Orthodontics: Growth and Development

Introduction

• Lecture by Ryan, an orthodontics resident.
• Focus on orthodontics, distinct from pediatric dentistry.
• Aim to prepare for board exams and provide clinical knowledge.

Growth vs. Development

• Growth: Increase in size/number of cells.
  • Hypertrophy: Increase in size of cells.
  • Hyperplasia: Increase in number of cells.
• Development: Increase in complexity or specialization.
  • Physiological/behavioral aspects.

Laws of Growth and Development

• Pattern: Predictable changes.
• Timing: Specific growth ages with variability.
• Variability: Individual differences.

Cephalocaudal Growth Gradient

• Parts near the cranium grow early.
• Body parts further away grow later.
• Examples:
  • Head size decreases proportionally from birth to adulthood.
  • Maxilla matures before mandible.

Scammon's Growth Curves

• Neural Growth: Rapid growth till age 6-7.
• Lymphoid Growth: Peaks at age 10, involutes during puberty.
• Genital Growth: Spikes during puberty.
• General Growth: Rapid growth after birth, spikes in puberty.
• Maxilla & Mandible: Maxilla follows neural curve, mandible follows general body growth.

Growth Curves

• Distance Curve: Cumulative growth over time.
• Velocity Curve: Rate of growth, peaks during growth spurts.

Growth Timing Indicators

• Chronological Age: Not always indicative of maturity.
• Dental Age: Poor indicator.
• Skeletal Age: Measured by CBM or hand-wrist methods.
• Biologic/Developmental Age: Best indicator, includes puberty markers.

Mechanisms of Growth

• Growth Sites vs. Centers
  • Sites: Areas where growth occurs.
  • Centers: Sites with autonomous growth capability.

Modes of Bone Growth

• Endochondral Ossification: Increases bone length from cartilage model.
• Intramembranous Ossification: Increases bone diameter from fibrous tissue.

Theories of Craniofacial Growth

• Suture Theory: Sutures as growth centers (debunked).
• Cartilage Theory: Cartilage as growth centers.
• Functional Matrix Theory: Soft tissue matrix determines growth.

Regions of Craniofacial Growth

• Cranial Vault: Intramembranous growth at sutures and surfaces.
• Cranial Base: Endochondral growth at synchondroses.
• Maxilla: Intramembranous growth at sutures and surfaces.
• Mandible: Mixed growth; endochondral at condyle, intramembranous at surfaces.

Growth Directions

• Mandibular Rotation: Affects facial height and bite.

Growth Trends

• Transverse: Stops growth at age 10-12.
• Anteroposterior: Stops growth at age 14-16.
• Vertical: Stops growth at age 18-20 or later.

Conclusion

• Summary and encouragement to subscribe for more content.