Optimizing Anterior En Masse Retraction with Miniscrew Anchorage

Abstract

In severely protrusive patients, skeletal anchorage from miniscrew is often used to avoid anchorage loss with preferred miniscrew location near centre of resistance (Cres) of posterior teeth. Biomechanical requirement for directing retraction force towards Cres of posterior teeth demands the insertion of miniscrew in loose mucosa, where risk of infection and failure increases. In addition, undesirable biomechanical side effects on anterior and posterior segments may be possible in all three planes, when continuous arch sliding mechanics are installed with miniscrew anchorage. This paper describes technique of molar-stabilizing power arm (MSPA) for simultaneous intrusion and retraction of anteriors with miniscrew placement at attached gingiva between 1st molar and 2nd premolar. Advantages of this technique include (i) the need of miniscrews placement in loose mucosa apically near the Cres of the posterior teeth is eliminated, (ii) the risk of infection and miniscrew failure is lowered since the miniscrew is placed in attached gingiva rather than the loose mucosa, and (iii) by adjusting vertical length or replacing MSPA, alteration of the retraction force vector is possible in all three planes; thus, need of removal and repositioning of the miniscrew (e.g., in correction of occlusal cant) can be eliminated.

Comparison of soft tissue changes between incisor tipping and translation after premolar extraction

“…In contrast, the emergence of skeletal anchorage systems, such as miniscrews, made it possible to achieve significant anterior teeth retraction. 7 - 9 Moreover, proper mechanics combined with miniscrews have enabled tooth movement close to bodily translations and even root movement of the incisors. 10 , 11 However, to our knowledge, few studies have evaluated soft tissue changes according to the retraction of the incisor root apex.…”

Temporary anchorage devices-steering the treatment of borderline orthognathic case to an orthodontic approach

“…So, inter radicular implants were a proven choice for the retraction of the maxillary anterior dentition. 4 Incorporation of miniscrews negated the side effects of anchorage taxation on the posterior segment because the retraction force was not reciprocal.as a result, the entire arch or the anterior segment rotates around the center of resistance.…”

Root resorption of maxillary incisors retracted with and without skeletal anchorage

“…46,66,67 Retraction force in this study was kept at 250 g per side, but forces ranging from 150 to 300 g have been widely reported, probably due to force dissipation factors. 15,16,[68][69][70][71][72][73][74][75] Elastic chains can cause force decay of about 40% during the first day of load application, 76 whereas the force delivered by nickel-titanium coil springs is significantly more stable. 77 Furthermore, during sliding mechanics, the friction at the bracket-wire interface dissipates the applied force, significantly reducing the net force transferred to the anterior teeth.…”