Insufficient bone volume is a frequent challenge in dental implant procedures. Bone grafting is often necessary to address this, with autogenous bone being the gold standard but limited by harvesting difficulties and donor site morbidity. Bio-Oss, a xenogeneic bone graft substitute, is widely used, but some studies indicate low cell viability and poor differentiation. In vitro studies are crucial for evaluating new bone graft materials' biocompatibility before animal and clinical trials. However, small bone particles can move or float during in vitro experiments, affecting result accuracy. This study aimed to evaluate the biocompatibility of Mega-oss and Mega-TCP, two new bone substitutes with lower market prices and easier sourcing than Bio-Oss. Sodium alginate, a biocompatible hydrogel-forming substance, was used to fix the bone particles and prevent movement during testing. The study hypothesized that Mega-oss and Mega-TCP would exhibit biocompatibility comparable to Bio-Oss, and that alginate gel fixation would improve the accuracy of in vitro tests.

The literature review highlights the need for alternative bone graft materials due to the limitations of autogenous bone grafts. Bio-Oss, while a leading product, shows limitations in cell viability and differentiation in some studies. The use of in vitro models for pre-clinical testing is emphasized, along with the challenges of working with small bone particles that can move during cell culture experiments. The biocompatibility and properties of sodium alginate as a potential fixative are discussed in the context of its use in other biomedical applications.

The study used MC3T3-E1 osteoblast cells and RAW 264.7 osteoclast-like cells. Mega-oss, Mega-TCP, and Bio-Oss particles were fixed with 3% sodium alginate gel using a CaCl2 crosslinking process. The efficiency of the alginate gel in preventing particle movement and floating was evaluated. Cell morphology was assessed using SEM. Cell viability and proliferation were measured using MTT assays. Alkaline phosphatase (ALP) activity and staining were used to assess osteoblast differentiation. Tartrate-resistant acid phosphatase (TRAP) staining was employed to evaluate osteoclast formation. A resorption pit assay measured the bone resorption activity of osteoclasts. Statistical analysis involved repeated measures ANOVA, multivariate ANOVA, and paired t-tests, with significance set at p < 0.05.

SEM analysis showed better cell spreading on Mega-oss and Mega-TCP compared to Bio-Oss. MTT assays demonstrated good cell viability for all three materials, with Mega-oss and Mega-TCP showing consistently higher values than Bio-Oss, particularly at later time points. ALP activity and staining revealed no significant difference in osteoblast differentiation capacity between Mega-oss, Mega-TCP, and Bio-Oss, all showing significantly higher activity than the control group (alginate alone). TRAP staining confirmed the formation of osteoclast-like cells. The resorption pit assay demonstrated significantly higher resorption rates for Mega-TCP and Mega-oss compared to Bio-Oss (24.4%, 15.3%, and 3.3%, respectively). The alginate gel effectively prevented particle movement and floating during the experiments.

The findings suggest that Mega-oss and Mega-TCP are promising alternatives to Bio-Oss as bone graft materials. Their superior cell adhesion, proliferation, and comparable osteoblast differentiation capabilities, coupled with higher resorption rates (except for the unexpectedly high resorption rate of Mega-TCP), make them attractive candidates. The use of alginate gel as a fixative proved successful in mitigating experimental artifacts caused by particle movement, offering a valuable improvement for in vitro bone material testing. The significantly higher resorption rate observed with Mega-TCP requires further investigation to understand its long-term implications. The study's results warrant further investigation through in vivo and clinical trials.

This in vitro study demonstrates that Mega-oss and Mega-TCP possess favorable characteristics for bone regeneration, showing comparable osteoblast differentiation to Bio-Oss, along with enhanced cell adhesion and proliferation. The use of sodium alginate gel as a fixative is proposed as a novel method for in vitro bone material testing. Further in vivo and clinical studies are needed to confirm these findings and assess the long-term performance of Mega-oss and Mega-TCP.

This study is limited to in vitro assessments. The results may not fully reflect the in vivo behavior of these materials. Further investigations, including animal studies and clinical trials, are necessary to confirm the findings and to assess the long-term effects and safety of Mega-oss and Mega-TCP. Additionally, exploring the genetic-level cellular changes would provide a more comprehensive understanding.