Toothwear and Occlusion Flashcards
Define “occlusion”
The study of the relationship between the upper and lower teeth when they are close together
What is the functional purpose of occlusion?
The functional purpose of bringing the teeth together is for chewing and swallowing
Which muscles are important for occlusion?
Temporalis, Masseter, Pterygoid muscles
What is the purpose of the muscles of mastication?
To move the jaws into position to allow the teeth to contact
Which position is the mandible in when the teeth are apart?
Rest position
Which position is the mandible in when there is maximal inter-cuspation of the teeth?
Intercuspal Position (ICP)
What is the intercuspal position (ICP)?
The position in which the teeth are maximally meshed together
It is the position the mandible aims for at the end of chewing.
Provides maximal stability for the teeth and the jaws
Describe the contact points of posterior teeth when the mandible is in the intercuspal position
The lower buccal cusps and upper palatal cusps occlude against the fossae and marginal ridges of the occluding teeth
Describe the contact points of the anterior teeth when the mandible is in the intercuspal position
The lower incisal edges and canine tips occlude against the cingulum area of the opposing teeth
Where are forces directed in teeth in ideal occlusal contacts?
Down the long axis of teeth
What can we use to assess suspected ICP?
Shimstock
Place the shimstock between opposing teeth and ask patient to bite down.
If the teeth are in ideal occlusion, should not be able to remove the shimstock.
How thick is shimstock?
10 microns
What is the purpose of articulating paper?
To assess the occlusion intra-orally.
Describe the features of a balanced occlusion
- Even, bilateral contacts in the ICP
- Anterior teeth contact evenly when the mandible protrudes
- Contact with teeth in the opposing arch
- Contact with adjacent teeth in the opposing arch
Describe the components of the temporomandibular joint
The head of condoyle fits into the mandibular fossa of the temporal bone
What happens to the head of condoyle during protrusion of the mandible?
The head of condoyle translates downwards and forwards in the mandibular fossa
How is “guidance” studied?
By observing movement of the mandible from ICP “outwards”
Describe group function
When the mandible swings laterally and there are several teeth contacting
What is canine guidance also known as?
Posterior discussion
Describe canine guidance
When the mandible moves laterally with the tips of the canines being the only teeth in the arch which are touching
What is an articulator and what can it be used for?
- A device in which dental casts are help in relationship to each other
- Can be used to replicate mandibular movements
Define “attrition”
- The loss of tooth substance caused by contact between occluding surfaces
- Caused by parafunctional rather than functional activity
Define “parafunction”
Purposeless clenching or grinding of the teeth (bruxism)
Define “erosion”
The loss of tooth substance by a chemical process (acid) not involving bacterial action
Define “abrasion”
Loss of tooth substance cased by abnormal rubbing from a non-dental object. Most commonly caused by a toothbrush
What is toothier often due to?
A combination of attrition, erosion and abrasion
What does translation mean in relation to movement of the jaw?
Downwards and forwards
What is the purpose of restorations in teeth?
Replace lost tooth tissue and to “restore” form, function and appearance
Why may restorations fail?
- Secondary (recurrent) caries
- Fracture of the restoration or tooth
- Pulp death
- Incompatibility with periodontal tissues
- Poor appearance
What can poorly fitting crown margins be associated with?
Gingivitis
What should an intra-oral examination include?
- Assessment of the occlusion, both static and functional
- Looking for signs of toothwear
- Evaluation of existing restorations
The jaw can be divided into “working” and “non-working” sides. What do these terms refer to?
- Rotation happens on the working side
- Translation happens on the non-working side
