Pattern of microimplant displacement during maxillary skeletal expander treatment: A cone-beam computed tomography study

OBJECTIVE: To analyze the microimplant (MI) displacement pattern on treatment with a maxillary skeletal expander (MSE) using cone-beam computed tomography (CBCT). METHODS: Thirty-nine participants (12 males and 27 females; mean age, 18.2 ± 4.2 years) were treated successfully with the MSE II appliance. Their pre- and post-expansion CBCT data were superimposed. The pre- and post-expansion anterior and posterior inter-MI angles, neck and apical inter-MI distance, plate angle, palatal bone thickness at the MI positions, and suture opening at the MI positions were measured and compared. RESULTS: The jackscrew plate was slightly bent in both anterior and posterior areas. There was no significant difference in the extent of suture opening between the anterior and posterior MIs (P > 0.05). The posterior MI to hemiplate line was greater than that anteriorly (P < 0.05). The apical distance between the posterior MIs was greater than that anteriorly (P < 0.05). The palatal thickness at the anterior MIs was significantly greater than that posteriorly (P > 0.01). CONCLUSIONS: In the coronal plane, the angulation between the anterior MIs in relation to the jackscrew plate was greater than that between the posterior MIs owing to the differential palatal bone thickness.