Garudapurana 1.213.47

1.213.47

tataḥ snānarṃ pkurvīta dantadhāvanapūrvakam /
mukhe paryuṣite nityaṃ bhavatyaprayato naraḥ //

one should then take a bath preceded by brushing the teeth. / When the mouth remains unwashed, a man is always impure;