Time-series Analysis of Continuous Oral Sounds and Acoustic Features of the Initial Masticatory Phase among Dentate and Edentulous Older Adults

Abstract

In Japan’s super-aged society, maintaining oral function is essential for supporting healthy life expectancy and quality of life. Mastication and swallowing are continuous processes, yet most conventional assessments of masticatory function require expectoration of food and do not capture the entire sequence leading to swallowing. Acoustic analysis of mastication may enable a continuous evaluation of oral function. This study compared 1) the time required from food intake to swallowing and 2) the acoustic characteristics of mastication during the first 10 seconds of mastication between dentate (D) older adults and complete denture (CD) wearers. Fifteen dentate and 15 edentulous participants wearing complete dentures were enrolled. Acoustic data during almond mastication were recorded three times using a sound level meter placed near the laryngeal region. Root mean square (RMS), amplitude, flatness, alpha index, and mastication-to-swallowing duration were included as exploratory parameters for evaluation. Appropriate parametric or non-parametric tests were used for comparisons, and time-series correlations among acoustic features were analyzed. Entire duration was significantly longer in the CD. The CD alsoexhibited significantly larger amplitude mean values, whereas the D showed significantly steeper amplitude slopes. Time-series analysis demonstrated significant correlations in amplitude, flatness, and alpha index only in the CD, and the correlation coefficient for flatness differed significantly between the two. These findings indicate that denture wearers require longer mastication and demonstrate distinct acoustic features compared with dentate individuals. Acoustic analysis may serve as a practical method for continuous evaluation of oral function in older adults.