Ideal occlusion and Selecting Equipment Flashcards
What is the ideal occlusion?
Distribution of load in the most favourable way
RCP = ICP - when closed posterior teeth contact and anterior teeth have light contact only
Forces directed through the long axis of the teeth
Posterior disclusion in eccentric positions
Mutual protection
Why do we want RCP to equal ICP?
When closed the posterior teeth contact and anteriors have light contacts
Occlusal load is directed through the long axis of te teeth
Condyles are positioned to distribute load into the bone with minimal muscular movement
What happens when RCP does NOT equal ICP?
Functioning in ICP requires more muscular activity to position the condyle and intraarticular disc
80-90% of population have RCP not equal to ICP
Bruxists may function on the RCP contact
- Damage vulnerable restorations
- Create wear facets on sound teeth
Bruxists may also grind in/from ICP
- Muscular activity increased
Why are forces down the long axis of the teeth favourable?
Distributes occlusal forces favourably Contacts on inclines result in horizontal forces - Wear - Tooth movement - Bone loss - Fracture of restorations
If restoring tooth with RCP not equal to ICP think about..?
Where RCP contact is
Tougher restorations
Multiple contact points
Minimise difference between RCP and ICP
What occurs in posterior disclusion? What happens if posterior contacts occur?
Anterior teeth disclude (separate) the posterior teeth Avoids lateral forces on posterior teeth Working side: group function NWS interference (undesirable) and protrusive interference (undesirable)
Anterior guidance?
Palatal surfaces of upper anteriors dictate the movement - interference occurs on mesial of lower and distal of upper teeth
How do teeth protect each other?
In ICP posterior teeth protect the anterior teeth
In excursions anterior teeth protect the posteriors
What allows canine guidance - why is canine guidance favoured?
Morphology of the canine Crown:Root Distant from the hinge Distant from the muscle Highly innervated
What occurs in group function?
Multiple contacts on working side
Define class I incisors
Lower incisor occludes at or below the upper incisor cingulum plateau
Define class II div I incisors
Lower incisor occludes behind the upper incisor cingulum plateau
Define class II div II incisors
Lower incisor occludes behind the upper incisor cingulum plateau
Upper central incisors are retroclined
Be careful with labial surface of lower incisor and palatal surface of upper incisor if restoring
Define class III incisors
Lower incisors occlude infront of the upper incisor cingulum plateau
Take care with occlusion when restoring - reproduce contacts or change them for the better
When restoring a tooth what should you do regarding occlusion?
Analyse existing occlusion - know the tooth contacts
Conforming - don’t introduce unfavourable contacts
Reorganising - work to the ideal occlusion
= Know RCP and ICP contacts pre and post op