Comparison of fatigue fracture strength by fixture diameter of mini implants

Yu-Ri Heo; Mee-Kyoung Son; Hee-Jung Kim; Han-Cheol Choe; Chae-Heon Chung

doi:10.4047/jkap.2012.50.3.156

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Heo, Son, Kim, Choe, and Chung: Comparison of fatigue fracture strength by fixture diameter of mini implants

Original Article

The Journal of Korean Academy of Prosthodontics

The Journal of Korean Academy of Prosthodontics 2012; 50(3): 156-161.

Published online: 31 July 2012

DOI: https://doi.org/10.4047/jkap.2012.50.3.156

Comparison of fatigue fracture strength by fixture diameter of mini implants

Yu-Ri Heo, DDS¹, Mee-Kyoung Son, DDS, MSD, PhD¹, Hee-Jung Kim, DDS, MSD, PhD¹, Han-Cheol Choe, PhD², Chae-Heon Chung, DDS, MSD, PhD¹

¹Department of Prosthodontics, School of Dentistry, Chosun University, Gwangju, Korea.

²Department of Dental Material, School of Dentistry, Chosun University, Gwangju, Korea.

Corresponding Author: Chae-Heon Chung. Department of Prosthodontics, School of Dentistry, Chosun University, 303 Pilmun-daero, Dong-gu, Gwangju, 501-825, Korea. +82 62 220 3820: jhajung@chosun.ac.kr

Received 4 April 2012 Revised 19 April 2012 Accepted 14 June 2012

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 30° 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 2×10⁶ cycles at diameter 2.0 mm, and until 5×10⁶ 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.

Keywords: Mini implant, Fatigue fracture, Strength

Figures and Tables

Fig. 1

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

Fig. 2

A schematic graphic design of the testing apparatus.

Fig. 3

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

Fig. 4

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

Fig. 5

Load-displacement curves of static loading test.

Fig. 6

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

Fig. 7

Load versus logarithmic number of cycles in dynamic fatigue test.

Fig. 8

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

Table 1

Mean values and standard deviations of compressive strength by fixture diameter of mini implants (unit: N)

^*; significant difference (P<.001)

Table 2

Number of cycles until failure by fixture diameter of mini implants (unit: cycles)

Load : 80%, 60% and 40% of the compressive strenghth for each diameter and 43 N.

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