<p> The purpose of this study was to evaluate the usefulness of the motivation scale score (MSS) for Japanese adults and investigate motivation related to the oral condition on receiving basic periodontal therapy using MSS.</p><p> The participants enrolled in this study were 221 patients with periodontal disease aged 20-64 years who visited a dental clinic in Shizuoka City, Japan for the first time. MSS was calculated using a 14-item-questionnaire concerning the patients’ motivation assessment scale, and principal component analysis of MSS was performed. The associations among MSS, items of oral health behavior, periodontal conditions [Bleeding on probing (BOP) rate, Periodontal inflamed surface area (PISA)], and oral hygiene status [O’Leary’s Plaque control record (PCR)] were evaluated at the baseline and after basic periodontal treatment.</p><p> MSS was shown to be useful in terms of reliability and validity and was classified into five factors. MSS and MSS-Factor 1 (oral hygiene practices) of participants with BOP of less than 10% were significantly higher than in of participants with BOP of more than 10% at the baseline. In addition, MSS and MSS-F1 were significantly higher among participants who received regular dental check-ups within a year and used interdental cleaning tools. MSS-F1 was significantly higher in non-smokers. By binominal logistic regression analysis, the use of interdental cleaning tools was significantly correlated with BOP of less than 10% at the baseline. All items related to oral conditions and oral health behavior improved after basic periodontal therapy, except for current smoking status. After basic periodontal therapy, MSS was significantly higher in participants with PCR of less than 20%, and MSS-F1 was significantly higher in participants who used interdental cleaning tools or were non-smokers.</p><p> It was revealed that MSS used in this study was useful and associated with the periodontal condition and oral health behavior at the baseline. The values of MSS and MSS-F1 significantly increased after basic periodontal therapy. The use of interdental cleaning tools was associated with a good oral condition and higher MSS. Therefore, high motivation might lead to a good oral condition in patients with periodontal disease through the use of interdental cleaning tools by influencing patients’ compliance to improve their oral health behaviors.</p>