When the tooth pulp becomes necrotic secondary to severe caries, infection can spread to become a potentially life-threatening cellulitis.
Untreated oral bacterial infection can cause:
Sinusitis, bacteremia, and brain abscess may occur due to direct bacterial extension into adjacent soft tissues, or systemically through the hematogenous route.
Child with right facial swelling due to cellulitis originating from a necrotic tooth
Hutchins K, Carras G, Erwin J, et al. Ventilator- associated pneumonia and oral care: A successful quality improvement project. Am J Infect Control. 2009; 37:590-7.