J Korean Acad Prosthodont.  2012 Jul;50(3):156-161. 10.4047/jkap.2012.50.3.156.

Comparison of fatigue fracture strength by fixture diameter of mini implants

• Heo YR
• Son MK
• Kim HJ
• Choe HC
• Chung CH

• KMID: 2000203
• DOI: http://doi.org/10.4047/jkap.2012.50.3.156

Abstract

PURPOSE
This study was conducted to obtain difference in fracture strength according to the diameter of one-body O-ring-type of mini implant fixture, to determine the resistance of mini implant to masticatory pressure, and to examine whether overdenture using O-ring type mini implant is clinically usable to maxillary and mandibular edentulous patients.
MATERIALS AND METHODS
For this study, 13 mm long one body O-ring-type mini implants of different diameters (2.0 mm, 2.5 mm and 3.0 mm) (Dentis, Daegu, Korea) were prepared, 5 for each diameter. The sample was placed at 30degrees from the horizontal surface on the universal testing machine, and off-axis loading was applied until permanent deformation occurred and the load was taken as maximum compressive strength. The mean value of the 5 samples was calculated, and the compressive strength of implant fixture was compared according to diameter. In addition, we prepared 3 samples for each diameter, and applied loading equal to 80%, 60% and 40% of the compressive strength until fracture occurred. Then, we measured the cycle number on fracture and analyzed fatigue fracture for each diameter. Additionally, we measured the cycle number on fracture that occurred when a load of 43 N, which is the average masticatory force of complete denture, was applied. The difference on compressive strength between each group was tested statistically using one-way ANOVA test.
RESULTS
Compressive strength according to the diameter of mini implant was 101.5 +/- 14.6 N, 149 +/- 6.1 N and 276.0 +/- 13.4 N, respectively, for diameters 2.0 mm, 2.5 mm and 3.0 mm. In the results of fatigue fracture test at 43 N, fracture did not occur until 2x106 cycles at diameter 2.0 mm, and until 5x106 cycles at 2.5 mm and 3.0 mm.
CONCLUSION
Compressive strength increased significantly with increasing diameter of mini implant. In the results of fatigue fracture test conducted under the average masticatory force of complete denture, fracture did not occur at any of the three diameters. All of the three diameters are usable for supporting overdenture in maxillary and mandibular edentulous patients, but considering that the highest masticatory force of complete denture is 157 N, caution should be used in case diameter 2.0 mm or 2.5 mm is used.

Keyword

Mini implant; Fatigue fracture; Strength

MeSH Terms

Bite Force
Collodion
Compressive Strength
Denture, Complete
Denture, Overlay
Fatigue
Fractures, Stress
Humans
Collodion

Figure

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  Fig. 1 O-ring type of mini implants (Dentis, Daegu, Korea). A: ∅2.0 mm, B: ∅2.5 mm, C: ∅3.0 mm.

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  Fig. 2 A schematic graphic design of the testing apparatus.

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  Fig. 3 Universal testing machine for static loading test (AGS-1000D, SHIMADZU Co., Japan).

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  Fig. 4 Fatigue testing machine for dynamic loading test (ADT-AV01K1N, SHIMADZU Co., Japan).

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  Fig. 5 Load-displacement curves of static loading test.

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  Fig. 6 Permanent deformed mini implants caused by static loading test. A: ∅2.0 mm, B: ∅2.5 mm, C: ∅3.0 mm.

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  Fig. 7 Load versus logarithmic number of cycles in dynamic fatigue test.

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  Fig. 8 Mini implants fractured by dynamic fatigue test. A: ∅2.0 mm, B: ∅2.5 mm, C: ∅3.0 mm.

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