Complete Denture Occlusion

Introduction to Occlusion

• Occlusion refers to the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.

Differences Between Natural and Complete Denture Occlusion

• Incising with anterior teeth affects all the teeth in complete dentures, unlike natural teeth where it primarily affects the anteriors.
• Proprioception allows avoidance of prematurities and interferences in natural teeth, but due to the lack thereof in complete dentures, interferences cannot be avoided.
• In natural teeth, bilateral balanced occlusion does not exist, but it may be necessary for complete denture stability.
• Natural teeth respond individually to forces, while all teeth in a complete denture respond as one unit and cause movement on the bases.
• Nonvertical forces are well-tolerated in natural teeth but are traumatic to supporting tissues in complete dentures.

Requirements of Complete Denture Occlusion

• Effective cutting and shearing of food requires good incisal and occlusal surfaces with sluiceways for escape.
• Minimal contact areas reduce force on ridges during mastication.
• Favorable tooth-to-ridge crest position is crucial for leverage.
• Reduced posterior cusp height helps manage horizontal forces.
• A reduced the buccolingual width of posterior teeth decreases force transmitted to the residual ridge.
• Occlusal forces should be directed vertically.
• Occlusal plane kept parallel to the mean foundation plane.
• Denture bases should settle without cusp interference.
• No anterior teeth contact is desired except during protrusion, with proper vertical/ horizontal overlap and flat incisal guidance.
• Stable occlusion is required in centric and eccentric relations.

Types of Complete Denture Occlusion

• There are three types: Balanced, Monoplane, and Lingualized Occlusion.

Balanced Occlusion

• Balanced occlusion is the bilateral, simultaneous anterior and posterior occlusal contact of teeth in centric and eccentric positions (GPT8).
• Bilateral and simultaneous contact of teeth in centric and eccentric positions is unique to complete dentures; in natural teeth, nonworking side contacts are pathologic.
• Enhance stability of the denture.
• Balanced occlusion is necessary during excursive movements like swallowing or bruxism.
• Equal contact of posterior teeth in centric relation is essential for mucosa health; this isn't emphasized for eccentric relations.

Lever Balance

• Lever balance is the relation of the tooth to its base of support and is important when food bolus is on one side with a space opposite.
• Teeth should be placed such that the resultant force direction on the chewing side is on the crest/slightly lingual.
• Denture bases should cover as wide an area as possible.
• Buccolingual width of the teeth should be reduced.

Factors Affecting Balanced Occlusion

• Five factors affect occlusal balance: condylar guidance, incisal guidance, orientation of the occlusal plane, compensating curves, and cuspal inclination.

Condylar Guidance

• Condylar guidance is the mechanical form in the articulator's upper posterior region that controls the mobile member's movement (GPT8).
• Duplicated in the articulator depending on the device's adjustability (semi/fully adjustable).
• A shallow condylar guidance leads to less posterior tooth separation in protrusion and requires shorter cusp teeth/flatter fossa for balanced occlusion.

Incisal Guidance

• Incisal guidance is the influence of contacting mandibular and maxillary anterior teeth surfaces on mandibular movements (GPT8).
• The incisal guide angle is between the horizontal plane of occlusion and a line between maxillary/mandibular incisal edges during maximum intercuspation
• If the incisal angle is steep, it requires steep cusps, steep occlusal plane and a steep compensating curve to obtain occlusal balance
• Should be flat as possible for aesthetics/phonetics, but never exceed condylar guidance to prevent denture instability.

Orientation of Occlusal Plane

• Occlusal plane is the average plane established by the incisal and occlusal surfaces of the teeth (planar mean of the curvature of these surfaces-GPT8).
• Established anteriorly by lower canine height near mouth commissure, and posteriorly by retromolar pad height.
• It should be oriented similarly to when natural teeth existed.

Compensating Curves

• Compensating curves are the anteroposterior and lateral curvatures in the alignment of the occluding surfaces and incisal edges of the artificial teeth, used to develop balanced occlusion (GPT).
• They include: - Anteroposterior curves that run help provide protrusive balance. - Mediolateral curves that run provide lateral balance.
• Steeper condylar guidance needs a steep compensating curve for occlusal balance or it will lead to the loss of balancing molar contact during lateral excursion.

Anteroposterior Curve/Curve of Spee

• The curve of Spee is the anatomic curve established by occlusal alignment, as projected onto the median plane, from the mandibular canine cusp tip through premolar and molar buccal cusp tips.
• It is necessary to obtain protrusive balance by preventing the need to tilt the occlusal plane, which destabilizes the upper denture.
• The curve's radius depends on incisal/condylar guidance.

Mediolateral Curve/Curve of Wilson

• Curve of Wilson: A curve that is convex downwards.
• Reverse Curve (Anti-Monson Curve): A curve of occlusion that is convex upwards, usually used to arrange the first premolars
• Monson Curve: Every cusp and incisal edge touches a segment of the surface of a sphere 8" in diameter with its centre in the region of the glabella. It is a a combination of the Curve of Spee and Curve of Wilson curves in three dimensions.
• Pleasure Curve: It is a combination of Monson and anti-Monson curves.

Cuspal Inclination

• Cuspal Inclination is the angle made by the average slope of a cusp with the cusp plane, measured mesiodistally/buccolingually. Its effects are on the occlusal plane and the compensating curves.
• Elimination of the mesiodistal cusp height is preferable in anatomic teeth.

Hanau's Quint

• Hanau's quint shows how each factor influences the others, affecting balanced occlusion.

Thielman's Formula

• Thielman's formula describes the interrelationship of the 5 factors affecting balanced occlusion:
  • Balanced occlusion (C) = (Condylar Guidance x Incisal Guidance) / (Occlusal plane X Cuspal inclination X Compensating curve)

Monoplane Occlusion

• Monoplane occlusion is the occlusal arrangement wherein posterior teeth have masticatory surfaces without cuspal height (GPT8).
• Based on the reduction of lateral forces on the denture to improve stability, and using nonanatomic teeth.
• Anterior teeth are arranged with a 2 mm overjet and no overbite.
• Balanced occlusion may be developed in eccentric relations using compensating curves or balancing ramps, even though it is not generally part of the scheme.
• The number/ buccolingual width of posterior teeth is is reduced to direct force to the ridge center.
• Easy teeth arrangement.
• Sufficiency with a simple nonadjustable articulator.
• An easier occlusal scheme when there Muscle incoordination, skeletal malocclusion and severe residual ridge resorption.

Disadvantages of Monoplane Occlusion

• Poor appearance due to use of nonanatomic teeth.
• Less chewing efficiency is reported.
• Use can lead to unstable dentures in patients with steep condylar guidance.

Lingualized Occlusion

• LIngualized Occlusion is a form of denture that occludes the maxillary lingual cusps with the mandibular occlusal surfaces in centric working and nonworking mandibular postiosn. This term is attributed to Earl Pound and described by S Howard Payne in 1941.
• Combines the balanced occlusion/monoplane concepts. Anatomic teeth are used in the arch with non-anatomic teeth used for mandibular arch.
• Traditional fully balanced occlusal schemes differ by only having the palatal maxillary teeth cusps contact the mandibular teeth in eccentric and centric relations.
• Teeth arrangement benefits from having a natural appearance and better chewing.
• Difficult teeth arrangement and a lack of scientific data to prove stability.
• It is not used for patient who severe ridge resorption or malrelated jaws.