Jaws are functional bones, and whenever a tooth or teeth are lost, they resorb over time. The height and width of residual alveolar bone will influence the feasibility and quality of endosseous implant-based prosthetic tooth restoration. Although recent reports support the reliability of short implants [Citation1] (4–7 mm), restoring the atrophic alveolar bone is still considered optimal [Citation2], especially in esthetically relevant areas (i.e., incisors to first premolar). This is because an optimal esthetic crown-to-implant ratio can only be obtained after restoring adequate height and width of the alveolar bone.
This leads us to take into consideration the various procedures for alveolar bone augmentation. Among these there are (1) bone transplants from the patient him or herself (autogenic transplant); (2) transplants from another individual of the same (allogenic transplant) or different (xenogeneic transplant) species; (3) distraction osteogenesis; and (4) using alloplastic materials in conjunction with particulate bony or synthetic grafts (guided bone regeneration, GBR).
Bone grafting is probably the most widely used and known procedure. Some might say that the most famous bone grafting procedure was the creation of Eve from Adam’s rib.
Aside from this debatable statement, the need for bone grafting the maxilla and mandible is a long-standing issue. Von Meeken [Citation3] is thought to have been the first to perform a (xenogenic) bone graft. He reconstructed the skull of a soldier with a piece of bone harvested from a dog. The graft took, but the soldier was excommunicated because he was no longer considered to be human. For this reason, he requested that the bone be removed, and he was readmitted to the church afterward.
A number of procedures have been proposed since the end of the 19th century, especially from German authors [Citation3]. Autogenous bone grafting is still considered to a broad extent the gold standard [Citation4]. It is optimal for several reasons including the fact that only autogenous bone possesses osteoinductive properties, i.e., there are living bone-producing cells and selective growth factors (namely, bone morphogenetic proteins, BMPs) within the graft.
If autografts work well, why have oral and maxillofacial surgeons felt the need for an alternative means to restore resorbed alveolar bone? The main concern here is morbidity. First, harvesting bone from another site results in pain, scars, and intrinsic weakening of the donor site and can expose the patient to complications. Furthermore, performing a second procedure increases operative times and may require a switch to general anesthesia, which is almost always required when extraoral sites are chosen. Even when the bone is harvested from intraoral sites, longer surgical times and obvious discomfort to the patient are unavoidable.
Knowing these downsides of autogenous grafts, surgeons and industries have teamed up over the years to find an alternative material to achieve the same result. Aside from anecdotal reports of coral or glass particulate, which obviously were soon abandoned, bone from the same species or other species as well as synthetic materials have been proposed.
Relying on bone obtained from human cadavers would seem ideal. However, a distinction has to be made between the two ways of processing human bone. One way is to fresh freeze the bone; here the bone is harvested from a cadaver and frozen at −80 °C without further treatment. After an initial hype, the use of fresh (wet) frozen bone has shown weaknesses [Citation5]. The other method is to dry freeze the cadaveric bone. This process consists of decellularizing and deantigenizing the graft with mechanical and chemical means and finally freezing it. This procedure is needed to avoid rejection activity and transmission of pathogens. Dry frozen bone can be cancellous, cortical, or cortico-cancellous. Cancellous bone blocks have been successfully used for horizontal reconstruction of single tooth alveolar bone loss [Citation6].
When the ampler portion of alveolar bone has to be reconstructed, however, the shell technique is a good procedure. In this technique, a thin block of cortical bone is placed at a proper distance from the resorbed bone. It is then fixed with screws, and the void is filled with autogenous or allogenic bone particulate. This technique has proven reliable, but the cortical bone is extremely stiff and can fracture while modeling, drilling holes for screws, or tightening the screws needed for osteosynthesis.
Given this context, Pabst et al. [Citation7] investigated the hypothesis that placing the graft in saline solution before managing it might make it more malleable, thus reducing the subsequent risk of fracture. They studied this by measuring breaking strength (BS) and flexibility (FX) as well as analyzing the graft under scanning electron microscopy after the graft was put into saline solution for 10, 30, or 60 minutes. Finally, they reported the frequency of fractures in rehydrated vs. non-rehydrated grafts in six patients.
BS and FX were significantly increased after 10 minutes of hydration, while additional hydration time did not result in a further increase. These results reflect a reduced likelihood of fracture in the clinical setting.
The conclusions drawn from this article are of particular significance to oral and maxillofacial surgeons. When engaging in preimplant alveolar reconstructive procedures with allogenic grafts, they can be aware of the fact that placing the graft in saline solution for 10 minutes reduces the likelihood of fracturing it during modeling or fixation and that 10 minutes of hydration in saline is sufficient.
The authors, however, have not studied the use of heated saline to hydrate the grafts, although they do state that this is something worth investigating in future research.
Heated water is routinely used to make malleable, resorbable plates and meshes. Although in this setting there is a known physical reaction happening in the resorbable materials, something similar might also happen in the collagen fibers that inhabit allogeneic grafts, making them further malleable.
Therefore, going back to the original question of this commentary “Do we still need to study an optimal procedure for jaw alveolar bone reconstruction?,” the answer is that it is still highly desirable because only enduring and constant research will lead to an optimal, reproducible, safe, and reliable method to perform alveolar bone reconstruction. This is particularly true for vertical reconstructions in which autogenous and allogeneic grafts show their most relevant weaknesses.
Disclosure statement
No potential conflict of interest was reported by the author(s).
References
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- Sakkas A, Wilde F, Heufelder M, Winter K, Schramm A. Autogenous bone grafts in oral implantology-is it still a “gold standard”? A consecutive review of 279 patients with 456 clinical procedures. Int J Implant Dent. 2017;3(1):23. doi:https://doi.org/10.1186/s40729-017-0084-4.
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- Kloss FR, Offermanns V, Kloss-Brandstätter A. CEComparison of allogeneic and autogenous bone grafts for augmentation of alveolar ridge defects–a 12-month retrospective radiographic evaluation. Clin Oral Implants Res. 2018;29(11):1163–1175. doi:https://doi.org/10.1111/clr.13380.
- Pabst A, Ackermann M, Thiem D, Kämmerer P. Influence of different rehydration protocols on biomechanical properties of allogeneic cortical bone plates: a combined in-vitro/in-vivo study. J Investig Surg. 2021;34(10):1158–1164. doi:https://doi.org/10.1080/08941939.2020.1767735.