Orthodontic retreatment of a patient with a severe deep bite and low-level horizontal impaction of the right mandibular second molars by using a custom-cast anchorage appliance and clear aligners: a case report.

BACKGROUND: A severe deep bite, when combined with an impacted mandibular second molar, presents a complex clinical challenge. Managing this condition requires not only precise control over tooth movements but also careful consideration of the relationship between the impacted tooth and its adjacent teeth. Orthodontists must conduct a thorough assessment of the patient's condition to develop a rational and feasible treatment plan.

CASE PRESENTATION: This report discusses a case involving a 24-year-old female patient who requested an orthodontic consultation of "anterior deep overbite", with a history of previous orthodontic treatment. Cone-beam computed tomography scans revealed parallel, low-level horizontal impaction of her right mandibular second and third molars. After extracting the upper right first premolar and the lower right third molar, a comprehensive treatment plan was initiated, combining clear aligners with a custom-cast anchorage appliance to guide the impacted tooth. Ultimately, the patient's deep overbite was corrected, and the impacted right mandibular second molar was successfully uprighted. A two year follow-up demonstrated stable treatment outcomes, with the impacted tooth exhibiting good periodontal health and normal pulp vitality. The bone condition around the second molar (MM2) was also favorable.

CONCLUSIONS: This case suggests that for adult patients with low-level horizontal impaction of the mandibular second molar, using a custom traction appliance with the appropriate force magnitude and direction can yield satisfactory clinical outcomes. Additionally, employing mini-implants in the anterior region as an adjunct to clear aligner therapy can correct a severe anterior deep overbite safely and effectively.