Occlusion (3 Determinants: MOM,TMJ & Teeth)

Articulators
1. What are they?
  1. Device to attach casts in order to simulate mandibular position and mandibular movement
    1. AKA
      1. Stimulates jaw movement
        Why is that important?
        Tells you the excursions, interferences
2. Types
  1. Semi-adjustable articulators
    1. Arcon
      1. AKA articulating condyle
        Condylar balls on lower member
      2. E.g
        Whipmix
        Undergrads
        Denar
        Used in primary care
      3. Similar to our anatomy
    2. Non-Arcon
      1. Condylar balls on upper member
      2. E.g
        Dentatus
      3. Uses
        Removeable pros
        No C&B
    3. ALL require the matching face bow
    4. Indications
      1. Multiple restorations
      2. Increases in OVD
      3. Change in anterior or lateral guidance
      4. Providing a stabilisation splint
3. How do you mount them?
  1. ICP
    1. For single restorations or where the relationship of the teeth is to be largely maintained
  2. CR (retruded arc of closure)
    1. Indications
      1. Re-organise occlusion
      2. Existing relationship of teeth is lost
      3. Alter OVD
      4. TMD
      5. C/C
    2. Requires a wax-up to plan reconstruction
    3. Definition
      1. Head of the condyle is situated as far anterior and superior as it possibly can within the mandibular fossa/glenoid fossa.
Facebows
1. What do they tell you?
  1. Intercondylar width (width between the condyles)
  2. Distance from the condylar hinge axis (space between the hinge and the dentition)
    1. Remember before you take a face bow do a full occlusal examination
      1. Record
        ICP contacts
        RCP contacts
        2 pairs of posterior & anterior contacts
  3. Relationship between condyle & maxilla
2. Types
  1. Whipmix
    1. Uses Nation relator
  2. Denar
    1. Uses 43mm above incisor edge of lateral incisor
  3. Dentatus
    1. Uses orbital pin
3. Interocclusal records
  1. Tells you the relationship between the maxilla & mandible
  2. In RCP
Guidance
1. Anterior guidance
  1. These are gliding contacts that should help to harmoniously guide the mandible in and out of ICP
  2. Should start of shallow then deepen
  3. Convex shape not tolerated well
    1. Would be class III
2. If the patient currently has a suitable pattern of guidance, then it is important to conform to it
3. Top tips
  1. Anterior RBB
    1. Guidance
      1. ICP on abutment & pontic
        If not
        Pontic will move around
      2. Protrusive on ONLY the retainer
        If on pontic then the tooth becomes compromised
        Mobile
        Drift
4. Always be thinking about ICP, lateral excursions and protrusive too!
  1. Especially for re-organising
5. Group function
  1. When several teeth are in contact on the working side during excursions
  2. Usually premolars & canines
6. RCP
  1. The first tooth contact when the condyles are seated in centric relation
    1. Make sure RCP isn't on the tooth you re prepping. its only relevant for re-organising occlusion cases
7. When do you use CR as opposed to ICP
  1. Re-organise occlusion from existing occlusal scheme into CR
  2. When you don't have a reproducible ICP
  3. When you want to increase the OVD as you no longer have stable ICP as teeth have been separated
Consequences of heavy contacts
1. TSL
2. Root fracture
3. Orthodontic tooth movement
4. Pulpitis +/- Apical periodontitis
Working side vs Non-working side
1. Working side
  1. Side the patient moves their mandible towards.
  2. Condyle rotates in excursion
2. Non-working side
  1. Side that the mandible is moving away from
  2. Condyle orbits
3. Interferences
  1. Any tooth contacts that stop smooth guidance in excursions
  2. To prevent
    1. Take out of occlusion before crown prep
  3. Avoid non-working side interferences!
    1. Never load non-functional cusps
Splints
1. Uses
  1. Managing TMD
  2. Managing bruxism
    1. Attrition is unlikely to occur alone
  3. Testing increases in OVD
    1. Used to be done now it's in composite
    2. Can be used whilst provisional appliances are placed
  4. Stabalisation of jaw position
2. Types
  1. Hard
    1. Lower = Tanner
    2. Upper= Michigan
3. Design
  1. Make sure all teeth that were in RCP are still in contact
  2. Ant teeth contact slightly less than posterior teeth
Causes of error in reproducing RCP on articulator
1. Facebow errors
  1. Bite fork
    1. Not tightened
    2. Wax not fixed
    3. Maxillary teeth not centered
  2. Jig assembly not tightened
  3. Condylar arms not located in ear canal
2. Interocclusal record errors
  1. Over softened BHW
  2. Not sufficiently softened
  3. If RCP is not stable on cast
    1. Consider Blue moose
3. Impression taking
4. Mounting error
Study Models
1. Impression
  1. Tray selection
    1. Needs to record all teeth with a surrounding space of at least 3mm
  2. Record free end saddles with compound
  3. Dry occlusal aspects of teeth apply thin layer of alginate before seating tray to avoid air locks on occlusal aspect

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Occlusion (3 Determinants: MOM,TMJ & Teeth)

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