To investigate the clinical effects of micro implant anchorage nail and Ni-Ti coilspring to lower the elongation molar.

60 patients with the first maxillary molar elongation were divided into 2 groups. 30 of them were treated with micro implant anchorage nail and Ni-Ticoil spring to lower the molar (observation group), and the other 30 patients were treated with segmental arch to lower the molar (control group). The average lowering time, depth and pain degree of the 2 groups were compared.

The average lowering time was faster and the overage lowering depth was greater in the observation group than that in the control group; the slight pain rate in the observation group was significantly higher than that in the control group (P <0.05), while the ratio of moderate pain and severe pain was significantly lower than that in the control group (P <0.05).

To lower the elongation molar with micro implant anchorage nail and Ni-Ti coilspring might have shorter course and less pain.