J Dent Rehabil Appl Sci.  2020 Sep;36(3):176-182. 10.14368/jdras.2020.36.3.176.

Effects of implant alignment and load direction on mandibular bone and implant: finite element analysis

• Chung H
• Park C
• Yun KD
• Lim HP
• Park SW
• Yang H

• KMID: 2512112
• DOI: http://doi.org/10.14368/jdras.2020.36.3.176

Abstract

Purpose
To evaluate the effects of load direction, number of implants, and alignment of implant position on stress distribution in implant, prosthesis, and bone tissue.
Materials and Methods
Four 3D models were made to simulate posterior mandible bone block: two implants and 3-unit fixed dental prosthesis (FDP) with a pontic in the center (model M1), two implants and 3-unit FDP with a cantilever pontic at one end (model M2), FDP supported by three implants with straight line placement (model M3) and FDP supported by three implants with staggered implant configuration (model M4). The applied force was 120 N axially or 120 N obliquely.
Results
Peak von Mises stresses caused by oblique occlusal force were 3.4 to 5.1 times higher in the implant and 3.5 to 8.3 times higher in the alveolar bone than those stresses caused by axial occlusal force. In model M2, the connector area of the distal cantilever in the prosthesis generated the highest von Mises stresses among all models. With the design of a large number of implants, low stresses were generated. When three implants were placed, there were no significant differences in the magnitude of stress between staggered arrangement and straight arrangement.
Conclusion
The effect of staggering alignment on implant stress was negligible. However, the number of implants had a significant effect on stress magnitude.

Keyword

finite element analysis; dental restoration failure; dental stress analysis; implant supported prosthesis; occlusal force

Figure

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  Fig. 1 The M1 model reproduced all characteristics of implant-abutment-prosthesis components and mandibular alveolar bone. Model has meshed with tetrahedral elements. All nodes on the lower surface of the tooth were constrained in all directions (X, Y, and Z), as a boundary condition. Static axial (L1) and 45o lingual directed oblique (L2) force of 120 Newton was applied to the tooth at occlusal contact points respectively.

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  Fig. 2 M1, M2, M3, and M4 models of implant-supported FDPs with various alignments and configurations.

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  Fig. 3 Maximum von Mises stresses generated in the implant fixture, screw, and abutment of hex external butt connection type by L1 load. Note the peak von Mises stress at the connector region of the cantilever pontic (M2).

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  Fig. 4 Maximum von Mises stresses generated in the implant fixture, screw, and abutment by L2 load. Note the peak von Mises stress at the abutment screw by L2. Stress concentration area in the implant was observed at the outer surface of the abutment and a contact interface between abutment and screw.

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  Fig. 5 The magnitude of maximum principal stresses generated in the supporting bone is shown in various colors. The blue color indicates where the compressive force has occurred, and the red color indicates where the tensile force has occurred.

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  Fig. 6 Model M2 shows the highest principal stress value, while model M4 shows the lowest stress value. Difference in the stress values between the M3 and M4 models was negligible. However, difference between stress values due to vertical load and lateral load was prominent.

Reference

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