Abstract
The goal of our study is to launch magnetic force-driven orthodontics. This continuous study investigated the influence of magnet position on tipping and bodily tooth movement, using 3D printing technology and digital analysis. Orthodontic typodont models (TMs) for space-closure were 3D printed to mimic maxillary central incisors. Nd-Fe-B magnets were placed in the middle third (Model-M), and the cervical third (Model-C), of the tooth. TMs, before and after movement, were digitally scanned and superimposed. The 3D digital coordinates (X, Y, and Z axes), and rotations (yaw, pitch, and roll) of the tooth crown and root, were calculated and compared between the two magnet position settings. Model-M showed higher rates of movement, but more rotation than Model-C (p < 0.01). The root apex of Model-M moved in the opposite direction of the crown (R = −0.29), indicating tipping movement. In contrast, the crown and root apex moved in the same direction (R = 0.56) in Model-C, indicating bodily movement. These patterns were confirmed in a typodont model of a moderate crowding case. The results validated that modifying the magnet position increased the amount of bodily tooth movement, and decreased rotation/tipping in an ex vivo setting.
Highlights
Rare earth magnets, such as Sm-Co and Nd-Fe-B magnets, are the strongest type of permanent magnet and were introduced in the 1970s and 1980s [1,2,3]
Rare earth magnets possess many qualities that are beneficial for orthodontic applications [1,4,7,8]
The magnet position and duration were both significant factors in crown movement in all three
Summary
Rare earth magnets, such as Sm-Co and Nd-Fe-B magnets, are the strongest type of permanent magnet and were introduced in the 1970s and 1980s [1,2,3] They are the most common rare earth permanent magnets in use today and less costly to produce than Sm-Co alloys [3,4,5,6]. Rare earth magnets can generate strong magnetic forces in a small physical form, allowing them to be bonded to teeth. The first report of the use of magnetic force to move teeth was in 1977 when Kawata and Takeda [12] described a technique using Co-Cr-Fe alloy magnetic brackets for the closure of anterior interdental spaces [1,3,4].
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