Optimizing Anterior En Masse Retraction with Miniscrew Anchorage

Pavankumar Janardan Vibhute

doi:10.1155/2011/475638

Pavankumar Janardan Vibhute

Open Access

https://doi.org/10.1155/2011/475638

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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.

Highlights

Maximum anchorage is commonly required in patients with severe protrusion
This paper shows how the biomechanics of anterior retraction are balanced in all three planes with stabilizing molars and eliminating the need of miniscrew placement in loose mucosa or additional miniscrews in anterior region
Place 1st and 3rd order bends as required in middle horizontal section of molar-stabilizing power arm (MSPA), so that it passively engages the slot of miniscrew after insertion of distal end section into auxiliary molar tube (Figure 4(b))

Summary

Introduction

Maximum anchorage is commonly required in patients with severe protrusion. Variable anchorage loss has been reported with conventional retraction by sliding mechanics in extraction cases [1,2,3]. For achieving the direction of force vector towards the centre of resistance (Cres) of posterior teeth with retraction and intrusion of anterior teeth, position of miniscrew is preferred in apical portion, between 2nd premolar and 1st molar or 1st and 2nd molars, near Cres of posterior segment [10]. The sliding mechanic retraction assembly with direct anchorage from miniscrew reported biomechanical drawbacks.

Results

Conclusion