Toothwear and Occlusion Flashcards
what is occlusion?
the study of the relationships between the upper and lower teeth when they are closed together
what is the functional purpose of bringing the teeth together?
for chewing and swallowing
what are the parts of the masticatory system?
teeth, periodontal tissues, jaws, temporo-mandibular joints, muscles of mastication, nervous control
what must occur for occlusion to occur?
the muscles of mastication have to move the jaws into position to allow the teeth to contact
where are forces transmitted during chewing?
down the long axes of the teeth into the robust base of the skull
what does the pulp do during chewing?
sends signals to the brain which sends signals to the muscles of mastication to regulate the movement of the jaws (sensitive feedback)
what does sensitive feedback do?
regulate the amount of force applied to the teeth which is important in tooth preservation
what does the resting position rely on?
neuromuscular memory
what is intercuspal position?
the position in which the teeth are maximally meshed together and the position the mandible aims for at the end of chewing
what is the occlusion pattern on posterior teeth?
the lower buccal cusps and upper palatal cusps occlude against the fossae and marginal ridges of the opposing teeth
what is the occlusion pattern on anterior teeth?
the lower incisal egses and canine tips occlude against the cingulum area of the opposing teeth
what happens if forces are not directed down the long axes of the teeth?
there can be teeth tilting and pain
what is balanced occlusion?
even, bilateral contacts in ICP
what does balanced occlusion provide?
stability
what does the mandibular condyle do during protrusion?
moves downwards and forwards in the mandibular fossa
what are the steps of chewing?
1 - jaw opens , 2 - moves left or right , 3 - jaw comes back up
when does group function occur?
when the mandible swings laterally and there are several teeth contacting
who is group function most commonly seen in?
patients with toothwear or unstable occlusions
what is 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?
a device in which dental casts are held in relationship to each other and which can replicate to varying extents mandibular movement
what do you do when examining occlusion?
look at tooth position in each arch - are there irregularities that might impact on the occlusion? look at the teeth in ICP - does it look stable, are there unopposed, drifted or over-erupted teeth? locate the contact points in ICP - where are they, how many are there? which teeth provide guidance in protrusion and lateral excursions?
what are the 3 types of toothwear?
attrition, erosion, abrasion
what is attrition?
the loss of tooth substance caused by contact between occluding surfaces
what is attrition caused by?
parafunctional rather than functional activity
what does parafunction mean?
purposeless clenching or grinding of the teeth (bruxism)
what are facets?
little bits of the teeth that are worn away that coincides with the opposing tooth
what is erosion?
the loss of tooth substance by a chemical process (acid) not involving bacterial action
what can be seen in tooth erosion?
dentine
what are the causes of tooth erosion?
diet, regurgitation, environmental
what is the effect of tooth erosion on amalgam restorations?
they appear to be raised above the clinical height of the crown as they are not affected by the acid
what is abrasion?
loss of tooth substance caused by abnormal rubbing from a non-dental object
what causes abrasion?
most commonly a toothbrush with overbrushing/trauma
in abrasion, how does the dentine surface get brushed away?
because the gum has receded
why may restorations fail?
secondary caries, fracture of the restoration or tooth pulp death, incompatibility with periodontal tissues, poor appearance
what is gingivitis associated with?
poorly fitting crown margins
what should an intra-oral exam include?
assessment of the occlusion - both static and functional, looking for signs of toothwear, evaluation of existing restorations
