Objectives

To investigate the effects of transpalatal (TPA) wire dimension and temporary skeletal anchorage device (TSAD) position on maxillary molar intrusion.

Materials and Methods

The maxillary molar intrusion measurement system included a maxillary acrylic model, TPA, TSADs, and a three-dimensional Force/Moment (F/M) sensor. The intrusion patterns were categorized into six groups: buccal-mesial, buccal-distal, buccal-mesiodistal, palatal-mesial, palatal-distal, and palatal-mesiodistal. TPA wire dimensions were designed to be 0.7 mm, 0.9 mm, and 1.2 mm. The force and moment loads of the maxillary first molar were measured by the F/M sensor.

Results

Single buccal or palatal TSADs induced torquing movement, and single mesial or distal TSADs tended to promote tipping movement. Mesiodistal TSADs would have eliminated tipping, but accentuated torquing movement. The TPA significantly reduced the force and moment experienced by the maxillary first molar along three-dimensional axes. The thicker the TPA wire, the smaller the force and moment to which the maxillary first molar was subjected.

Conclusions

Precise placement of TSADs might have a substantial influence on tooth movement and should be determined in accordance with specific clinical requirements. Increasing the TPA wire dimension could diminish the tipping, torquing, and rotation during TSAD-assisted maxillary molar intrusion, but these tendencies could not be completely eliminated.

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Author notes

a

Graduate Student, Department of Orthodontics, Shanghai Xuhui District Dental Center, Shanghai, China.

b

Resident, Department of Stomatology, Shanghai Fifth People’s Hospital, Fudan University, Shanghai, China.

c

Professor and Chair, Department of Orthodontics, Shanghai Xuhui District Dental Center, Shanghai, China.

d

Assistant Project Scientist, Department of Orthodontics, Shanghai Ninth People’s Hospital, Collage of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

e

Professor and Chair, Department of Orthodontics, Shanghai Ninth People’s Hospital, Collage of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

f

Private Practice, Shanghai Huaguang Dental Clinic, Shanghai, China.

The first two authors contributed equally to this work.