three year analysis of peri implant bone level after allogenic bone block augmentation

Purpose:  Allogenic bone blocks may be utilized as an alternative pre-implant augmentation procedure for the reconstruction of deficient alveolar bone in cases, in which the transplantation of autogenous bone is impossible or not desired. The present study investigates radiologically detectable changes of peri-implant bone level around dental implants placed into allogenic bone- block augmentations compared to implants placed into non-augmented bone. Material and methods:  14 patients of the study-group received 40 allogenic bone-blocks and 60 implants in both, maxilla and mandible in a two-step approach. The human study was approved by the ethics-commission of the Wilhelms-Universitat Munster, Germany. Radiologic examinations were carried out directly after implant insertion, after prosthetic restoration plus one and three years after prosthetic loading. All radiographs were digitalized, calibrated and measured computer- assisted. The control group contained 14 patients who had received 53 implants without augmentation. Data of the two groups were compared statistically, using the non-parametric Wilcoxon-test (α=0.05/4=0,0125). The two primary end-points of the study were defined as a)  total bone loss 3 years after prosthetic loading and b)  bone loss in the years 2 and 3 after prosthetic loading Results:  The radiological peri-implant bone loss at the distal sites after 36 months was 0.72 mm in the study group (median; 25-Q: 0.27 mm; 75-Q: 1.11 mm) and 0.37 mm in the control group (25-Q: 0.15 mm; 75-Q: 0.71 mm). The difference between the groups is statistically significant (p=0.004). At the mesial sites (study-group: 0.52 mm; control-group: 0.41 mm; p=0.179) and at all other examination intervals the differences between the two groups were not significant. Neither did we find any statistically significant differences within the study-group between implants placed in the maxilla versus the mandible or in the anterior versus the posterior region. Conclusion:  Loss of peri-implant bone around dental implants with previous allogenic bone block augmentation seems to be slightly greater compared to implants placed into native bone. However, the detected median values for both groups are within the physiological range and are in accordance with data recently published for implants with autogenous bone grafts, GBR and without augmentation. Keywords: Allogenic; Allogeneic; Alveolar bone; Atrophy; Augmentation; Bone block; Clinical-controlled study; Dental implant; Peri-implant bone level; Radiological study