Reliability and validity of a quantitative color scale to evaluate masticatory performance using color-changeable chewing gum

In the present study, we developed a novel color scale for visual assessment, conforming to theoretical color changes of a gum, to evaluate masticatory performance; moreover, we investigated the reliability and validity of this evaluation method using the color scale. Ten participants (aged 26–30 years) with natural dentition chewed the gum at several chewing strokes. Changes in color were measured using a colorimeter, and then, linear regression expressions that represented changes in gum color were derived. The color scale was developed using these regression expressions. Thirty-two chewed gums were evaluated using colorimeter and were assessed three times using the color scale by six dentists aged 25–27 (mean, 25.8) years, six preclinical dental students aged 21–23 (mean, 22.2) years, and six elderly individuals aged 68–84 (mean, 74.0) years. The intrarater and interrater reliability of evaluations was assessed using intraclass correlation coefficients. Validity of the method compared with a colorimeter was assessed using Spearman’s rank correlation coefficient. All intraclass correlation coefficients were > 0.90, and Spearman’s rank-correlation coefficients were > 0.95 in all groups. These results indicated that the evaluation method of the color-changeable chewing gum using the newly developed color scale is reliable and valid