Study of the re-osseointegration of implant fixture after mechanical unscrewing

Ji-Hoon Jang; Jin Hyun Cho; Cheong Hee Lee

doi:10.4047/jkap.2010.48.3.209

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Jang, Cho, and Lee: Study of the re-osseointegration of implant fixture after mechanical unscrewing

ORIGINAL ARTICLE

J Korean Acad Prosthodont 2010;48(3):209-214.

Published online: 18 October 2010

DOI: https://doi.org/10.4047/jkap.2010.48.3.209

Study of the re-osseointegration of implant fixture after mechanical unscrewing

Ji-Hoon Jang, MSD, DDS, Jin Hyun Cho, MSD, DDS, Cheong Hee Lee, MSD, DDS, PhD^∗

Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea

∗Corresponding Author: Cheong Hee Lee Department of Prosthodontics, School of Dentistry, Kyungpook National University, 188-1 Samduk 2ga, Jung-gu, Daegu, 700-412, Korea +82 53 600 7651: e-mail, chlee@knu.ac.kr

Received 30 June 20106 July 2010 Accepted 9 July 2010

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

The purpose of this study was to investigate whether the re-osseointegration of the implants that had mechanical unscrewing possibly occurred or not. Furthermore, if it happened, the degree of re-osseointegration was evaluated by comparing with previous osseointegration.

Materials and methods

The smooth implant (commercial pure titanium 99%) specimens, whose diameter and length was 3.75 mm, 4 mm, respectively were produced. Two implants were inserted into each tibia of 7 New Zealand female white rabbits weighing at least 3.0 kg. The torque removal force for each implant after 6 weeks of implants placement was measured and included in group I . The torque removal forces were assessed after the fixtures were re-screwed to original position and the subjects were allowed to have 4 more weeks for healing and included in group II. One rabbit was sacrificed after first measurement and produced 4 slide specimens in group I, and two rabbits were sacrificed after 2nd measurement, 7 slide specimens, in group II for histomorphologic investigations. All slide specimens were assessed based on the proportion of BIC (bone-implant contact) as well as CBa (Bone area in the cortical passage) value produced by counting the screw threads embedded in the compact bones under the optical microscopic analysis (×20). Statistical analysis was conducted to evaluate the torque removal force, BIC and CBa between group I and II.

Results

As for the torque removal force, the result was 10.8 ± 3.6 Ncm for group I and 20.2 ± 9.7 Ncm for group II. Furthermore, the torque removal force of group II increased by 98.1% in average compared to group I (P < .05). On the other hand, histomorphologic analysis displayed that there was no statistical significance in BIC and CBa values between group I and the group II (P > .05), and RT/BIC and RT/CBa between group I and group II were statistically significant (P < .05).

Conclusion

It is possible to obtain more substantial re-osseointegration within shorter periods than the period needed for the initial osseointegration in case of iatrogenically unscrewed implants.(J Korean Acad Prosthodont 2010;48:209-14)

Keywords: Re-osseointegration, Bone-implant contact (BIC), Torque removal force (RT), CBa (Bone area in the cortical passage)

REFERENCES

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Fig. 1.

Schematic diagram of experimental implant.

Fig. 2.

Digital torque gauge (Ncm).

Fig. 3.

Light microscopic findings of group I (Left) and group II (Right) (Vilanueva Bone Stain, × 20). Bone implant contact was formed at the thread parts through the cortical bone.

Table 1.

Removal torque value (Ncm) at each group

Group	n	Removal torque	Rate of increase (%)
I	20	10.8 ± 3.6	98.10
II	20	20.2 ± 9.7
P value	0.0015∗

^∗ denote significant difference at the .05 level between groups

Table 2.

BIC & CBa ratio comparison between groups

Group	n	BIC (%)	CBa
I	4	58.7 ± 9.5	7.73 ± 0.15
II	7	69.0 ± 10.5	7.70 ± 1.29
P value		0.145	0.961

BIC: bone-implant contact; CBa: Bone area in the cortical passage

Table 3.

RT/BIC and RT/CBa value comparisons between groups

Group	RT/BIC	RT/CBa
I	0.25 ± 0.06	1.90 ± 0.40
II	0.46 ± 0.16	4.16 ± 1.44
P value	0.036∗	0.0051∗

RT: removal torque; BIC: bone-implant contact; CBa: Bone area in the cortical passage

^∗ denotes significant difference at the .05 level between groups

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