Improving Biocompatibility and Mechanical Properties of Titanium Implants in Orthopedic Surgeries: The Role of Machining Depth in Enhancing Surface Interaction with Bone Tissue.

Objectives: This study comprehensively examined the influence of cutting depth during dry milling on the structural, mechanical, and biocompatibility characteristics of commercially pure titanium. The primary objective was to evaluate how variations in cutting depth can alter the crystallite size, microstrain, and wear resistance, as well as to investigate their correlation with essential biocompatibility parameters including cellular interactions, osteointegration potential, and corrosion resistance in a simulated body fluid environment. Understanding these interrelations is crucial for improving the overall performance of titanium implants used in biomedical applications. Methods: Pure titanium specimens were precisely machined at cutting depths of 0.1, 0.2, and 0.3 mm under dry conditions, ensuring that all other machining parameters remained constant. The structural characteristics were analyzed using X-ray diffraction to determine crystallite size and microstrain variations. Wear resistance was evaluated through sliding wear tests that quantified material loss, while biocompatibility performance was assessed via immersion tests in simulated body fluid. This evaluation included corrosion resistance measurements, quantification of calcium-phosphate deposition on the surface, and analysis of the initial interactions with osteoblast-like cells to determine cellular affinity and bioactivity. Results: The experimental results indicated that increasing the cutting depth led to a significant reduction in crystallite size (28, 50, and 25 nm for 0.1, 0.2, and 0.3 mm, respectively) and a corresponding increase in microstrain (0.0011, 0.0011, and 0.009). Specimens machined at cutting depths of 0.2 and 0.3 mm exhibited superior wear resistance, with lower weight losses (7.9 and 5.3 mg) compared with the 0.1 mm specimen (12.1 mg). Biocompatibility assessments revealed that higher cutting depths enhanced corrosion resistance, promoted calcium-phosphate deposition, and improved osteointegration potential. Conclusion: optimizing the cutting depth to 0.2-0.3 mm during dry milling can substantially improve both mechanical performance and biocompatibility, offering valuable guidance for implant manufacturing and long-term in vivo functionality.