## Core Concept
The period of mixed dentition refers to the stage of dental development where both primary (baby) teeth and permanent (secondary) teeth are present in the mouth. This stage is a critical phase in dental development as it involves the transition from primary to permanent dentition.

## Why the Correct Answer is Right
The mixed dentition period typically starts around the age of 6 years when the first permanent molars and incisors begin to erupt, replacing some of the primary teeth. It lasts until about 12-13 years of age, when most of the primary teeth have been replaced by permanent teeth, except for the wisdom teeth which usually appear much later. Therefore, the correct age range for the mixed dentition period is between 6 to 12-13 years.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not accurately represent the age range for the mixed dentition period.
- **Option B:** This option is incorrect for similar reasons; it does not correctly reflect the duration of the mixed dentition period.
- **Option D:** This option suggests an age range that is too narrow or not accurate for the mixed dentition period.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the mixed dentition period is crucial for orthodontic assessment and intervention, as it allows for the identification and management of potential dental and skeletal discrepancies early on. Clinicians often use this period to assess the need for orthodontic treatment and to guide the eruption of teeth.

## Correct Answer: C.