Plaque Index Calculator
Silness-Löe Plaque Index with 0–3 scoring criteria for all tooth surfaces. Score 6 Ramfjord index teeth or full dentition, calculate mean plaque index, classify oral hygiene status, and generate clinical documentation.
NM Clinically reviewed byDr. Nikhil Mahajan, PT, MPT · Jan 15, 2026Silness-Löe Plaque Index — Scoring Criteria Reference
| Score | Criteria | Detection method | Clinical significance |
|---|---|---|---|
| 0 | No plaque | No plaque on probe | No plaque present — ideal |
| 1 | Film of plaque | Run probe along margin — plaque visible on tip | No plaque present — ideal |
| 2 | Moderate plaque | Visible to naked eye | No plaque present — ideal |
| 3 | Abundant plaque | Visible to naked eye | No plaque present — ideal |
Mean Plaque Index — Classification and Clinical Response
| Mean PI | Classification | Recall interval | Clinical action |
|---|---|---|---|
| 0 | Excellent | 12 months | Positive reinforcement, maintenance |
| 0.1–0.9 | Good | 6–12 months | Oral hygiene reinforcement, fluoride |
| 1.0–1.9 | Fair | 3–6 months | OHI + professional polishing; identify problem areas |
| 2.0–3.0 | Poor | 3 months | Intensive OHI, scaling, caries risk assessment; CAMBRA if indicated |
Plaque Index: Clinical Guide for Dental Professionals
The Plaque Index (PI) was developed by Silness and Löe in 1964 as a method for assessing the thickness of plaque at the gingival margin in clinical trials and patient monitoring. Unlike indices that measure plaque extent (area), the Silness-Löe PI measures plaque thickness — particularly the soft deposit in the gingival crevice that causes gingivitis.
The Ramfjord Index Teeth Protocol
In epidemiological surveys, scoring is commonly limited to the six Ramfjord index teeth — teeth #3, #9, #12, #19, #25, #28 (universal numbering) — chosen to represent all regions of the dentition. Each of the four surfaces (mesial, distal, buccal, lingual) is scored 0–3. The mean score across all 24 surfaces (6 teeth × 4 surfaces) gives the mean plaque index. This protocol reduces assessment time while maintaining statistical validity for population comparisons.
Relationship Between Plaque Index and Gingival Health
Löe and Silness demonstrated a strong correlation (r = 0.84) between the Plaque Index and the Gingival Index — higher plaque scores consistently predicted higher gingival inflammation scores. A mean PI below 1.0 is associated with clinical gingival health in most populations. A PI above 2.0 is consistently associated with generalised gingivitis and elevated risk of periodontitis progression.