Success of miniscrews used as anchorage for orthodontic treatment: analysis of different factors

Abstract

ObjectivesTo examine factors involved in clinical success of miniscrew implants used for orthodontic anchorage in the upper jaw. Materials and methodsOne hundred and forty-four patients (93 females and 51 males) were fitted with a total of 324 miniscrew implants of two different morphologies (cylindrical and conical), and of different lengths and diameters. The clinical factors examined were screw length, side of insertion, miniscrew shape and diameter, bone quality, skeletal type, and relationship between bone quality and skeletal type and patient age. ResultsThe mean overall success rate of the implants was 91.4%. The length and shape of the miniscrews significantly influenced the success rate, whereas side of insertion (left or right), screw diameter and skeletal type showed no significant effects. Poor (soft) bone quality and good (hard) bone quality are risk factors for miniscrew failure, with the best results obtained when the screws are inserted into bone of medium quality (10-15Ncm). ConclusionIn the posterior areas of the upper jaw, long, conical miniscrews showed a significantly greater success rate. An insertion torque of 10Ncm to 15Ncm is also a significant index of higher success rate.