Introduction 

From research conducted in 19 countries, about 19% of the population wears dentures (1). For every five individuals you walk by, one of them could possibly be wearing dentures! However, one of the big challenges to having dentures is having a strong bone foundation to hold the dentures, and this is where dental bone grafting solves this problem. Bone grafting isn’t just used for dentures though, it can also be due to bone loss, fractures, and even gum disease (2).

Bone grafting is a surgical procedure in which bone tissue is positioned to stimulate bone growth in certain areas of the body to either repair bone density or fractures. Bone grafting is used in dentistry for bone trauma, serving as a foundation for implants and crowns. For example, when the jawbone loses density or volume, implants and crowns are unstable. Bone grafting prevalence depends on the patient’s oral health, age, medical history, and specific dental needs. Because not one person has the same jawbone as their neighbor, bone grafting can either be common or uncommon. If one suffers tooth trauma or has a weak jaw from the natural aging process, it can lead to more dental visitations to restore volume or density.

Bone grafting has been around for thousands of years, dating from ancient Egyptian primitive bone grafting techniques. In 1668, the first heterologous bone graft surgery was performed by a Dutch surgeon by the name of Job van Meekeren in war. He took a dog skull bone fragment and put it in a soldier! The soldier wanted it removed, and to the surgeon’s surprise, the bone fragment was fused into the soldier’s skull (4). It wasn’t until recently in 1861 that the term “bone graft” was defined in a research by Leopold Ollier. In the early 1900s, people recognized the superiority of using grafts from their own bodies over grafts from a human tissue bank as it provided more integrity of the graft and surrounding bone. This is likely due to the advancement of human knowledge of the human immune system as grafts from bone banks could trigger an immune response if blood groups are not compatible (5). Now with increasing knowledge of bone healing, treatment and mechanism options for bone grafting have increased, leading to new synthetic sources (6). Between 1992 and 2007, an estimated 1.7 million people followed this procedure (7). This review will specifically cover current developments in dental bone grafting and its future as the field is rapidly transforming for the better, striving to find better practical solutions to increase public health. 

Discussion

Current Developments in Bone Grafting: Allo-DDM

Currently, a dental bone graft consists of four sources: autogenous (a graft from your own body), allograft (a graft from a human tissue bank), xenograft (a graft from an animal tissue bank), and alloplastic (a graft synthetically manufactured to mimic bone tissues). Although there are different types, all bone grafts act as a scaffold for your bone cells to regenerate by themselves (2). Like when your cells repair broken skin, bone cells react to bone grafts. No matter the source, dental bone grafts come in four types: socket preservation, ridge augmentation, sinus lift, and periodontal. In general, bone grafting in these four types aims to either fill in the missing bone or prevent bone loss (2). For example, in socket preservation, it helps reduce bone loss after a tooth extraction as the jaw bone has a natural tendency to quickly narrow, losing its original shape and proportions because the bone quickly resorbs, resulting in 30-60% loss in bone volume in the first six months (2). Bone loss can compromise the ability to place a dental implant (to replace the tooth), or its aesthetics and functional ability. 

A current development in dental bone grafting is the use of Allogenic Demineralized Dentin Matrix (Allo-DDM); a new grafting material derived from the demineralized dentin matrix of a human donor’s tooth (8). The process itself removes the mineral content of the tooth and utilizes the organic compounds rich in proteins and growth factors to act as a scaffold for bone regeneration, called bone augmentation. This is different from the previously prominent method of Auto-DDM that proved clinical efficacy with favorable wound healing and new bone formation (9).

From 2013-2016, a clinical test was performed on 18 patients who underwent socket preservation with Allo-DDM (10). These patients were evaluated for early complications at the early surgical stage and for historical evaluation. After undergoing a secondary surgical procedure at the Seoul National University Bundang Hospital and Seoul in Dental Clinic, and being monitored between 7-10 days, the results proved that there were no remarkable early or late complications with the use of Allo-DDM (10). In fact, bone regeneration of Allo-DDM was comparable to the prominent method, Autogenous DDM (10). Allo-DDM has been shown to work well because, despite the source coming from a human donor’s tooth, the same organic compounds rich in proteins and growth factors were able to perform the same as autogenous (from the same source), expanding the range of our bone graft sources. Although this approach is still being tested for its accuracy and efficacy, it is an alternative for future bone grafting (8).

The Future of Dental Bone Grafting: Adhesive Hydrogel

Currently, one of the most impressive technologies in this field is the first adhesive hydro-gel, generated by UCLA School of Dentistry researchers (11). In context, before having surgical dental implants, it is almost always necessary to have a bone grafting procedure to ensure a stable area for the implant. Usually, this procedure ends with a protective membrane, made out of non-resorbable materials. Many who undergo bone grafting procedures have trouble with keeping the protective membrane in place through their day-to-day schedules and the bone graft sometimes inevitably spills out. UCLA's hydro-gel aims to solve this problem. The hydro-gel contains an alginate-based solution, made to retain water through its molecular structure, imitating ocean mussels. The use of alginates work well for this kind of procedure because when hydrated, they become a sticky gum-like substance that adhesive sticks to sites. 

After the UCLA School of Dentistry researchers had produced their hydrogel, they tested their product in an 18-week study on rats. The rat models used had peri-implantitis, an infectious disease that causes inflammation around dental implants of the gum and its bone structure, however, when the researchers applied their hydrogel in the mouths of the rats they saw significant improvement in the regeneration of bone around the implants (12). Unlike older methods that were not proven 100% sustainable in aqueous environments, the alginate hydrogel has remarkable surgical efficacy.

Conclusion and Future Implications

Given the prevalence of dental implants and reconstruction, there is a clinical need for improved technology in bone grafting.  The UCLA hydrogel represents a promising direction for future research given the advantages it has displayed thus far over traditional methods.  Further, the hydrogel has the potential to dramatically reduce the cost for surgeries because bone grafting itself is intricate while hydrogel is just a transportation gel. Additionally, the gel has been shown to be biodegradable and therefore could replace older bone graft procedures where the risk for inflammation could be higher. Studies still need to be conducted with human tissue to assess biocompatibility with various cell types and tissues and combination with nanomaterials and to measure inflammation at varying time points after implantation. If dental procedures had primarily used expensive bone grafting procedures and now there is a new aqueous-friendly invention, then the future for bone grafting will change, specifically making dental work more affordable and accessible. 

Methods

This review was conducted by searching Google Scholar and Pubmed online databases for journal articles on this topic.