Insertion torque values and success rates for paramedian insertion of orthodontic mini-implants : A retrospective...

Orthodontic mini-implants (OMIs) are a reliable method to provide temporary orthodontic anchorage. We hypothesized that there is an optimal insertion torque (<10 Ncm) that can be used to ensure the success of self-drilling OMIs in the paramedian region.

Included were 40 (26 females, 14 males) consecutive patients requiring palatal skeletal anchorage. Mean age was 17.3 years (range 11.0-44.6 years) for female patients and 15.7 years (range 10.6-36.9 years) for male patients. A total of 22 patients received a Beneslider according to Wilmes for the distalization of maxillary first molars, 10 patients received a Mesialslider for the mesialization of maxillary first molars, and 8 patients received a bone-borne rapid palatal expansion (RPE) appliance. Torque values of 10-15 Ncm were recorded in 46.3% of the OMIs and 15-20 Ncm in 35% of OMIs. OMIs that endured the orthodontic force applied for ≥6 months were considered as success.

The overall success rate was 98.8%. No significant differences were found between insertion torque values with respect to the right and left sides, Jarabak's ratio, facial axis, and Frankfort to mandibular plane angle. There were no significant differences in the OMIs insertion torques with regard to the different appliances. No association was found between insertion torque and vertical skeletal morphology.

With an overall success rate of 98.8%, the study hypothesis that greater insertion torque (>10 Ncm) will decrease the success rate and increase palatal OMI failure was rejected.