Phd in INDUSTRIAL AND MANAGEMENT ENGINEERING

Thesis title: Green Additive Manufacturing for an innovative sustainable design in endodontic instruments

The present work focuses on an integrated approach aimed at analysing the design and optimisation of NiTi alloy rotary instruments for endodontics, with particular attention to the introduction of the axial cavity and the study of associated manufacturing technologies, as well as the use of the innovative ‘Endotester’ testing system. Numerical simulations were conducted to evaluate the mechanical behaviour of endodontic instruments with different cross-sectional designs under complex loading conditions, highlighting the criticalities due to cyclic fatigue and torsion failure, phenomena that traditionally limit the reliability of NiTi instruments in curved canals. The optimisation procedure made it possible to explore different geometric configurations by analysing the influence of characterising geometric parameters, such as taper and pitch of the cutting edge helix. The introduction of an axial cavity designed to reduce overall weight and improve stress distribution during use, while also facilitating the flow of irrigants along the channel, is the innovative aspect of this work. Through a multi-objective design process, it was possible to define an axially hollow geometry capable of exhibiting a fatigue life that is approximately 88% longer and an improvement in torsion behaviour by virtue of a 15.4% reduction in resistant torque. An in-depth study was also devoted to the manufacturing technologies for the realisation of the axial cavity. Advanced processes such as waterjet, laser drilling and micro EDM were analysed. It was thus possible to identify the most suitable manufacturing technology, not only on the basis of efficiency and performance criteria, but also on the sustainability of the process. In the meantime, with the aim of creating a system that would allow the realisation of standardised tests for the evaluation of mechanical behaviour, the design and manufacture of an innovative test bench for rotary endodontic instruments was conducted. This test bench was developed with a modular and flexible design, capable of simulating the realistic operating conditions of such instruments, guaranteeing the reproducibility and reliability of measurements. The integration of advanced sensors made it possible to collect accurate data in real time, allowing detailed analysis of the performance of the tested devices.