Occlusion (3 Determinants: MOM,TMJ & Teeth)

Occlusion (3 Determinants: MOM,TMJ & Teeth)

1. Articulators

   • What are they?
     • Device to attach casts in order to simulate mandibular position and mandibular movement
       • AKA
         • Stimulates jaw movement
           • Why is that important?
             • Tells you the excursions, interferences
   • Types
     • Semi-adjustable articulators
       • Arcon
         • AKA articulating condyle
           • Condylar balls on lower member
         • E.g
           • Whipmix
             • Undergrads
           • Denar
             • Used in primary care
         • Similar to our anatomy
       • Non-Arcon
         • Condylar balls on upper member
         • E.g
           • Dentatus
         • Uses
           • Removeable pros
           • No C&B
       • ALL require the matching face bow
       • Indications
         • Multiple restorations
         • Increases in OVD
         • Change in anterior or lateral guidance
         • Providing a stabilisation splint
   • How do you mount them?
     • ICP
       • For single restorations or where the relationship of the teeth is to be largely maintained
     • CR (retruded arc of closure)
       • Indications
         • Re-organise occlusion
         • Existing relationship of teeth is lost
         • Alter OVD
         • TMD
         • C/C
       • Requires a wax-up to plan reconstruction
       • Definition
         • Head of the condyle is situated as far anterior and superior as it possibly can within the mandibular fossa/glenoid fossa.

2. Facebows

   • What do they tell you?
     • Intercondylar width (width between the condyles)
     • Distance from the condylar hinge axis (space between the hinge and the dentition)
       • Remember before you take a face bow do a full occlusal examination
         • Record
           • ICP contacts
           • RCP contacts
           • 2 pairs of posterior & anterior contacts
     • Relationship between condyle & maxilla
   • Types
     • Whipmix
       • Uses Nation relator
     • Denar
       • Uses 43mm above incisor edge of lateral incisor
     • Dentatus
       • Uses orbital pin
   • Interocclusal records
     • Tells you the relationship between the maxilla & mandible
     • In RCP

3. Guidance

   • Anterior guidance
     • These are gliding contacts that should help to harmoniously guide the mandible in and out of ICP
     • Should start of shallow then deepen
     • Convex shape not tolerated well
       • Would be class III
   • If the patient currently has a suitable pattern of guidance, then it is important to conform to it
   • Top tips
     • Anterior RBB
       • Guidance
         • ICP on abutment & pontic
           • If not
             • Pontic will move around
         • Protrusive on ONLY the retainer
           • If on pontic then the tooth becomes compromised
             • Mobile
             • Drift
   • Always be thinking about ICP, lateral excursions and protrusive too!
     • Especially for re-organising
   • Group function
     • When several teeth are in contact on the working side during excursions
     • Usually premolars & canines
   • RCP
     • The first tooth contact when the condyles are seated in centric relation
       • Make sure RCP isn't on the tooth you re prepping. its only relevant for re-organising occlusion cases
   • When do you use CR as opposed to ICP
     • Re-organise occlusion from existing occlusal scheme into CR
     • When you don't have a reproducible ICP
     • When you want to increase the OVD as you no longer have stable ICP as teeth have been separated

4. Consequences of heavy contacts

   • TSL
   • Root fracture
   • Orthodontic tooth movement
   • Pulpitis +/- Apical periodontitis

5. Working side vs Non-working side

   • Working side
     • Side the patient moves their mandible towards.
     • Condyle rotates in excursion
   • Non-working side
     • Side that the mandible is moving away from
     • Condyle orbits
   • Interferences
     • Any tooth contacts that stop smooth guidance in excursions
     • To prevent
       • Take out of occlusion before crown prep
     • Avoid non-working side interferences!
       • Never load non-functional cusps

6. Splints

   • Uses
     • Managing TMD
     • Managing bruxism
       • Attrition is unlikely to occur alone
     • Testing increases in OVD
       • Used to be done now it's in composite
       • Can be used whilst provisional appliances are placed
     • Stabalisation of jaw position
   • Types
     • Hard
       • Lower = Tanner
       • Upper= Michigan
   • Design
     • Make sure all teeth that were in RCP are still in contact
     • Ant teeth contact slightly less than posterior teeth

7. Causes of error in reproducing RCP on articulator

   • Facebow errors
     • Bite fork
       • Not tightened
       • Wax not fixed
       • Maxillary teeth not centered
     • Jig assembly not tightened
     • Condylar arms not located in ear canal
   • Interocclusal record errors
     • Over softened BHW
     • Not sufficiently softened
     • If RCP is not stable on cast
       • Consider Blue moose
   • Impression taking
   • Mounting error

8. Study Models

   • Impression
     • Tray selection
       • Needs to record all teeth with a surrounding space of at least 3mm
     • Record free end saddles with compound
     • Dry occlusal aspects of teeth apply thin layer of alginate before seating tray to avoid air locks on occlusal aspect