Magnets have many advantages for orthodontic applications. The purpose of this study was to investigate the effect of the magnet position on the tipping and bodily tooth movement using 3D digital analysis ex vivo.
Orthodontic typodont models for space-closing (2mm diastema) were created, mimicking maxillary central incisors. Tooth models (10mm crown and 14mm root length) created by 3D printer were used for the typodont model. Nd-Fe-B magnets were placed in the middle of the tooth (Model-M) and the cervical area (Model-C). The typodonts were immersed in a hot water-bath at 55℃ to initiate tooth movement. The scanned typodont data before and after tooth movement were superimposed, and 3D coordinates (X, Y, Z) on the tooth were obtained. The root apex data was also obtained by superimposing the designed tooth model on the crown portion of the typodont model. 3D movement of the crown and the root apex, moving speed, degree of rotation (yaw, pitch, and roll) in 2 models were analyzed and compared by Pearson’s correlation confidents. Moderate crowding typodont cases were treated with two magnet position settings, and patterns of tooth/root movement and rotation were compared.
The largest movement was observed in the X-axis as intended. Model-M indicated higher moving speed and more tooth rotation than Model-C. In Model-M, the root apex moved to the opposite direction of the crown movement with a negative correlation. In contrast, the crown and root apex moved in the same direction with a positive correlation in Model-C. In the ex vivo moderate crowding case, Model-C created bodily movement, in which the cusp and root apex both moved in the same direction with less tooth rotation.
The results of this study validated that modifying the position of the applied magnetic force was able to increase the amount of bodily tooth movement and decrease unwanted rotation/tipping in an ex vivo setting.