**Question:** All are true about permanent teeth, except:-

A. Permanent teeth have a different number of teeth than primary teeth.
B. Root formation in permanent teeth continues throughout life.
C. Teeth erupt continuously throughout an individual's life.
D. Permanent teeth have no pulp canals.

**Core Concept:**

Permanent teeth are the teeth that remain in the oral cavity throughout an individual's life. They are replaced by the primary (baby) teeth during childhood and maintain the dental arch structure and function into adulthood. The dental formula for permanent teeth is:

1. 10 incisors
2. 8 canines
3. 8 premolars
4. 4 molars

**Why the Correct Answer is Right:**

Option A is incorrect because permanent teeth do not have a different number than primary teeth. Both sets have the same number of teeth, but they differ in their arrangement and morphology. Primary teeth are smaller and simpler than permanent teeth, and they serve as placeholders for the permanent teeth to erupt and occupy the dental arch.

Option B is correct: Root formation in permanent teeth does not continue throughout life. The process of root formation, known as dentinogenesis, occurs during the development stage of tooth germs during embryonic stage, and then continues during the postnatal stage in which the root growth and mineralization occur. After the root formation is completed, the root growth ceases, and the tooth becomes fully mature.

Option C is incorrect because teeth do not erupt continuously throughout an individual's life. Eruption is a gradual process that starts at birth and ends around the age of 18 years. After eruption, the tooth remains stable in the dental arch, and there is no continuous eruption throughout life.

Option D is incorrect because the pulp chamber and root canals contain vascular and neural structures, which are essential for tooth vitality and sensation. The presence of pulp canals is necessary for tooth sensitivity and innervation.

**Why Each Wrong Option is Incorrect:**

Option A is incorrect because the dental formula (10 incisors, 8 canines, 4 premolars, and 4 molars) applies to both primary and permanent teeth. Primary teeth have a different morphology but the same number of teeth.

Option B is incorrect because the root formation ceases after completion of dentinogenesis.

Option C is incorrect because eruption is a gradual process and does not continue throughout an individual's life.

Option D is incorrect because the absence of pulp canals would render the tooth non-vital and incapable of sensation, which is essential for proper tooth function and health.

**Clinical Pearls:**

The process of eruption is crucial for proper eruption of teeth into the oral cavity and ensures proper function and aesthetics. The dental formula (10 incisors, 8 canines, 4 premolars, and 4 molars) is important for understanding dental anatomy and the development of teeth in the oral cavity.

**Why the Correct Answer is Correct:**

The correct answer, D, highlights the importance of dental pulp and root canals for tooth vitality