J Korean Acad Prosthodont.  2010 Jul;48(3):209-214. 10.4047/jkap.2010.48.3.209.

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

• Jang JH
• Cho JH
• Lee CH

• KMID: 2195557
• DOI: http://doi.org/10.4047/jkap.2010.48.3.209

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 (x20). 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.

Keyword

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

MeSH Terms

Female
Hand
Humans
New Zealand
Nitrogen Mustard Compounds
Osseointegration
Rabbits
Tibia
Titanium
Torque
Nitrogen Mustard Compounds
Titanium

Figure

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  Fig. 1. Schematic diagram of experimental implant.

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  Fig. 2. Digital torque gauge (Ncm).

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  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.

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