Enamel-Only Caries — Silent Demineralization
Acid dissolves enamel minerals before any pain begins.
- ~2.5 mm: Enamel thickness (thickest over cusps)
- 96%: Enamel mineral content (hydroxyapatite)
- None: Symptoms at this stage (no nerve involvement)
- High: Reversibility (remineralization possible)
How enamel caries forms
Plaque bacteria ferment sugars into acid, dissolving enamel crystals.
Why no symptoms yet
Enamel has no nerves, so early decay stays painless.
White-spot lesions can still remineralize with fluoride.
Typical management
Fluoride varnish and diet change often halt progression.
Dentin Caries — Sensitivity Begins
Decay crosses into dentin, and nerves start to notice.
- ~45,000/mm²: Dentin tubule density (near pulp)
- Faster: Decay spread rate (dentin is softer than enamel)
- Sensitivity: Typical symptom (to cold or sweets)
- Filling: Standard treatment (composite or amalgam)
Dentin structure
Microscopic tubules connect dentin directly toward the pulp nerve.
Why sensitivity starts
Fluid shifts inside tubules trigger nerve signals under stimuli.
Dentin decay spreads faster than enamel decay ever does.
Treatment window
A simple filling now usually prevents deeper pulp involvement.
Deep Dentin Near Pulp — Reversible Pulpitis
The lesion nears the pulp, inflaming it but not killing it.
- <1 mm: Remaining dentin (to pulp roof)
- Reversible: Pulp condition (inflammation only)
- Lingering: Pain pattern (brief after stimulus)
- Pulp protection: Treatment goal (indirect pulp cap)
What reversible pulpitis means
Pulp is inflamed but can heal if decay is removed.
Diagnostic clue
Sharp pain that fades quickly signals reversible inflammation.
Delay here risks tipping the pulp into irreversible damage.
Treatment approach
A protective liner plus filling shields the pulp from exposure.
Pulp Exposure — Irreversible Pulpitis
The pulp is breached and inflammation can no longer resolve.
- Direct: Pulp exposure (bacteria enter chamber)
- Spontaneous: Pain pattern (unprovoked, throbbing)
- None: Healing potential (pulp cannot recover)
- Root canal: Required treatment (RCT)
Irreversible pulpitis
Bacterial invasion overwhelms the pulp beyond self-repair.
Why pain changes
Pressure inside the closed chamber causes constant throbbing pain.
Spontaneous, unprovoked pain is the hallmark warning sign.
Only remaining option
Root canal therapy removes infected pulp and seals the canal.
Pulp Necrosis — Infection & Abscess
The pulp dies completely, and infection can spread beyond the tooth.
- Dead: Pulp vitality (no blood supply)
- High: Infection risk (periapical abscess)
- Variable: Pain pattern (may reduce as nerve dies)
- RCT or extraction: Treatment options (depends on tooth viability)
What necrosis means
Blood supply is lost and pulp tissue fully dies.
Abscess formation
Bacteria exit the root tip, forming a periapical abscess.
Pain can paradoxically ease as nerve tissue dies off.
Final treatment choice
Root canal saves the tooth; extraction removes it entirely.