## 4 Discussion
### Functionalization with Strontium
In this range, there is a significant enhancement in osteoblast differentiation and proliferation, indicating that low doses of strontium can effectively promote bone cell activity and growth. Additionally, new bone formation is highly stimulated, suggesting that these concentrations are optimal for bone regeneration applications. This is consistent with studies such as those  
In the moderate concentration range (2.5% to 5%), the biomaterials continue to exhibit non-cytotoxic effects. Osteoblast differentiation remains high, and proliferation is moderate to high, supporting the earlier findings that strontium enhances cellular activities conducive to bone regeneration. Moderate osteoclast inhibition is observed, which helps in balancing bone formation and resorption. The new bone formation remains high, making this range suitable for therapeutic applications that require robust bone regeneration, as supported by studies from [PERSON] et al. (2019) and [PERSON] et al. (2020). As the concentration increases to the intermediate range (5% to 10%), there is a noticeable shift in the biological effects. Low levels of cytotoxicity begin to appear, indicating that higher strontium concentrations may pose some risks to cell viability. Osteoblast differentiation and proliferation are moderate, while osteoclast inhibition remains effective. New bone formation continues to be high, though it is crucial to monitor cytotoxic effects at these concentrations. This range is a critical balance point where the benefits of bone regeneration need to be weighed against the potential cytotoxic risks. At high concentrations (10% to 20%), the cytotoxic effects become more pronounced, with moderate cytotoxicity levels observed. Osteoblast differentiation and proliferation decrease significantly, indicating that high doses of strontium may inhibit these crucial processes. Osteoclast inhibition is low, and new bone formation is moderate, suggesting that while some regenerative effects are still present, the overall efficacy is reduced due to the adverse effects on cell viability and activity. These findings align with the studies by [PERSON] et al. (2019), which reported reduced cellular activities at higher strontium concentrations. At very high concentrations (20% and above), the biomaterials exhibit high cytotoxicity, severely limiting their applicability in bone regeneration. Osteoblast differentiation and proliferation are minimal, and osteoclast inhibition is negligible. New bone formation is also minimal, indicating that such high doses are detrimental to both cell viability and the overall bone regeneration process. This concentration range should be avoided in therapeutic applications due to the significant cytotoxic effects and reduced regenerative potential. These findings underscore the importance of selecting appropriate strontium concentrations to maximize therapeutic benefits while minimizing potential adverse effects. Further research should focus on refining these concentration ranges and exploring the underlying mechanisms to optimize the use of strontium-doped calcium phosphate biomaterials in clinical applications.