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Objectives: To investigate the effects of irradiation lasers and light-emitting diode (LED) light on root resorption in rat molars during orthodontic tooth movement (OTM)., Materials and Methods: Twenty-one 12-week-old Wistar male rats were divided into three groups: OTM only (control [CG]), OTM and LED irradiation (DG), and OTM and low laser irradiation therapy (LG). The distance between the first and second molars was used to evaluate the amount of tooth movement. The mesial surfaces of the distopalatal roots were analyzed by scanning electron microscopy, and the area of the resorption was calculated., Results: Statistical analysis showed a decreased amount of tooth movement in the exposed DG or LG compared with CG, which was statistically significant ( P = .031 and P = .004, respectively). However, when the DG and LG groups were compared, no statistically significant differences were found ( P = .504). The root resorption areas were similar between CG and DG. However, statistically significant differences were found between LG and CG ( P = .014) and LG and DG ( P = .038)., Conclusions: Phototherapy did not enhance tooth movement, while infrared laser irradiation did increase root resorption.

Introduction: A previous study with scanning electron microscopy showed that orthodontic root resorption occurs at the lateral surfaces of premolar roots for 2 to 6 weeks after orthodontic rotation. The purpose of this investigation was to observe how resorbed cementum repairs during rotation movement., Methods: Twenty-one mandibular first premolars from 12 patients, orthodontically indicated for extraction, were used. They were intra-individually divided into 2 groups: 8 teeth were not moved (control group), and 13 were rotated (experimental group). In the experimental group, a rotational force (25 g both buccally and lingually) with a precise biomechanical model, individually calibrated, was applied for 2, 3, 4, or 6 weeks. After extraction, the teeth were fixed and decalcified, and 8 were conventionally processed for transmission electron microscopy, and 13 teeth were processed for high-resolution immunocytochemistry by using an antibody against osteopontin. The samples were analyzed in a transmission electron microscope., Results: This examination showed areas of repair in previously resorbed lacunae in the experimental group. Both the clastic cells and the root surface showed immunolabeling for osteopontin. In addition to areas of cementum resorption and various degrees of cell and extracellular matrix degeneration, active cementoblasts and fibroblasts in several stages of differentiation and activity appeared adjacent to newly synthesized collagen fibers, thus reestablishing the function of the periodontal ligament., Conclusions: We concluded that cementum repair occurs after resorption during rotation movement and that noncollagenous matrix protein osteopontin plays a role in both resorbing and repairing.

Objective: To identify clastic cells on the root surfaces of torqued human premolars., Materials and Methods: A continuous force of 600 cNmm was applied to upper first premolars in patients 13-16 years of age by using a precise biomechanical model with superelastic wires (NiTi-SE). The 28 teeth in 14 patients were divided into five groups (control [nonmoved], and moved for either 1, 2, 3, or 4 weeks) and processed for tartrate-resistant acid phosphatase (TRAP) histochemistry and transmission electron microscopy., Results: Mononuclear TRAP-positive cells appeared at 2 weeks, where as large multinucleated TRAP-positive cells were numerous at 3 and 4 weeks. Ultrastructural examination revealed many clastic cells in contact with resorption lacunae. In addition, some cementoblast-like cells appeared secreting new cementum over previously resorbed lacunae., Conclusions: In general, resorption lacunae and the number of clastic cells, which increased with the duration of the applied force, were found on the cementum surface at the pressure areas. Some signs of cementum repair were also noticed, even with the maintenance of the level of the force.

The aims of this study were to investigate the presence, location, and severity of root resorption after orthodontic rotation for different lengths of time. Eighteen mandibular first premolars due to be extracted from 9 patients were intraindividually divided into 2 groups. Eight teeth were not moved (control group), and 10 teeth were rotated (experimental group) with a force of 50 g delivered by elastomeric modules through symmetrical brackets bonded on the buccal and lingual surfaces (25 g buccally and 25 g lingually) for periods of 2, 3, 4, and 6 weeks. The teeth were extracted, fixed, and treated with 2% sodium hypochlorite to remove the organic tissue components and then dehydrated in ethanol, air-dried, coated with gold, and analyzed in a scanning electron microscope. Examination by scanning electron microscopy revealed many concavities (resorption lacunae) on the root surfaces of all rotated teeth. The resorption areas were located mainly at the medial root third, in regions that corresponded to the prominent zones of the roots. The resorption lacunae in the teeth moved for longer time periods were deeper, often affecting the underlying root dentin, and were mainly at the medial root third. Both the apical and cervical thirds were clearly less affected at all the studied intervals. The root surfaces at the nonprominent root zones did not show signs of resorption.