Background Oral hypofunction is defined as the reversible stage preceding oral dysfunction. However, its assessment and management need further examination and consideration. Objective The present study aimed to examine the current state of oral hypofunction among outpatients at the university hospital. Methods New outpatients underwent medical interviews and detailed assessment of oral hypofunction at their initial visit to our dental department. Oral hypofunction was diagnosed if the results of three of the following seven assessment items were below cut‐off values: poor oral hygiene, oral dryness, reduced occlusal force, decreased tongue‐lip motor function, decreased tongue pressure, decreased masticatory function and deterioration of swallowing function. The relationships between factors used to diagnose oral hypofunction as well as the distributions of assessment values were clarified. Results Seventy‐five of 209 patients (35.9%) were finally diagnosed with oral hypofunction. Diagnosis of oral hypofunction was significantly related to patient age, Eichner index, a chief complaint of dental or periodontal disease or ill‐fitting dentures and a history of neurodegenerative disease. The lowest quintile values for poor oral hygiene, oral dryness and decreased masticatory performance were all above current cut‐off values. Reduced occlusal force contributed strongly to the diagnosis of oral hypofunction. Conclusion Oral hypofunction in dental outpatients at a university hospital was associated with patient age, medical history and chief complaint at presentation. Diagnosis of oral hypofunction can be closely related to reduced occlusal force. The validity of cut‐off values for assessments of oral hypofunction needs further consideration.

Although enzymes of thermophilic organisms are often very resistant to thermal denaturation, they are usually less active than their mesophilic or psychrophilic homologues at moderate or low temperatures. To explore the structural features that would improve the activity of a thermophilic enzyme at less than optimal temperatures, we randomly mutated the DNA of single-site mutants of the thermostable Thermus thermophilus 3-isopropylmalate dehydrogenase that already had improved low-temperature activity and selected for additional improved low-temperature activity. A mutant (Ile279 → Val) with improved low-temperature activity contained a residue that directly interacts with the adenine of the coenzyme NAD(+), suggesting that modulation of the coenzyme-binding pocket's volume can enhance low-temperature activity. This idea was further supported by a saturation mutagenesis study of the two codons of two other residues that interact with the adenine. Furthermore, a similar type of amino acid substitution also improved the catalytic efficiency of another thermophilic dehydrogenase, T. thermophilus lactate dehydrogenase. Steady-state kinetic experiments showed that the mutations all favorably affected the catalytic turnover numbers. Thermal stability measurements demonstrated that the mutants remain very resistant to heat. Calculation of the energetic contributions to catalysis indicated that the increased turnover numbers are the result of destabilized enzyme-substrate-coenzyme complexes. Therefore, small changes in the side chain volumes of coenzyme-binding residues improved the catalytic efficiencies of two thermophilic dehydrogenases while preserving their high thermal stabilities and may be a way to improve low-temperature activities of dehydrogenases in general.

IntroductionDeclining oral function may affect subsequent physical frailty in the older population. The aim of this longitudinal study was to summarise data on patients who underwent functional oral examination and evaluate the impact of management on patients with oral hypofunction (OHF).MethodsDental outpatients aged over 65 years at their initial visit to the Niigata University Hospital received detailed assessment of seven oral function items to diagnose oral hypofunction using diagnostic criteria defined by the Japanese Society of Gerodontology. Patients with OHF at the first assessment received management including oral health guidance for low function and dental treatment. They were re‐evaluated approximately 6 months later and the two assessments were compared. According to the results of the second assessment, the patients were divided into two groups: OHF improved and OHF re‐diagnosed.ResultsOf the 273 patients who underwent the first assessment, 86 (31.5%) were diagnosed with OHF and received management. Of those, 42 (48.8%) completed the second assessment. Comparing the first and second assessment, significant improvement was observed in oral hygiene, occlusal force, tongue–lip motor function of /pa/, mastication and swallowing. The change in values from the first assessment demonstrated a significant difference between the OHF improved and re‐diagnosed groups only in occlusal force.ConclusionManagement for patients with OHF can contribute to the improvement of poor oral function, and an increase in occlusal force was notable in the recovery from OHF.

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