Influence of thermoplastic appliance thickness on the magnitude of force delivered to a maxillary central incisor during tipping.
BACKGROUND
The aim of the study was to quantify the forces delivered by thermoplastic appliances made of 2 materials with 2 thicknesses to a maxillary central incisor during tipping.


METHODS
Two materials were tested, each in 2 thicknesses: Erkodur (Erkodent Erich Kopp GmbH, Pfalzgrafenweiler, Germany) 1.0 and 0.8 mm, and Biolon (Dreve Dentamid GmbH, Unna, Germany), 1.0 and 0.75 mm. For each material, 5 appliances were produced. To measure the forces applied, an isolated measuring tooth, part of a standardized resin model, was deflected in 0.05 degrees steps from 0 degrees to 0.42 degrees in the vestibular and palatine directions, after placing the respective appliance on the model. For statistical analysis, the force components Fx/tipping and Fz/intrusion at a displacement of +/- 0.151 mm from the incisor edge were selected. Means and standard deviations were calculated. The Wilcoxon 2-sample test for group pairings was used.


RESULTS
The norms for the mean Fx forces ranged from 1.62 (SD, 0.41) to 5.35 N (SD, 0.63). The mean Fz forces were between 0.07 (SD, 0.13) and -2.47 N (SD, 0.34). The highest intrusive forces were measured during vestibular displacement of the measuring tooth. The forces delivered by the thick appliances were overall significantly higher (P <0.0001) than those of the thin materials. The forces delivered by the Biolon appliances were generally significantly higher (P <0.0001) than those for the Erkodur materials.


CONCLUSIONS
The forces applied were mostly too high when compared with those stated in the literature as ideal. In addition to thickness, the thermoforming process influences the magnitude of the force delivered by a thermoformed appliance.
Hahn
Wolfram
W
Department of Orthodontics, Georg-August-University of Göttingen, Göttingen, Germany. weahahn@aol.com
Dathe
Henning
H
Fialka-Fricke
Julia
J
Fricke-Zech
Susanne
S
Zapf
Antonia
A
Kubein-Meesenburg
Dietmar
D
Sadat-Khonsari
Reza
R
D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D008422:Materials Testing; D008437:Maxilla; D009068:Movement; D016382:Orthodontic Appliance Design / Q000295:instrumentation / Q000379:methods; D010969:Plastics / Q000737:chemistry*; D011095:Polyethylenes / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D014087:Tooth Movement Techniques / Q000295:instrumentation*; D019415:Torque
D003764:Dental Materials; D010969:Plastics; D011095:Polyethylenes; D011145:Polyvinyls; C477722:polyethylene-polyvinylacetate copolymer