Orthodontic Biomechanics Flashcards

In the sliding mechanics method of space closure, resistance to movement is chiefly due to:

Answer: Friction between the archwire and bracket slot

Sliding mechanics require overcoming friction/binding between the wire and bracket during tooth translation.

Frictionless (loop) mechanics differ from sliding mechanics because they:

Answer: Use closing loops to deliver force without sliding along the wire

Loop mechanics activate bends/loops to move teeth without the tooth sliding along the archwire, avoiding friction.

A stiffer (larger cross-section or higher-modulus) archwire generally delivers:

Answer: Higher force per unit of deflection

Increased stiffness raises the load-deflection rate, delivering more force for a given activation.

Nickel-titanium archwires are favored in early alignment because they:

Answer: Provide light, continuous force over a wide range of deflection (superelasticity)

NiTi wires exhibit superelasticity, giving light, relatively constant forces even when heavily deflected.

First-order (in-out) bends in an archwire control tooth position in which dimension?

Answer: Faciolingual (labiolingual) crown position

First-order bends adjust the in-out (faciolingual) position of the crowns along the arch.

Third-order movement (torque) refers to control of:

Answer: Buccolingual root/crown inclination

Third-order bends or slot-wire engagement control faciolingual root/crown inclination, known as torque.

Decreasing the interbracket distance (bringing brackets closer together) affects the wire by:

Answer: Increasing stiffness and force for a given deflection

Shorter interbracket spans reduce the working length of wire, increasing stiffness and force.