Objective. This paper aims to quantify the effect of wire material, dimension, and deflection on the most identifiable feature of the six-geometries: the moment dissociation point (force system with no moment on the lesser angled bracket), which may or may not occur at the classically defined geometry IV. Materials and Methods. A six-degree of freedom load cell was used to measure the force systems in different combinations of wire materials, wire dimensions, total angle of bracket, and interbracket distance. Brackets were progressively rotated through Burstone and Koenig’s six geometries and the moment on the right bracket was plotted against the ratio of the angle of the two brackets. Regression analysis was used to determine the angular relationship where the actual moment dissociation point occurred for each variable combination. The moment dissociation points were statistically compared. Results. There were significant differences in the moment dissociation points in the variables studied. A shift in the moment dissociation point toward what is classically considered a geometry III, with lower interbracket distance ratios (IBDr = the ratio of distances a) the higher angle bracket to the bracket slot plane intersection and b) total interbracket distance) with linear materials and low wire deflections was observed. Higher deflections showed a pattern more consistent with the theoretical geometry IV (IBDr 0.33). Superelastic phase transformation at extremely high deflections led to a shift towards a geometry III (lower IBDrs). Conclusions. The moment dissociation point was not always coincident with a geometry IV as classically defined by Burstone and Koenig. Variables including wire material properties, dimension, and wire deflection affect the location of the moment dissociation point to different extents. The classic geometries as defined by Burstone and Koenig are a simplification of a complex wire deflection problem, especially with phase transforming pseudoelastic wires. In clinical situations, where one is attempting to create or predict the force system on brackets, these data should be taken into consideration, especially to avoid inconsistent force systems.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


School of Dentistry

First Advisor

Viecilli, Rodrigo F.

Second Advisor

Caruso, Joseph M.

Third Advisor

Rynearson, R. David

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Orthodontic Wires; Orthodontic Appliances; Orthodontic Appliance Design;

Subject - Local

Moment Dissociation Point; Six-degree of freedom load cell; Force systems;



Page Count


Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives