Stability of Augmented Bone and Its Influencing Factors After Simultaneous Guided Bone Regeneration With Implant Placement in the Posterior Mandible: A Retrospective Study

To analyse the stability of augmented bone and its influencing factors after simultaneous guided bone regeneration (GBR) with implant placement in the posterior mandible. A total of 165 implants in 102 patients were included. General information, peri-implant soft-tissue parameters and complications were recorded. Cone-beam computed tomography images at preoperative (T0), immediate postoperative (T1), post-healing (T2) and the latest follow-up (T3) were collected. Buccal bone width, height, bone distance (BD) and augmented bone volume (ABV) were assessed. Bone augmentation range was classified into inside-contour (IC) group and outside-contour (OC) group based on BD values. Factors influencing the augmented bone volume resorption rate (ABV%) were analysed. During the follow-up period of 12-88 months, the mean ABV% was 47.56% ± 20.29%, predominantly occurring between T1 and T2. The OC group showed higher ABV% compared to the IC group (p < 0.001). BD of the IC and 0-1 mm OC groups was less than 0, while BD of the 1-2 and > 2 mm OC groups was near 0 at T3. Bone augmentation range (p < 0.001), non-contained defects (p = 0.001) and 2-mm healing abutments (p = 0.008) significantly influenced ABV%. Simultaneous GBR with implant placement in the posterior mandible provided predictable volumetric stability of the augmented bone. OC grafts resorbed towards individual phenotypical dimensions, whereas 1-2 mm over-augmentation might optimise contour maintenance. Non-contained defects compromised volumetric stability, while the 2-mm healing abutments enhanced stability compared to cover screws.