Measurement of initial displacement of canine and molar in human maxilla under different canine retraction methods using digital holographic interferometry

Abstract. An application of digital holographic interferometry for the measurement of the initial displacement of canine and molar in the human maxilla, under different canine retraction mechanisms, is presented. The objective of this study is to determine and compare the canine and molar displacements with and without transpalatal arch (TPA) on 0.018-in. stainless steel (SS) and 0.019-  ×  0.025-in. SS arch-wires, using three different canine retraction sliding mechanism methods: nickel–titanium (Ni–Ti)-closed coil-spring, active tie-back, and elastomeric chains. The proposed technique is highly sensitive and enables the displacement measurement of the canine and molar in human maxilla under different canine retraction methods, more precisely and accurately compared with its counterparts. The experiment was conducted on a dry human skull without mandible with intact dental arches and aligned teeth. The experimental results reveal that Ni–Ti-closed coil-spring produces maximum initial canine displacement, followed by active-tie back and elastomeric chain. It was also found that initial canine and molar displacements were more on 0.018-in. SS arch-wire as compared with 0.019  ×  0.025-in. SS arch-wire. Further, the initial displacement of the molar was less when TPA was taken as an anchorage in comparison to without anchorage.