Impacted teeth are common and are often treated with orthodontic eruption, but periodontal problems associated with the process can evade detection. Profound destruction of the periodontium of an impacted tooth or adjacent teeth can occur. This case report describes the orthodontic eruption of 4 impacted canines in a 19-year-old woman. An open surgical approach was used. Within 6 months of treatment, the maxillary right canine and the lateral incisor experienced severe periodontal destruction, resulting in questionable prognoses for the teeth. Plaque control, periodontal architecture, and subgingival microflora were examined as local etiologic factors of periodontal destruction associated with orthodontic eruption of impacted teeth. Plaque control measures were evaluated, and the consequences of orthodontic tooth movement in the presence of inadequate plaque control were considered. Areas of periodontal architecture made vulnerable by the surgical exposure of the impacted teeth were identified, and the effect of orthodontic force on the periodontium was explored. An increase in putative periopathogens in the subgingival microflora after orthodontic appliance placement was observed. Microbiologic monitoring for pathologic levels of periopathogens and antibiotic therapy were considered. Orthodontic treatment of impacted teeth might require additional professional and personal plaque control measures, 3-dimensional diagnostic imaging, and control of putative periopathogens to preserve the health of the periodontium.