Which teeth are examined in the OHI-S?
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NBDHE Review · Dental Indices (Community Health and Research Principles)
OHI-S (Simplified Oral Hygiene Index) and Gingival Index
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In 30 seconds
The NBDHE tests your knowledge of the two most commonly encountered oral hygiene and gingival assessment indices: the Simplified Oral Hygiene Index (OHI-S) by Greene and Vermillion, and the Gingival Index (GI) by Löe and Silness. You must be able to identify the index teeth used in each system, interpret numerical scores, and understand what each index measures (and, crucially, what it does NOT measure). Expect questions that ask you to select the appropriate index for a given clinical or research scenario.
The college version
Core Review
The Simplified Oral Hygiene Index (OHI-S)
Developed by Greene and Vermillion in 1964, the OHI-S is a rapid assessment tool for quantifying oral cleanliness at the population level. Unlike comprehensive indices, the OHI-S examines only six specific teeth (known in periodontics as the Ramfjord teeth), selected because they are representative of the entire dentition:
| Tooth Number (Universal) | Tooth | Rationale |
|---|---|---|
| #3 | Maxillary right first molar | Posterior maxillary segment |
| #8 | Maxillary right central incisor | Anterior maxillary segment |
| #14 | Maxillary left first molar | Posterior maxillary segment |
| #19 | Mandibular left first molar | Posterior mandibular segment |
| #24 | Mandibular left central incisor | Anterior mandibular segment |
| #30 | Mandibular right first molar | Posterior mandibular segment |
Two components:
DI-S (Debris Index — Simplified): Assesses soft debris (plaque, food debris, materia alba) on the tooth surface. For each of the six index teeth, the buccal and lingual surfaces are examined. The scoring criteria:
| Score | Criteria |
|---|---|
| 0 | No debris or stain present |
| 1 | Soft debris covering ≤1/3 of the tooth surface, or extrinsic stain without debris |
| 2 | Soft debris covering >1/3 but ≤2/3 of the tooth surface |
| 3 | Soft debris covering >2/3 of the tooth surface |
DI-S = Sum of all debris scores ÷ Number of surfaces scored
CI-S (Calculus Index — Simplified): Assesses supragingival and subgingival calculus on the same six teeth. Subgingival calculus is detected with an explorer. Scoring:
| Score | Criteria |
|---|---|
| 0 | No calculus present |
| 1 | Supragingival calculus covering ≤1/3 of the surface |
| 2 | Supragingival calculus covering >1/3 but ≤2/3, or flecks of subgingival calculus |
| 3 | Supragingival calculus covering >2/3, or a continuous band of subgingival calculus |
CI-S = Sum of all calculus scores ÷ Number of surfaces scored
OHI-S = DI-S + CI-S
Clinical Ratings:
| OHI-S Score | Rating |
|---|---|
| 0.0–1.2 | Good |
| 1.3–3.0 | Fair |
| 3.1–6.0 | Poor |
Substitution rule: If a designated index tooth is missing, the adjacent tooth in the same segment may be substituted. In practice, if tooth #3 is missing, substitute tooth #2 or #4.
The Gingival Index (GI)
Developed by Löe and Silness in 1963 and published alongside their landmark experimental gingivitis study, the Gingival Index assesses the severity of gingival inflammation — not plaque, not periodontitis, not attachment loss. The GI examines four gingival units per tooth: mesial papilla, distal papilla, buccal margin, and lingual margin. Each unit is scored independently, then scores are averaged.
GI Scoring Criteria (0–3):
| Score | Criteria | Clinical Description |
|---|---|---|
| 0 | Normal gingiva | Pale pink, stippled, firm, no bleeding on probing |
| 1 | Mild inflammation | Slight change in color, slight edema, NO bleeding on probing |
| 2 | Moderate inflammation | Redness, edema, glazing, BLEEDING ON PROBING present |
| 3 | Severe inflammation | Marked redness, edema, ulceration, tendency toward SPONTANEOUS bleeding |
Critical NBDHE distinction: The difference between Score 1 and Score 2 is bleeding on probing. Score 1 = no bleeding; Score 2 = bleeding on probing; Score 3 = spontaneous bleeding.
Areas examined per tooth:
- Disto-buccal papilla
- Buccal marginal gingiva
- Mesio-buccal papilla
- Lingual marginal gingiva (includes disto-lingual, lingual marginal, and mesio-lingual as a single unit)
To calculate GI for a tooth: Sum of scores at all 4 units ÷ 4. To calculate GI for an individual: Sum of all tooth GIs ÷ Number of teeth examined.
Interpretation (individual mean GI):
- 0.1–1.0 = Mild gingivitis
- 1.1–2.0 = Moderate gingivitis
- 2.1–3.0 = Severe gingivitis
Comparison with Related Indices
| Index | What It Measures | Scoring | Key Distinction |
|---|---|---|---|
| GI (Löe & Silness) | Gingival inflammation severity | 0–3 per gingival unit | Color, edema, BOP |
| Modified GI (Lobene) | Gingival inflammation | 0–4 | Non-invasive (no probing); assesses visual changes only |
| Gingival Bleeding Index (Ainamo & Bay) | Presence/absence of BOP | Dichotomous (bleeding: yes/no) | Simplest; only assesses bleeding after probe sweep |
| Sulcus Bleeding Index (Mühlemann & Son) | Bleeding after probing | 0–5 | Assesses bleeding severity (time and extent) |
What These Indices Do NOT Measure
A critical NBDHE concept: Indices measure what they were designed to measure, and no more.
- OHI-S measures oral cleanliness (debris + calculus). It does NOT measure gingivitis, periodontitis, or caries. A patient can have an OHI-S of 0 (perfectly clean) and still have severe periodontitis from past disease.
- Gingival Index measures gingival inflammation. It does NOT measure periodontitis, attachment loss, or bone loss. A patient with severe periodontitis in maintenance may have a GI of 0–1 (controlled inflammation) despite significant attachment loss.
- Neither index is reversible in the same way: Oral debris is transient (you can brush and reduce DI-S). Gingival inflammation is reversible (treated gingivitis returns GI to 0). Calculus is semi-permanent until removed. By contrast, DMFT is irreversible — once a tooth is Filled, it always counts as F.
Clinical/Board Application
Board-style question set-up: "A dental hygienist is collecting data for a community oral health screening. She uses an index that examines six specific teeth for debris and calculus, scoring each on a 0–3 scale. Which index is she using?"
Answer: OHI-S. The six specific teeth (Ramfjord teeth), the debris and calculus components, and the 0–3 scale are characteristic of the OHI-S.
Common Traps
- Trap: Confusing OHI-S with GI. If the question mentions "debris and calculus" → OHI-S. If it mentions "color, edema, bleeding" → GI.
- Trap: Thinking Score 1 on the GI includes bleeding. Score 1 is mild inflammation WITHOUT bleeding. Bleeding on probing kicks in at Score 2.
- Trap: Misidentifying the Ramfjord teeth. Remember: first molars (not second!) and central incisors (not laterals!). Universal numbers: 3, 8, 14, 19, 24, 30.
- Trap: Using GI to assess periodontitis severity. GI only measures gingival inflammation. A patient can have a low GI with severe attachment loss.
Eli explains
The same idea, in plain words
Explain it like I’m 10
The OHI-S is like a cleanliness report card for six key teeth. It checks two things: how much gunk (debris) is on the teeth and how much hardened gunk (calculus/tartar) has built up. Score 0–3 for each. The Gingival Index is different — it's an inflammation detector. It checks the gums around your teeth for redness, swelling, and bleeding. Score 0 means happy pink gums. Score 1 means a little red but no bleeding. Score 2 means bleeding when the hygienist pokes. Score 3 means bleeding even without being touched. They measure completely different things!
Key takeaways
- OHI-S uses six Ramfjord teeth: #3, #8, #14, #19, #24, #30
- OHI-S = DI-S (debris) + CI-S (calculus); range 0–6
- Good: 0–1.2; Fair: 1.3–3.0; Poor: 3.1–6.0
- GI (Löe & Silness): 0 = normal, 1 = mild (no BOP), 2 = moderate (BOP present), 3 = severe (spontaneous bleeding)
- GI assesses 4 gingival units per tooth: disto-buccal, buccal, mesio-buccal, lingual
- Score 1 vs. Score 2 hinge = bleeding on probing
- OHI-S measures cleanliness, GI measures inflammation — completely different constructs
- Q1: Which teeth are examined in the OHI-S?
- A. All erupted permanent teeth
- B. Six specific teeth: maxillary right and left first molars, mandibular left and right first molars, maxillary right and mandibular left central incisors ✓ — These are the Ramfjord teeth (#3, #14, #19, #30, #8, #24), chosen to represent the entire dentition.
- C. All anterior teeth only
- D. All posterior teeth only
- Q2: A patient has slightly red, edematous gingiva that does NOT bleed upon probing. According to the Löe & Silness Gingival Index, the score is:
- A. 1 ✓ — Score 1 represents mild inflammation (slight color change, slight edema) WITHOUT bleeding on probing. The absence of bleeding is the key differentiator from Score 2.
- B. 0
- C. 2
- D. 3
- Q3: An OHI-S score of 2.8 corresponds to which clinical rating?
- A. Good
- B. Fair ✓ — The Fair range is 1.3–3.0. An OHI-S of 2.8 falls within this range.
- C. Poor
- D. Excellent
Quick check
3 questions here. Answers stay hidden until you check.
A patient has slightly red, edematous gingiva that does NOT bleed upon probing. According to the Löe & Silness Gingival Index, the score is:
Choose an answer, then check it.
An OHI-S score of 2.8 corresponds to which clinical rating?
Choose an answer, then check it.
Study toolsYou’ll learn to
You’ll learn to
- Identify the six index teeth (Ramfjord teeth) used in the OHI-S
- Calculate OHI-S scores: Debris Index (DI-S), Calculus Index (CI-S), and combined OHI-S
- Interpret OHI-S scores using the established clinical rating scale (Good, Fair, Poor)
- Describe the Gingival Index (Löe & Silness) scoring system (0–3) and the tissues assessed
- Differentiate the Gingival Index from the Modified Gingival Index and the Gingival Bleeding Index
- Select the appropriate index for given clinical or research purposes
Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.