Lecture 12 Determinants of Occlusal Morphology I Flashcards
what are the factors that determine the patterns of mandibular movements
-TMJs
- anterior teeth
to maintain harmony the posterior teeth need to pass close to but _____ the opposing teeth during mandibular movement
not contact
what are the structures that control mandibular movement
-TMJs influence posterior movement of mandible
- anterior teeth influence anterior movement of mandible
what is the condylar guidance angle
the angle at which the condyle moves away from the horizontal plane
condylar guidance is considered to be a _____
“fixed factor”
as the mandible protrudes or moves laterally the incisal edges of the mandibular anterior teeth occlude with ____
the lingual surfaces of the maxillary anterior teeth
what determines the amount of vertical movement of the mandible
the steepness of the lingual surfaces
the anterior teeth determine how____
the anterior portion of the mandible moves
the anterior guidance is considered to be a _____
variable factor
what is the morphology of the tooth influenced by
the pathway it travels across its opposing tooth or teeth
what are the components of mandibular movement
vertical component
horizontal component
the length of a cusp and the distance it extends into the depth of an opposing fossa depends on:
- anterior controlling factor of mandibular movement
- posterior controlling factor of mandibular movement
- the nearness of the cusp to those controlling factors
what do vertical determinants control
-the function of the superior inferior movenet
- cusp height and fossa depth
what do horizontal determinants influence
the direction of grooves and ridges on the occlusal surfaces and the placement of the cusps in the horizontal plane
what are the vertical determinants
-condylar guidance
-anterior guidance
-nearness of the cusp to the controlling factor
- plane of occlusion
- curve of spee
mandibular lateral translation movement
what are the posterior controlling factors
-fixed factors
- condylar guidance
-TMJs
as the mandible is protruded the condyle descends along ____
the articular eminence
is the condylar guidance angle greater when the mandible makes a lateral movement or when the mandible makes a protrusive movement
when the mandible makes a lateral movement
the steeper the eminence:
- the more the condyle must move inferiorly
- there is greater vertical movement
- allows for steeper posterior cusps
what is anterior guidance altered by
-restorations
-orthodontics
-extractions
-caries
- habits
-tooth wear
what is the anterior guidance angle
the angle formed by the intersection of the horizontal plane and the disclusive pathway of the anterior teeth
what is the anterior guidance angle influenced by
vertical overlap and horizontal overlap
what does increased VO do to anterior guidance angle? increased HO?
increased VO: increases it
increased HO: decreases it
the nearer a tooth is to the TMJ, the ____ the joint anatomy will influence its ecentric movement and the ____the anterior teeth influence its movement
more; less
what are other factors that influence cusp height
-plane of occlusion
-curve of spee
- mandibular lateral translation movement
as the plane of occlusion becomes more parallel to the angles of eminence the posterior cusp tips must be made _____
shorter
what is the curve of spee
-anteroposterior
- curve extending from the tip of the mandibular canine along the buccal cusp tips of the mandibular posterior teeth
with a short radius the curve will be more _____ than with a longer radius
acute
the flatter the plane of occlusion the ____the cusp height can be
greater
if the curve of spee has a short radius: the angle at which the mandibular teeth move away from the maxillary teeth will be ____ than with a long radius , therefore the cusps will need to be _____
less; shorter
if the plane of occlusion is rotated more anterior:
-more teeth anterior to perpendicular line
- taller cusps
if the plane of occlusion is rotated more posterior
-more teeth posterior to perpendicular reference line
-shorter cusps
what is the bennett movement
the mandibular lateral translation is a sideshift of the mandible during lateral movements
what does how much inward movement there is depend on
-morphology of the medial wall of the fossa on the orbiting side
inner portion of the TM ligament attached to the lateral pole of the rotating condyle
describe the TM ligament
-very tight
- pure arcing movement around the rotating condyle
- no lateral translation of the mandible
-not common
in lateral translation movement, the more medial the medial wall is from the condyle___
the more lateral translation movement
the lateral translation movement is described in
-amount
-timing
-direction
the greater the amount of lateral translation the ____the posterior cusps must be
shorter
what does laterosuperior movement require about cusp tips
shorter
what does lateral inferior movement allow about cusp tips
taller
what is the greatest influence on occlusal harmony
lateral translation timing
what is early translation called
immediate lateral translation or immediate shideshift
what is late lateral translation called
- progressive lateral translation or progressive sideshift
when is immediate lateral translation seen
before the condyle begins to translate from the fossa
the more immediate the movement the -___the cusps must be
shorter
the steeper the condylar guidance:
the taller the cusps
the greater the vertical overlap:
the taller the cusps
the greater the horizontal overlap
the shorter the cusps
the more parallel plane of occlusion to condylar guidance
the shorter the cusps
the more acute the curve of spee:
the shorter the cusps
the greater the lateral translation movement:
the shorter the cusps
the more superior movement of the rotating condyle
the shorter the cusps
the greater the immediate side shift:
the shorter the cusps
