## **Core Concept**
Cementum is a thin layer of bone-like material covering the root of a tooth. It is a mineralized tissue that plays a crucial role in tooth anchorage by facilitating the attachment of the periodontal ligament fibers. The composition of cementum is similar to that of bone but with some differences in its organic and inorganic components.

## **Why the Correct Answer is Right**
Cementum has a unique composition that allows it to perform its function. The inorganic component of cementum is primarily hydroxyapatite, which is similar to other calcified tissues in the body. The inorganic content in cementum is approximately 45-50%, which is less compared to enamel (about 96%) but more than dentin (about 70%). This specific percentage allows cementum to have the necessary hardness for tooth anchorage while still being slightly more flexible.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a much lower percentage of inorganic components than what is known for cementum.
- **Option B:** This option suggests a higher percentage, which is more characteristic of enamel than cementum.
- **Option D:** This option suggests a slightly higher percentage than the correct answer but still within a plausible range; however, it does not accurately reflect the known composition of cementum.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that cementum continuously deposits throughout life, which allows for the compensation of tooth wear. However, this deposition can sometimes lead to ankylosis, especially in cases of dental trauma. Understanding the composition and function of cementum is crucial for dental and periodontal health.

## **Correct Answer:** . 45-50%