Japanese study reveals higher prevalence of oral development issues in community children than clinic data

A new Japanese study indicates that developmental insufficiency of oral function (DIOF) may be more widespread among primary school children in the community than previously believed, highlighting the importance of active screening and early intervention.

A new Japanese study suggests that developmental insufficiency of oral function, a condition known as DIOF, may be more common in community children entering primary school than it is in clinic-based samples. Researchers who assessed 92 children aged five to seven found that 21 met the diagnostic criteria, giving a prevalence of about 23%. That is far higher than the 2.4% reported in a national database study of dental patients in 2022, and below but still much closer to the roughly 40% rate seen in nursery school children than to clinic figures, according to the related research. The findings point to a gap between the children seen in dental practice and the broader population, and they reinforce the view that DIOF may often go unrecognised without active screening.

The study, published in the Journal of Oral Rehabilitation, focused on oral functions linked to eating and speaking, as well as nutritional status and eating habits. The most common signs among affected children were incomplete lip closure and unusually long or short chewing time. Both were significantly more frequent in the DIOF group than among children without the condition. Other indicators included delayed tooth eruption, weak biting force, irregular chewing patterns, tongue protrusion and inconsistent eating amounts. The researchers said these patterns suggest that underdeveloped muscles around the mouth may play a role, not just dental alignment problems.

To assess chewing ability, the team used colour-changing chewing gum and measured colour shifts after a set number of chews. They also compared reported food habits, including how often children ate hard foods and whether they liked them. After adjusting for sex and body size, the researchers found a relationship between DIOF and preference for hard food, although not with frequency of intake. They cautioned that the cross-sectional design means the study cannot show cause and effect. Still, they argued that children’s reluctance to eat harder foods could be tied to weaker oral function, or that poorer oral function may make such foods less appealing.

The study also found lower nutrient intake in children with DIOF, even though the measured amounts remained within recommended levels for age. The authors noted that the dietary survey used in the study is designed for older children and may be less precise in younger age groups, but they said the result still raises the possibility that oral function affects how much children eat. That interpretation fits with broader Japanese research stressing that oral function develops early in life and needs continued support through school age. Reviews cited by the researchers say infancy and early childhood are crucial for building healthy eating habits, while school years are a key time for education and reinforcement.

The authors concluded that dietary guidance may help support oral function development and that schools could be an important setting for teaching children about chewing and mouth muscle use. They also called for further research in older children who do not attend dental clinics, as well as studies testing whether food-based guidance can improve oral development. More work is also needed to validate the checklist used in routine Japanese paediatric dental practice, since several items rely on parental observation and subjective judgement.