## 4 Discussion
Therefore, the early treatment of oral diseases causing tooth loss and the early restoration of missing teeth may prevent irreversible changes in the orofacial muscles, particularly the tongue and bucciator, in healthy older adults. Third, we found an association between diabetes and reduced lip compression strength, although no such association with tongue elevation strength or cheek compression strength was observed. A study by [PERSON] et al. [63] on community-dwelling older adults similarly reported that diabetes can lead to a decline in or loss of muscle mass and function. The primary mechanisms underlying this decline in older adults with diabetes are reportedly the loss of anabolism due to increased insulin resistance, an increase in inflammatory mediators such as tumor necrosis factor-\(\alpha\) and interleukin-6, and an increase in oxidative stress [64]. Conversely, another study suggested that diabetes increased the prevalence of sarcopenia by two to three times [65]. Unfortunately, this study did not measure the participants' blood glucose levels, and this hypothesis requires further research. Finally, in our univariate analysis, all orofacial muscle strengths tended to be lower in participants who used dentures or who reported that their dentures were uncomfortable compared to those who did not use dentures, although the final regression model did not confirm this association. This may be due to the fact that only a small number of participants (approximately 30%) used dentures; therefore, in future studies, the sample size should be expanded to accurately evaluate various characteristics related to dental prostheses. Contrary to our hypothesis, unstimulated salivary flow rates were associated with lip compression strength in the final regression model but not with tongue or cheek compression strengths. One possible explanation is that since over half of the participants (54.2%) had normal salivary flow rates, a reduced saliva flow may not have had significant adverse effects on tongue or cheek muscle strengths in most of the older adults. We also speculated that the function of lip muscles may be more sensitive to the amount of saliva, which acts as a lubricant, because the orbicularis oris, the main muscle of the lips, is not firmly attached directly to the bone but rather to other oral muscles [66]. A normal individual secretes about 1.5 L of saliva per day [45], and the decrease in salivary flow rates with age is largely due to polypharmacy [67]. Saliva protects teeth and mucosa because of its antibacterial properties and contains, in addition to approximately 99% water, mucins produced in various salivary glands that function as lubricants during mastication, swallowing, and speaking [68]. Therefore, future studies should further explore the relationship between various properties of saliva, including its quantity and composition, with orofacial muscle strength. This study is significant as it demonstrates that orofacial muscle strength (tongue elevation, cheek compression, and lip compression) can be negatively impacted by a poor oral health status, such as a reduced number of remaining teeth, leading to weakened orofacial strength in healthy older adults living independently in the community without a history of dysphagia. These findings may contribute to the early detection of the functional decline of orofacial muscles, a risk factor for dysphagia, among healthy older adults living in the community, and could support the development of effective intervention strategies to improve orofacial muscle strength. However, this study has several limitations. Firstly, although the number of participants in this study exceeded the minimum sample size required for multiple linear regression, the generalizability of the findings may be limited due to the small number of final participants and the sampling method (convenience sampling).