MTech Thesis Colloquium: Mr. Astik Kumar (22/04/26)
Thesis title:
A study on Materials, Manufacturing, and Biological aspects of Micro Ceramic Injection Moulded Zirconia Toughened Alumina.
Faculty advisor(s):
Prof. Subodh Kumar and Dr. Prosenjit Das
When?
22nd April, 2026 (Wednesday), 02:00 PM (India Standard Time)
Where
KI Vasu Auditorium, Department of Materials Engineering
Abstract:
Zirconia-toughened alumina (ZTA) orthodontic brackets manufactured through micro ceramic injection moulding (μ-CIM), addressing material formulation, process optimisation, mechanical performance, aesthetics, and biocompatibility. The feedstock was prepared by combining 90 wt.% α-Al₂O₃ with 10 wt.% ZrO₂ (3Y-TZP) using a CAB/PEG/SA/PTZ binder system at 58 vol.% solids loading. Mixing was carried out using a sigma-blade mixer at 160°C for 60 minutes to ensure homogeneity. Optimal injection-moulding temperatures were established as 180/175/170°C for the machine and 40°C for the mould to produce defect-free green brackets with weight variation within ±3%. Subsequent de-binding and sintering yielded densities of up to 4.06 g/cm³. It exhibited good mechanical properties: Vickers hardness of 1722 ± 19 HV, nano-hardness of 21 GPa, Young’s modulus of 184 GPa, shear bond strength of 7.1 MPa, tie-wing fracture strength of 338 MPa and friction coefficients of 0.32–0.33. Biological testing also yielded favourable results. Human gingival fibroblast viability exceeded 90% at both 24 and 72 hours, surpassing the ISO 10993-5 cytotoxicity threshold. A 28-day rat implantation study showed normal kidney function, stable calcium levels, and low inflammatory markers, with only mild liver enzyme elevation and a limited local tissue response, neither of them indicative of serious harm. Aesthetically, the brackets changed their colour from chalky white to a light yellowish colour, which is the original colour of human teeth, particularly from black coffee, after 72 hours.
μ-CIM ZTA brackets demonstrate a promising combination of mechanical properties, bond integrity, and biocompatibility. However, reducing residual internal defects and improving stain resistance remain key priorities before clinical translation can be fully realised.