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Stability of paramedian inserted palatal mini-implants at the initial healing period: a controlled clinical study


Corresponding author:

Dr. Manuel Nienkemper

Department of Orthodontics


Moorenstr. 5, 40225 Düsseldorf


Tel.: +492118104477

Fax: +492118119510




To assess the stability development of paramedian in comparison with midpalatal inserted mini-implants.

Material and methods

The test group consisted of 21 consecutively treated patients (13.7 ± 4.6 years). In each patient, a mini-implant was inserted paramedian in the anterior palate. Measurement of the insertion depth (ID), the maximum insertion torque (IT), and resonance frequency analysis (RFA) was performed at T0. RFA was repeated after 2 weeks (T1), 4 weeks (T2), and 6 weeks (T3). Correlations between measuring methods were calculated. RFA values at different times were tested for statistical differences. Data were compared with a group of patients who received median mini-implants of the same size.


Initial stability was 14.06 ± 4.35 Ncm (IT) and 26.60 ± 5.28 ISQ (RFA) with an ID of 7.02 ± 1.04 mm. RFA and IT (r = 0.49, = 0.023) showed a moderate significant correlation. Stability remained relatively constant, showing no significant differences between measurement times. Overall, RFA values decreased non-significantly by 2.25 ± 6.85 ISQ to a level of 24.35 ± 5.39 after 6 weeks. Comparing development of stability over time, it was found that significant differences were present at T0 and T1 (T0: −9.54 ISQ, P < 0.0001; T1: −3.69, P = 0.041).


Paramedian inserted mini-implants provided sufficient stability. Showing a lower primary stability, RFA values did not differ from the control group from week four on, as no significant decrease in stability occurred at the initial healing period.