Biomechanical analysis on mandibular anterior teeth during unilateral mandibular molar Protraction with different movement patterns: a finite element analysis.

OBJECTIVES

To evaluate the biomechanical effects on mandibular anterior teeth during second molar protraction using different movement patterns following unilateral mandibular first molar loss.

MATERIALS AND

METHODS

A 3D finite element model was developed to simulate unilateral mandibular first molar absence. Three protraction movement patterns were studied: (A) traction hook, (B) anchorage screw, and (C) anchorage screw with extended arm. A 2 N traction force was applied with an archwire-bracket friction coefficient of 0.2. Tooth displacement and movement direction were analyzed.

RESULTS

All three movement patterns affected mandibular anterior teeth differently. The traction hook method showed minimal influence on both anterior teeth and molar displacement. The anchorage screw method demonstrated improved protraction but caused significant displacement of anterior teeth away from the edentulous site and pronounced labial inclination. Adding an extended arm reduced labial inclination and enhanced intrusion of anterior teeth while increasing molar displacement, however, anterior dental movement away from the edentulous site is notably increased.

CONCLUSIONS

Adverse effects on anterior teeth are inevitable during mandibular second molar protraction, regardless of the space closure technique employed. The traction hook produced minimal displacement overall. The anchorage screw with extended arm effectively reduced anterior teeth labial inclination while enhancing molar protraction, though careful attention to midline control is necessary.