The mouth takes in and gives out — nourishment enters, words exit. The sealed mouth cannot speak or eat; the dream of a mouth full of something (gum, stones, endless substance) that prevents speech is a classic image of obstructed expression.
Positive Resonance
Nourishment received, expression released, the kiss, taste of life
Shadow Aspect
Sealed expression, swallowing words, the mouth stopped, biting your tongue
Nuances
Mouth sealed: expression prevented
Mouth full, cannot speak: obstruction of the sayable
Swallowing something whole: accepting without processing