Seeing Berenice smile is the inciting incident that sends Egaeus and his mental illness on a downward spiral of twisted obsession. So caught in the throes of his fixation with Berenice’s teeth, Egaeus begins to personify them, assigning the organs a degree of sentience that reveals the extent of his devolving mental state:
I shuddered as I assigned to them in imagination a sensitive and sentient power, and, even when unassisted by the lips, a capability of moral expression.
Despite the fact that Berenice is the one who smiles and thus reveals her teeth for him to see, Egaeus imagines instead that “the teeth of the changed Berenice disclosed themselves slowly” to his view. By portraying her teeth as capable of not only action but “moral expression,” Egaeus imbues these inanimate objects with human characteristics, reflecting his utter loss of reason. The fact that he imagines the teeth revealing themselves “slowly” adds a terrible, sensuous quality to the moment, and this heightens his perverse desire for them. It is notable that Berenice’s teeth are the sole part of her body that remains healthy as her illness withers her away. By personifying Berenice’s teeth, Egaeus dismisses her imminent physical death in favor of his own lively mental dreamscape.