Quartz 4

L6 PosteriorToothArrangment

15 min read

Complete Dentures: Preclinical1

Posterior Tooth Arrangement & Trial Insertion2

Complete Denture Overview

**Treatment Schedul

Goal of Complete Denture Occlusion

Note

The primary goal of complete denture occlusion is the comprehensive rehabilitation of mastication, phonetics, and aesthetics, while ensuring minimal to no trauma to the supporting oral tissues. Unlike natural teeth, which move individually in their sockets under load, artificial teeth in a denture move as a single unit on a common base. This group movement necessitates specific occlusal arrangements to achieve denture stability during function. The main objective of these arrangements is to control occlusal contacts to maintain stability during mastication.

e**

VisitOperatorProcedure
Visit 1Clinician
Laboratory		Patient evaluation & primary impressions
Diagnostic casts & special trays
Visit 2Clinician
Laboratory		Secondary impressions
Bead & box, master casts, base & rims
Visit 3Clinician
Laboratory		Contour rims, OVD, MMR, shade & mould selection
Articulation & tooth setting
Visit 4Clinician
Laboratory		Wax try-in
Finalisation & processing
Visit 5ClinicianAssessment & issue
Instructions for care
Visit 6ClinicianPost operative review, post insertion instructions

Posterior Tooth Arrangement3

Complete Denture Occlusal Schemes

Classification

  • Bilateral Balanced
  • Lingualised
  • Canine Guidance
  • Group Function
  • Monoplane

Bilateral Balanced4

The bilateral, simultaneous posterior occlusal contact of teeth in maximal intercuspal position and eccentric positions.

  • ==Working Movement: During a lateral movement (e.g., to the right), the teeth on the right side achieve contact between the upper buccal cusps and lower buccal cusps, and between the upper palatal cusps and lower lingual cusps.==
  • ==Balancing Movement: Simultaneously, the teeth on the non-working side (the left side in this example) make contact between the upper palatal cusps and the lower buccal cusps. This balancing contact helps to reseat and stabilize the denture.==

Factors Affecting Balanced Occlusion5

  • Incisal Guide Angle
  • Condylar Guidance
  • Compensating curves (antero-posterior & transverse)
  • Orientation of occlusal plane
  • Cuspal Inclination

Limitation

During the incision of hard foods (e.g., a carrot), the posterior teeth will separate, creating a fulcrum at the anterior teeth that can potentially displace the dentures. However, once the incisors penetrate the food and tooth-to-tooth contact is re-established, the posterior teeth will come back into contact, helping to reseat the dentures.

Lingualised67

this form of denture occlusion articulates the maxillary lingual cusps with the mandibular occlusal surfaces in centric occlusion, working and nonworking mandibular positions;

Info

Introduced by Giese in 1927, this scheme is designed to combine the food penetration advantages of anatomic (cusped) teeth with the mechanical freedom of non-anatomic (flat) teeth.

  • ==Concept: It involves articulating only the maxillary lingual cusps with the occlusal surfaces of the mandibular teeth in centric, working, and non-working positions.==
  • ==Tooth Selection: Often utilizes anatomic teeth for the maxillary denture and modified non-anatomic or semi-anatomic teeth for the mandibular denture.==
  • ==Modification: The occlusion is

Canine Guidance8

A form of mutually protected articulation in which the vertical and horizontal overlap of the canine teeth disclude the posterior teeth in the excursive movements of the mandible.

  • ==Applicability: This scheme is more suitable for the natural dentition, where individual tooth roots are firmly embedded in bone and can resist horizontal forces.==
  • ==Limitation in Dentures: In complete dentures, sole contact on the canines during an excursive movement tends to create a tipping force that can displace the entire denture base.==

Group Function9

Multiple contact relations between the maxillary and mandibular teeth in lateral movements on the working-side whereby simultaneous contact of several teeth acts as a group to distribute occlusal forces.

  • ==Applicability: Like canine guidance, this is better suited to the natural dentition.==
  • ==Limitation in Dentures: This scheme eliminates the balancing side contacts that are crucial for reseating and stabilizing a complete denture during function.==

Monoplane10

an occlusal arrangement wherein the posterior teeth have masticatory surfaces that lack any cuspal height.

  • ==Challenge: Without the incorporation of compensating curves, the posterior teeth will separate during protrusive and excursive movements, leading to instability.==
  • ==Solution: To counteract this, a

Significance of the Occlusal Plane11

ORIENTATION OF OCCLUSAL PLANE12

The occlusal plane is defined as imaginary plane established by the incisal and occlusal surfaces of the teeth

  • ==Transverse Orientation: Should be parallel to the interpupillary line.==
  • ==Anteroposterior Orientation: Should be parallel to Camper’s plane (the line running from the ala of the nose to the tragus of the ear).==

“.

  • The orientation of the occlusal plane is important as slight variations will lead to occlusal instability.

  • It should be in harmony with the other components of the masticatory system.

  • It forms the basis by which occlusal surfaces of teeth can be related to one another and to other structures of the head.

  • The height of the occlusal plane of the lower teeth should be at the level of the resting tongue.

  • ==Too Low: The patient may bite their tongue.==

    • ==Too High: The patient will have difficulty moving the food bolus during mastication, and the excessive tongue movements required may dislodge the denture.==

Compensating Curves13

The compensating curves are artificial curves introduced into the complete denture occlusion. They are so-called because they compensate for the space (Christensen’s Phenomenon) formed between the posterior occlusal surfaces during eccentric (translatory) mandibular movements.

Factors Affecting Compensating Curves14

  1. Condylar Guidance → A steep condylar path needs a steep compensating curve for occlusal balance.
  2. Incisal Guidance
  3. Occlusal Plane
  4. Cuspal inclination → A steep incisal guidance requires posterior teeth with high (steep) cuspal inclines, a steep occlusal plane and a steep compensating curve in order to attain occlusal balance. Ideally the incisal guidance should be kept as low as aesthetics and phonetics permit.

Best Evidence Consensus Statement (Goldstein et al., 2021)

A 2021 consensus statement on complete denture occlusion provided the following conclusions:

  1. ==There is strong evidence that an average patient with good residual ridges and no neuromuscular issues will function adequately with any properly fabricated occlusal scheme.==
  2. ==There is neither strong support for nor against bilateral balanced schemes regarding patient satisfaction, preference, or chewing ability.==
  3. ==There is some support for the idea that non-balanced occlusion may lead to increased alveolar bone loss.==
  4. ==Bilateral balanced schemes are needed for patients with compromised stability and retention (e.g., Prosthodontic Diagnostic Index categories 3 and 4).==

Posterior Tooth Selection1516

Anteriorly Aesthetics is the most important factor

Posteriorly Function is the most important factor

Factors Affecting Tooth Selection1718

**Alveolar Ridge Anatomy

Info

The shape of the residual ridge is a primary determinant of cuspal inclination:

  • ==Well-shaped Ridge: Anatomic teeth with deep cusps (e.g., 30° or 33°) can be used.==
  • ==Average Height Ridge: Modified cusp teeth (e.g., 10° or 20°) are recommended.==
  • ==Flat Ridge: Flat plane (0°) teeth are indicated to minimize lateral displacement forces. Note that flat cusp teeth are the least efficient for mastication.==

**

  • Occluso-gingival length

    • available inter-ridge space

  • Less bulky teeth should be selected where space is restricted.

  • Mesiodistal width

    • governed by length and slope of mandibular ridge
    • From distal of canine to anterior of retromolar pad

  • Posterior teeth should not be set further back than the anterior limit of the retromolar pad.

  • Shade

    • same as for the anterior teeth

  • Form of the occlusal surface (cuspal inclination)

    • Anatomical (30°, 33°, 40°)
    • Semi-anatomical (10°, 20°, 22°)
    • Non-anatomical (0°)

  • Determined by both alveolar ridge anatomy and the patient's condylar guidance. Steeper guidance allows for higher cuspal inclination.

  • Material

    • acrylic resin
    • composite resin
    • porcelain

**Tooth Availabili

OQA Mold Guide

A printed mold guide is available that recommends posterior molds based on size and shape to match anterior selections. The guide lists tooth dimensions and cross-sectional profiles for each mold, which is a useful clinical reference.

ty**

IPN 10° Posteriors19

CodeTypeDimensions
330Portrait - BioformX = 30.00, U = 7.70, L = 8.25, Y = 32.00
332Portrait - BioformX = 32.00, U = 8.50, L = 9.25, Y = 34.50
334Portrait - BioformX = 34.00, U = 9.30, L = 9.40, Y = 36.50
336PortraitX = 36.00, U = 9.50, L = 10.10, Y = 38.50

IPN 33° Posteriors

CodeTypeDimensions
30MPortrait - BioformX = 30.00, U = 8.80, L = 8.50, Y = 32.50
30LPortrait - BioformX = 30.00, U = 7.90, L = 8.25, Y = 32.50
32MPortrait - BioformX = 32.00, U = 8.80, L = 9.00, Y = 34.50
32LPortrait - BioformX = 32.00, U = 8.50, L = 8.75, Y = 35.00
34MPortrait - BioformX = 34.00, U = 9.30, L = 9.50, Y = 36.50
34LPortrait - BioformX = 34.00, U = 9.00, L = 9.75, Y = 36.75

Tooth Positioning2021222324

**Neutral Zon

Note

The neutral zone is the space within the oral cavity where the outward forces from the tongue are balanced by the inward forces from the cheeks and lips.

  • ==Buccal Placement: If teeth are placed too far buccally, pressure from the buccinator muscle will tend to displace the denture.==
  • ==Lingual Placement: If teeth are placed too far lingually, the tongue will displace the denture laterally or lift it.==

e**

**Maxillary Posteriors

Setting to a Mandibular Denture

The starting point is the axial inclination of individual teeth and their relationship to the occlusal plane. In the preclinical exercise, maxillary teeth are set to a pre-existing mandibular denture, which may require adjustments to standard positions to achieve the best articulation.

Standard Tooth Positions

  • ==First Premolar: Positioned in firm contact with the canine. Both buccal and palatal cusps touch the occlusal plane, and the long axis is vertical.==
  • ==Second Premolar: Both cusp tips touch the occlusal plane, and the long axis is vertical.==
  • ==First Molar: The mesiolingual cusp touches the plane. The mesiobuccal and distal cusps are progressively raised off the plane.==
  • ==Second Molar: Positioned further above the plane, continuing the smooth, flowing curve established by the preceding teeth.==

Occlusal View Alignment

  • A straightedge should touch the buccal surfaces of the canine, both premolars, and the mesiobuccal cusp of the first molar.
  • A second straightedge should touch the buccal cusps of the first and second molars, indicating a separate alignment.

**

**Completed Tooth Arrangement

Intercuspal Position

Success

The final setup should show an intimate relationship between opposing teeth, with close intercuspation and no interproximal spaces.

Working and Balancing Movements

  • ==Working Side: A lateral movement of ~2 mm should show close interdigitation of the teeth on the working side.==
  • ==Balancing Side: The palatal cusps of the upper teeth should contact the buccal cusps of the lower teeth.==

Protrusive Movement

Info

A small protrusive movement (~1 mm) should demonstrate contact between both anterior and posterior teeth, ensuring stability.

Final Wax-Up and Contouring

  • ==Root Forms: Root forms are carved into the wax to mimic the natural root anatomy. Some artistic license can be used to create a more natural and symmetrical appearance. Root forms are less prominent posterior to the second premolars, reflecting the greater bulk of alveolar bone in that region.==
  • ==Palatal Contour: A thin wax sheet can be adapted to the palate to create an even thickness and replicate the rugae form. While this is claimed to assist with phonetics, many patients request the ridges be polished smooth later.==

**

Trial Insertion2526272829303132

**Clinical Chec

Base Stability and Retention

The trial denture bases must be stable and retentive to allow for accurate clinical checks.

k**

  • Occlusion

  • Lip support

    • Anteroposterior lip position
      • Esthetic line (E-line).⁹ Joins the nasal tip to soft tissue pogonion. The upper lip should be 4 mm and the lower lip 2 mm behind this line in adults. This is very dependent on nasal and chin projection.
      • Steiner line (S-line).¹⁰ Joins soft tissue pogonion to the midpoint between subnasale and nasal tip. The lips should touch this line.
      • Harmony line (H-line).¹¹ A line from soft tissue pogonion touching the upper lip should bisect the nose.
      • Profile line (of Merrifield).¹² A tangent to the chin and vermilion border of both lips should ideally bisect the nose.
    • Relationship of upper lip to nasal columella
      • Nasolabial angle is formed between the nasal columella and the upper lip slope. Average value: 85–120°. Depends on anteroposterior position of maxillary incisors and anterior maxilla, the morphology of the upper lip, as well as the vertical position of the nasal tip.
    • Relationship of lower lip to chin
      • Labiometal angle is formed between the lower lip and chin, and depends on the lower incisor inclination and anterior lower face height. Average value: 110–130°.
      • Excessively proclined lower incisor teeth, a prominent chin and a reduced lower anterior facial height may lead to an acute labiometal angle.

  • Midline and facial midline

  • Occlusal plane

  • Buccal corridor

  • Teeth

    • ✓ Shade
    • ✓ Shape
    • ✓ Embrasure
    • ✓ Position
    • ✓ Inclination

  • Teeth display (smiling and rest position)

  • Extension posterior

    • Correct extension
    • Under-extended

  • ==Over-extension: May cause ulceration of the soft palate or displace the denture during function.==

  • Phonetics

    • To produce the sounds f, v and ph:
      • the lower lip is brought into contact with the incisal edges of the upper anterior teeth
      • these labiodental sounds serve as an excellent test for determining the proper plane of occlusion and placement of the anterior teeth

  • ==The ‘th’ sound is also tested in this group.==

    • To produce the sounds of s, z and c:
      • the tip of the tongue is in slight contact with the hard palate’s most anterior portion
      • the lateral margins of the tongue are in minimal contact with the lingual surfaces of the posterior teeth
      • the mandible is in a protruded position
      • a narrow slit like channel is formed between the tongue and palate
      • shape variations of the channel will affect clarity of speech

  • Occlusal vertical dimension

    • interocclusal clearance = 2 – 5 mm

  • Maximum intercuspation

    • should occur on posterior path of closure

  • In complete dentures, maximum intercuspation should coincide with the retruded contact position (centric relation). This is because edentulous patients lack the periodontal ligament proprioception that allows dentate individuals to have a separate, habitual intercuspal position.

  • Centric and eccentric interferences

    • working
    • balancing
    • protrusive

  • ==Minor Interferences: Can be corrected at the chairside.==

    • ==Major Interferences: May require significant tooth repositioning in the laboratory, necessitating another trial insertion appointment.==

  • Overjet - horizontal overlap

  • Overbite - vertical overlap

    • Incisal Guidance: Inversely related to denture stability

  • The incisal guide angle should be kept as shallow as possible while meeting aesthetic and phonetic requirements.

Patient Assessment3334353637

  • With patient:

    • Assess aesthetics
    • Seek patient input
    • Gain patient acceptance

  • Provide the patient with a mirror and actively seek their opinion on the appearance.

    • Be prepared to modify the arrangement based on valid patient concerns.

Thank You3839

Any questions? Contact me

Dr Ian Lander ian.lander@uwa.edu.au

’s’, ‘z’ and ‘c’

  • the tip of the tongue is in slight contact with the hard palate’s most anterior portion
  • the lateral margins of the tongue are in minimal contact with the lingual surfaces of the posterior teeth
  • the mandible is in a protruded position
  • a narrow slit like channel is formed between the tongue and palate
  • shape variations of the channel will affect clarity of speech

Trial Insertion2526272829303132

Clinical Check

  • Occlusion

  • Lip support

  • Midline and facial midline

  • The dental and facial midlines should coincide if possible, with a maximum acceptable deviation of 4 mm.

  • Occlusal plane

  • Should be parallel to the interpupillary line.

  • Buccal corridor

  • Teeth

    • ✓ Shade
    • ✓ Shape
    • ✓ Embrasure
    • ✓ Position
    • ✓ Inclination

  • Teeth display (smiling and rest position)

  • Extension posterior

  • Phonetics

Note

The wax material and potential undercuts may affect phonetics at this stage compared to the final polished denture.

Thank You3839

Any questions? Contact me

Dr Ian Lander
ian.lander@uwa.edu.au

Footnotes

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