Objectives: The aim of this study was to evaluate marginal bone resorption at two different implant shapes focussing on differences between high recruiting implant centers and low recruiting implant centers. Materials and Methods: Inclusion criteria were two missing teeth in the lower jaw distal of the incisor. No augmentation procedures and a planned fixed restauration. In all patients one straight Astra implant (3.5 or 4.0 mm) and one conical Astra (4.5 or 5.0 mm) were inserted. 18 centers participated and included 125 patients with 318 implants. Panoramic X-ray images were taken at 5, 12 and 24 months. Results: Mean insertion depth at implant insertion was 0.18 mm subcrestal for straight implants and 0.27 for conical implants. One implant loss was observed. The table lists mean radiologic bone resorption in mm: 6 months12 months24 months Implant shape:Straight implants0,830,830,96 Conical implants0,710,630,95 Center:=15 implants0,710,611,46 > 15 Implants0,830,790,81 Schlagwörter: Astra Tech, marginal bone resorption, high recruiting implant centers, low recruiting implant centers