Clinical outcome of mini-screws used as orthodontic anchorage

Implants and orthodontics are an important combination to obtain intraoral anchorage and eliminate the disadvantages linked with extraoral anchorage such as compliance problems, aesthetical, and social factors. The mini-screw is a simple, relatively low-cost method to provide intraoral anchorage.

The aims of this study were to evaluate clinical success and longevity of mini-screws during orthodontic treatment and to assess the patient's opinion.

Fifty mini-screws were inserted in the mandible and maxilla of 21 patients with a flapless technique under local anesthesia. The patients were recalled after 2 weeks and from then on every other 2 months, and periodontal parameters and stability of the screws were evaluated at regular intervals. Patients received a questionnaire to assess their opinion regarding the treatment.

Thirty-three mini-screws (64%) remained stable sufficiently long to obtain the effect during the orthodontic movement. The survival was comparable in mandible or maxilla, and not related to the orthodontic forces applied or time of activation of the load. The results do suggest that a waiting period of 1 week before loading improves success, and mini-screws inserted into the anterior region score better also compared to the posterior region. Initial periodontal parameters, which are very important in prognosis of orthodontic treatment, are not influencing the success rate in the examined group. Patients complained in 40-50% of the cases of pain during or after surgery, but this did not negatively affect the final general satisfaction with the treatment.

The mini-screw implant is an easy and an inexpensive method for temporary anchorage of orthodontic appliances. The functioning time is short, however, and retreatment may often be required.