. 20, 2009; 722-728.doi: 10.1111/j.1600-0501.2009.01710.x.