Factors affecting friction in the pre-adjusted appliance

Area of Science:

• Orthodontics
• Biomaterials Engineering
• Dental Mechanics

Background:

• Friction between orthodontic brackets and archwires is a critical factor influencing treatment efficiency.
• Understanding how varying bracket types, archwire dimensions, tip, and torque affect friction is essential for optimizing tooth movement.

Purpose of the Study:

• To quantify the frictional forces generated by different straightwire brackets and archwire dimensions under varying tip and torque.
• To compare friction between stainless steel and cobalt chromium brackets.
• To determine the impact of tip and torque on frictional resistance.

Main Methods:

• A custom jig was designed to measure bracket-archwire friction.
• Forces were measured using an Instron machine during bracket translation.
• Stainless steel and cobalt chromium brackets were tested with 0.019x0.025 and 0.021x0.025 inch stainless steel archwires.
• Tip angles ranged from 0 to 3 degrees, and torque values from 0 to 6 degrees in 2-degree increments.

Main Results:

• Static and kinetic friction values were similar (2.2 N vs. 2.1 N).
• Friction was comparable between stainless steel (2.1 N) and cobalt chromium (2.2 N) brackets.
• The 0.021x0.025 inch archwire generated three times more friction (3.0 N) than the 0.019x0.025 inch archwire (1.2 N).
• Increased tip and torque significantly increased friction, with each degree of tip producing approximately twice the friction of comparable torque.

Conclusions:

• Archwire dimensions significantly influence friction, with larger wires generating substantially more resistance.
• Tip and torque are critical variables that increase frictional forces during orthodontic treatment.
• Space closure should be completed using a 0.019x0.025 inch archwire before transitioning to a 0.021x0.025 inch wire for final tooth alignment to minimize friction.