Mandibular Full-Arch Fixed Prostheses Supported on 4 Implants with Either Axial Or Tilted Distal Implants: A 3-Year Prospective Study

PurposeThis prospective study evaluated the clinical and radiographic outcome of distally cantilevered 4-implant-supported fixed mandibular prostheses (4-ISFMP) with distal implants either in axial or distally tilted direction. Material and MethodsForty-one mandibulary edentulous patients received acrylic veneered 4-ISFMP with casted framework. Based on distal implant placement direction patients were assigned to 2 groups: 21 patients with four (2 anterior/2 posterior) axial implants (axial-group I) and 20 patients with 2 anterior axial/2 distal tilted implants (tilted-group II). Patients were prospectively followed for 3 years by annual examinations of implants and prosthetic survival rates including assessment for biological and mechanical complications. Additionally, peri-implant marginal bone resorption [MBR], pocket depth [PD], plaque index [PI], bleeding index [BI] and gingival index [GI], and calculus index [CI] were evaluated at each annual follow-up. Results37/41 patients (19 axial-group I, 18 tilted-group II) and 148/164 implants were followed at the 1-, 2-, and 3-year evaluation (dropout rate: 11.8%) presenting no implant and denture loss (100% survival). The overall, MBR at year 1, 2, and 3 was 1.110.4 mm, 1.26 +/- 0.42 mm, and 1.40 +/- 0.41 mm, respectively, representing a significant (p<.001) continuing time depending annual reduction. MBR and PD did not differ between anterior and posterior regions in both groups or for anterior and posterior regions between the groups. PI and CI were significantly (p<.001) higher for implants in anterior regions than for posterior regions in both groups. Moreover, posterior implant regions showed significantly (p<.001) higher PI and CI for axial-group I than for tilted-group II over time. Biological and mechanical complications as well as GI and BI did not differ between the groups over a 3-year follow-up period. ConclusionFor clinical implant and prosthesis outcome no statistical significant mean differences were noted for distally cantilevered 4-ISFMP supported by distal implants placed in tilted or axial direction.