Eruption and Calcification Patterns of Primary and Secondary Teeth

 Eruption and Calcification Patterns of Primary and Secondary Teeth

Eruption pattern of primary and permanent teeth

Outline

• Definition
• Stages of tooth eruption
• Phases of deciduous tooth eruption
• Chronology of primary and permanent dentition
• Theories of tooth eruption

Definition of Eruption

Eruption is the natural physiological process by which a tooth moves from its developmental site to its functional position in the oral cavity. It involves the movement of developing teeth through bone and mucosa to reach the occlusal plane.
Tooth calcification refers to the deposition of calcium salts in dental enamel.

Stages of Tooth Eruption

1. Primary dentition stage: All teeth are primary.
2. Mixed dentition stage: Both primary and permanent teeth are present.
3. Permanent dentition stage: Only permanent teeth remain.

Nola’s Stages of Eruption (1960)

At birth, alveolar processes are underdeveloped. Natal teeth, typically early-emerging central incisors, may appear. Unless pathological, they should not be casually extracted.

Phases of Deciduous Tooth Eruption

1. Pre-eruptive movement: Tooth germ moves within the jaw.
2. Eruptive movement: Tooth actively erupts into oral cavity.
3. Post-occlusal movement: Maintains position in occlusion despite growth and wear.

Pattern of Primary Tooth Eruption

• Typically completed by 24–30 months
• Variations based on ethnicity and gender (may erupt earlier in boys)
• Spacing (primate spaces) is normal and helps accommodate permanent teeth

Primate Spaces:

• Maxillary: between lateral incisor and canine
• Mandibular: between canine and first molar

Chronology of Tooth Development: Primary Dentition

(Slide refers to timeline—include table/image if needed in actual post)

Mixed Dentition Period

Begins with eruption of mandibular first molars and ends with loss of last primary tooth (~age 11–12).

Eruption of Permanent Teeth

• Pre-emergent: Crown formation and slow migration; requires bone and root resorption.
• Post-emergent: Rapid eruption to occlusal level followed by equilibrium (slow phase).

Primary Failure of Eruption

A syndrome where posterior teeth fail to erupt despite bone resorption. These teeth are unresponsive to orthodontic forces.

Theories of Tooth Eruption Mechanisms

1. Root Elongation

Eruption may be driven by root growth pushing teeth occlusally. However, some rootless teeth erupt, suggesting this is not the sole factor.

2. Hydrostatic Pressure

Tissue fluid pressure from periapical vasculature may push teeth upward.

3. Periodontal Ligament Traction

Fibroblasts generate tractional force through oblique alignment, pulling the tooth upward.

4. Bone Remodeling

Bone forms beneath erupting teeth and resorbs above, creating a path. The dental follicle is essential for coordinating this remodeling.

5. Genetic Pre-Programming / Cellular-Molecular Determinants

Multiple genes and signaling molecules (e.g., CSF, MCP-1, growth factors) regulate eruption timing and mechanism.

Chronology of Permanent Dentition Development