Iterative finite element analysis of molar uprighting using superelastic Nickel Titanium spring: introducing an...

Area of Science:

• Biomaterials Science
• Computational Mechanics
• Orthodontics

Background:

• Superelastic Nickel Titanium (NiTi) alloys exhibit complex nonlinear behavior challenging finite element (FE) simulations in orthodontics.
• Standard FE models struggle with realistic stress evolution, leading to inaccurate force predictions for NiTi appliances.

Purpose of the Study:

• To introduce and validate an Element-Iteration-Specific (EIS) material model for simulating superelastic NiTi behavior in FE analysis.
• To investigate the biomechanics of molar uprighting using a NiTi spring and estimate clinical treatment duration.

Main Methods:

• A 2D FE model simulated a mesially tilted molar uprighted with a NiTi spring.
• The EIS algorithm updated element-specific material parameters iteratively based on stress-strain states, ensuring continuous behavior simulation.

Main Results:

• The simulation achieved 23.3° molar uprighting over an equivalent 14-week clinical period.
• Physiologic Periodontal Ligament (PDL) stress and accurate tracking of NiTi's martensitic transformation were observed.
• The NiTi spring generated initial counter-clockwise moment and normal extrusive force.

Conclusions:

• The EIS framework accurately captured NiTi's nonlinear, history-dependent response.
• Clinically relevant predictions were achieved, validating the computational approach for NiTi orthodontic appliances.
• This provides a foundation for optimizing appliance design and enhancing orthodontic treatment outcomes.