A case of dense bone island in a girl aged 10 years, 1 month old is presented. The lesion was asymptomatic and was an incidental finding on a radiograph taken for another purpose. Nine months after the patient's first visit, an obvious inclination of adjacent teeth was identified. The size and density of the lesion had increased by 10 and 7%, respectively. As the patient was still in adolescence, the lesion may increase in size and density, potentially resulting in further problems such as increased inclination of the adjacent teeth. In addition, the presence of the lesion may complicate any future orthodontic treatment. The lesion should be kept under observation until its growth ceases.