Volume 39, Issue 6 , Pages 554-560, June 2010
Sandwich osteotomy for vertical and transversal augmentation of the posterior mandible
Article Outline
- Abstract
- Patients and methods
- Results
- Discussion
- Competing interests
- Funding
- Ethical approval
- References
- Copyright
Abstract
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 4.61mm). Horizontal gain ranged from 2.0 to 6.3 (mean value 3.42mm). 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.
Key words: sandwich osteotomy, alveolar ridge augmentation, atrophic posterior mandible, interpositional autograft, implant placement
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 crest1, 2, 5, 8, 16. 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 4mm above the mandibular canal and a transverse width of 3mm minimum, measured using digital volume tomography (DVT); patients did not have medical or psychological problems that could impede graft or implant success (Table 1).
Table 1. Clinical features of patients treated with segmental mandibular sandwich osteotomy.
| 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 Left | 12 | Yes | 5 |
| 2 | F | 55 | Lateral oblique line | Right Left | 10 | Yes | 4 |
| 3 | F | 67 | Lateral oblique line | Right Left | 12 | Yes | 3 |
| 4 | M | 39 | Lateral oblique line | Left | 14 | No | 2 |
| 5 | M | 64 | Lateral oblique line | Right Left | 13 | No | 2 |
| 6 | M | 38 | Lateral oblique line | Left | 15 | Only screws | 1 |
| 7 | F | 54 | Lateral oblique line | Right Left | 10 | Yes | 5 |
| 8 | M | 46 | Lateral oblique line | Right Left | 11 | Yes | 6 |
| 9 | F | 67 | Lateral oblique line | Right | 18 | No | 2 |
| 10 | M | 53 | Lateral oblique line | Right Left | 16 | Yes | 4 |
| 11 | F | 68 | Lateral oblique line | Left | 13 | Yes | 1 |
| 12 | F | 65 | Lateral oblique line | Right Left | 5 | Yes | 4 |
| 13 | F | 68 | Lateral oblique line | Right Left | 8 | No | 4 |
The segmental mandibular sandwich osteotomy technique involved an elliptical incision 10–12mm 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 2mm below the ridge bone and approximately 1.5–2mm above the mandibular canal. The vertical mesial osteotomy was made 2mm 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 2mm 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).
Fig. 1.
Horizontal and vertical osteotomies carried out with a piezoelectric surgical device to obtain the cranial bone fragment.
Fig. 2.
Upfracture of the cranial bone fragment using a chisel.
Fig. 3.
Mobilisation of cranial bone fragment and the interpositional bone graft. The lateral aspect of the cranial bone fragment was elevated more than the lingual aspect.
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 (Fig. 4, Fig. 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).
Fig. 4.
Postoperative panoramic radiograph showing the interpositional bone graft in both sites of the mandible.
Fig. 5.
Lingual deviation of the cranial segment and placement of the interpositional bone graft obtained from the lateral oblique line.
Fig. 6.
The interpositional bone graft is stabilized with miniplates and screws.
Fig. 7.
Collagen resorbable membrane covering the graft site.
Antibiotic prophylaxis with penicillin 10 mega iv (Grünenthal GmbH, Aachen, Germany) at the moment of surgery and amoxicillin (Amoxicillin Rathiopharm GmbH, Ulm, Germany) 1000mg every 8h for 7 days, was prescribed postoperatively. Postoperatively, ibuprofen 600mg every 8h 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).
Fig. 8.
Plate removal and implant holes 12 weeks after grafting. View of the vestibular bone showing complete integration of the interpositional bone graft.
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, 10mm posterior to the mental foramen. Horizontal bone augmentation was measured on the same mental region at the upper point of the alveolar crest.
Results
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.
Table 2. Vertical and transverse bone gain post augmentation and implant features.
| Patient number | Implant position | Height gain (mm) | Width gain (mm) | Implant diameter (mm) | Implant length (mm) | Complications |
|---|---|---|---|---|---|---|
| 1 | 36 | 7.2 | 6.3 | 3.5 | 8 | No |
| 35 | 3.5 | 11 | ||||
| 46 | 6.4 | 4.6 | 3.5 | 8 | ||
| 45 | 3.5 | 8 | ||||
| 44 | 3.5 | 9 | ||||
| 2 | 36 | 5.5 | 5.2 | 4.1 | 10 | No |
| 35 | 3.3 | 12 | ||||
| 12 | ||||||
| 45 | 5.2 | 6 | 3.3 | 10 | ||
| 46 | 4.1 | |||||
| 3 | 36 | 7.6 | 4.3 | 4.1 | 10 | No |
| 10 | ||||||
| 45 | 7.8 | 3.5 | 3.3 | 10 | ||
| 46 | 4.1 | |||||
| 4 | 36 | 4.5 | 3.5 | 4.8 | 10 | No |
| 37 | 4.8 | 10 | ||||
| 5 | 46 | 3.0 | 4.0 | 4.1 | 10 | No |
| 2.0 | 2.6 | 4.1 | ||||
| 36 | 10 | |||||
| 6 | 46 | 4.5 | 3.2 | 4.1 | 10 | Hypoaesthesia |
| 7 | 37 | 4 | 3.1 | 4.5 | 9 | Hypoaesthesia |
| 36 | 3.5 | 11 | ||||
| 47 | 6.3 | 3.2 | 4.0 | 8 | ||
| 46 | 3.5 | 8 | ||||
| 45 | 3.5 | 8 | ||||
| 8 | 34 | 3.3 | 2.0 | 4.1 | 8 | Hypoaesthesia |
| 35 | 4.1 | 8 | Abscess | |||
| 36 | 4.8 | 6 | ||||
| 45 | 4.4 | 2.6 | 3.3 | 12 | ||
| 46 | 3.3 | 12 | ||||
| 47 | 3.3 | 12 | ||||
| 9 | 45 | 6.2 | 2.3 | 4.1 | 12 | No |
| 46 | 4.1 | 12 | ||||
| 10 | 36 | 3.0 | 2.3 | 4.1 | 10 | Hypoaesthesia |
| 37 | 4.1 | 10 | ||||
| 46 | 3.0 | 3.1 | 4.1 | 10 | ||
| 47 | 4.1 | 10 | ||||
| 11 | 36 | 3.1 | 2.3 | 4.0 | 11 | No |
| 12 | 36 | 3.0 | 3.2 | 3.3 | 8 | Hypoaesthesia |
| 37 | 4.1 | 8 | ||||
| 8 | ||||||
| 44 | 3.5 | 2.5 | 3.3 | 8 | ||
| 45 | 4.1 | |||||
| 13 | 45 | 3.4 | 2.2 | 3.5 | 8 | Mucositis |
| 46 | 4.0 | 8 | ||||
| 35 | 4.2 | 3.5 | 3.5 | 8 | ||
| 36 | 4.0 | 8 | ||||
In one patient, wound healing was affected by mucositis; this was resolved without sequelae. In another patient an intraoral vestibular abscess was treated with drainage without any sequelae at follow-up. No dehiscence was observed during follow-up.
Vertical gain ranged from 2.0 to 7.8mm (mean 4.61mm). Horizontal gain ranged from 2.0 to 6.3 (mean 3.42mm). Patients received implants 12 weeks after the bone reconstructive procedure. Forty-one implants were placed at 22 surgical sites involving 13 patients. Two implant systems were used: Straumann Dental Implant System (Basel, Switzerland) and Astra Tech Implants (AstraZeneca, Sweden). There were no specific criteria for the selection of implant systems. No implant was lost during the observation period due to lack of osseointegration.
Discussion
In cases of atrophic mandible, the distance to the mandibular canal and the transverse decrease in bone is an anatomic limitation for prosthetic rehabilitation with endosseous implants. Several techniques have been used to solve this problem, such as block bone grafts3, alveolar distraction osteogenesis1, titanium mesh12 and transposition of the alveolar nerve5. Autologous materials, such as bone and cartilage, and allogenic materials, such as hydroxyapatite or bone substitutes, and their combinations, have been used for ridge augmentation18. Autologous bone grafting is regarded as superior to the others in terms of postoperative and long-term outcomes16.
The first reports about applying the sandwich technique in the mandible appeared in 197715. Since then, variations of this surgical technique have been described by several authors7, 10, 13, 14, 15.
In a retrospective study13 of sandwich technique osteotomy, the median vertical gain in the posterior mandible was 6–7mm, measured by CT scan. In a study of 10 graft sites over 1–4 years, Jensen10 reported that all dental implants presented osseointegration and maintenance of alveolar form. Another study in the anterior mandible by the same authors reported stable and aesthetic results over 5 years with a vertical gain of 3–6mm11. The vertical gains in the present study were similar to several other reports11, 13. The present results showed substantial variability of values. The technique used in the present study also made it possible to obtain a transversal bone gain, unlike other reports10.
In the authors’ experience, the most difficulty aspect of using the sandwich technique is the precision required to save the mandibular nerve in the horizontal osteotomy. The major advantage of this technique is the possibility of increasing bone height and width with less morbidity than other techniques. In particular, no dehiscence was observed unlike techniques using only graft or titanium mesh. This is because the incision is paracrestal and the mobile mucosa is elastic enough to close without tension and without additional periosteal release incisions. Another advantage, especially with respect to implants, is that vascularisation is maintained in the bone ridge throughout augmentation intervention thus the interface at the implant shoulder in terms of hard-to-soft tissue to implant interface is kept as true to the original as possible.
In order to preserve the blood supply, it is of fundamental importance that the lingual pedicle of the soft tissue is not damaged. An experimental study confirmed that the lingual pedicle was able to maintain the viability of the coronal bone segment, allowing for rapid remodelling of the interpositional autogenous bone graft6.
Some studies claim that this technique should only be applied in patients with at least 6mm of bone above the mandibular canal13. Jensen et al.11 consider maximum vertical movement to be about 5mm in the anterior maxillary region and up to 8mm in the posterior mandibular region. Robiony et al.14 claim that vertical movement can reach up to 10mm in the anterior maxilla without compromising blood supply. In the authors’ experience, sandwich osteotomy in the posterior region of the mandible can reach nearly 8mm. Another important consideration when using the sandwich osteotomy technique is that the cranial bone fragment must not be less than 5mm thick14. From the authors’ point of view, it is possible to obtain a cranial bone fragment without any necrosis with a height of 2–3mm.
Autologous bone, because of its osteoinductive effect, is the optimal augmentation material19. Potential morbidity at the donor site, mainly in the iliac crest, has been reported4. None of the patients in this clinical report experienced any such complications. The choice of the autogenous bone donor site depends on the quantity of bone required. Intraoral bone grafts are a convenient source for alveolar reconstruction because of bone origin similarity and low morbidity. In this report, iliac bone grafts were used when a large amount of bone was needed or when extended augmentation was needed in both jaws.
Unlike Marchetti et al.13 who observed no signs of impaired sensibility after the sandwich osteotomy technique, the current report found a high rate of sensory mental nerve disturbances after reconstruction (44% of patients). This was probably due to flap retraction. Jensen10 found transient paraesthesia in all patients, lasting up to 6 weeks, and all the patients in the present report recovered within this time. Other studies report neurosensory dysfunction after interpositional bone graft7, 10.
Although there are several bone augmentation techniques, osteotomy osteogenesis has advantages. Alveolar distraction osteogenesis has the greatest potential for vertical bone gain, with reports of a 9.9mm mean bone gain (range 4–15mm)2. Sandwich osteotomy osteogenesis has the advantage of restoring vertical bone deficit together with transverse gain in dimension without undesired bone segment displacement, is less time-consuming and is less uncomfortable for the patient. Onlay grafting has been shown to produce considerable resorption17 and does not have the advantage of original bone in the superior peri-implant region. Although nerve transposition maintains the vertical bone, it involves a high risk of permanent neurosensory disturbance9. It would seem that the choice of technique is based more on surgeon experience than on evidence of efficacy.
In conclusion, segmental mandibular sandwich osteotomy is recommended to meet the dimensional requirements of preimplant bone augmentation in atrophic posterior mandible. Future studies involving long-term follow-up are needed to evaluate the permanence of these results and implant survival.
Competing interests
None declared.
Funding
None.
Ethical approval
Not required.
References
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- . Clinical and experimental results of a sandwich-technique for mandibular alveolar ridge augmentation. J Maxillofac Surg. 1977;5:199–202
- . Autologous bone grafts and endosseous implants: complementary techniques. J Oral Maxillofac Surg. 1996;54:486–494
- . The combined use of two endosteal implants and iliac crest onlay grafts in the severely atrophic mandible by a modified surgical approach. Int J Oral Maxillofac Surg. 2005;34:152–157
- . Reconstruction of the severely resorbed mandible with interposed bone grafts and hydroxylapatite. A 2–3 year follow-up. Int J Oral Maxillofac Surg. 1988;17:157–160
- . Maxillary sinus augmentation with the xenograft Bio-Oss and autogenous intraoral bone for qualitative improvement of the implant site: a histologic and histomorphometric clinical study in humans. Int J Oral Maxillofac Implants. 2001;16:23–33
PII: S0901-5027(10)00095-0
doi:10.1016/j.ijom.2010.03.002
© 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Volume 39, Issue 6 , Pages 554-560, June 2010
