Thread Pitch Variant in Orthodontic Mini-screws: A 3-D Finite Element Analysis

Document Type : Research Paper


1 Graduate MS Student, School of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran

2 Assistant Professor, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran


Orthodontic miniscrews are widely used as temporary anchorage devices to facilitate orthodontic movements. Miniscrew loosening is a common problem, which usually occurs during the first two weeks of treatment. Macrodesign can affect the stability of a miniscrew by changing its diameter, length, thread pitch, thread shape, tapering angle and so on. In this study, a 3-D finite element analysis was done to show the effect of thread pitch variant on the stress distribution pattern of the screw-cortical bone interface. While orthodontic forces were applied, stresses were usually concentrated at the first thread of the screw in contact with the cortical bone. The cortical bone provided a significant percentage of stability compared to the trabecular bone against orthodontic forces. Therefore, spongy bone was removed from the finite element analysis. The changes of maximum von Mises stresses were shown on the charts. The results showed that stresses decreased with decrease in thread pitch, but they increase when thread pitch becomes less than a certain value. The pattern of stress distribution differed when the stresses were increased. The results are beneficial for the design of an ergonomic dual miniscrew, with better properties than the commercially available miniscrews and based on the results, a new dual miniscrew is recommended.


Main Subjects

[1]. Chang J.Z.C., Chen Y.J., Tung Y.Y., Chiang Y.Y., Lai E.H.H., Chen W.P., Lin C.P., 2012, Effects of thread depth, taper shape, and taper length on the mechanical properties of mini-implants, American Journal of Orthodontics and Dentofacial Orthopedics, 141(3): 279-288.
 [2]. Basaran G., Ayna E., Basaran E.G., Unlu G., 2010, Restoration of posterior edentulous spaces after maxillary molar intrusion with fixed appliances (case report), Journal Of International Dental And Medical Research, 3(2): 69-74.
[3]. Lin T.S., Tsai F.D., Chen C.Y., Lin L.W., 2013, Factorial analysis of variables affecting bone stress adjacent to the orthodontic anchorage mini-implant with finite element analysis, American Journal of Orthodontics and Dentofacial Orthopedics 143(2): 182-189.
 [4]. Sathapana S., Forrest A., Monsour P., Naser‐ud‐Din S., 2013, Age‐related changes in maxillary and mandibular cortical bone thickness in relation to temporary anchorage device placement, Australian dental journal 58(1): 67-74.
[5]. Lim S.A., Cha J.Y., Hwang C.J., 2008, Insertion torque of orthodontic miniscrews according to changes in shape, diameter and length, The Angle Orthodontist 78(2): 234-240.
[6]. Yu J.H., Lin Y.S., Chang W.J., Chang Y.Z., Lin C.L., 2014, Mechanical effects of micro-thread orthodontic mini-screw design in relation to artificial cortical bone thickness, J Med Biol Eng 34: 49-55.
 [7]. Abuhussein H., Pagni G., Rebaudi A., Wang H.L., 2010, The effect of thread pattern upon implant osseointegration, Clinical oral implants research21(2): 129-136.
 [8]. Handa A., Hegde N., Reddy V.P., Chandrashekhar B.S., Arun A.V., Mahendra S., 2011, Effect of the thread pitch of orthodontic mini-implant on bone stress- A 3D finite element analysis, inflammation 4: 7.
[9]. Curtis R.V., Watson T.F. (Eds.), 2014, Dental Biomaterials: Imaging, Testing and Modelling, Elsevier.
[10]. Duaibis R, Kusnoto B., Natarajan R., Zhao L., Evans C., 2012, Factors affecting stresses in cortical bone around miniscrew implants: a three-dimensional finite element study, The Angle Orthodontist 82(5): 875-880.
 [11]. Eraslan O., İnan Ö, 2010, The effect of thread design on stress distribution in a solid screw implant: a 3D finite element analysis, Clinical oral investigations 14(4): 411-416.
 [12]. Alexander H., Ricci J.L., Hrico G.J., 2009, Mechanical basis for bone retention around dental implants, Journal of Biomedical Materials Research Part B: Applied Biomaterials 88(2): 306-311.
 [13]. Tsouknidas A., Maropoulos S., Savvakis S., Michailidis N., 2011, FEM assisted evaluation of PMMA and Ti6Al4V as materials for cranioplasty resulting mechanical behaviour and the neurocranial protection, Bio-medical materials and engineering 21(3): 139-147.
[14]. Hofmann D.C., Suh J.Y., Wiest A., Lind M.L., Demetriou M.D., Johnson W.L., 2008, Development of tough, low-density titanium-based bulk metallic glass matrix composites with tensile ductility, Proceedings of the National Academy of Sciences 105(51): 20136-20140.
[15]. Ahangari A.H., Geramy A., Valian A., 2008, Ferrule designs and stress distribution in endodontically treated upper central incisors: 3D finite element analysis, Journal of Dentistry of Tehran University of Medical Sciences 5(3): 105-110.
[16]. Yu J.H., Lin Y.S., Chang W.J., Chang Y.Z., Lin C.L., 2014, Mechanical effects of micro-thread orthodontic mini-screw design in relation to artificial cortical bone thickness, J Med Biol Eng 34: 49-55.
[17]. Kim Y.K., Kim Y.J., Yun P.Y., Kim J.W., 2009, Effects of the taper shape, dual-thread, and length on the mechanical properties of mini-implants, The Angle orthodontist 79(5): 908-914.
  • Receive Date: 21 April 2015
  • Revise Date: 21 August 2015
  • Accept Date: 21 August 2015