Are interventions for accelerating orthodontic tooth movement effective?

The Effects of Static Magnetic Field on Orthodontic Tooth Movement in Mice

The application of static magnetic field (SMF) has been considered an effective and noninvasive method to accelerate orthodontic tooth movement. The objective of this study was to explore the effects of SMF on orthodontic tooth movement in mice. A total of 105 Balb/c mice (body mass: 25-30 g) were divided into experimental group (SMF + force, 48), control group (force only, 48), and blank group (neither SMF nor force, 9). After the placement of orthodontic appliances, the experimental group was exposed to the SMF environment generated by Neodymium-iron-boron (NdFeB) magnets with an intensity of 20-204 mT. At 1, 3, 7, 14, 21, and 28 days after appliance insertion, eight animals in both experimental and control groups were sacrificed and the left maxillae were dissected to measure the distance of tooth movement, respectively. Meanwhile, the width of periodontal ligament (PDL), length of hyalinized zone, and the number of osteoclasts were evaluated by hematoxylin-eosin and tartrate-resistant acid phosphatase staining. We finally found that the experimental group demonstrated an enhanced rate and greater cumulative amount of tooth movement than the control group (0.2887 ± 0.0041 mm vs. 0.2114 ± 0.0089 mm, P < 0.05). On Days 7, 14, and 28, the experimental group also displayed a significantly greater width of PDL. Earlier formation and removal of the hyalinized zone, and significantly more osteoclasts were observed in the experimental group as well. The results suggested that SMF may be a promising nonsurgical intervention to accelerate orthodontic tooth movement. © 2021 Bioelectromagnetics Society.

Atypical extraction treatment for failing replanted maxillary and mandibular incisors with space closure of 2 mandibular incisors in the same quadrant

We report the successful orthodontic treatment of a 13-year-old girl who had been involved in an accident with avulsion of her maxillary right central incisor and both mandibular left incisors. Fifteen months after replantation of the teeth, all showed severe root resorption with apical inflammation and had to be extracted. After compensatory removal of the maxillary left central incisor, all 4 extraction sites were closed within 20 months of active orthodontic treatment to avoid implant-prosthodontic replacement. By sequential extraction of the 2 hopeless replanted equilateral mandibular left incisors and common-sense management of straightwire mechanics, it was possible to move the right central incisor across the mandibular midline and close the large space completely. To our knowledge, no case report about orthodontic closure of 2 adjacent extraction spaces in the same quadrant has been published.