Abstract: Objective To evaluate the clinical effect of miniscrews combined with NiTi segment arch on the longdistance mesial movement of the mandibular second and third molars to close the extraction space of first molars. Methods Sixteen cases with severe caries of mandibular first molar, healthy second molar and third molar were selected. The mesial and distal roots of mandibular first molar were extracted in different stages. Miniscrew was used to provide anchorage, and NiTi segmental archwire was used to provide single couple and double couple for realizing bodily movement of molars in the space closing. Graphpad prism 6.0 software package was used for paired t test with data collected before and after treatment. Results All the second molars moved in place and a good occlusal relationship was established. There was no significant difference in the axis of the second molar and mandibular incisor and the probing depth after treatment. Ten third molars moved in place by themselves and another 6 cases were assisted by local segmental archwire. Conclusion The miniscrews combined with NiTi segment archwire can provide the necessary force and moment to realize mesial bodily movement of the molars.

Key words: miniscrew, molar protraction, force couple, NiTi segment archwire