**Core Concept**
Plaque index is a measure used to quantify the amount of dental plaque on the teeth. It is an essential tool in assessing the effectiveness of oral hygiene practices and the risk of periodontal diseases. The plaque index is typically evaluated using a visual scoring system.

**Why the Correct Answer is Right**
The correct answer is the option that does not measure the plaque index. The most commonly used methods to measure the plaque index are the Silness-Loe Plaque Index (SLI), the Quigley-Hein Plaque Index (QHPI), and the Turesky-Gilmore-Glickman (TGG) Plaque Index. These methods involve visually assessing the presence and extent of plaque on the teeth.

**Why Each Wrong Option is Incorrect**
**Option A:** The Silness-Loe Plaque Index (SLI) is a widely used method to measure the plaque index, so it is not the correct answer.
**Option B:** The Quigley-Hein Plaque Index (QHPI) is another commonly used method to measure the plaque index, making it an incorrect option.
**Option D:** The Turesky-Gilmore-Glickman (TGG) Plaque Index is also a valid method to measure the plaque index, so it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
To accurately measure the plaque index, dental professionals must be trained in the specific method being used and must assess the teeth in a standardized manner. This involves evaluating the presence and extent of plaque on the teeth, as well as any signs of gingivitis or periodontal disease.

**Correct Answer:** D.