## Core Concept
Tooth age estimation is a method used in forensic odontology to determine an individual's age. This process involves analyzing the changes that occur in teeth over time, such as growth, development, and wear. The most reliable criteria for age estimation from teeth often involve assessing the development and morphological changes.

## Why the Correct Answer is Right
The correct answer, . (Root development), is considered a reliable criterion for age estimation because root formation and closure follow a relatively predictable timeline. Studies have shown that root development can be used to estimate age, especially in subadults. This method assesses the stage of root formation, from the initial formation of the root to its complete closure, which occurs at different ages in various populations.

## Why Each Wrong Option is Incorrect
- **Option A:** . (Attrition) - Attrition, or tooth wear, is influenced by diet, oral hygiene, and environmental factors, making it less reliable for age estimation due to its variability.
- **Option B:** . (Cementum apposition) - While cementum does continue to deposit with age, this process is less predictable and not as commonly used for age estimation as root development.
- **Option D:** . (Secondary dentin formation) - Secondary dentin formation is a continuous process throughout life and can be used for age estimation. However, it might not be as precise as root development because the rate of formation can vary.

## Clinical Pearl / High-Yield Fact
A key point to remember is that while root development is a reliable method for age estimation, especially in younger individuals, it requires knowledge of the specific developmental stages and their correlation with age. This method is often used in conjunction with other age estimation techniques for a more accurate assessment.

## Correct Answer: C. Root development.