Developmental Insufficiency of Oral Function in Japan: A Review of Its Background, Diagnostic Framework, and Management System

Oral function is a developmental construct that integrates mastication, swallowing, speech, breathing, and lip closure. Insufficient acquisition of these functions during childhood may adversely affect long-term oral health and craniofacial growth. Japan recognized this issue early and introduced developmental insufficiency of oral function (DIOF) as a reimbursable condition in 2018, followed by the continuous refinement of its assessment and management framework. This review summarizes the background, definition, diagnostic criteria, examination methods, management strategies, and insurance systems related to DIOF in Japan and discusses their implications for pediatric dentistry and health policy in Korea. In Japan, DIOF refers to a condition in which eating, speech, and other oral functions have not developed sufficiently or have been acquired abnormally in the absence of a clear structural abnormality. DIOF is diagnosed using a checklist-based assessment system. The key elements of the Japanese model include separate assessment pathways before and after completion of weaning, quantitative evaluation of lip-closing force and tongue pressure, management plans centered on lifestyle habit guidance and functional training, and an insurance reimbursement structure supporting these interventions. Tongue pressure and lip-closing force have been proposed as useful objective indicators for evaluating oral functional development and monitoring treatment outcomes in growing children. The Japanese experience suggests that pediatric dental care in the era of declining birth rates should expand from a tooth- and occlusion-centered model to a function-oriented model. It may provide a valuable foundation for developing Korean criteria and management strategies for pediatric oral functional disorders.