W2 Maxillo-Mandibular Relationship

Learning Objectives

• Importance of MMR
• Clinical Relevance
• Laboratory-clinical workflow for MMR
  • 1. Maxillary rim adjustment
  • Mandibular rim adaptation
  • Establish VD
  • didn’t finish

Importance of MMR

• Why MMR matters in edentulous cases
• Reconstruction of tooth position and occlusion
• Determines aesthetic outcomes
• Establishes vertical dimension and horizontal jaw relations

Key components

• See “Hanaus Quinte”

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
  • 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”

Centric relation

• Centric relation according to GPT-10: a physiologically and musculoskeletal stable position

Laboratory work

Clinical workflow

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

Steps

1. Maxillary rim adjustment

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
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. 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 incisor display

Decreasing the nasolabial angle causes the incisal display to increase

Normal incisal display readings

• See Vig and Brundo 1978 readings
• As the patient gets older, lips drop lower

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

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

**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)

**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

d. Labial contour (12 o’clock assessment) and Buccal contour

2.Mandibular rim adaptation

a. Evaluation of stability b. Reproducible position

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

**D. Interocclusal record **

• can git it from :
  • habitual position
  • Centric relation
    • multiple ways to get centric relation
      • chin point
        • 1. Patient seated
        • 2. 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. Jaw will be more relaxed to guide into centric relation
      • gothic arch tracing
        • technique sensitive , not easy
      • 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 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

**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

**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

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

5. Facial Markings

• midline
• canine lines
• smile lines

Midline

• should come right under the tip of the nose
• ‘

canine lines

• right under the ala of the nose ‘

6. Bite registration

• carve out the nick an nothchin
• d) interocclusal record -get paitet to bitedown and get bitereg, tell the patient to bite down without moving at all