Effect of a highly bioactive calcium alkali orthophosphate-based bone grafting material as compared to a tricalcium phosphate bone substitute on osteogenesis after sinus floor augmentation in patients

Over the last 25 years, the use of dental implants to replace missing teeth has become a standard treatment in modern dentistry. However, implant therapy can be a challenge in patients with insufficient bone volume. Pre-implantology procedures for alveolar ridge augmentation serve as the basis for c...

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Main Author: Ensir, Hana Ayad
Contributors: Knabe-Ducheyne, Christine (Prof. Dr. ) (Thesis advisor)
Format: Doctoral Thesis
Published: Philipps-Universität Marburg 2020
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Summary:Over the last 25 years, the use of dental implants to replace missing teeth has become a standard treatment in modern dentistry. However, implant therapy can be a challenge in patients with insufficient bone volume. Pre-implantology procedures for alveolar ridge augmentation serve as the basis for creating sufficient bone volume and quality for oral rehabilitation in these patients. Sinus floor augmentation is a well-recognized procedure for the augmentation of the atrophic alveolar ridges of the posterior maxilla. Although autologous bone grafts are the gold standard, they have the disadvantages of the additional surgical operations required, the risk of morbidity in the donor region, and the need for general anesthesia to obtain iliac crest grafts, which have led to an increasing search for alternatives. This has led to intensive research to develop suitable synthetic bone replacement materials. Ideal bone graft substitutes should serve as a guide and provide a surface in which bone formation is induced. The migration of osteoprogenitor cells to the material surface, which differentiate into osteoblasts and secrete bone matrix, results in mineralized bone matrix. In addition, the bone graft should be relatively rapidly resorbable in order to resorb within the newly formed bone in case of rapid bone formation. This should lead to complete replacement by the new, functional bone tissue. This is of great importance for ridge augmentation in view of inserting dental implants into the augmented areas, since osseointegration can only occur between the implant surface and the bone tissue. The use of β-tricalcium phosphates (β-TCP), which are osteoconductive, as bone substitute material for ridge augmentation has become an established procedure. However, the resorption rate of β-TCP is 1-2 years in humans. A new type of calcium phosphate ceramics are glassy crystalline silica-containing calcium alkali orthophosphates with the main crystalline phase Ca2KNa (PO4)2, which have been developed to achieve a higher chemical solubility and degradability. Previous in vitro and in vivo studies have shown that these materials had a stronger stimulating effect on osteoblastic function, bone formation and osteogenesis than tricalcium phosphates. In the present clinical study, the effect of silica- containing calcium alkali orthophosphate (Si-CAOP, Osseolive) on osteogenesis and osteogenic marker expression was studied in comparison to β-tricalcium phosphates (β-TCP, Cerasorb M) in biopsies obtained 6 months after sinus floor augmentation in 24 patients. Cylindrical biopsies were processed for immunohistochemical investigations on hard tissue sections using the osteogenic markers osteocalcin, collagen type I, bone sialoprotein, and alkaline phosphatase. Immunohistochemical detection of the angiogenic marker (von Willebrand factor) was also established on some Osseolive samples for the investigation of blood vessel formation. Histomorphometric analysis of the histological sections was performed in two areas of interest: central and apical near the Schneiderian membrane. The area fraction of the bone and particles was measured histomorphometrically in both areas. Furthermore, a semi-quantitative analysis of osteogenic marker expression in osteoblasts, osteocytes, mesenchymal cells, fibrous matrix, osteoid and bone matrix was performed. In addition, a tartrate-resistant acid phosphatase stain was used to detect osteoclast activity. Our histological evaluation showed that both materials caused bone matrix deposition within the particles, bone ingrowth and increasing bone formation, which was still actively progressing in an apical direction 6 months after implantation. This was accompanied by an increasing resorption of the bone substitute material. This process was more advanced in biopsies grafted with the Si-CAOP 6 months after sinus floor augmentation than in biopsies grafted with β-TCP. No complications, such as undesirable inflammatory tissue reactions or implant loss, were observed in either patient group. In the central region of the specimens, bone formation and resorption varied between the two materials, but these differences were not statistically significant, while in the apical region of the Si-CAOP augmented biopsies there was higher bone formation and significantly (p≤ 0.05) greater particle resorption than in biopsies after augmentation with β-TCP. In the Si-CAOP group, this was associated with higher expression of osteogenic markers in the osteoid, osteocytes and bone matrix. In initial studies on angiogenic marker expression, the Si-CAOP particles showed a promotion of vascular ingrowth during bone formation. In summary, both test materials enabled bony regeneration of resorbed alveolar ridges by sinus floor augmentation in the human posterior maxilla, with Si-CAOP displaying higher biodegradability and inducing stronger bone formation when compared to the β-TCP material. This work confirmed the higher stimulatory effect of Si-CAOP with a porosity of 75% on osteogenesis in 12 patients by generating comprehensive histological, immunohistochemical and histomorphometric data for an evidence-based application of this promising bioactive material. A further study will include a larger number of patients, a split-mouth design, the determination of the bone-particle contact, further investigations on angiogenesis and investigations on the volume stability of the augmentation material through the evaluation of cone-beam CT data in order to expand the database for the evidence-based application of the silicon-containing calcium-alkali orthophosphate Osseolive.
Physical Description:96 Pages