Aim: Canine retraction is an important part of orthodontic treatments and should be coincided with preservation of posterior anchorage, The strain energy input of different appliance designs in teeth PDL is assessed.
Materials and methods: Eight 3D finite element (FE) models of upper right maxillary molars and second premolar were designed. The models contained teeth, their PDL, and bone with their attachments. Combinations of wire cross scetion(round and rectangular), force application on the first or second molar, including or excluding the second molar, and adding the second molar to the system via ligature wire is considered in different models. The strain energy input to the PDL of different teeth was evaluated.
Results: Engagement of all teeth, force application to the second molar resulted in 0.00017129 mJ and shifting toward applying force to the first molar resulted in 0.00017398 mJ. When the second molar was free from wire but laced; this energy finding was 0.00014499 mJ which increase to 0.0003991 mJ when the second molar was really out of the system. Findings for the rectangular wire were 0.00000084, 0.000001148, 0,0001026, and 0.0002929 respectively.
Conclusion: Rotation prevention of the second molar is the key point in using its anchorage value.