Complete Denture Occlusion Rola M. Shadid, BDS, MSc
Occlusion the static relationship between the incising or masticating surfaces of the maxillary and mandibular teeth, or tooth analogs Articulation the contact relationship between the occlusal surfaces of teeth during function
• Centric occlusion • Eccentric occlusion * Protrusive occlusion Lateral occlusion
Working side the side toward which the mandible moves in a lateral excursion Non working (balancing) side that side of the mandible that moves toward the median line in a lateral excursion.
Occlusal Schemes For CD Balanced articulation Nonbalanced articulation (linear or monoplane articulation) Lingualized articulation Functionally generated occlusal scheme
Balanced Occlusion/Articulation • Bilateral simultaneous contact betw. anterior & posterior teeth during all centric and eccentric positions • There should be no interferences during movement from centric position to eccentric positions • The movements should be in harmony with TMJ & neuromuscular control
Advantages of Balanced Occlusion • To improve stability & retention • To decrease soreness & resorption of residual ridge • To improve oral comfort of the patient
Mechanics Of Balanced Occlusion Christensen’s phenomenon*
How Could You Achieve Balanced Occlusion In CD?
Factors That Affect Occlusal Balance
Factors Affecting Balanced Occlusion (Hanau’s Quint) * 1. Condylar Guidance 2. Incisal Guidance 3. Plane of occlusion 4. Cuspal inclination 5. Compensating curve.
Condylar Guidance* Mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossae The posterior determinent of mandibular movement
Condylar Guidance Angle The angle formed by an imaginary horizontal line at the superior head of the condyle and the path that the condyle will pass through during function Varies from individual to individual because of anatomical differences
Incisal Guidance * It’s the influence of the contacting surfaces of the mandibular & maxillary anterior teeth on mandibular movement
Incisal Guidance Angle The angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation
Incisal Guidance Angle This angle varies directly with the vertical overbite and inversely with the horizontal overjet This angle is set to 10˚ in CD and not exceeding 20˚
Incisal Guidance ↓ Incisal Guidance Angle by ↑ horizontal overlap
Incisal Guidance • For CD, the incisal guidance should be as shallow as esthetics and phonetics will permit when arrangement of anterior teeth to reduce protrusive displacing forces
Incisal Guidance ↓ Incisal Guidance Angle by either: * ↑ horizontal overlap ↓ vertical overlap
If Increased Incisal Guidance Angle For CD? During protrusion: Upper denture drops at the back Lower denture slides backward
Plane Of Occlusion Its inclination can be altered slightly * It is not as important as other factors
Cusp Height & Angulation * It is the smooth gliding of the cusp tips along the cusp inclines of the opposing teeth to provide balanced articulation
Cusp Height & Angulation • Anatomic teeth are easier to balance than nonanatomic teeth • Cuspal inclines should not be too steep as it can increase lateral forces • It is possible to decrease cuspal height by using compensating curves
Compensating Curves Artificial curves introduced into complete denture occlusion to achieve balanced occlusion Are among the most important determinents of occlusal balance
Compensating Curves The anteroposterior curving (in the median plane) and the mediolateral curving (in the frontal plane) within the alignment of the occluding surfaces and incisal edges of artificial teeth that is used to develop balanced occlusion
The Curvatures In Natural Dentition Curve of Spee An arc of a circle 65 mm to 70 mm radius that touches the tips of all the mandibular teeth when the skull is viewed laterally; when continued it touches the anterior surface of the condyles
The Curvatures In Natural Dentition Curve Of Monson A proposed ideal curve of occlusion in which each cusp and incisal edge touches or conforms to a segment of the surface of a sphere 4 inches (102 mm) in radius with its centre in the region of the glabella.
Compensating Curves Anteroposterior curve * Mediolateral curve ¤
Compensating Curves § The steepness of the curve necessary to achieve balance is the result of guiding influence of angle of condylar guidance and angle of incisal guidance § It is functionally and mechanically advantageous to keep compensating curve as modest as possible → This is accomplished by setting as shallow an incisal guidance as phonetics, esthetics permit
Theilmann’s Formula IGx. CG = CHx. OPx. CC
According To The Formula • To achieve balanced occlusion: For high condylar guidance we need to have high compensating curve, occlusal plane and cuspal height. • To achieve balanced occlusion: For high incisal guidance we need to have high compensating curve, occlusal plane and cuspal height.
According To The Formula To achieve balanced occlusion, the steeper the condylar guidance, the greater the cusp height toward the posterior or the steeper the compensating curves
According To The Formula To achieve balanced occlusion, the steeper the compensating curves, the less the cusp height toward the posterior
Question Q) Suppose that the incisal guidance is set and the condylar guidance is steeper than your chosen 20 degree teeth. To obtain balanced occlusion in your complete denture, what should you do? a. steepen the compensating curves in both sagittal and frontal planes b. steepen the compensating curves in only sagittal but not frontal plane c. decrease the inclination of occlusal plane d. decrease the steepness of compensating curves in both sagittal and frontal planes e. steepen the condylar guidance f. none of the above
Occlusal Schemes For CD
Philosophies of Denture Occlusion • Many philosophies of arranging denture occlusion • No definitive scientific studies prove one occlusal scheme clearly superior
Occlusal Schemes Balanced articulation Nonbalanced articulation (linear or monoplane articulation) Lingualized articulation Functionally generated occlusal scheme
Lingualized Occlusion Max. lingual cusps contact central fossae/marginal ridge ~ 1 mm space between buccal cusps
Lingualized Occlusion • Lingualized occlusion is a type of bilaterally balanced occlusal schemes * • Anatomic teeth are used in the maxilla opposing a flatcusped, or shallow cusped mandibular tooth.
Lingualized Occlusion • Forces directed toward lingual side • Maxillary lingual cusps articulate with the mandibular central fossae • Elimination of contacts on the buccal cusps in both centric and eccentric • The aim is to provide greater masticating efficiency and the elimination of lateral interferences
Lingualized Occlusion Lingualized (lingual contact) • Maxillary anatomic (33°) • Mandibular Teeth • Steep Condylar Guidance • Shallow cusped (Anatoline) • Shallow Condylar Guidance • Non-anatomic (Portrait 0°)
Lingualized Occlusion Verify centric No max. buccal cusp contacts in: • Centric • Lateral excursions
Contraindications Of Balanced Occlusion & Lingualized Occlusion Extreme cases of the following: Difficulty in obtaining repeatable centric record (incoordination, jaw malrelations) Severe ridge resorption (lateral forces displace the denture) may more easily be handled with a monoplane scheme
Monoplane Articulation (Neutrocentric Concept) • Cuspless teeth (0°) on a flat plane with 1. 5 -2. 0 mm overjet • No cusp to fossa relationship • No anterior contacts in centric position
Monoplane Articulation • Eliminate cusps • lateral forces reduced • improves stability • Simplifies tooth arrangement
Monoplane Articulation • No overbite (would cause tilting) • Overjet of 2 mm is used to create an illusion of overbite
Monoplane Articulation • Excursions - may or may not contact on balancing sides • Depends on condylar inclination and other aspects of the tooth arrangement
Monoplane Articulation • Anterior teeth make contact in excursions • Modifications have been proposed to minimize the tilting potential: • Compensating curves
Monoplane Occlusion without condylar influence
Monoplane Articulation Advantages • Technically easier to achieve • Use when: – Difficulty obtaining repeatable centric records (muscle incoordination) – Skeletal malocclusion (Class II, III) – Severe residual ridge resorption – Reduces horizontal forces
Monoplane Articulation Disadvantages • Poorer appearance • Can be unstable if condylar guidance is steep (posterior teeth separate, leaving only the anteriors in contact)
Monoplane Articulation Contraindications: • The patient has high expectations for improved appearance • Very steep condylar guidance may make a monoplane scheme less stable, unless modifying ramps or compensating curves are used.
When 1. 5 -2. 0 mm of overjet can be set, a lingualized occlusion (left) can have overbite set. Monplane occlusion (right) should normally have no overbite set.