Surgical procedure
The horizontal augmentation of the mandible was conducted using the modified shell technique.6 A crestal incision in the gingival margin followed by mesial and distal relief incisions were made to expose the defect (Fig. 3). The periosteum was carefully separated from the host bone on both the lingual and buccal sides in order to achieve proper soft tissue mobilization. Using a piezoelectric device, the cortical layer of the residual bone was perforated in order to create a bleeding recipient site, which accelerates the vascularization and vitalization of the allogenic grafting material (Fig. 4).7 The allogenic cortical strut was shaped with a diamond burr to match the defect and attached to the mandibular bone using titanium osteosynthesis screws (Fig. 5). As the cortical strut remains avital and implants need to be placed in vital bone to ensure proper osseointegration, the space between the cortical strut and the residual bone was filled with cancellous allogenic bone chips rehydrated in blood, which will eventually be remodeled into vital bone tissue (Figs. 6,-7).
Prosthetic procedureAfter the edges of the cortical strut were blunted, the surgical site was covered with a pericardium collagen membrane (Jason® membrane), which was adapted to the defect and fixed onto the ridge using titanium pins (Fig. 8). The fixation of the membrane is important, as it prevents both the displacement of the grafting material and irritation of the mandibular nerve (mental nerve). In order to prevent soft tissue perforation, an additional membrane was placed over the augmented ridge, and a combination of mattress and single-button sutures was used to maintain proper, tension-free wound closure (Fig. 9). A panoramic radiograph and two CBCT-scans were recorded to check the situation before and after the intervention in order to demonstrate the pronounced horizontal bone augmentation and assess changes in radiopacity and bone volume (Figs. 10-12).
Following 5 months of uneventful healing, the patient presented for the next procedure, which included the insertion of two fixed dental implants and simultaneous soft tissue thickening (Fig. 13). The previously placed incision lines were reopened in order to remove the titanium osteosynthesis screws used for cortical strut fixation (Fig. 14). Vital, bleeding and robust bone was found within the granule-filled space adjacent to the avital cortical strut, which was flush-mounted in the new formed bone tissue (Fig. 15). Horizontal bone gain was sufficient for stable and fully submerged implantation of the designated Straumann BLT implants with a torque value of 35 Ncm (Figs. 16-17). Subsequently, cover screws were inserted in the implants, and bone substance, which was being removed during placement of the pilot drill, was used for contouring around the implant shoulders (Fig. 18). Prior to wound closure, which was performed with double-sling sutures, a porcine collagen matrix (botiss mucoderm®) was placed over the augmentation site to thicken the soft tissue (Figs. 19-20). A radiographic control image was recorded in order to assess implant position and bone density within the augmented area (Fig. 21).
Following 3 months of healing, the thickened soft tissue presented a natural and healthy appearance, so that papilla shaping could be achieved by the installation of gingival formers to set the course for a positive aesthetic final outcome (Figs. 22-23). Well-conditioned soft tissue was found 5 weeks later when the gingiva formers were removed and the final prosthetic restoration was installed (Fig. 24).
