the extensive loss of the alveolar ridge and teeth in the posterior mandible presents a complex case for reconstruction . several augmentation techniques are currently utilized to create sufficient bone volume for predictable placement of endosseous implants in such cases . the numerous surgical approaches proposed consist of autogenous bone grafts , alloplastic materials 18 , and recently , alveolar distraction osteogenesis 9 . after tooth loss , the alveolar ridge undergoes a continuous resorptive process that is severely accelerated by denture wear 10 . this process is the most pronounced during the first 12  months after the tooth extractions 11,12 . extensive resorption of the alveolar ridge in a vertical direction may compromise implant placement and prosthetic rehabilitation . the continuing resorption of the alveolar ridge will eventually result in insufficient bone height superior to the ian , making dental implant placement impossible without performing augmentation of the alveolar bone in terms of height . the augmentation procedure above the ian provides sufficient bone for implant placement and allows for long - term successful restoration of missing teeth with implant - supported prosthesis . all the methods suggested should take into consideration patient - related issues , which consist of pain , swelling , sensory nerve disturbances , incidence of graft failure and resorption , and functional long - term restoration . the reconstruction of vertically atrophic posterior mandibles with onlay bone grafts has been well documented , but the results have not been promising . different donor sites ( symphysis menti , calvaria , iliac crest ) have been used as sources of autogenous bone . vermeeren and associates 13 demonstrated bone resorption up to 50% even when autogenous onlay grafts were used . rigid fixation of the graft material is imperative to prevent microrotation , which can result in nonunion or fibrous union of the graft material . the use of expanded polytetrafluoroethylene membranes is a treatment option for posterior mandibular reconstruction that has been used with varying degrees of success , as reported by various authors 15,16 . tinti and coworkers 17 commented that vertical augmentation is a highly sensitive technique , predictable only when the surgical protocol is followed strictly . vertical ridge augmentation of the atrophic maxilla and mandible by means of a titanium mesh and autogenous bone grafts has been used successfully and has gained popularity since its introduction 18,19 . the titanium mesh used must be fixed by titanium screws , and infection is a common complication 18 that may cause loss of grafted bone , resulting in failure . visor osteotomy was first described in 1975 by harle 20 to increase the absolute height of the atrophic edentulous mandible . in this technique , when the procedure is applied to vertical ridge augmentation in the posterior mandible , the mandible is split vertically and , unfortunately , the width of the ridge is reduced . the sandwich technique , which uses bone block graft positioned between osteotomized bony segments , was developed by schettler 21 in 1974 stoelinga and colleagues 22 combined the visor osteotomy and sandwich techniques to augment the severely atrophic edentulous mandible with success 22 . a 49-year - old female patient was presented with a bilaterally atrophic mandible and a need for implant therapy . a thorough radiographic examination using cone - beam tomography revealed mandibular ridges that were not suitable for immediate implant placement in terms of height ( 6.2  mm on the left side and 7.2 on the right side . the patient was suggested the augmentation of the ridge using an interpositional block of allogeneic bone under local anesthesia . the patient gave her written informed consent , and a preoperative radiograph ( fig.1a ) , computerized tomographic ( ct ) scan and cone - beam tomography of the left and right mandibular ridges were obtained ( fig.1b ) . the mucoperiostal flap was raised to expose the mental foramen , and the mental nerve was identified , this helps to design the horizontal bone cut . then , two other vertical bone cuts were performed on the extremities of the horizontal cut . the more mesial vertical cut was performed 2  mm away from the adjacent tooth . the bone segment was then raised upward to leave space for the bone graft ( fig.2 ) , with no disturbance of the lingual periosteum . an allogeneic bone block was inserted interpositionally and placed in the middle of the space formerly created without any fixation between the basal segment and the cranial segment ( fig.3a ) the remaining spaces in both ends were filled with particular bone graft ( fig.3b ) . the wound was then closed primarily with 4 - 0 vicryl u - shaped suture . a postoperative cone - beam x - ray and ct scan were obtained to assess the new vertical height of the mandible ( fig.4a and b ) . after 3  months of healing , a crestal incision on the attached gingiva was made . the mucoperiostal flap was detached and endosseous implants were inserted using the classical approach , two into the right side , and three in the left side of the mandible , measuring 4  mm in diameter and 10  mm in length . the primary stability was relatively high ( fig.5 ) , and allowed for placement of the healing abutments ( fig.6 ) . post surgical follow - up visits were carried out at months 1 , 3 , 6 , 12 , 18 , and 24 after the surgical procedure . at each follow - up procedure , after 2  years of follow - up , the patient s conditions were optimal , the hard and soft tissue did not show any changes . ( a ) allogenic bone block inserted interpositionally and placed in the middle of the space between the two bone segments . ( b ) cone - beam tomography of the new mandible heights after the surgical procedure . moderate to severe posterior mandibular atrophy was successfully treated with interpositional sandwich osteotomy bone grafts . this led to the successful placement of implants and fixed prosthetic implant restorations , thus allowing ever more patients to be considered for implant treatment . the technique , which has been recently revisited , permits dental rehabilitation in terms of raising the bone above the nerve , reshaping the alveolar crest , and normalizing the interocclusal distance and the crown - implant ratio .
key clinical messagethe continuing resorption of the alveolar ridge will eventually result in insufficient bone height superior to the ian , making dental implant placement impossible . 
 the augmentation procedure above the ian in terms of height provides sufficient bone for implant placement and allows long - term successful restoration of missing teeth with implant - supported prosthesis .