Portable universal tensile testing machine for studying mechanical properties of superelastic biomaterials

A portable universal tensile testing machine for single and cyclic loading of superelastic biomaterials is presented. It’s an alternative to large-sized stationary universal testing machines. The machine is designed to obtain uniaxial cyclic tension stress-strain curves of materials with a low elastic modulus, including biological tissues. Its portability allows using it in various conditions: classrooms, production laboratories, and in the field. An interface has been developed to connect it to a computer. Computer output of experimental data allows recording and displaying load-displacement curves, setting the number of cycles, limits, and rate of cyclic deformation. Several examples of testing various biomaterials are presented. The functional advantage of the device is the wide tensile testing speed range of 0.01-10 mm/s and cyclic loading, which allow capturing viscoelastic and superelastic behavior of biomaterials.

Simulation of superelastic NiTi wire force application on orthodontic alignment case

Nickel Titanium (NiTi) orthodontic wires are the most accurate initial wires to align the teeth by producing the less painful bone remodeling. Coupling their mechanical response, while they are engaged in the oral cavity, with the bone remodeling would permit to elucidate the reaction and the effect of this wire during the orthodontic tooth alignment. Therefore, A two-dimensional numerical long-term orthodontic tooth correction was performed to simulate a tooth intrusion movement. This simulation was achieved by taking into consideration the effect of an orthodontic appliance action on three multiteeth models. The superelastic behavior of the NiTi wire was integrated in the computer software ABAQUS via a UMAT subroutine. The orthodontic arch was initially deformed to simulate its insertion in brackets and then unloaded to apply an orthodontic load and produce initial tooth displacement. A bone remodeling process was implemented to displace the teeth depending on the strain within the periodontal ligament. The results were obtained for a treatment period of 30 days. The NiTi wire was able to recuperate its initial position, and the teeth were aligned. The numerical results of the teeth displacement were in agreement with what is expected to be produced during the alignment phase.

Investigation into the Hybrid Production of a Superelastic Shape Memory Alloy with Additively Manufactured Structures for Medical Implants

The demographic change in and the higher incidence of degenerative bone disease have resulted in an increase in the number of patients with osteoporotic bone tissue causing. amongst other issues, implant loosening. Revision surgery to treat and correct the loosenings should be avoided, because of the additional patient stress and high treatment costs. Shape memory alloys (SMA) can help to increase the anchorage stability of implants due to their superelastic behavior. The present study investigates the potential of hybridizing NiTi SMA sheets with additively manufactured Ti6Al4V anchoring structures using laser powder bed fusion (LPBF) technology to functionalize a pedicle screw. Different scanning strategies are evaluated, aiming for minimized warpage of the NiTi SMA sheet. For biomechanical tests, functional samples were manufactured. A good connection between the additively manufactured Ti6Al4V anchoring structures and NiTi SMA substrate could be observed though crack formation occurring at the transition area between the two materials. These cracks do not propagate during biomechanical testing, nor do they lead to flaking structures. In summary, the hybrid manufacturing of a NiTi SMA substrate with additively manufactured Ti6Al4V structures is suitable for medical implants.