Simultaneous vs. Staged Guided Bone Regeneration

The surgical approach was described in detail elsewhere [13 (link)]. Briefly, in both groups’ local anesthesia (4% articaine-hidrocloride with 0.0001% epinephrine - Ultracain DS Forte, Sanofi-Aventis, Paris, France), a midcrestal incision was placed on the keratinized mucosa with no. 15 blades (Aesculap, Braun AG, Tuttlingen, Germany). The midcrestal incision was continued intracrevicularly at the two adjacent teeth mesially and distally both buccally and orally with no. 15C blades. In case of posterior edentulism, the midcrestal incision line length was two-thirds of the entire surgical area, and one-third length was continued mesially to the neighboring two teeth. No vertical-releasing incisions were performed. A full-thickness buccal flap was reflected with elevators up to the MJ, followed by split-thickness mucosal flap preparation over the mucogingival line (MJ). Subsequently, the underlying periosteal layer was elevated from the bone surface. In the simultaneous group, 3.3-mm or 4.1-mm diameter bone level implants (Straumann AG, Basel, Switzerland) were placed in a prosthetically predefined position using surgical guides. No implants with 3.3-mm diameter were placed in molar positions. All implants were positioned supracrestally according to their preplanned prosthetic positions. A single-use disposable bone scraper (Safescraper, Osteogenics Biomedical, Lubbock, TX, USA) was used to harvest AP from the lateral surface of the adjacent alveolar ridge. Bone chips were mixed with BDX (Bio-Oss, Geistlich AG, Wolhusen, Switzerland) in a 1:1 ratio. The 1:1 mixture of AP + BDX was placed laterally and supracrestally to the alveolar ridge. A non-resorbable high-density PTFE (d-PTFE) membrane (Cytoplast, Osteogenics Biomedical, Lubbock, USA) was fixed with titanium pins (Frios Membrane Tacks, Dentsply, York, USA). Double-layer suturing was performed using 4-0 horizontal mattress sutures (Supramid, Braun AG, Tuttlingen, Germany) in order to cover the membrane with the periosteal layer, while 5-0 horizontal mattress and non-interrupted sutures (Supramid, Braun AG, Tuttlingen, Germany) were utilized to close the mucosal layer and to reach a tension-free wound closure. Sutures were removed after 14 days.
In the staged group, at 9 months, a split-thickness flap was elevated in the same way as described above. The titanium pins and the d-PTFE membrane were removed, and 3.3-mm or 4.1-mm diameter bone level implants (Straumann AG, Basel, Switzerland) were placed in a prosthetically predefined position using a surgical template (Fig. 1a–p). Also, in this group, no implants with 3.3-mm diameter were placed in molar positions. The flap was closed with horizontal mattress sutures and single interrupted sutures. Soft tissue augmentation was performed at the time of implant placement if the vertical dimension of the soft tissue thickness was less than 2 mm over the inserted implants. Two months later, in cases where less than 3-mm width of keratinized mucosa was present, palatal epithelialized free gingival grafts were harvested and placed. After another 2 months, implant uncovery was performed.Fig. 1

Case presentation of patient no. 11, (case no. 13 - left mandible) from the staged group. a Baseline CBCT scan, parasagittal section: 2 months after tooth extraction, horizontovertical alveolar defect. b Baseline CBCT scan, frontal section: 2 months after tooth extraction, horizontovertical alveolar defect. c Clinical view of edentulous mandible. d Split-thickness flap preparation. e Bovine-derived xenograft (Geistlich Bio-Oss) and particulate autogenous bone graft. f Adaptation of non-resorbable membrane (Osteogenics Cytoplast) over the composite graft. g Membrane fixation using titanium pins. h Double-layer suturing: tension-free periosteal layer closure with horizontal mattress sutures. i Mucosal layer closure with horizontal mattress and non-interrupted sutures. j Wound healing 2 weeks after surgery. k Postoperative CBCT scan: 9 months after GBR parasagittal section: vertical bone gain. l Postoperative CBCT scan: 9 months after GBR, frontal section: vertical and horizontal bone gain. m Membrane removal at 9 months reentry. n Optimal amount of hard tissue for implant placement. o Guided implant placement (Straumann bone level). p Prosthetically driven implant positioning

In the simultaneous group, membranes and titanium pins were removed at 9 months after the first surgery, and the implants were only uncovered if an adequate peri-implant soft tissue width (i.e., at least 3 mm) surrounding the implants was present (Fig. 2 a–n). Soft tissue augmentation was performed at the time of membrane removal if the peri-implant soft tissue thickness (vertical dimension) was less than 2 mm. The above described reconstruction of keratinized tissues was performed 2 months before the second-stage surgery only in cases without an adequate width and thickness or absence of keratinized tissue.Fig. 2

Case presentation of patient no. 4 (case no. 5 - right mandible) from the simultaneous group. a Baseline CBCT scan, parasagittal section: horizontovertical alveolar defect. b Baseline CBCT scan, frontal section: horizontovertical alveolar defect. c Clinical view of edentulous mandible. d Split-thickness flap preparation. e Guided implant placement, supracrestally positioned implant (Straumann bone level). f Adaptation of non-resorbable membrane (Osteogenics Cytoplast) over the composite graft. g Membrane fixation using titanium pins. h Double-layer suturing. i Postoperative intraoral X-ray. j Healed alveolar ridge 9 months after simultaneous GBR. k Membrane removal at 9 months reentry. l, m, n Optimal amount of hard tissue; previously placed distal implant is covered with hard tissue, additional implant placed mesially