Orthodontic mini-implant stability at different insertion depths : Sensitivity of three stability measurement methods.
OBJECTIVE
The purpose of this work was to evaluate the influence of insertion depth on the stability of orthodontic mini-implants. Sensitivity of three different methods to measure implant stability based on differences in insertion depth were determined.


METHODS
A total of 82 mini-implants (2 × 9 mm) were inserted into pelvic bone of Swabian Hall pigs. Each implant was inserted stepwise to depths of 4, 5, 6, 7, and 8 mm. At each of these depths, three different methods were used to measure implant stability, including maximum insertion torque (MIT), resonance frequency analysis (RFA), and Periotest(®). Differences between the recorded values were statistically analyzed and the methods tested for correlations.


RESULTS
Almost linear changes from each insertion depth were measured with the values of RFA [implant stability quotient (ISQ) values range from 1-100], which increased from 6.95 ± 2.85 ISQ at 4 mm to 34.63 ± 5.51 ISQ at 8 mm, and with those of Periotest(®) [periotest values (PTV) range from -8 to 50], which decreased from 13.24 ± 4.03 PTV to -2.89 ± 1.87 PTV. Both methods were found to record highly significant (p < 0.0001) changes for each additional millimeter of insertion depth. The MIT increased significantly (p < 0.0001) from 153.67 ± 69.32 Nmm to 261 ± 103.73 Nmm between 4 and 5 mm of insertion depth but no further significant changes were observed as the implants were driven deeper. The RFA and Periotest(®) values were highly correlated (r = -0.907).


CONCLUSIONS
Mini-implant stability varies significantly with insertion depth. The RFA and the Periotest(®) yielded a linear relationship between stability and insertion depth. MIT does not appear to be an adequate method to determine implant stability based on insertion depth.
Department of Orthodontics, Heinrich-Heine University, Moorenstrasse 5, 40225, Düsseldorf, Germany. manuel.nienkemper@uni-duesseldorf.de.
Manuel
M
Nienkemper
Department of Orthodontics, Heinrich-Heine University, Moorenstrasse 5, 40225, Düsseldorf, Germany.
Natascha
N
Santel
Department of Orthodontics, Heinrich-Heine University, Moorenstrasse 5, 40225, Düsseldorf, Germany.
Ralf
R
Hönscheid
Department of Orthodontics, Heinrich-Heine University, Moorenstrasse 5, 40225, Düsseldorf, Germany.
Dieter
D
Drescher
D001863:Bone Screws; D003757:Dental Implantation / Q000379:methods*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000379:methods*; D003799:Dental Stress Analysis / Q000379:methods; D019544:Equipment Failure Analysis; D066298:In Vitro Techniques; D009038:Motion; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D010384:Pelvic Bones / Q000502:physiology* / Q000601:surgery*; D019415:Torque
Insertion depth; Mini-implants; Models animal; Orthodontics; Skeletal anchorage