JBiSE  Vol.1 No.1 , May 2008
Comparative Analysis of Internal and External-Hex Crown Connection Systems - A Finite Element Study
Abstract: The abutment connection with the crown is fundamental to the structural stability of the implant system and to the prevention of mechanical exertion that can compromise the success of the implant treatment. The aim of this study is to clarify the difference in the stress distribution patterns between implants with internal and external-hex connections with the crown using the Finite Element Method (FEM). Material and Methods: The internal and external-hex connections of the Neoss and 3i implant systems respectively, are considered. The geometrical properties of the implant systems are modeled using three-dimensional (3D) brick elements. Loading conditions include a masticatory force of 200, 500 and 1000N applied to the occlusal surface of the crown along with an abutment screw torque of 110, 320 and 550Nmm. The von Mises stress distributions in the crown are examined for all loading conditions. Assumptions made in the modeling include: 1. half of the implant system is modeled and symmetrical boundary conditions applied; 2. temperature sensitive elements are used to replicate the torque within the abutment screw. Results: The connection type strongly influences the resulting stress characteristics within the crown. The magnitude of stress produced by the internal-hex implant system is generally lower than that of the external-hex system. The internal-hex system held an advantage by including the use of an abutment between the abutment screw and the crown. Conclusions: The geometrical design of the external-hex system tends to induce stress concentrations in the crown at a distance of 2.89mm from the apex. At this location the torque applied to the abutment screw also affects the stresses, so that the compressive stresses on the right hand side of the crown are increased. The internal-hex system has reduced stress concentrations in the crown. However, because the torque is transferred through the abutment screw to the abutment contact, changing the torque has greater effect on this hex system than the masticatory force. Overall the masticatory force is more influential on the stress within the crown for the external-hex system and the torque is more influential on the internal-hex system.
Cite this paper: nullSTADEN, R. , GUAN, H. , LOO, Y. and W. JOHNSON, N. (2008) Comparative Analysis of Internal and External-Hex Crown Connection Systems - A Finite Element Study. Journal of Biomedical Science and Engineering, 1, 10-14. doi: 10.4236/jbise.2008.11002.

[1]   Y. Maeda, T. Satoh, M. Sogo, “In vitro differences of stress concentrations for internal and external hex implant–abutment connections: a short communication,” Journal of Oral Rehabilitation, vol. 33, pp. 75–78, 2006.

[2]   B. R. Merz, S. Hunenbart, U. C. Belser, “Mechanics of the implant–abutment connection: an 8-degree taper compared to a butt joint connection,” International Journal of Oral and Maxillofacial Implants, vol. 15, pp. 519–526, 2000.

[3]   A. Khraisat, R. Stegaroiu, S. Nomura, O. Miyakawa, “Fatigue resistance of two implant/abutment joint designs,” Journal of Prosthetic Dentistry, vol. 88, pp. 604–610, 2002.

[4]   S. Capodiferro, G. Favia, M. Scivetti, G. De Frenza, R. Grassi, “Clinical management and microscopic characterisation of fatique-induced failure of a dental implant,” Case report. Head and Face Medicine, vol. 22, issue. 2, pp. 18, 2006.

[5]   P. Gehrke, G. Dhom, J. Brunner, D. Wolf, M. Degidi, A. Piattelli, “Zirconium implant abutments: fracture strength and influence of cyclic loading on retaining-screw loosening,” Quintessence International, vol. 37, issue. 1, pp. 19-26, 2006.

[6]   A. Khraisat, “Stability of implant-abutment interface with a hexagon-mediated butt joint: failure mode and bending resistance,” Clinical Implant Dentistry and Related Research, vol. 7, issue. 4, pp. 221-228, 2005.

[7]   F. H. G. Butz, M. Okutan, J. R. Strub, “Survival rate, fracture strength and failure mode of ceramic implant abutments after chewing simulation,” Journal of Oral Rehabilitation, vol. 32, issue. 11, pp. 838-843, 2005.

[8]   K. J. Anusavice, P. H. Dehoff, “Influence of metal thickness on stress distribution in metal-ceramic crowns,” Journal of Dental Research, vol. 65, issue. 9, pp. 1173-1178, 1986.

[9]   K. J. Anusavice, “Stress distribution in metal-ceramic crowns with a facial porcelain margin,” Journal of Dental Research, vol. 66, issue. 9, pp. 1493-1498, 1987.

[10]   K. J. Anusavice, “Influence of incisal length of ceramic and loading orientation on stress distribution in ceramic crowns,” Journal of Dental Research, vol. 67, issue. 11, pp. 1371-1375, 1988.

[11]   H. Y. Suzuki, “Finite element stress analysis of ceramics crown on premolar. Relation between ceramics materials and abutment materials,” Nippon Hotetsu Shika Gakkai Zasshi, vol. 33, issue. 2, pp. 283-293, 1989.

[12]   T. Hino, “A mechanical study on new ceramic crowns and bridges for clinical use,” Osaka Daigaku Shigaku Zasshi, vol. 35, issue. 1, pp. 240-267, 1990.

[13]   B. Zhang, H. Wang, “Three-dimensional finite element analysis of all-ceramic crowns of the posterior teeth,” Hua Xi Yi Ke Da Xue Xue Bao, vol. 31, issue. 2, pp. 147-148, 2000.

[14]   K. A. Proos, J. Ironside, G. P. Steven, “Finite element analysis studies of an all-ceramic crown on a first premolar,” International Journal of Prosthodontics, vol. 15, issue. 4, pp. 404-412, 2002.

[15]   A. Imanishi, T. Ohyama, T. Nakamura, “3-D Finite element analysis of all-ceramic posterior crowns,” Journal of Oral Rehabilitation, vol. 30, issue. 8, pp. 818-822, 2003.

[16]   Strand7 Pty Ltd, Strand7 Theoretical Manual, Sydney, Australia, 2004.

[17]   Neoss Pty Ltd, Neoss Implant System Surgical Guidelines, United Kingdom, 2006.

[18] (accessed 12th July 2006).

[19]   R. C. van Staden, H. Guan, Y. C. Loo, N. W. Johnson, N. Meredith, “Stress Evaluation of Dental Implant Wall Thickness using Numerical Techniques,” Applied Osseointegration Research, (In Press), 2008.

[20]   A. R. Curtis, A. J. Wright, G. J. Fleming, “The influence of simulated masticatory loading regimes on the bi-axial flexure strength and reliability of a Y-TZP dental ceramic,” Journal of Dentistry, vol. 34, issue. 5, pp. 317-325, 2005.

[21]   D. H. DeTolla, S. Andreana, A. Patra, R. Buhite, B. Comella, “Role of the finite element model in dental implants,” Journal of Oral Implantology, vol. 26, issue. 2, pp. 77-81, 2000.

[22]   J. P. Geng, K. B. Tan, G. R. Liu, ”Application of finite element analysis in implant dentistry: a review of the literature,” Journal of Prosthetic Dentistry, vol. 85, issue. 6, pp. 585-598, 2001.