Relationships Between Salivary Biomarkers and Oral Function in Elderly People Using a Saliva Testing Device

Background/Objectives: Oral functional decline is associated not only with impaired oral conditions, such as poor oral hygiene, oral dryness, decreased occlusal force, reduced masticatory performance, low tongue pressure, impaired tongue-lip motor function, and dysphagia, but also with deterioration in overall systemic health. Saliva plays a crucial role in maintaining oral function. This study investigated the relationships between conditions related to oral functional decline and salivary biomarkers. Methods: Elderly people residing in the Kyotango area were evaluated using oral function assessments, including the oral hygiene status, salivary flow rate, occlusal force, masticatory performance, tongue pressure, tongue-lip motor function, and swallowing function. Salivary biomarkers were evaluated using an oral environment assessment system (SillHa, Arkray, Kyoto). The biomarkers tested included cariogenic bacteria, acidity, buffering capacity, leukocytes, protein, and ammonia. Statistical analyses were performed using SPSS version 30 (IBM, Armonk, NY, USA). Results: Significant differences and correlations were observed between salivary biomarkers and five of the seven assessment criteria for oral functional decline: a poor oral hygiene status, oral dryness, decreased occlusal force, impaired tongue-lip motor function, and decreased masticatory function. A poor oral hygiene status was associated with the bacterial count and cariogenic bacteria. Oral dryness was associated with the salivary flow rate, acidity, and buffering capacity. Decreased occlusal force was associated with the number of remaining teeth, cariogenic bacteria, acidity, leukocytes, and protein. Impaired tongue-lip motor function was associated with the /pa/, /ta/, and /ka/ sounds and leukocytes. Decreased masticatory function was associated with masticatory performance, cariogenic bacteria, leukocytes, and protein. Conclusions: The present results suggest the potential of salivary biomarker testing using this assessment system as a simple and practical screening tool for identifying oral functional decline. Furthermore, salivary biomarker testing may be useful in oral function assessments.