Clinical effectiveness of ramus mini-implants in orthodontic traction of impacted mandibular second molars

Abstract Objective The main objective was to analyse the clinical effectiveness of ramus mini-implant-assisted traction of mandibular second molars with eruption disturbances. Materials and Methods A prospective study was carried out during a 3-year period. A total of 16 patients with 19 impacted mandibular second molars underwent surgical exposure followed by implant-assisted orthodontic traction. The pre- and post-treatment cone-beam computed tomography, and pre-, in-, and post-treatment panoramic radiographs were collected and measured for the changes in space, angles and alveolar bone at pre-, in-, and post-treatment stages. Results Mandibular second molars showed progressive uprighting (the angle between MM2 and the mandibular plane increased to 95.70 ± 11.96°, p < .0001) and improved root parallelism (the angles between MM2 and the mandibular second premolar decreased to 8.45 ± 7.06°, p < .0001) after the treatment. While molar crowns exhibited no significant deviation from the standard arch form, roots predominantly shifted lingually (2.29 ± 1.84 mm lingually at post-treatment, p < .05). Regarding alveolar bone changes, there was a significant increase of bone height at the distal side of the mandibular first molar (p < .05), coupled with a decrease of bone height at the mesial side of the second molar (p < .05). Root lengths of all patients indicated no statistical significance before and after treatment (p = .63). Conclusion Mini-implants placed at the mandibular ramus region are clinically effective in the orthodontic traction of impacted mandibular second molars. The orthodontic traction favours periodontal regeneration between first and second molars and bears no or minimal risk of root resorption of mandibular second molars.