Prosthodontics

Key Concepts & Definitions

Christensen's Phenomenon

• Definition: Posterior gap that occurs when anterior teeth meet edge-to-edge
• Clinical Significance: Demonstrates the need for proper anterior guidance
• Application: Critical in complete denture design and occlusal rehabilitation

Vertical Dimension & Occlusal Relationships

Increased Vertical Overlap

• Compensation: Managed by the curve of Spee
• Clinical Impact: Affects anterior guidance and posterior disclusion

Vertical Dimension at Rest

• Priority: First step in establishing jaw relations
• Definition: Facial height when mandible is in physiologic rest position
• Clinical Method: Measured from nose to chin with 2-4mm freeway space

Centric Relations & Condylar Positions

Centric Relation (CR)

• Definition: Anterior-superior condyle position in glenoid fossa
• Characteristics:
  • Most retruded, unstrained position
  • Reproducible reference position
  • Independent of tooth contact

Terminal Hinge Position

• Movement: Pure hinge movement around transverse horizontal axis
• Range: First 12-25mm of mouth opening
• Clinical Use: Reference for centric relation records

Condylar Inclination

• Determination: Established using protrusive records
• Significance: Programs articulator for mandibular movement simulation
• Average Values: 30-60 degrees from horizontal

Anatomical Reference Lines & Points

Camper's Line

• Landmarks: From ala of nose to superior border of ear
• Application: Approximates occlusal plane orientation
• Clinical Use: Initial guide for denture occlusal plane

Beyron Point

• Location: 13mm anterior to tragus on tragus-canthus line
• Function: Anatomical reference for condylar guidance angle
• Clinical Relevance: Used in some articulator systems

Occlusal Curves

Curve of Spee (Anteroposterior)

• Function: Compensates for increased vertical overlap
• Clinical Application: Maintains posterior contact during protrusive movements
• Depth: Typically 1.5-2mm in natural dentition

Wilson Curve (Mediolateral)

• Alternative Name: Mediolateral curve
• Orientation: Buccal-lingual curvature of occlusal surfaces
• Function: Maintains contact during lateral excursions

Monson Sphere

• Diameter: 8 inches (20.3 cm)
• Concept: Theoretical sphere encompassing all occlusal surfaces
• Center: Located in glabella region

Balanced Occlusion

Achieving Balance

• Method: Grind lingual incline of facial cusp on balanced side
• Definition: Simultaneous contact on working and non-working sides
• Application: Essential in complete dentures, controversial in natural teeth

Clinical Considerations

• Complete Dentures: Mandatory for stability
• Natural Teeth: Group function preferred over balanced occlusion
• Implant Prosthetics: Modified approaches based on proprioception

Articulator Systems

Monson Articulator

• Basis: Arbitrary motion theory
• Principle: Uses average anatomical values
• Limitations: Cannot reproduce individual patient variations
• Clinical Use: Suitable for simple cases with average anatomy

Semi-Adjustable Articulators

• Advantage: Accommodate individual patient parameters
• Requirements: Face-bow transfer and protrusive records
• Applications: Complex rehabilitative cases