J Dent Rehabil Appl Sci.  2017 Sep;33(3):189-198. 10.14368/jdras.2017.33.3.189.

Stress distribution of implants with external and internal connection design: a 3-D finite element analysis

• Chung H
• Yang SP
• Park JH
• Park C
• Shin JH
• Yang H

• KMID: 2394642
• DOI: http://doi.org/10.14368/jdras.2017.33.3.189

Abstract

PURPOSE
This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design.
MATERIALS AND METHODS
Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction.
RESULTS
Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model.
CONCLUSION
Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

Keyword

implant; abutment-implant connection; finite element analysis; stress distribution; biomechanics

MeSH Terms

Bite Force
Crowns
Finite Element Analysis*
Molar

Figure

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  Fig. 1 (A) Cross sectional view of disassembled implant components with external hex connection (EXHEX), (B) Disassembled implant, crown and supported mandible of EXHEX model.

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  Fig. 2 (A) Cross sectional view of disassembled implant components with internal conical connection (INCON), (B) Disassembled implant, crown and supported mandible of INCON model.

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  Fig. 3 All nodes on the lower surface of the tooth were constrained in all directions (X, Y and Z), as a boundary condition. The static axial (L1) and oblique (L2) forces were applied vertically on the tooth at the occlusal contact points. 3-D solid models were meshed with tetrahedral elements.

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  Fig. 4 Maximum von Mises stresses generated in the restoration, implant and supporting bone by L1 and L2 loads. Note oblique occlusal force produced much greater peak stress in implant than that in axial load.

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  Fig. 5 Maximum von Mises stresses generated in the implant fixture, screw and abutment of external hex butt connection type by L1 and L2 loads. The deflection is 10-fold magnified for visualization. Note the peak von Mises stress around the second thread of the screw by L2.

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  Fig. 6 Maximum von Mises stresses generated in the implant fixture, screw and abutment of internal conical connection type by oblique occlusal load. The deformation is 10-fold magnified for visualization. Note the peak von Mises stress at top collar region of the implant fixture and around the third thread of the screw by L2.

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  Fig. 7 Bucco-lingual cross sectional view of stress distribution inside the implant connection interface with external hex (EXHEX) and internal cone (INCON). The deformation is 10-fold magnified for visualization. Note stresses concentration is observed around the implant - abutment - screw assembly interface.

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  Fig. 8 Cross sectional view of equivalent strain (με) distribution inside the implant connection assembly of EXHEX and INCON models. The deformation is 10-fold magnified for visualization. Note the opening gap between implant and abutment as a result of the L2 loading.

Reference

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