Overview
This lecture explains the concept of balanced occlusion in complete dentures, its significance, and the five major factors that affect it, collectively known as Hanau's Quint.
Natural Teeth vs. Complete Denture Occlusion
- In natural teeth, protrusive movement creates a wedge-shaped space (Christensen's phenomenon) between posterior teeth.
- In complete dentures, such spaces can cause lifting, instability, and loss of denture retention.
- A three-point contact (one anterior, two posterior) is necessary in complete dentures for stability during all jaw movements.
Definition and Importance of Balanced Occlusion
- Balanced occlusion is bilateral, simultaneous, anterior and posterior contact of teeth in centric and eccentric positions.
- Centric occlusion: contact when the mandible is in centric relation (a repeatable, bone-to-bone position).
- Eccentric positions: any mandibular position other than centric.
- Posterior tooth contact must be maintained in centric, lateral, and protrusive movements.
- Balanced occlusion enhances denture stability and protects denture-bearing tissues from trauma and resorption.
Hanau's Quint: Five Factors Affecting Balanced Occlusion
- The five factors are: condylar guidance, incisal guidance, orientation of the occlusal plane, compensating curves, and cuspal inclination.
Condylar Guidance
- Determined by the slope of the articular eminence; cannot be altered clinically.
- Steep condylar guidance requires longer cusps; shallow guidance requires shorter cusps/flatter fossae.
Incisal Guidance
- Angle between occlusal plane and line joining maxillary and mandibular incisors.
- Steeper incisal guidance increases posterior tooth separation during movements.
- To compensate, increase horizontal overlap and reduce incisal guide angle as much as possible.
Orientation of the Occlusal Plane
- Anterior tooth height set by the lower canine at mouth commissure; posterior by retromolar pad height.
- Plane should be parallel to the ala-tragus line but serves only as a starting reference.
Compensating Curves
- Anterior-posterior curve (Curve of Spee) helps maintain protrusive balance.
- Mediolateral curve (Curve of Wilson) maintains balance in lateral movements of the jaw.
Cuspal Inclination
- Refers to the angle of a tooth's cusp relative to the occlusal plane.
- Teeth closer to condylar guidance are more influenced by it; those closer to incisal guidance are more influenced by it.
- Buccolingual and anterior-posterior inclinations increase from premolars to molars.
Key Terms & Definitions
- Balanced Occlusion — Bilateral, simultaneous, anterior and posterior tooth contact in all jaw positions.
- Centric Relation — A maxillomandibular position with bone-to-bone contact, independent of tooth contact.
- Condylar Guidance — Slope of the mandibular condyle path in the temporomandibular joint.
- Incisal Guidance — The angle formed by the overlap of the upper and lower incisors.
- Occlusal Plane — The average plane established by the incisal and occlusal surfaces of the teeth.
- Compensating Curve — Curvature in teeth arrangement to ensure denture stability during jaw movements.
- Cuspal Inclination — The angle of a tooth's cusp relative to the occlusal plane.
- Hanau's Quint — Five factors influencing balanced occlusion: condylar guidance, incisal guidance, occlusal plane, compensating curve, cuspal inclination.
- Christensen’s Phenomenon — Posterior separation of teeth during protrusive movement in natural dentition.
Action Items / Next Steps
- Review the basics of Hanau’s Quint.
- Prepare for a detailed study on compensating curves or Hanau's Quint in future lectures, as per instructor's next video.
- Visit the course website for the complete denture syllabus if interested.