Permanent teeth

Permanent teeth, also known as secondary or adult teeth, are the final set of teeth that replace deciduous (primary) teeth. These teeth emerge during childhood and adolescence, and unlike primary teeth, they are meant to last a lifetime. Permanent teeth play a vital role in chewing, speaking, and maintaining facial structure.

Anatomy

Permanent teeth have a complex structure designed to endure constant use and resist wear. Each tooth consists of the following parts:

Crown

• The visible part of the tooth above the gumline.
• Covered by enamel, which protects against mechanical and chemical damage.

Neck

The narrow region where the crown and root meet, surrounded by gums.

Root

• Embedded in the jawbone, anchoring the tooth securely within the alveolar socket.
• Covered by cementum and held in place by the periodontal ligament.

Enamel

• The outermost and hardest layer, made of hydroxyapatite crystals.
• Provides protection against decay and wear.

Dentin

• Located beneath the enamel, forming the bulk of the tooth.
• Contains microscopic tubules that transmit signals to the pulp.^[2]

Pulp

• The innermost part containing nerves, blood vessels, and connective tissue.
• Supplies nutrients and sensations to the tooth.

Cementum

A calcified layer covering the root and connecting it to the periodontal ligament.

Periodontal Ligament

• Connective tissue fibers that attach the tooth to the alveolar bone.
• Acts as a shock absorber during chewing and biting.^[3]

Types of Permanent Teeth

A complete set of permanent teeth consists of 32 teeth, divided into four groups based on their structure and function:

Incisors (8)

• Four in the upper jaw and four in the lower jaw.^[5]
• Sharp and chisel-shaped for cutting and slicing food.

Canines (4)

• Two in the upper jaw and two in the lower jaw.
• Pointed for tearing and grasping food.

Premolars (8)

• Four in each jaw, located between canines and molars.
• Broad, flat surfaces for crushing and grinding food.

Molars (12)

• Six in each jaw, including wisdom teeth (third molars).
• Large and flat for grinding and breaking down food into smaller particles.

Development and Eruption of Permanent Teeth

Development

Permanent teeth begin to develop beneath the gums during infancy, even before the primary teeth have erupted. Their development is completed in stages, starting with the calcification of enamel and dentin, followed by the formation of roots.

Eruption Timeline

The eruption of permanent teeth typically follows a predictable sequence:

• 6–7 years: First molars and lower central incisors.
• 7–8 years: Upper central incisors and lateral incisors.
• 9–10 years: First premolars.
• 10–12 years: Second premolars and canines.
• 11–13 years: Second molars.
• 17–25 years: Third molars (wisdom teeth).

By the age of 12–14 years, most children have their full set of permanent teeth, except for the wisdom teeth, which may erupt later or remain impacted.

Function

• Chewing and Digestion
  • Incisors cut food into smaller pieces.
  • Canines tear and hold food.
  • Premolars and molars grind and crush food, facilitating digestion.^[1]
• Speech and Pronunciation
  • Teeth aid in articulation and pronunciation of words.
  • They work with the tongue and lips to produce distinct sounds.
• Aesthetic and Facial Support
  • Teeth provide structure to the face, maintaining shape and balance.
  • Proper alignment enhances facial aesthetics and boosts confidence.
• Preservation of Jawbone Density: Roots of teeth stimulate the jawbone, preventing bone loss and maintaining its density.
• Spacing and Alignment: Permanent teeth maintain proper spacing and alignment, preventing malocclusion and related issues.

Differences Between Permanent and Deciduous Teeth

• Number: Permanent teeth consist of 32 teeth, whereas deciduous teeth have 20 teeth.
• Size: Permanent teeth are larger and more robust.
• Enamel Thickness: The enamel in permanent teeth is thicker, providing greater protection.
• Roots: Permanent teeth have longer and stronger roots.
• Replacement: Permanent teeth are irreplaceable, unlike deciduous teeth, which are naturally shed.

Wisdom Teeth and Their Challenges

Wisdom teeth, or third molars, are the last to erupt and often pose problems due to lack of space in the jaw.

• Impaction – Failure to fully emerge, leading to pain and swelling.
• Infection – Partially erupted wisdom teeth are prone to infection and decay.
• Crowding – Can push adjacent teeth out of alignment.^[6]

Extraction is commonly performed to prevent complications.

Orthodontic Importance

Misaligned permanent teeth can cause bite problems, speech difficulties, and uneven wear. Orthodontic treatments, such as braces or clear aligners, correct these issues and improve dental function and aesthetics.