The allogeneic shell technique for alveolar ridge augmentation: a multicenter case series and experiences of more than 300 cases

Abstract

Purpose Allogeneic cortical bone plates (CP) might be used for alveolar ridge augmentation as an alternative to autogenous grafts (AG) and bone substitutes (BS). We report about a multicenter case series and our experiences of more than 300 cases using CP and the shell technique for reconstruction of the alveolar process to illustrate surgical key steps, variations, and complication management. Methods Different types of alveolar ridge defects were augmented using the shell technique via CP. The space between the CP and the alveolar bone was filled with either autogenous or allogeneic granules (AUG, ALG) or a mixture of both. Implants were placed after 4–6 months. Microscopic and histological assessments were performed. In addition, space filling using AUG, ALG and bovine BS was discussed. Results Scanning electron microscopy demonstrated the compact cortical structure of CP and the porous structure of ALG allowing micro-vessel ingrowth and bone remodeling. Histological assessment demonstrated sufficient bone remodeling and graft resorption after 4–6 months. In total, 372 CP cases and 656 implants were included to data analysis. The mean follow-up period was about 3.5 years. Four implants failed, while all implant failures were caused by peri-implantitis. Next, 30 CP complications were seen, while in 26 CP complications implant placement was possible. CP rehydration, stable positioning by adjusting screws, smoothing of sharp edges, and a tension-free wound closure were identified as relevant success factors. Space filling using ALG and a mixture of AUG/ALG resulted in sufficient bone remodeling, graft resorption and stability of the augmented bone. Conclusions CP and the shell technique is appropriate for alveolar ridge augmentation with adequate bone remodeling and low complication rates. Allografts can prevent donor site morbidity and therefore may decrease discomfort for the patient.

Bone reconstruction of extensive maxillomandibular defects in adults

“…138,142,143 Also, three-dimensional printed templates and rigid resorbable barrier systems were reported as being applied as shells. 142,[144][145][146][147] Like meshes, the shells are stable over the long term, and even complex defects can be reconstructed precisely using two or more bone shells. 148 The main complication constitutes dehiscences, which can be an even more frequent problem in extended augmentations 141 ; in cases of autogenous shells taken from the ramus, a similar complication rate was reported.…”

“…Another way to stabilize the particulate graft materials to reconstruct significant bone defects is the shell technique, which can be performed using autogenous or allogeneic cortical plates in different alveolar ridge defects 136–141 . In brief, a thin cortical block (“shell”) is used to create a three‐dimensional, secluded, stable space filled with autologous bone and/or a bone substitute material, enabling osseous regeneration (Figure 7).…”

“…Like meshes, the shells are stable over the long term, and even complex defects can be reconstructed precisely using two or more bone shells 148 . The main complication constitutes dehiscences, which can be an even more frequent problem in extended augmentations 141 ; in cases of autogenous shells taken from the ramus, a similar complication rate was reported 149 . Unfortunately, the shell technique is mostly reported for considerably more minor defects (< 3–4 mm), and studies on more extensive reconstructions are scarce, even although these are biologically possible 150–154 .…”

“…[136][137][138][139][140][141] In brief, a thin cortical block ("shell") is used to create a three-dimensional, secluded, stable space filled with autologous bone and/or a bone substitute material, enabling osseous regeneration (Figure 7). 138,142,143 Also, three-dimensional printed templates and rigid resorbable barrier systems were reported as being applied as shells. 142,[144][145][146][147] Like meshes, the shells are stable over the long term, and even complex defects can be reconstructed precisely using two or more bone shells.…”

Platelet Rich Fibrin for rehydration and pre-vascularization of an acellular, collagen membrane of porcine origin

“…Still, in clinical use, they are rigid, requiring additional mini-screws or pins for stabilization, and must be removed in a follow-up procedure before de nitive restoration. In addition, gingival recessions and membrane exposure can occur during the healing process, resulting in wound infection and subsequent early removal of the membrane [5,10]. Here, biodegradable materials improved the clinical outcome without requiring a second intervention to remove the foreign material.…”