J Korean Acad Prosthodont.  2010 Jul;48(3):215-223. 10.4047/jkap.2010.48.3.215.

Influence of microthread design on marginal cortical bone strain developement: A finite element analysis

• Chun SG
• Cho JH
• Jo KH

• KMID: 2195558
• DOI: http://doi.org/10.4047/jkap.2010.48.3.215

Abstract

PURPOSE
The present study was aimed to evaluate the level of cortical bone strain during the placement of an implant. The primary concern was to investigate if the extent of overloading area near the marginal bone could be affected by microthread fabricated at the cervical 1/3 of an implant.
MATERIALS AND METHODS
Three dimensional finite element analysis was used to simulate the insertion of 3 implants. Control model was 4.1 x 10 mm implant (Submerged model, Dentis Co,, Daegu, Korea) equipped with a main thread only. Type I was with main thread and microthread, and Type II had similar thread pattern but was of tapered body. A PC-based finite element software (DEFORM 3D ver 5, SFTC, Columbus, OH, USA) was used to calculate a total of 3,600 steps of analysis, which simulated the whole insertion.
RESULTS
Results showed that the strain field in the marginal bone within 1 mm of the implant wall was higher than 4,000 micro-strain in the control model. The size of bone overloading was 1-1.5 mm in Type I, and greater than 2 mm in Type II implants.
CONCLUSION
These results indicate that the marginal bone may be at the risk of resorption on receiving the implant for all 3 implant models studied. Yet, the risk was greater for Type I and Type II implants, which had microthread at the cervical 1/3.

Keyword

Implant; Microthread design; Finite element method

MeSH Terms

Finite Element Analysis
Sprains and Strains

Figure

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  Fig. 1. Geometry of 3 different implant systems. A: Control; straight body without microthread, B: Type I; straight body with microthread, C: Type II; tapered body with microthread.

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  Fig. 2. Finite element model. A: FE mesh model showing the implant prior to its placement and the axis system, B: cross sectioned cortical bone, dimensions of the threaded groove and the 3 reference points to record strain development during the implant placement.

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  Fig. 3. Rigid-plastic property data of cortical bone (virtually perfect plasticity was assumed for cortical bone, i.e. stress of 136 MPa was assigned at strain of 10 as compared to the yield stress, 135 MPa).

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  Fig. 4. Radial strain development in the cortical bone at 6 stages of implant insertion. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in control model implant.

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  Fig. 5. Radial strain development in the half of cortical bone. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in control model implant.

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  Fig. 6. Radial strain development in the cortical bone at 6 stages of implant insertion. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in Type I implant.

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  Fig. 7. Radial strain development in the half of cortical bone. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in Type I implant.

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  Fig. 8. Radial strain development in the cortical bone at 6 stages of implant insertion. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in Type II implant.

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  Fig. 9. Radial strain development in the half of cortical bone. A: initial, B: 1 turn, C: 2 turn, D: 3 turn, E: 4 turn, F: 4.5 turn in Type II implant.

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  Fig. 10. Radial strains recorded at the 3 reference points around. A: control, B: Type I and C: Type II implants during the placement. Significantly high strains were associated with either with the insertion of the imperfect thread (control), or with microthread (Type I and Type II).

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