Initial forces and moments delivered by removable thermoplastic appliances during rotation of an upper central incisor.
OBJECTIVE
To determine the forces and moments delivered to a maxillary central incisor during rotation by three different thermoplastic appliances with identical thickness.


METHODS
Five identical appliances were manufactured from each of three materials (Ideal Clear 1.0 mm, Erkodur 1.0 mm, Biolon 1.0 mm). An upper central incisor fixed in a measuring device was rotated around its central axis in 0.5-degree steps to +/-2.5 degrees, +/-5 degrees, and +/-7.5 degrees (equivalent to an activation of +/-0.17 mm, +/-0.34 mm, and +/-0.51 mm of the incisor edge) in the clockwise and anticlockwise directions with the respective appliance fixed in place. For statistical analysis, the moments Tz (rotation) and forces Fz (intrusion) were tested. Means and standard deviations for Tz and median and 25% and 75% quantiles for Fz were calculated. An analysis of variance (ANOVA) was performed.


RESULTS
The minimal moment was determined at a rotation of -0.17 mm (-7.3 Nmm, +/-0.8), and the maximal moment at a deflection of -0.51 mm (-71.8 Nmm. +/-2.5) was recorded. The minimal value for Fz was measured at an activation of -0.17 mm (0.0 N), and the highest intrusive forces were evaluated for a rotation of -0.51 mm (-5.8 N). The particular material sometimes had a significant (P < .05) influence on the forces delivered and the moments.


CONCLUSIONS
During rotation with aligners, an intrusive force can also be observed. The direction of rotation, and the materials used all exert an influence on the force delivery properties of the appliance.
Hahn
Wolfram
W
Department of Orthodontics, Georg-August-University, Goettingen, Germany. weahahn@med.uni-goettingen.de
Engelke
Benjamin
B
Jung
Klaus
K
Dathe
Henning
H
Fialka-Fricke
Julia
J
Kubein-Meesenburg
Dietmar
D
Sadat-Khonsari
Reza
R
D000704:Analysis of Variance; D003799:Dental Stress Analysis; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D008437:Maxilla; D016382:Orthodontic Appliance Design; D009968:Orthodontic Appliances, Removable; D010969:Plastics; D012399:Rotation; D014087:Tooth Movement Techniques / Q000295:instrumentation*
D010969:Plastics