Abstract
Developmental and eruption abnormalities are common and can result in progressive dental diseases. Ectopic eruption of the affected tooth may be the result of these processes. This study aims to report the occurrence of a permanent mandibular tooth in a horizontal position, with retention of the corresponding deciduous tooth, in a miniature horse. A 2-year-old female miniature horse was admitted to the veterinary hospital with a hard swelling on the left mandibular ramus, which had been growing continuously for three months. After a complete evaluation, it was concluded that the swelling was tooth 307, unerupted, immature, in a horizontal position between teeth 306 and 707. It was decided to extract tooth 307, keeping the corresponding deciduous tooth as a mechanical barrier to food entry. The extraction was performed by lateral alveolotomy, syndesmotomy, and retrograde repulsion. Postoperative alveolar infection progressed with apical contamination of tooth 707, requiring its extraction for clinical resolution of the condition. After 60th postoperative day, adequate alveolar healing, reduction in the depth of the intraoral fistula, and complete closure of the external fistula were observed. The patient was discharged from the hospital and has not shown any new clinical signs since then.