Natyashastra
दष्टं च दन्तक्रियया चिबुकं त्विह लक्ष्यते । कुट्टनं दन्तसंघर्षः संस्फोटः खण्डनं मुहुः ॥ १४९॥
and Daṣṭa. Kuṭṭana—when the upper teeth clatter with the lower ones. Khaṇḍana—when (the two lips) repeatedly come together with each other.
english translation
daSTaM ca dantakriyayA cibukaM tviha lakSyate । kuTTanaM dantasaMgharSaH saMsphoTaH khaNDanaM muhuH ॥ 149॥
hk transliteration by Sanscript