| Stage | Code | Radiographic Depth |
|---|---|---|
| Sound | 0 | No radiolucency |
| Initial | RA 1 | Outer 1/2 of enamel |
| Initial | RA 2 | Inner 1/2 of enamel ± EDJ |
| Moderate | RA 3 | Outer 1/3 of dentin |
| Moderate | RB 4 | Middle 1/3 of dentin |
| Extensive | RC 5 | Inner 1/3 of dentin (clinically cavitated) |
| Extensive | RC 6 | Into the pulp (clinically cavitated) |
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