Overview

A periapical abscess is a collection of pus at the tip of a tooth root, caused by bacterial infection of the pulp that has spread into surrounding bone. Unlike an acute abscess with obvious pain and swelling, a chronic periapical abscess may be completely painless — a silent infection slowly destroying bone, detected incidentally on X-rays at routine check-ups.

Symptoms

• Acute: throbbing pain, facial swelling, fever, difficulty opening the mouth
• Chronic: often completely painless; dark shadow around root tip on X-ray
• A small pimple or sinus tract on the gum that intermittently weeps fluid
• A tooth that has darkened in colour; tenderness when biting
• A previously root-treated tooth with recurring symptoms

Causes & Risk Factors

• Deep dental caries infecting the pulp and spreading to the root tip
• Failed or incomplete root canal treatment allowing bacterial recontamination
• Cracked tooth with pulp involvement; dental trauma causing pulp necrosis

Complications

• Spread of infection to surrounding bone (osteomyelitis)
• Sinus infection if upper teeth involved; cyst formation expanding and destroying bone
• Loss of the tooth; life-threatening spread in immunocompromised patients

Diagnosis

Periapical X-rays and OPG show the characteristic dark shadow around the root tip. Vitality testing confirms the tooth is non-vital. CBCT 3D scanning for complex cases. Chronic lesions may require biopsy to exclude cysts or other pathology.

Treatment

• Root canal treatment: cleans, shapes, and seals infected canals eliminating infection
• Root canal retreatment when a previous root canal has failed
• Apicoectomy (endodontic surgery): surgical removal of the infected root tip when conventional treatment cannot resolve the lesion
• Extraction if the tooth is unsalvageable; antibiotics to control acute infection before definitive treatment

Prevention

• Treat dental decay promptly before it reaches the pulp
• Ensure root canal treatment is technically adequate — seek specialist endodontic care for complex cases
• Regular X-rays at check-ups to detect silent periapical infections before they become large
• Attend all follow-up appointments after root canal treatment

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