Decline in tongue pressure is one of the main symptoms of oral frailty, and the tongue pressure test is used to diagnose it. Based on the results of previous studies, the criteria for the diagnosis of low tongue pressure was set at a maximum tongue pressure of less than 30 kPa. The evidence is based on the standard values of maximum tongue pressure in age groups, differences in maximum tongue pressure between patients with dysphagia, elderly people requiring nursing care and healthy people, difference by diet texture, and results of previous studies on frailty, sarcopenia and tongue pressure. However, depending on the results of future studies, the diagnostic criteria for tongue pressure should be revised. Because of its simplicity, the tongue pressure test has been used in many studies. In the future, we hope that the members of Japanese Society for Stomatognathic Function will make further use of this technology for the early detection and treatment of oral frailty in the field of nursing care prevention.

In this paper, we introduced some reports of evaluation criteria of Oral Flail, and the new established methods of chewing ability evaluation in Oral Flail. However, it is hard to say that evaluation of oral function as well as chewing ability is applied in daily clinical practice. Dentist and dental care workers are required to re-realize the importance of oral function evaluation including chewing ability and practice oral function evaluation in daily clinic.

Emerging evidences had revealed that diminished oral function of the elderly population may lead to the impairment of their systemic health, functioning, and quality of lives. The disease concept of oral hypofunction has been established as a new pathology which dentistry should manage, The maximum bite force, which had been used as the surrogate indicator of chewing ability, is now included in the diagnostic criteria of oral hypofunction. However, the cutoff value of reduced bite force for the diagnosis of oral hypofunction lacks solid scientific bases. This paper aimed to discuss how to utilize bite force data to evaluate oral function of the elderly population.