Objectives: This study aimed to investigate the lost school days due to dental diseases among adoles-cents and to assess their oral health in relation to their socio-demographic characteristics. Methods: A total of 881 adolescents (middle school: 453, high school: 428) were surveyed using a self-administered questionnaire. The questionnaire was composed of questions relating to the subject’s socio-demographic characteristics and lost school days due to dental diseases. The lost school days due to dental diseases included absence and early leave. The differences in the lost school days by socio-demographic characteristics were analyzed by chi-square test and t-test. Results: In the past year, 2% of adolescents were absent from school (approximately 2 days of ab-sence), 7.6% left school early (about 3 days of early leave), and 8.3% were absent from school or left school early (about 4 days of absence and early leave) because of dental diseases. The most common reason for absence from school was dental caries (31.8%), followed by malocclusion (9.3%), periodontal disease (7%), and maxillofacial trauma (2.3%). Dental caries was the most common reason (18%) for early leave, followed by malocclusion (8.8%), maxillofacial trauma (2.6%), and periodontal disease (1.8%). Absence from school was higher when the educational background of the respondent’s father was mid-dle-school graduate or lower (5.6%: middle-school graduates or lower, 1.6%: high-school graduates, 1.8%: college graduates or higher). High school students with dental diseases (11.7%) were absent or went on early leave to a greater extent than middle school students (5.1%).Conclusions: To reduce lost school days due to dental diseases among adolescents, different strate-gies are required including prevention and early treatment of dental caries and avoidance of maxillofacial trauma.

Keywords: Adolescents, Dental caries, Dental diseases, Oral health, School loss