Enamel erosion: how acid dissolves the hardest tissue in the body

Enamel erosion is not caries, and it is not mechanical wear. It is chemical dissolution of mineral by acid. No bacteria, no plaque — only an acidic environment in which hydroxyapatite passes into solution. It happens invisibly. It becomes visible late — when enamel has already thinned.

What erosion is: the chemistry

Hydroxyapatite — the principal mineral of enamel — dissolves at pH below 5.5 (for enamel) and below 6.0 to 6.5 (for dentine). When an acidic solution contacts the tooth surface, hydrogen ions react with phosphate groups in the crystal lattice, breaking the crystal apart.

The degree of damage depends on:

• Buffer capacity — the solution's ability to resist neutralisation by saliva. Higher buffer capacity means longer acid exposure.
• Titratable acidity — total acid load that must be neutralised.
• Contact time — sipping juice slowly over an hour is worse than drinking it in one go.
• Calcium and phosphate content of the beverage — their presence reduces erosive potential.

Typical erosion sources:

• Citrus fruits and their juices (pH 2.0–3.5)
• Carbonated soft drinks (pH 2.5–4.0)
• Sports drinks (pH 2.9–4.5)
• Vinegar and vinegar-based dressings
• White wine (pH 3.0–3.5)
• GERD — chronic gastric acid exposure (pH 1.5–3.5)

Erosion vs caries: a fundamental difference

Caries is a localised process in the presence of plaque. First demineralisation, then cavitation. Characteristic sites: fissures, interproximal spaces, cervical areas.

Erosion is a diffuse process. It affects horizontal tooth surfaces, incisal edges, and cusps. Characteristic appearance: "cupping" on molar occlusal surfaces, transparency of incisal edges, "rounding" of cusps. When dentine begins to show through, the tooth becomes yellowish. At this stage, sensitivity to cold and sweet appears.

Erosion works slowly and invisibly. By the time teeth start reacting to cold or look shorter, enamel has already been partially lost.

BEWE: the clinical assessment tool

BEWE (Basic Erosive Wear Examination) is a standardised clinical index for erosion assessment, developed in 2008 (Bartlett, Ganss, Lussi). Each sextant of the mouth is scored 0–3; maximum cumulative score is 18.

The index is used as a screening tool, not detailed diagnosis. A high BEWE is a signal for detailed risk assessment (diet, GERD, bruxism) and intensified prevention.

The common mistake: brushing immediately after acidic food

After acid contact, enamel is temporarily softened — its surface layer is demineralised and structurally weaker. Brushing at that moment mechanically removes the softened surface, amplifying mineral loss.

The rule: after acid exposure (lemon juice, carbonated drink, vomiting):

1. Rinse with water or a bicarbonate solution.
2. Wait at least 30 to 60 minutes.
3. Then brush as normal.

What protects

• Fluoride — incorporates into partially demineralised hydroxyapatite, forming fluorapatite which is more acid-resistant. Fluoride toothpaste after acid exposure (with the 30-minute delay) is the standard preventive step.
• Saliva — the primary neutraliser. Xerostomia dramatically amplifies the erosive potential of any acid exposure.
• Water instead of prolonged acidic beverage sipping — reduces contact time significantly.
• Using a straw for acidic drinks — reduces direct tooth contact.

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Sources:

• Systematic review and meta-analysis on erosive tooth wear in primary dentition (2025). PMC11788517
• Lussi A, Jaeggi T. (2008). Erosion — diagnosis and risk factors. Clin Oral Investig. PMID 18228059
• Bartlett D, Ganss C, Lussi A. (2008). Basic Erosive Wear Examination (BEWE): a new scoring system for scientific and clinical needs. Clin Oral Investig. PMID 18228057
• Frontiers in Dental Medicine (2022). Dynamic interplay of dietary acid pH and enamel erosion. https://doi.org/10.3389/fdmed.2022.1040565
• ADA. Dental Erosion. https://www.ada.org/resources/ada-library/oral-health-topics/dental-erosion