Effects of mechanical properties of thermoplastic materials on the initial force of thermoplastic appliances

Abstract

Orthodontic forces delivered by thermoplastic appliances depend on the material, thickness, and amount of activation. Mechanical properties of the polymers obtained by nanoindentation testing are predictive of force delivery by these appliances.

Effects of thermoforming on the physical and mechanical properties of thermoplastic materials for transparent orthodontic aligners

“…Previous studies compared the surface hardness values for various thermoplastic materials before thermoforming 3132. Vickers hardness was also measured to compare the transfer of force and energy according to the type and thickness of the thermoplastic material, and it was found that the hardness affected the orthodontics force 2533. In the present study, the surface hardness of Essix A+ and Essix ACE increased after thermoforming, whereas that of Duran and eCligner showed no significant changes.…”

Stress relaxation properties of four orthodontic aligner materials: A 24-hour in vitro study

“…Previous three-point bending and nanoindentation tests 4 have been used by many researchers to study the stiffness of such materials after in vitro and in vivo wear, highlighting the importance of exerting sufficient force to move the teeth in a programmed fashion but not so much as to damage their periodontal support. However, we are among the first research groups to investigate their stress relaxation properties.…”

“…Unfortunately, however, none of the four aligner materials we tested demonstrated all of these characteristics. 8 That being said, although the thickness of the aligner material has a great influence on the force it develops, 4 those in clinical use, whether single-or double-layer, are not all of the same thickness, so we were unable to compare identical samples in this regard.…”

“…1 Clear aligners are also advantageous in that they are removable, tailor-made in sequence on patient-specific malocclusion setups, and capable of progressively guiding teeth into their programmed positions. [2][3][4] However, not every aligner is created equal, and those currently on the market differ in terms of their construction material, thickness, and clinical protocol.…”

“…For instance, in 2004, Shuster et al 13 observed a significant increase in aligner stiffness after intraoral wear, ascribing this to the effect of chewing forces and salivary enzymes. Kohda et al 4 compared the elastic moduli, hardness, and force generated by three different aligner materials and thicknesses, finding that both factors had a radical effect on the system of forces that the aligner exerts on the teeth, and therefore their orthodontic performance.…”