The aim of this study is to describe the treatment outcome after alveolar ridge augmentation in the atrophic posterior mandible by segmental sandwich osteotomy combined with an interpositional autograft prior to placement of endosseous implants. Thirteen consecutive patients (five males, mean age 48 years, and eight females, mean age 61 years) were included in this study. The postoperative course was uneventful in six patients. Sensory disturbances in the mental nerve were found in five patients, all of them with hypoaesthesia. None of these patients complained of permanent sensory disturbances. Vertical gain ranged from 2.0 to 7.8 mm (mean value 4.61 mm). Horizontal gain ranged from 2.0 to 6.3 (mean value 3.42 mm). A total of 41 implants were placed in 22 surgical sites, 12 weeks after bone reconstruction. In conclusion, segmental mandibular sandwich osteotomy is recommended to meet the dimensional requirements of preimplant bone augmentation in atrophic posterior mandible.
A number of factors have to be considered prior to implant placement in the severely atrophied posterior mandible. They include the dimensional hard tissue problem at the implantation site (which creates an unfavourable crown/implant ratio leading to mechanical failure of the implant system), distance to the inferior alveolar nerve, the amount of keratinized gingiva, and the situation of the mobile mucosa with respect to the alveolar crest . A dimensional change of the bone resulting from augmentation techniques is associated with a healing period. In addition to the healing of the bone graft to the recipient site, there is often a need for soft tissue correction, usually after dental implant insertion. This requires attention to the interface between the surface of the augmented hard tissue site and the secondarily transplanted keratinized gingiva. A properly vascularized bone is necessary so that the mucosal graft and the dental implant have adequate biological surroundings. The aim of the present study was to assess if the technique proposed can meet the dimensional requirements of preimplant bone augmentation in the case of the severely atrophic posterior mandible and if it can provide a less invasive treatment approach.
Patients and methods
Thirteen consecutive patients (five males and eight females) from the Department of Oral and Maxillofacial Surgery, Hannover Medical School were included in this study. Their mean age was 48 years for males and 61 years for females. All patients showed atrophy in the posterior mandible and were treated by segmental mandibular sandwich osteotomy combined with an interpositional autograft. There were 22 surgical sites, involving four patients with one posterior edentulous area and nine patients with two posterior edentulous areas. The following enrolment criteria were fulfilled: patients were partially edentulous with atrophic mandibles in the posterior region, behind the canine region, with an estimated bone height of at least 4 mm above the mandibular canal and a transverse width of 3 mm minimum, measured using digital volume tomography (DVT); patients did not have medical or psychological problems that could impede graft or implant success ( Table 1 ).
|Patient number||Gender||Age||Donor site||Bone graft location||Follow-up graft (months)||Osteosynthesis||Number of dental implants|
|1||F||44||Lateral oblique line||Right
|2||F||55||Lateral oblique line||Right
|3||F||67||Lateral oblique line||Right
|4||M||39||Lateral oblique line||Left||14||No||2|
|5||M||64||Lateral oblique line||Right
|6||M||38||Lateral oblique line||Left||15||Only screws||1|
|7||F||54||Lateral oblique line||Right
|8||M||46||Lateral oblique line||Right
|9||F||67||Lateral oblique line||Right||18||No||2|
|10||M||53||Lateral oblique line||Right
|11||F||68||Lateral oblique line||Left||13||Yes||1|
|12||F||65||Lateral oblique line||Right
|13||F||68||Lateral oblique line||Right
The segmental mandibular sandwich osteotomy technique involved an elliptical incision 10–12 mm from the ridge bone in the labiobuccal gingiva of the edentulous area. A mucoperiosteal flap was raised without detaching the lingual and the crestal mucoperiosteum to expose the labiobuccal cortical bone of the posterior atrophic mandible and the mental nerve. Two vertical and one horizontal osteotomies were made with a piezoelectric surgical device (Piezosurgery, Mectron) ( Fig. 1 ). The horizontal osteotomy was located at least 2 mm below the ridge bone and approximately 1.5–2 mm above the mandibular canal. The vertical mesial osteotomy was made 2 mm distal to the last tooth and the vertical distal osteotomy was made based on the implant-graft treatment planning. The cranial fragment was not less than 2 mm thick. Using a small chisel, the osteotomy was completed by breaking the lingual cortical and the coronal bone fragment was carefully mobilized by rotation and elevation ( Fig. 2 ). The lateral aspect of the cranial segment was elevated more than the lingual aspect, producing a transverse width increase in addition to the vertical augmentation effect ( Fig. 3 ).
A block autograft was placed as an interpositional graft between the mobilized cranial fragment and the basal bone, and particulated autograft was placed in the gaps around the interpositional graft. The block bone grafts were harvested with a piezoelectric surgical device and the particulated autograft was harvested with the safescraper (Divisione Medicale Meta C.G.M. SpA., Villa, Italy). At two surgical sites only particulated bone harvested with a safescraper from the lateral oblique line was placed as an interpositional graft ( Figs 4 and 5 ). The intraoral grafts were taken from the lateral oblique. The cranial bone fragment was fixed to the mandibular base bone with two titanium miniplates and miniscrews (Synthes GmbH, Umkirch, Germany) at 15 surgical sites ( Fig. 6 ); only two miniscrews were used at one surgical site; and no fixation except for a stable interposition was used at six surgical sites. All grafts were covered with a porcine collagenous resorbable membrane (Bio-Gide, Geistlich, Wolhusen, Switzerland) ( Fig. 7 ). The flap was sutured in two layers, inner layer submucosal mattress sutures and outer layer suturing mucosa, with Vicryl 4-0 (Ethicon).
Antibiotic prophylaxis with penicillin 10 mega iv (Grünenthal GmbH, Aachen, Germany) at the moment of surgery and amoxicillin (Amoxicillin Rathiopharm GmbH, Ulm, Germany) 1000 mg every 8 h for 7 days, was prescribed postoperatively. Postoperatively, ibuprofen 600 mg every 8 h during the first 3 days was administered as a non-steroidal analgesic. Postoperative instructions included not allowing the use of dental prosthesis and oral hygiene with 0.2% chlorhexidine mouth rinse. Sutures were removed after 10 days, intraorally and at the donor site. Removable prostheses or provisional fixed prostheses were not allowed in the reconstructed areas for at least 2 weeks after surgery.
Under local anaesthesia, the miniplates and miniscrews were removed 12 weeks after the reconstructive procedure. Forty-one endosseous implants were placed using surgical templates ( Fig. 8 ).
Clinical evaluation was performed to assess complications at donor sites, the integration and resorption of grafts, and suitability for correct placement of endosseous implants. Clinical examination was carried out 10 days, 6 weeks and 12 weeks after augmentation and 10 days, 6 weeks and 12 weeks after implant placement. A radiological study was carried out with panoramic radiography before and immediately after graft augmentation, and with DVT (Newtom Deutschland AG, Germany) before surgery and 3 months after graft augmentation just before implant placement.
Vertical and horizontal bone augmentation was determined by analysing and comparing DVT immediately before and 3 months after augmentation. Vertical bone augmentation was measured from the upper border of the mental foramen to the upper border of the alveolar crest in the premolar region. In the molar region, it was measured from the upper border of the mandibular canal to the upper border of the alveolar crest, 10 mm posterior to the mental foramen. Horizontal bone augmentation was measured on the same mental region at the upper point of the alveolar crest.
Table 2 gives the results for patients treated by segmental mandibular sandwich osteotomy combined with interpositional autograft. Regarding bone grafts, the minimum and the maximum follow-ups were 5 and 18 months (mean 12.07 months). The postoperative course was uneventful in six patients. Sensory disturbances in the mental nerve occurred in five patients all of them with hypoaesthesia. None of these patients complained of permanent sensory disturbances. The maximum duration of these sensory disturbances was 6 weeks.
|Patient number||Implant position||Height gain (mm)||Width gain (mm)||Implant diameter (mm)||Implant length (mm)||Complications|