What causes tooth discoloration in an adult?

Causes of Tooth Discoloration in Adults

Tooth discoloration in adults results from three primary mechanisms: extrinsic staining from dietary chromogens and smoking, intrinsic discoloration from systemic medications (particularly tetracyclines) or pulpal necrosis, and internalized stains where external agents penetrate through enamel defects. 1

Extrinsic Causes (Surface Staining)

Dietary and lifestyle factors are the most common causes of tooth blackening in adults:

• Smoking, tea, and coffee consumption are the primary promoting factors for brown-to-black surface integuments 2
• Poor oral hygiene leads to plaque accumulation, which serves as a substrate for chromogenic bacteria and dietary stains 3, 4
• Antibacterial mouthrinses can cause chemical alteration of the acquired pellicle, resulting in brown discoloration 2
• Betel nut (paan) chewing and tobacco products produce characteristic dark staining 3

These extrinsic stains deposit directly on the tooth surface or within the pellicle layer and typically respond to professional cleaning 1.

Intrinsic Causes (Within Tooth Structure)

Medication-Induced Discoloration

Tetracycline antibiotics cause permanent discoloration when incorporated during tooth development, but adult-onset staining also occurs:

• Minocycline (commonly used for acne) causes unique "black bones," "black or green roots," and blue-gray to gray darkening of permanent tooth crowns in adults 5
• The prevalence of tetracycline/minocycline staining is 3-6% 5
• Discoloration varies from yellow or gray to brown depending on dose and duration 5
• Other medications causing tooth discoloration include various systemic drugs, though tetracyclines are most notorious 3

Pulpal Necrosis and Trauma

Gray discoloration indicates pulpal necrosis following dental trauma or infection:

• Pulpal necrosis causes teeth to appear gray in color 6
• This occurs after intrusive luxation, subluxation, or other traumatic injuries 6
• Observation for tooth discoloration is recommended following any dental trauma as a sign of pulpal compromise 6

Fluorosis-Related Discoloration

Severe enamel fluorosis can develop brown staining in adults:

• After tooth eruption, teeth with moderate or severe fluorosis may develop areas of brown stain 6
• This occurs when childhood fluoride exposure caused enamel hypomineralization that subsequently accumulates pigments 6
• The severe form manifests as pitted, brittle enamel with brown discoloration 6

Internalized Stains

Extrinsic stains can penetrate into dentine through structural defects:

• Enamel cracks, infractions, or defects allow surface chromogens to enter the tooth structure 1
• These appear as intrinsic discoloration but originate from external sources 1
• More difficult to treat than simple surface staining 1

Systemic and Metabolic Causes

Chronic kidney disease patients on dialysis may experience specific oral changes:

• Brown discoloration can occur in children with renal disease, though the relationship is complex 6
• Altered salivary composition affects tooth mineralization 6

Clinical Algorithm for Evaluation

When assessing tooth discoloration, determine:

1. Distribution pattern: Single tooth (trauma/pulpal necrosis) vs. multiple teeth (systemic/dietary causes) 6
2. Color characteristics: Gray (pulpal necrosis), brown (fluorosis, staining, medications), yellow-brown (tetracyclines) 6, 5
3. Medication history: Specifically ask about tetracyclines, minocycline, and antibacterial mouthrinses 3, 5, 2
4. Trauma history: Any previous dental injury suggesting pulpal compromise 6
5. Dietary and lifestyle factors: Coffee, tea, smoking, betel nut use 3, 2
6. Oral hygiene status: Plaque accumulation and periodontal disease 4, 3

Key Clinical Pitfalls

Do not assume all discoloration is benign: Gray discoloration of a single tooth warrants dental referral within days to evaluate for pulpal necrosis and potential abscess formation 6. Minocycline-induced discoloration is permanent and should be considered before prescribing long-term therapy in adults concerned about aesthetics 7, 5.