This study aimed to evaluate the effectiveness of lateral ridge augmentation in 36 patients with severely atrophic alveolar ridge using allogeneic bone grafts in a framework technique. A thinned allogeneic cortical graft was screwed to the alveolar ridge, leaving a hollow space that was filled with particulated allogeneic cortical bone. Thirty-six patients who received surgical lateral block augmentation using allogeneic bone grafts were involved in this study. Implants were placed in a second session after a mean time of 6.3 months. The surgical technique and the reasons for failure of surgery in three patients are described. Additionally, properties of allogeneic bone grafts are reviewed. In 33 patients, dental implants were successfully installed and continued to be well maintained at the last follow-up (91.7% success). In three patients, dental implants could not be installed (8.3% failure) as the graft was lost because of wound dehiscence; however, repeat surgery was successfully carried out in all three. The use of allogeneic bone grafts in lateral ridge augmentation of the maxilla and mandible showed successful clinical results. It seems to be a reliable material for reconstructing a severely atrophic alveolar ridge. It presents a good alternative to autogenous bone regarding augmentation because it offers good ossification, less morbidity, unlimited availability and shorter duration of surgery, and lower costs.
A severely atrophied alveolar ridge is quite common in elderly patients and prevents the installation of dental implants. Implant placement requires a suitable quantity and quality of bone. Successful osseointegration of dental implants depends on sufficient bone surrounding the implant. Extensively deficient bone can be augmented in many ways and by using different kinds of bone substitute materials. A very common procedure is transplantation of autogenous bone blocks.1,2
The present golden standard is the use of autogenous bone, wherein the donor and recipient are the same person.3,4 This procedure presents osteoconductive, osteoinductive, and osteogenetic properties3–5 but has several disadvantages. Additional surgery is required, which is associated with corresponding risks, complications, and higher incidents of morbidity. Also, the duration of surgery is longer, and therefore the cost is higher. In most cases, using bone from the iliac crest also requires general anesthesia. In addition, autogenous bone is mostly limited.6–9 The use of allogeneic bone, that is, human donor bone, can overcome these disadvantages.
The following study aims to evaluate the use of allogeneic bone grafts for lateral ridge augmentation to enable the installation of dental implants. A well-working frame technique is presented. Thinned allogeneic cortical grafts were screwed to the alveolar ridge, leaving a hollow space that was filled with particulated allogeneic cortical bone. The properties of allogeneic bone are described and reasons for failure of surgery in three patients are analyzed.
Materials and Methods
Patients and materials
Between July 2008 and July 2010, 36 patients (18 women and 18 men) with an average age of 49 years underwent surgery at the Dorow-Clinic in Waldshut, Germany. All patients suffered from a severely atrophied alveolar ridge of the upper and lower jaw, making lateral augmentation necessary for successful installation of dental implants. Inclusion criteria for the study were defined as follows:
Atrophic alveolar ridge with need of sole lateral augmentation to install dental implants
Framework-like augmentation as the surgical technique
Use of allogeneic bone as the grafting material
Implants installed in a second intervention
A cone-beam computerized tomography (CBCT) was created preoperatively to display the bony structures and precisely evaluate augmentative surgery indications. We defined success in this study as the ability to install dental implants in the augmented sites. We have been using allogeneic bone grafts in our clinic for only a few years now. Ideally, the desired outcome ought to be the success of the subsequent prosthetic treatment. Because we are only one part of the medical referral chain, we have not been able to keep track of all patients involved in this study. Also, not all of the patients have yet been restored prosthetically. Consequently, the focus of the study has been on the augmentation exclusively.
Allogeneic bone transplants were used in all patients. All grafts were obtained from Argon Medical (city, country), the German distributor for allogeneic dental transplants processed by the German Institute for Cell and Tissue Replacement in Berlin (Deutsches Institut für Zell- und Gewebeersatz [DIZG]).
The DIZG uses a specific peracetic acid-ethanol–based sterilization (PES) procedure on its transplants. This is a validated procedure that has proved to be a reliable method for sterilizing human bone transplants.10–13 Bone grafts are first cleaned and defatted with a chloroform-methanol mixture. The next step is the actual sterilization with peracetic acid. Ethanol is used to reduce the surface tension. After 4 hours of vacuum incubation, a buffer agent is applied. Eventually, the grafts are freeze-dried and packaged aseptically. Processing demonstrably renders inactive the following viruses: HI-Virus 2, hepatitis A virus, polio virus, pseudorabies virus as a template for human herpes virus, porcine parvovirus as a template for human parvovirus B19, and bovine viral diarrhea virus as a template for the hepatitis C virus. A reduction in the titer of viable microorganisms (Staphylococcus aureus, Enterococcus faecium, Pseudomonas aeruginosa, Bacillus subtilis, Clostridium sporogenes, Mycobacterium terrae, and Candida albicans as well as spores of B subtilis and Aspergillus niger) below the detection level are also achieved.10–13
An antibiotic was given preoperatively with an intravenous drip (2000 mg amoxicillin with 200 mg clavulanic acid). Local anesthesia was performed by using a minimum of 4 mL of high-dose articaine (1:100.000). A crestal incision was made on the alveolar ridge. Vertical releases were cut into the vestibule if needed (Figure 1). A full-thickness mucoperiosteal flap was displaced to gain access to the bone. This was then followed by contouring and thinning of the cortical graft (femur graft, 12 × 50 × 5 mm, Osteograft, Argon Medical) by means of rotating instruments to a thickness of approximately 0.3–0.5 mm to fit the alveolar ridge (Figure 2).
Shape forming of the graft was carried out by visual judgment. The mental foramen was spared if necessary and not covered by grafting material. Rough edges were rounded. These shells were then perforated and fixed to the alveolar ridge with at least 2 steel screws (OsteoScrew, Argon Medical), leaving a hollow space between the frame and alveolar ridge. The hollow space between bone and frame was filled with particulated cortical bone (Osteograft, Argon Medical), which had been previously soaked for 5 minutes in venous blood taken from the antecubital fossa (Figures 3 and 4).
It is essential that the frame be fixed in such a way that it is rendered absolutely immobile. Only by this immobility can transformation of the particulated bone into the patient's own bone occur.
Slitting of the periosteum guarantees a strainless and tight wound closure. An absorbable, porcine, and slowly resorbing collagen membrane (Osteogide, Argon Medical; resorption time, 14–16 weeks) was placed onto the allograft. Both maxilla and mandible were operated on using the same technique. All patients received a prescription for an antimicrobial prophylaxis (875 mg amoxicillin with 125 mg clavulanic acid twice a day for 5 days) and an analgesic (600 mg ibuprofen as needed). Clinical and radiographic examinations were done during the pre- and postoperative phase, by means of CBCT or orthopantogram (Figures 5 through 7). Sutures were removed after 14 days.
The table shows all results and data. Thirty-six patients underwent augmentative surgery of the alveolar ridge using the framework technique with allogeneic bone grafts. In 33 patients (91.7%) we were able to successfully install implants in the newly formed supportive bone in a second surgery. Implantation was carried out after an average time of 6.3 months. The graft was lost in 3 patients (8.3%), and implants could not be installed. Because many patients are referred to our we know that implants were definitely installed in these patients by colleague dentists. Because the exact date of implantation is not known, however, these dates were not included in our study. Average time of follow-up after augmentation was 15.9 months. Average time of follow-up after implantation was 9.6 months.
This study confirms the results of previous studies. Allogeneic bone grafts work very well as a bone substitute material. Augmentation with allogeneic grafts will result in healthy bone and can result in suitable dimensions for uncompromising installation of dental implants.6,14–18
An often mentioned criticism concerning allogeneic bone grafts is the possibility of transmission of disease and antigenicity. Various studies have analyzed these potential disadvantages. When modern PES sterilization is used to process human donor grafts, safety can be ensured.10–13 The PES sterilization used by the DIZG is an internationally standardized and validated sterilization method10 that inactivates potential viruses, bacteria, fungi, and spores. Since 1985, more than 250.000 PES-sterilized allogeneic bone grafts of the DIZG have been transplanted. At the time of writing, there have been no reports of transmission of disease or immunologic response.
Another frequent point of criticism is a possible loss of biologic properties due to sterilization. However, PES-sterilized grafts show osteoconductive and osteoinductive characteristics. Various studies have unanimously reported that PES sterilization has no significant effects on reduction of osteoinductive properties on allogeneic bone grafts.19–22 Various growth factors (bone morphogenetic protein [BMP] 2, BMP-4, insulin-like growth factor 1, transforming growth factor ß1, vascular endothelial growth factor, and platelet-derived growth factor) are detectable after PES sterilization22 and promote bone regeneration.
The following advantages can also be cited. There is, for example, no limitation on procurement; any quantity or quality is easily obtainable. Figure 8 shows an example of an extensive augmentation with allogeneic bone. It is doubtful that such results would be as economically viable with autogenous bone or other bone substitutes. The costs are relatively low and therefore such grafting results are reasonable. Furthermore, such grafts have a shelf-life of 5 years.
Coming back to the three patients in whom treatment was unsuccessful, the blame lies with wound dehiscence. In all three patients, repeat surgery was performed, and the subsequent results look promising. Extensive repeat surgery on autogenous bone is very difficult or even impossible, and grafting material is often limited. In contrast, allogeneic bone grafts are available in every quantity and quality, making repetition of an unsuccessful augmentation more acceptable from a patient's point of view.
Regarding the successful treatments, the surgical technique used is quite specific. Instead of the often described use of a block (with cortical and cancellous bone), we used thinned out and contoured cortical bone as a framework and cortical granulate as the actual augmentation material. During one screw-removing surgery the frame was not incorporated, but it was easily removed, revealing healthy, newly formed bone. This occurred because the granulate remodels faster than the cortical framework.
Postoperative follow-up ranges to 15.9 months from first augmentative surgery and 9.6 months from installation of dental implants. Only patients with successfully installed implants were considered in this study. A longer range could not be analyzed yet, because of the relatively recent application of the grafting materials. The short follow-up period could be a point of criticism of this study, but considering the relatively quick remodeling time (compared with some xenogenic bone substitutes), a longer period may not be necessary to assess success. After a healing time of only 6 to 9 months, histologic studies have found vital, newly formed bone, sparse remaining allograft particles, and no evidence of any inflammatory infiltration.23–26 Allogeneic bone grafts show histologic characteristics analogous to those of autogenous bone chips.15 After healing, allogeneic bone is completely transformed into the recipient's own bony tissue.27 Still, further studies should be carried out to address the issue of the long-term success of dental implants in allogeneic grafts.
Our experience and the results of various studies show that allogeneic bone grafts can be used successfully for bone augmentation of the atrophic alveolar ridge of the upper and lower jaw. After a period of healing, the resultant bone is identical to autogenous bone. Moreover, use of allogeneic bone has more advantages than use of autogenous bone.