Finite element analysis of different force directions in miniscrew assisted en masse retraction cases

This study aims to evaluate the effects of different force directions on tooth movement in miniscrew assisted en masse retraction. En masse retraction of anterior teeth is simulated by applying 200g of force via a closing coil between a power arm located on the main archwire between lateral and canine, and a miniscrew between the roots of 2nd premolar and 1st molar. To simulate different force vectors,6 analysis models are created by applying force from two different levels of power arm (5mm,8 mm) to three different levels of miniscrew (6 ,8,,12 mm). FEM Analysis is used to evaluate displacements in three planes. Analysis results reveal that,an increase in the length of retraction hook, increases the amount of mesiodistal tipping of anterior teeth .Mesiodistal tipping of posterior teeth tends to decrease as the height of miniscrew increases. On buccapalatinal plane, when low retraction hook is used, palatinal movement of anterior teeth increases when the miniscrew height is decreased, however when high retraction hook is used palatinal tipping of anterior teeth increases. More buccal tipping of posterior teeth is examined when low retraction hook is used. As the miniscrew height increases buccal tipping of posterior teeth tends to increase. On vertical plane, as the length of the retraction hook increases, more intrusion is detected on anterior teeth, extrusion is seen in posterior area and the amount of movement increases when the retraction hook length is increased. When low retraction hook is used, an increase in miniscrew height increases the amount of superior movement.