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Unequal outer and inner bow configurations: comparing 2 asymmetric headgear systems
Tamar Brosh1, Schay Portal, Ofer Sarne
1Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel. tbrosh@post.tau.ac.il
Summary
Asymmetric headgear effectively corrects Class II molar relationships. Outer-bow designs are best for bilateral issues, while inner-bow designs suit unilateral Class II subdivisions, offering tailored molar distalization forces.
Area of Science:
- Orthodontics
- Craniofacial Mechanics
Background:
- Asymmetric headgear is utilized when differential molar distalization forces (MDF) are required for Class II molar relationship correction.
- This addresses cases needing distinct forces on the right and left sides of the jaw.
Purpose of the Study:
- To investigate and compare the effectiveness of two asymmetric cervical-pull headgear configurations.
- To quantify the molar distalization forces (MDF) generated by outer-bow and inner-bow asymmetric designs.
Main Methods:
- Two asymmetric headgear configurations were tested: outer-bow with varied hook lengths and inner-bow with added stops.
- Molar distalization forces (MDF) and extraoral forces (EF) were measured using fork transducers and a testing machine.
Main Results:
- Outer-bow asymmetry with a 40-mm difference created a 2.17-fold greater MDF on the longer side (7:3 ratio).
- Inner-bow asymmetry (3-4 stop configuration) at 10 N EF yielded MDF ratios of 7:3 (stop/no-stop) and 10:0.
- Unilateral MDF was observed on the stop side with zero MDF on the no-stop side at low-to-medium EF.
Conclusions:
- Outer-bow asymmetric headgear is recommended for bilateral unequal Class II relationships.
- Inner-bow asymmetric headgear is suitable for unilateral Class II relationships (Class II subdivision).