The Journal of Contemporary Dental Practice

Register      Login



Volume / Issue

Online First

Related articles

VOLUME 19 , ISSUE 11 ( November, 2018 ) > List of Articles


A Comparison of Torque Stress on Abutment Screw of External Hexagon and Morse Taper Implant

Luiz R Paranhos, Eduardo dos S Rodrigues, Paula Benetti, Pâmela L Santos

Keywords : Abutment, Dental implant, Dental prosthesis, Rehabilitation oral

Citation Information : Paranhos LR, Rodrigues ED, Benetti P, Santos PL. A Comparison of Torque Stress on Abutment Screw of External Hexagon and Morse Taper Implant. J Contemp Dent Pract 2018; 19 (11):1306-1311.

DOI: 10.5005/jp-journals-10024-2423

License: CC BY-NC 4.0

Published Online: 01-10-2018

Copyright Statement:  Copyright © 2018; The Author(s).


Aim: This three-dimensional (3D) finite element analysis observed the stress distribution on the prosthetic screws on external hexagon implant and morse taper implant with different tightening loads. Materials and methods: For this, two different 3D models assembly were obtained from the manufacturer and transferred to finite element analysis software: External hex implant model (EHM), and Morse taper implant model (MTM), both compounds by 3.75 x 7 mm implant, abutment and abutment screw. Bolt pretension force was applied on the shaft next to the threads of the prosthetic abutment. Preload was calculated using the torque on the prosthetic screw as recommended by the manufacturer (EHM30 and MTM20) and 10 Ncm torque above the manufacturer recommendations (EHM40 and MTM30). Maximum von mises equivalent stresses were obtained on the screws. Results: Preload values results were 243.18N (EHM30), 229.71N (MTM20), 324.24N (EHM40) and 344.57N (MTM30). In EHM30, EHM40 and MTM20 models the maximum stresses were below the yield strength of the abutment screw material. However, the maximum stress in MTM30 model was higher than the reference value. Conclusion: The torque loads above the manufacturer recommendations can cause plastic deformation in the MT abutment screw threads. The screws of morse taper implant can be more sensitive to higher loads than external hexagon implant. Clinical significance: The adequate torque can result in screw loosening, while fracture may occur if torque is excessive. Abutment screw suffers many screwing cycles in its lifetime in a way that some tightening forces are above manufacturer recommendations.

PDF Share
  1. Bulaqi HA, Mashhadi MM, Safari H, Samandari MM, Geramipanah F. Dynamic nature of abutment screw retightening: finite element study of the effect of retightening on the settling effect. J Prosthet Dent. 2015;113(5):412-419.
  2. Lemos CAA, de Souza Batista VE, de Faria Almeida DA, Júnior JFS, Verri FR, Pellizzer EP. Evaluation of cement-retained versus screw-retained implant-supported restorations for marginal bone loss: A systematic review and meta-analysis. J Prosthet Dent. 2016;115(4):419-427.
  3. Zweers J, van Doornik A, Hogendorf EAH, Quirynen M, Van der Weijden GA. Clinical and radiographic evaluation of narrow- vs. regular-diameter dental implants: a 3-year follow-up. A retrospective study. Clin Oral Implants Res. 2015;26(2):149-156.
  4. Pjetursson BE, Brägger U, Lang NP, Zwahlen M. Comparison of survival and complication rates of tooth-supported fixed dental prostheses (FDPs) and implant-supported FDPs and single crowns (SCs). Clin Oral Implants Res. 2007;18:97-113.
  5. Gotfredsen K, Wiskott A. Consensus report - reconstructions on implants. The Third EAO Consensus Conference 2012. Clin Oral Implants Res. 2012;23:238-241.
  6. Lang LA, Kang B, Wang R-F, Lang BR. Finite element analysis to determine implant preload. J Prosthet Dent. 2003;90(6):539-546.
  7. Kitagawa T, Tanimoto Y, Odaki M, Nemoto K, Aida M. Influence of implant/abutment joint designs on abutment screw loosening in a dental implant system. J Biomed Mater Res - Part B. 2005;75(2):457-463.
  8. Hasan I, Keilig L, Bourauel C, Lückerath W. The effect of screw preload and framework material on the success of cementable fixed partial prostheses: A finite element study. Ann Anat - Anat Anz. 2015;199:58-66.
  9. Wang K, Geng J, Jones D, Xu W. Comparison of the fracture resistance of dental implants with different abutment taper angles. Mater Sci Eng C. 2016;63:164-171.
  10. Spazzin AO, Henrique GE, Nóbilo M, Consani RL, Correr- Sobrinho L, Mesquita MF. Effect of retorque on loosening torque of prosthetic screws under two levels of fit of implantsupported dentures. Braz Dent J. 2010;21(1):12-17.
  11. Farina AP, Spazzin AO, Xediek Consani RL, Mesquita MF. Screw joint stability after the application of retorque in implant-supported dentures under simulated masticatory conditions. J Prosthet Dent. 2014;111(6):499-504.
  12. Jung R, Zembic A, Pjetursson BE, Zwahlen M, S. Thoma D. Systematic review of the survival rate and the incidence of biological, technical, and aesthetic complications of single crowns on implants reported in longitudinal studies with a mean follow-up of 5 years. Clin Oral Implants Res. 2012;23: 2-21.
  13. Bacchi A, Regalin A, Bhering CLB, Alessandretti R, Spazzin AO. Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating. J Adv Prosthodont. 2015;7(5):375.
  14. Winkler S, Ring K, Ring, JD, Boberick, KG. Implant screw mechanics and the settling effect: an overview. J Oral Implantol. 2003;29(5):242-245.
  15. Guzaitis KL, Knoernschild KL, Viana M a G. Effect of repeated screw joint closing and opening cycles on implant prosthetic screw reverse torque and implant and screw thread morphology. J Prosthet Dent. 2011;106(3):159-169.
  16. Jörn D, Kohorst P, Besdo S, Rücker M, Stiesch M, Borchers L. Influence of lubricant on screw preload and stresses in a finite element model for a dental implant. J Prosthet Dent. 2014;112(2):340-348.
  17. Sones AD. Complications with osseointegrated implants. J Prosthet Dent. 1989;62(5):581-585.
  18. Ugurel CS, Steiner M, Isik-Ozkol G, Kutay O, Kern M. Mechanical resistance of screwless morse taper and screwretained implant-abutment connections. Clin Oral Implants Res. 2013;26(2):137-142.
  19. Imam AY, Moshaverinia A, Chee WWL, McGlumphy EA. A technique for retrieving fractured implant screws. J Prosthet Dent. 2014;111(1):81-83.
  20. Yilmaz B, Mascarenhas F. Salvaging an implant with damaged internal threads. J Prosthet Dent. 2015;114(2):301-304.
  21. Carneiro T de APN, Prudente MS, e Pessoa RS, Mendonça G, Das Neves FD. A conservative approach to retrieve a fractured abutment screw–Case report. J Prosthodont Res.2016;60(2): 138-142.
  22. Siamos G, Winkler S, Boberick KG. The relationship between implant preload and screw loosening on implant-supported prostheses. J Oral Implantol. 2002;28(2):67-73.
  23. Doolabh R, Dullabh HD, Sykes LM. A comparison of preload values in gold and titanium dental implant retaining screws. South Afr Dent J. 2014;69(7):316-320.
  24. Moreira W, Hermann C, Pereira J, Balbinoti J, Tiossi R. A three - dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants. Eur J Dent. 2013;7(4):484-491.
  25. Mattheos N, Li X, Zampelis A, Ma L, Janda M. Investigating the micromorphological differences of the implant-abutment junction and their clinical implications: a pilot study. Clin Oral Implants Res. 2015;1:1-10.
  26. Zhang G, Yuan H, Chen X, Wang W, Chen J, Liang J, et al. A Three-Dimensional Finite Element Study on the Biomechanical Simulation of Various Structured Dental Implants and Their Surrounding Bone Tissues. Int J Dent. 2016;1: 1-9.
  27. Peixoto, H.E., Bordin, D., Cury, A.A.D.B., da Silva, W.J., Faot, F. The role of prosthetic abutment material on the stress distribution in a maxillary single implant-supported fixed prosthesis. Mater Sci Eng C. 2016;65:90-96.
  28. Silva GC, Cornacchia TM, de Magalhães CS, Bueno AC, Moreira AN. Biomechanical evaluation of screw-and cementretained implant-supported prostheses: A nonlinear finite element analysis. J Prosthet Dent. 2014;112(6):1479-1478.
  29. Freitas-Júnior AC, Rocha EP, Bonfante E a., Almeida EO, Anchieta RB, Martini AP, et al. Biomechanical evaluation of internal and external hexagon platform switched implantabutment connections: An in vitro laboratory and three-dimensional finite element analysis. Dent Mater.2012;28(10):218-228.
  30. Macedo JP, Pereira J, Faria J, Pereira CA, Alves JL, Henriques B, et al. Finite element analysis of stress extent at peri-implant bone surrounding external hexagon or Morse taper implants. J Mech Behav Biomed Mater. 2017;71:441-447.
  31. Takahashi JM, Dayrell AC, Consani RL, de Arruda Nóbilo MA, Henriques GE, Mesquita MF. Stress evaluation of implantabutment connections under different loading conditions: a 3D finite element study. J Oral Implantol. 2015;41(2):133-137.
PDF Share
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.