unilateral outer bow expanded cervical headgear force system: 3d analysis using finite element method

o bjectives: headgears are among the effective orthodontic appliances to achieve treatment goals. unilateral molar distal movement is sometimes needed during an orthodontic treat- ment, which can be achieved by an asymmetric headgear. different unilateral headgears have been introduced. the main goal of this study was to analyze the force system of uni- lateral expanded outer bow asymmetric headgears by the finite element method (fem). materials and methods : six 3d finite element models of a mesiodistal slice of the maxilla containing upper first molars, their periodontal ligaments (pdls), cancellous bone, cortical bone, and a cervical headgear with expanded outer bow attached to maxillary first molars were designed in solidworks 2010 and meshed in ansys workbench ver. 12.1. the mod- els were the same except for the degree of outer bow expansion. the outer bow ends were loaded with 2-newton force. the distal driving force and the net moment were evaluated. results : a decrease in the distalizing force in the normal side molar from 1.69 n to 1.37 n was shown by increasing the degree of unilateral expansion. at the same time, the force increased from 2.19 n to 2.49 n in the expanded side molar. a net moment increasing from 2.26 n.mm to 4.64 n.mm was also shown. conclusion : unilateral outer bow expansion can produce different distalizing forces in mo- lars, which increase by increasing the expansion.