Participants
We enrolled 38 elderly women (76.7 ± 5.7 years) in this study. Participants were aged > 65 years during the investigation, living in their own homes, walking independently, and participating in their community salon programs or preventative care more than once a week.
First, we visited the community salons in each area to explain the outline of our research and requested participation in our study. Following this, dental hygienist conducted a survey wherein the numbers of teeth of individuals who agreed to participate in the study were determined (primary survey). After that participants who agreed to participate in secondary survey underwent a second survey, parameters other than the number of teeth were measured at the Yamagata
Prefectural University of Health Sciences.
Variables
Endothelial function
FMD was measured as an endothelial function using an instrument equipped with software for monitoring the brachial artery diameter (UNEX38G, Unex Co. Ltd., Japan) (Figure1-a). Measurements were taken in 15-20 min. The subjects were placed in supine position with a blood pressure cuff placed around the forearm (Figure1-b, c). The brachial artery was scanned longitudinally 5-10 cm above the elbow by ultrasonic echo. When the clearest B-mode image of the anterior and posterior intimal interfaces between the lumen and vessel wall was obtained, both the tracking gates were placed on the intima, the artery diameter was automatically tracked, and the waveform of diameter changes over a cardiac cycle was displayed in real time using the FMD mode of the tracking system. After measuring the blood pressure, the blood pressure cuff was inflated to 50 mmHg above systolic pressure for 5 min and released. Changes in the blood vessel diameter were measured for 2 min after the 5 min inflation. The baseline diameter was defined by measuring the minimum blood vessel diameter for 20 s after releasing the blood pressure cuff. FMD was automatically calculated as a percentage change in the peak vessel diameter from the baseline value. Endothelial dysfunction is suspected in less than 4% of cause [14]. The measurements were taken by one researcher. Figure1-a, b, c shows the measuring tool and subjects position.
Occlusal force
Occlusal force was measured using an occlusal force meter (GM10, Nagano Keiki, Japan) (Figure1-d, e). Measurements were taken twice on the left side, and the larger value was considered as the final value. The subjects were instructed to bite as hard as possible to take measurements during contraction [15].
Advanced glycation end products An increasing in the levels of AGEs is thought to affect aging. In this study, AGEs as indicators of aging, were measured using the AGE Reader (AGE Reader SU 4, Dignoptics, Netherlands) [16, 17]. The subjects were seated, with their forearm on the AGE Reader in pronation position [18]. Measurements were taken three times on the same side of the forearm, and the average value was
considered as the final values.
Grip strength
Grip strength was measured using a Jamar hand dynamometer (SH-5001, SAKAI med, Japan). The subjects were seated; with elbow joint flexed at 90°and both their feet shoulder-width apart. Measurements of the dominate hand were taken twice, and the largest value was considered as the final value.
Statistical analysis
The normality of the data was confirmed using the Shapiro-Wilk test. Correlations between parameters were assessed by bivariate simple correlation analysis. For age, occlusal force, grip strength, FMD, and AGEs spearman`s rank correlation coefficient was used for analysis. Multiple regression analysis was performed with degree of FMD as dependent variables, and occlusal force, grip strength, AGEs, and age as independent variables. IBM SPSS version 24 (IBM Japan, Tokyo, Japan) was used for all analyses, and p < 0.05 was considered statistically significant.