What Are the Stages of Bone Formation?
The formation of bone is mainly through three mechanisms:
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Osteogenesis: In this mechanism, the osteoprogenitor cells contained within the graft material are capable of forming ossification centers.
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Osteoinduction: In this mechanism, bone matrix-producing cells are induced by precursor cell differentiation.
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Osteoconduction: The graft material acts as a scaffold for new bone deposition produced by osteocytes or bone cells.
What Is the Need for Bone Augmentation Protocols?
Natural tooth loss, if not replaced immediately, will result in altered dimensions of the bone. In patients with less bone density or resorbed bone, bone augmentation before dental implant surgery is required. The bone resorption post the tooth loss or extraction would be horizontal or vertical. Research indicates that immediately after tooth extraction, there is an eventual loss of 1 mm or more with a vertical bone loss that may exceed 7 mm. Also, there is a clinical challenge of placing dental implants in the upper jaw region, i.e., while replacing premolars and molars, because the posterior part of the maxilla is very near or close to the maxillary sinus. After tooth loss or extraction, bone density of both the upper and lower jaw are affected considerably. As the bone density and volume would become limiting factors for the long-term success of dental implants by affecting the phenomenon of osseointegration, bone augmentation procedures are most frequently performed in cases that require minimal bone height for dental implant fusion or the bone-implant contact fusion to occur. One of the safest and most followed protocols before bone graft or augmentation is the maxillary sinus lift surgery or the minimally invasive sinus lift surgery.
Why Should Sinus Membrane Space Be Elevated or Maintained?
In sinus lift surgery, space is created between the sinus membrane and the maxillary sinus to induce adequate bone formation. Autogenous bone grafts (bone grafts taken from one's own body) are considered the gold standard materials that supply growth factors, cells, and the support needed for maintaining tissue structure and compatibility with dental implants. When the bone grafts form a scaffold and induce the maxillary sinus mucosa to promote bone formation in that area, sinus lift surgery along with augmentation or grafts is considered the most successful in patients with altered bone height. However, the recent research on the usage of space maintained at the sinus membrane without using bone graft material has come to light that has also promised successful long-term results for dental implant success. Using space-maintained sinus membrane in suitable patients also helps eliminate the need for bone graft materials required for augmenting bone. Not only has this method shown new and adequate bone formation, but in vivo and in vitro potential to induce bone has also been demonstrated by these sinus membranes. The critical criterion for sinus membrane space usage is that there should be a residual bone height of at least 4 to 5 mm. Residual bone height remains the most crucial factor affecting implant success over time compared to other local variables for osseointegration. In addition, the elevation of the sinus membrane should also be sufficient in the case of maxillary implants because there is a potential risk of perforation associated when the implant length does not correspond to the proper elevation of the sinus membrane.
Why Should an Alternative Be Considered to Conventional Bone Grafting?
However, the methodology of bone grafting is accompanied by certain complications, such as the risks associated with infections and resorption during the healing process. Graft materials usage can also lead to increased surgical time, an increase in the patient's total treatment time because of the gap between augmentation and implantation that would last three to six months, and other risks like bleeding, edema, or inflammation.
Sinus Membrane Screw Fixation: Maxillary sinus membranes can be firmly maintained using screws. The screws used by the dental implantologist are made of PLLA (Poly L lactide or hydroxyapatite). The screw material used for membrane fixation should have high mechanical strength, absorbability, and osteoconductivity. In addition, these screw materials subjected to UV treatment positively influence bone cells and increase regeneration capacity. However, research on the screw material subject to UV and non-treated UV screws is still ongoing. But most implant dentists, before considering the ideal screw material for sinus membrane fixation, are now focusing on the UV irradiation treatment for screws that can help promote and differentiate osteoblasts or bone-forming cells.
What Is the Histologic Evidence for Sinus Membrane Space Success?
The histologic evidence for maintaining the sinus membrane space is attributed to the natural regenerative ability of the sinus membrane, which is by the capacity to induce several osteogenic markers. In addition, the sinus membrane also contains mesenchymal cells called progenitor cells that respond to bone morphological proteins, i.e., BMP 6, BMP 7, BMP2, etc. Therefore, the implant dentist should always consider the mandatory sinus lift technique without using any grafting materials by raising the sinus membrane and can be held for a sufficient period to allow enough bone to form in the region.
Conclusion:
Hence to conclude, the technique of maxillary sinus lift by using absorbable screw materials like UV-treated hydroxyapatite or poly L lactic acid for inducing bone formation would be helpful in the long-term treatment success of dental implants and an alternative treatment strategy for conventional bone graft methods.
