Clinical measurement of force systems upon activation of transpalatal arch in the treatment of unilateral crossbite.
OBJECTIVE
in this study, forces and moments acting on the molars were theoretically determined by means of small-deflection analysis when an asymmetric third-order activation of the TPA was carried out.


METHODS
the transpalatal arch (TPA) is used to correct unilateral crossbites through the application of buccal root torque to the anchorage molar and lingual root torque to the contralateral molar in crossbite, combined with expansion. Unfortunately, the complex force systems created at the molars upon activation of the TPA cannot be easily estimated.


RESULTS
our computations revealed that the vertical forces developed on the molars when both ends of the TPA are inserted into the lingual sheaths (two-couple system) is four-times greater than those when only one end is tied to the lingual sheath as a single-point contact (one-couple system).


CONCLUSIONS
we propose a method of clinical estimation of the force system in a two-couple system by directly measuring the vertical force produced by the one-couple system.
Yoshida
N
N
Department of Orthodontics, Nagasaki University, School of Dentistry, Nagasaki, Japan.
Koga
Y
Y
Jost-Brinkmann
P G
PG
Kobayashi
K
K
D000465:Algorithms; D001696:Biomechanical Phenomena; D006801:Humans; D008310:Malocclusion / Q000628:therapy*; D008954:Models, Biological; D008963:Molar / Q000503:physiopathology; D010155:Palatal Expansion Technique; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques; D014092:Tooth Root / Q000503:physiopathology; D019415:Torque