This document discusses acute gingival infections, including primary herpetic gingivostomatitis, necrotizing ulcerative gingivitis (NUG), and pericoronitis. NUG is characterized by necrosis and sloughing of gingival tissues due to an impaired host response allowing pathogenic bacteria to invade. Clinically, it presents with crater-like gingival ulcers, pseudomembranes, pain, and systemic symptoms. The etiology involves both specific bacteria like fusospirochetal complexes and an underlying host immunosuppression. Treatment focuses on improving nutrition, antibiotics, and palliative care. Differential diagnosis includes herpes, desquamative gingivitis,