ADELINA GRIGORE, CAMELIA SZUHANEK, DOINA ONISEI, ANGHEL CERNESCU A COMPARATIVE STUDY REGARDING THE DEFORMATION VALUES OF ORTHODONTIC ALIGNERS Orthodontic therapy using aligners is a modern treatment option among adult patients. In order to have an optimal control of the orthodontic resuslts, there is a need for knowing the deformation values that can appear in each type of aligner, the optimal thickness values of the appliances and the needed number of aligners for each case. The deformation values for a 0.2 mm repositioned lower central incisor were measured with the use of some strain gauges applied at this level, after a manual set-up was manufactured. Different orthodontic forces were applied on each aligner in order to compare the deformation value during the dental correction. The thickness values of the aligners that were used for this study were 0.625 mm, 0.75 mm and 1 mm. The 0.625 mm aligner had the lowest deformation value dueto a high elasticity of the material.