A prospective clinical trial of single Astra Tech 4.0 or 5.0 diameter implants used to support two-unit cantilever bridges: results after 3 years

Objective: To evaluate the use of a single Astra Tech implant to support a two-unit cantilever fixed dental prosthesis. Materials and method: Twenty-nine subjects with an edentulous space (at least equivalent to two bicuspid units) in the premolar/molar segments of the maxilla or mandible with opposing natural teeth or a fixed/removable prosthesis were treated. They were provided with either a 4 or 5.0mm diameter fixture MT OsseoSpeed. Prostheses were constructed using a cast-to abutment as a one-piece unit with porcelain fused to precious metal to allow direct screw retention. Results: Subjects expressed a high satisfaction with treatment, including appearance and function. The most important complication was abutment screw loosening. It occurred as a single episode in four subjects and in another six subjects the loosening was recurrent. Bone levels were stable and there were no significant differences in radiographic bone height between cantilever and non-cantilever sides of the implant at any time point. Conclusion: Single implants can be successfully used to support two-unit cantilever FDPs in the premolar region. A common factor could not be identified in relation to abutment screw loosening.