Effects of Mechanical Properties of Lingual Lever Arm on the Displacement Pattern of Anterior Segment: A Finite Element Analysis
Ji-Sung Jang, Yun-Jin Koo, Byeong-Tak Keum, Young-Chel Park, Kee-Joon Lee
Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea
Purpose: The purpose of this study was to investigate the effects of mechanics properties of lingual lever arm on the displacement pattern of maxillary anterior segment.
Methods: A finite element model was constructed based on average dental study model. The lever arm was designed as 20 mm in length, with or without splinting wire. Wire stiffness was set as .016×.022 stainless steel, .018×.025 stainless steel or structure with indefinite rigidity. The mechanical property of PDL was simulated based on recent studies. Point of force application was simulated as that of either midpalatal or palatal interradicular miniscrews. Initial tooth displacement was compared depending on the presence of the splint wire, stiffness of the main archwire and the property of periodontal ligament.
Results: Compared to the non-splint lever arm, splinted lever arm decreased the lingual tipping of incisors and buccal displacement of canine, inducing translation of 4 anterior teeth at lever arm length 16.85 mm (palatal slope miniscrews) and 19.01 mm (midpalatal miniscrew). When the wire stiffness was increased, buccal displacement of canine was decreased. Differences in the mechanical properties of PDL affected not only the pattern of displacement, but also the amount of displacement at each condition.
Conclusion: The results indicate that splinting of lever arms and wire stiffness of main arch provides additional resistance to deformation of the main archwire, implicating predictable tooth movement during anterior retraction.
Key words: Lingual lever arm, Anterior segment, Finite element, Splint, Stiffness
Korean J Lingual Orthod 2014;3(1):1-12