J Adv Prosthodont.  2015 Jun;7(3):240-248. 10.4047/jap.2015.7.3.240.

Does matching relation exist between the length and the tilting angle of terminal implants in the all-on-four protocol? stress distributions by 3D finite element analysis

• Li X
• Cao Z
• Qiu X
• Tang Z
• Gong L
• Wang D

• KMID: 2284710
• DOI: http://doi.org/10.4047/jap.2015.7.3.240

Abstract

PURPOSE
To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework.
MATERIALS AND METHODS
Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle (0degrees, 30degrees and 45degrees) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point.
RESULTS
1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress.
CONCLUSION
Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required.

Keyword

All-on-Four; Edentulous mandibles; Fixed prosthesis; Implant; Finite element analysis; Stress

MeSH Terms

Finite Element Analysis*
Mandible
Molar
Neck
Prostheses and Implants

Figure

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  Fig. 1 Schematic diagram of the model design and implant ID.

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  Fig. 2 The maximum von Mises stresses of 4 implants in the five implant configuration model groups.

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  Fig. 3 Stress contours of the four implants in the five model groups. The color scale revealed that from left to right, the stress increased. To show the position of the maximum stress, each model group was observed from different directions. The implants with the red mark were the #1 implants on the loading side. (A) Tilt30-L, (B) Tilt30-S, (C) Tilt0-S, (D) Tilt45-S, (E) Tilt45-L.

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  Fig. 4 Contours of the maximum von Mises stress level at the implant-bone interfaces of the five model groups (the #1 implant lied in the end of the right side). The color scale revealed that from left to right, the stress increased. (A) Tilt45-L, (B) Tilt30-L, (C) Tilt30-S, (D) Tilt0-S, (E) Tilt45-S.

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  Fig. 5 The maximum von Mises stress in the five model groups at the implant-bone interface.

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  Fig. 6 Stress distribution contours showed on the tissue surface of the framework in the five model groups (the end of the left side was the corresponding site to the #1 implant on the loading side). The color scale revealed that from left to right, the stress increased. (A) Tilt30-L, (B) Tilt0-S, (C) Tilt30-S, (D) Tilt 45-S, (E) Tilt 45-L.

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  Fig. 7 The maximum von Mises stress on the framework in the five model groups.

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