The use of an orthodontic appliance implicates to completely understand all his fisical, mechanical and clinical characteristics
in order to obtain and control all the effects that it could produce.
The purpose of this article is to englobe constrution and activation aspects of the QH appliance that allow to achieve the
required movements for molars and premolars transversal correction.
(Rev Esp Ortod. 2002;32(3):253-262)