Quartz 4

W2 Maxillo-Mandibular Relationship_integrated

9 min read

Learning Objectives

  • Importance of MMR
  • Understand why Maxillomandibular Relationship (MMR) is important.
  • Clinical Relevance
  • Identify clinical variables and the clinical/laboratory workflow for MMR.
  • Laboratory-clinical workflow for MMR
      1. Maxillary rim adjustment
    • Mandibular rim adaptation
    • Establish VD
    • Determine overjet, mark facial landmarks, and perform bite registration.

Importance of MMR

  • Definition: MMR is the step used to obtain the patient's bite. It is essential for edentulous cases but also used for partially dentate patients who lack stable occlusal stops.
  • Why MMR matters in edentulous cases
  • Reconstruction of tooth position and occlusion
  • Determines aesthetic outcomes
  • Establishes vertical dimension and horizontal jaw relations
  • ==The “Blueprint”: Wax rims serve as the blueprint for the final denture. The technician will set teeth exactly where the rims are positioned on the ridge according to the clinician’s landmarks.==

Key components

  • See “Hanaus Quinte”
  • ==Hanau’s Quint: Named after the engineer who designed the first articulator, this concept emphasizes the relationship between the occlusal plane, vertical dimension, and jaw relations.==

Horizontal jaw relations

Habitual Position

  • Habitual Position: mandibular position adopted through learened neruomuscular patterns of closure, representing the position a patient habitually closes into during function
    • may be obesrved in patiens with existing or previous dentures (muscle memory).
    • may be considreed only if it is:
      • reproducible
      • comfortable
      • free from deflection
      • consistent with a physiologic mandibular position
    • Limitation: may represent a compensated or pathologic position
  • “Is learned and muscle driven”
  • ==Clinical Use: If a habitual position is reproducible and comfortable, it can be used, but with caution. It is often easier for patients to adapt to their “normal” bite.==

Centric relation

  • Centric relation according to GPT-10: a physiologically and musculoskeletal stable position
  • ==Clinical Use: Used when a patient does not have a stable habitual bite. The clinician “programs” or guides the patient into this position.==

Laboratory work

  • The lab works strictly with what the clinician provides. If the MMR is sent with a 5mm overjet or an open bite, the lab will set the teeth in that exact (potentially incorrect) position.

Clinical workflow

Patient position = upright position (90 degress to the frankfort plae)

  • ==Patient Positioning: The patient must be seated upright (90 degrees). If the head is tilted back, the jaw drops posteriorly, creating an inaccurate, retruded recording.==

Steps

1. Maxillary rim adjustment

  • ==Rule: Adjust the maxillary rim first and completely ignore the mandibular rim during this stage.==
a. Evaluation of border extension and fit

Maxillary rim importance

  1. A common reason for maxillary rims to drop is due to overextension, fix it with acrylic burr a. ==Adjustments: Use a straight handpiece with an acrylic burr to trim overextended borders.==
  2. Sometimes patients don’t have enough anatomy, so put some denture adhesive to help with the visit a. the final denture should be more retentive than the base and rim because the undercuts won’t be blocked out b. If the patient has significant bone resorption, use denture adhesive (e.g., Polident) during the MMR session to ensure stability for accurate measurements.
b. Incisor Display ⇐> Nasolabial angle
  • What is more important incisor display or nasolabial angle?
    • Both are important, they are both correlated

Correlation between nasolabial angle and incisal display

Decreasing the nasolabial angle causes the incisal display to increase

  • ==Nasolabial Angle: Ideally between 90 to 105 degrees.==
  • Normal incisal display readings
  • See Vig and Brundo 1978 readings
  • As the patient gets older, lips drop lower
  • ==Incisor Display: Varies by age and gender. Younger females typically show 3-4mm; older patients may show 0mm or have a “negative” display due to loss of lip elasticity and tooth wear.==
  • ==Interdependence: Both must be assessed together. If the labial contour is too thick, it affects the display and the angle.==
C. Incisal plane and Camper’s plane
  • Foxplane
    • use three fingers to stabilize in patients mouth , one left ,one right and one to support the anterior
    • Look patient directly at the eyes
      • make sure it is parallel to the interpupillary line
      • you can use any random instrument and line it up with hte line to see
    • Then move to the side of the patient
      • Make sure the ala-tragal line/ campers plane is parallel to the fox plane
  • ==Assessment Technique: Stand in front of the patient to check the interpupillary line, then stand to the side to check the ala-tragus line.==
Scenarios

note , in these scenarios you are already happy with the nasolabial angle and incisal display **Scenario 1

  1. Incisal plane = canted to the right
  2. Camper’s plane right = parallel
  3. Camper’s plane left = parallel Solution: Reduce wax on the right anterior quadrant
  • ==Transcript Note: Adjust only the anterior segment of the rim where the cant occurs; do not touch the posterior.==

**Scenario 2

  1. Incisal plane = canted to the right
  2. Campers’ plane right = downwards posteriorly
  3. Camper’s plane left = parallel Solution: reduce wax on the right side (half arch)
  • ==Transcript Note: Reduce the entire right side (anterior and posterior) to correct the plane.==

**Scenario 3 **

  1. incisal plane = parallel
  2. Camper’s plane right = downwards posteriorly
  3. Camper’s plane left = upwards posteriorly Solution 1:
  • reduce wax on the right posterior quadrant
  • Add wax on left posterior quadrant To align the incisal plane with Camper’s plane

**Solution 2: **

  • reduce wax on the right side (half arch) and left anterior quadrant

  • Apply a uniform wax layer across the arch to restor incisal display

  • ==Refinement Tip: Use a hot metal plate/scraper to ensure the occlusal surface remains perfectly flat after adjustments.==

d. Labial contour (12 o’clock assessment) and Buccal contour
  • ==12 o’clock Assessment: Stand behind the reclined patient to view labial fullness and canine eminence from above.==
  • ==Buccal Corridor: Ask the patient to smile. Ensure there is a “normal” amount of negative space (black space) in the corners of the mouth—not completely absent and not too wide.==

2.Mandibular rim adaptation

  • ==Rule: The mandibular rim is a “follower.” Once the maxillary rim is set, do not touch it again; all subsequent adjustments for contact are made to the mandibular rim.==
A. Evaluation of stability
  • Assess in the same way as maxillary ring, make sure its seated properly
  • the mandibular rim may be floating a little bit because the tongue gets in the way
  • You should be able to see rim to rim even contact
    • shouldn’t see any overbite
    • shouldn’t see any areas higher than the other
B. Reproducible position
  • habitual position OR centric relation record
  • Ensure the mandibular rim makes even, flat contact with the maxillary rim. If it hits on one side only, trim the high side until contact is simultaneous.
**D. Interocclusal record **
  • can git it from :
    • habitual position
    • Centric relation
      • multiple ways to get centric relation
        • chin point
            1. Patient seated
            1. Touch chin and ask patient to relax
            • try to relax them by shaking the jaw, most of the time they get relaxed but some will resist and won’t be able to do chin point
          • 3. Ask the patient to put their tongue to the back, and guide the jaw into closure without forcing it backward.
        • gothic arch tracing
          • technique sensitive , not easy
          • A specialized equipment involving a central bearing point (screw and plate) to find the stable position.
        • bimanual manipulation
          • thumbs placed on buccal flange on lower base and rim
          • index finders hold the edge of the mandible
          • Ask patient to cloze slowly while you’re guiding it into cr
          • Do this multiple times to make sure the patient is biting in the same way

3. Establish VD

Use the following: - Anatomical references - Facial proportion - Freeway space

  • ==Rest Vertical Dimension (RVD): Measured when the patient is relaxed (lips slightly apart, after swallowing or saying “M”).==
  • ==Occlusal Vertical Dimension (OVD): Measured when the rims are in contact.==

Anatomical references

  • anterior landmark = commisures of mouth
  • Posterior landmark = retromolar pads
  • anterior height = 18 mm
  • posterior height 1/2 - 1/3 of retromolar pad weidth

Facial proportion

  • use the facial thirds to restore the patient
  • ==Measurement Tools: Use a Willis Gauge (base of nose to chin).==

**Freeway space

  • RVD - OVD = Freeway space (2-4mm)

When freeway space is more than 4, you need to add wax to the mandibular rim, if less than 2 you need to trim from the mandibular rim

Swallowing assessment

  • this is an antiquated way
  • rims come together with a very light contact at the beginning of the swallowing cycle

Phonetics:

  • using labiodental sounds
  • this method is normally used with try-ins but is too finnicky for MMR stage
  • While "S" sounds are used in literature, they are difficult to test with thick wax rims and are better suited for the "try-in" stage.

**Patient-perceived comfort

  • Actually ask the patient if they like it

4. Establish overjet

a) anterior overjet
  • Class I jaw relation: 1 mm
  • overjet controls:
    • speech
    • lip position
    • tooth aestehtics
  • Set to approximately 1 mm for aesthetics and phonetics.
b) posterior overjet
  • normal overjet is 1 mm
  • if patients have lost all their teeth they will have some amount of resoprtion
    • maxilla resorbs upward and inward, reducing arch wide
    • mandible resorbs outwards and increases width
    • this causes overbite
  • ==Crossbite: In cases of severe resorption, teeth may need to be set in a crossbite to prevent cheek/tongue biting and ensure stability.==
  • ==Avoid: “Edge-to-edge” posterior setups, which often cause cheek biting.==

5. Facial Markings

  • midline
  • canine lines
  • smile lines
Midline
  • should come right under the tip of the nose
  • Marked at the center of the philtrum/tip of the nose.
canine lines
  • right under the ala of the nose
  • Helps the lab determine the width of anterior teeth.
Smile Line
  • Determines the height of the teeth. The lab should set teeth so the "gummy" part of the denture is not visible during a normal smile.

6. Bite registration

  • carve out the nick an nothchin
  • ==Preparation: Carve V-shaped “nicks” in the maxillary rim and box-shaped “notches” in the mandibular rim (posterior to the canine lines).==
  • d) interocclusal record -get paitet to bitedown and get bitereg, tell the patient to bite down without moving at all
  • ==Material Application:==
    • Apply adhesive to the mandibular rim.
    • Have the patient bite into the predetermined reproducible position (CR or Habitual).
    • While the patient is biting, inject registration material into the nick/notch spaces.
  • ==Verification: Ensure the midlines coincide every time the patient closes. Remove the rims, ideally in one piece.==

Graph View