Relative wire stiffness due to lingual versus labial interbracket distance

Area of Science:

• Orthodontics
• Biomaterials Science
• Dental Mechanics

Background:

• Orthodontic treatment with lingual appliances requires adapting conventional mechanotherapy used for labial appliances.
• Placing brackets on the lingual surface significantly reduces interbracket distances in the anterior arch regions compared to labial placement.

Purpose of the Study:

• To quantify the reduction in interbracket distances with lingual appliances.
• To determine the effect of decreased interbracket distances on orthodontic arch wire stiffness.
• To develop wire equivalence charts for clinical use in lingual orthodontics.

Main Methods:

• Measurements of interbracket distances were taken from models of 30 patients treated with either lingual or labial appliances.
• A ratio comparing lingual to labial interbracket distances was calculated (1:1.47).
• Stiffness of 25 orthodontic wires was evaluated in first-, second-, and third-order bending at lengths corresponding to the measured ratios.

Main Results:

• Decreased interbracket distance in lingual orthodontics increases apparent arch wire stiffness.
• Wires used with lingual appliances exhibit approximately 3 times the stiffness for first- and second-order bends compared to labial appliances.
• Wires show approximately 1.5 times the stiffness for third-order bends with lingual appliances.

Conclusions:

• Lingual appliance use significantly alters arch wire stiffness due to reduced interbracket distances.
• Developed wire equivalence charts facilitate direct comparisons of arch wire stiffness between labial and lingual systems.
• These findings are crucial for clinicians managing arch wire flexibility during initial alignment and detailing in lingual orthodontics.