How this tool works
The Simplified Oral Hygiene Index (Greene and Vermillion, 1964) has two parts. The Debris Index (DI-S) scores soft deposits and stain. The Calculus Index (CI-S) scores hard deposits. Each of six surfaces gets a 0–3 score for each part.
- DI-S = sum of the debris scores ÷ number of surfaces scored.
- CI-S = sum of the calculus scores ÷ number of surfaces scored.
- OHI-S = DI-S + CI-S.
The paper calculates individual scores to one decimal place, so the calculator rounds DI-S and CI-S to one decimal and then adds them. That way the record adds up exactly as you'd write it on paper. Each part runs from 0 to 3, and the OHI-S from 0 to 6.
Worked example: debris scores 1, 0, 2, 1, 1, 2 and calculus scores 0, 0, 1, 2, 0, 1 on all six surfaces. DI-S = 7 ÷ 6 = 1.2. CI-S = 4 ÷ 6 = 0.7. OHI-S = 1.9.
The six index surfaces
| Surface | Tooth (FDI / Universal) | If it can't be scored |
|---|---|---|
| Buccal | Upper right first molar (16 / #3) | Next fully erupted molar behind it (17, then 18) |
| Labial | Upper right central incisor (11 / #8) | Upper left central incisor (21) |
| Buccal | Upper left first molar (26 / #14) | 27, then 28 |
| Lingual | Lower left first molar (36 / #19) | 37, then 38 |
| Labial | Lower left central incisor (31 / #24) | Lower right central incisor (41) |
| Lingual | Lower right first molar (46 / #30) | 47, then 48 |
On the posterior teeth, the paper scores the first fully erupted tooth distal to the second premolar. That's usually the first molar, but sometimes the second or third. Each buccal or lingual "surface" covers half the tooth's circumference, including half of the mesial and distal surfaces.
Rules from the paper:
- Score only fully erupted permanent teeth: the occlusal or incisal surface has reached the occlusal plane.
- Skip teeth with full crowns, and surfaces reduced in height by caries or trauma. Score the alternate tooth instead.
- You need at least 2 of the 6 surfaces to calculate an individual score.
Scoring criteria (paraphrased)
| Score | Debris | Calculus |
|---|---|---|
| 0 | None, and no stain | None |
| 1 | Soft debris on up to 1/3 of the surface, or extrinsic stain alone | Supragingival calculus on up to 1/3 of the exposed surface |
| 2 | Debris on more than 1/3 but no more than 2/3 | Supragingival calculus on more than 1/3 but no more than 2/3, or flecks of subgingival calculus at the cervical area |
| 3 | Debris on more than 2/3 | Supragingival calculus on more than 2/3, or a continuous heavy band of subgingival calculus |
The paper estimates debris by running the side of an explorer along the surface. Score debris first, then calculus, on each surface.
Interpreting the score
The 1964 paper gives no cut-offs. This commonly taught interpretation is a convention, and teaching sources vary slightly:
| Rating | OHI-S | DI-S or CI-S |
|---|---|---|
| Good | 0.0–1.2 | 0.0–0.6 |
| Fair | 1.3–3.0 | 0.7–1.8 |
| Poor | 3.1–6.0 | 1.9–3.0 |
Bands are applied to the one-decimal values, so there are no gaps. For research, report the numbers rather than the labels. For groups, Greene and Vermillion average the individual scores and allow one or two decimals.
Limits
The OHI-S samples six surfaces, so it describes hygiene in the whole mouth only roughly. It records deposits, not gum inflammation: pair it with the Gingival Index for that, or use the Plaque Index when you want plaque at the gum margin.
Frequently asked questions
Which teeth are used for the OHI-S?
What if an index tooth is missing?
How many surfaces do I need?
What is a good OHI-S score?
Sources
- Greene JC, Vermillion JR. Journal of the American Dental Association 68:7-13. The Simplified Oral Hygiene Index. 1964. Accessed October 26, 2026.
- Mandal SK (SlideShare teaching slides, secondary source). Periodontal indices final. Convention only. These slides list poor as 3.0–6.0; the calculator uses 3.1–6.0 so the bands don't overlap. Accessed October 26, 2026.
Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.