Comparative study of torque expression and its biomechanical effects: spherical self-ligating bracket with lock-hook...

Area of Science:

• Orthodontics
• Biomaterials Science
• Finite Element Analysis

Background:

• Effective torque control is essential for successful orthodontic treatment outcomes.
• This study investigates a new spherical self-ligating bracket's torque capabilities.
• Comparison is made against conventional and passive self-ligating systems, analyzing periodontal ligament (PDL) biomechanics.

Purpose of the Study:

• To compare the torque expression of a novel spherical self-ligating bracket with a lock-hook system against established bracket systems using finite element analysis.
• To evaluate the biomechanical changes within the periodontal ligament (PDL) during torque application.
• To assess the clinical efficacy of the novel bracket system in correcting tooth inclination.

Main Methods:

• Finite element modeling of a maxillary central incisor, PDL, and alveolar bone.
• Comparative analysis of three bracket systems: spherical self-ligating with lock-hook, passive self-ligating (Damon), and conventional (Discovery).
• Application of a 20° palatal root torque and calculation of torque moment, von Mises stress, and strain in the PDL.

Main Results:

• The spherical self-ligating bracket generated approximately 1.6 times more torque (27.8 N·mm) than Damon (17.5 N·mm) and Discovery (17.3 N·mm) brackets at 20° twist.
• Increased twist angle correlated with higher von Mises stress and strain in the PDL.
• An optimal torque range of 10.2–17.5 N·mm was identified for the maxillary incisor, maintaining PDL stress below 0.026 MPa and good strain area above 50%.

Conclusions:

• The spherical self-ligating bracket with a lock-hook system demonstrates a significant improvement in torque expression.
• The identified optimal torque range ensures effective and safe tooth movement.
• The novel bracket system shows clinical potential for correcting undesirable tooth inclinations.