Determinants of Occlusal Morphology Flashcards
THE FACTORS THAT DETERMINE THE PATTERNS OF
MANDIBULAR MOVEMENT ARE: (2)
the TMJs and anterior teeth
TO MAINTAIN HARMONY THE POSTERIOR TEETH NEED TO
PASS CLOSE TO BUT NOT —, THE OPPOSING TEETH
DURING MANDIBULAR MOVEMENT.
CONTACT
STRUCTURES THAT CONTROL MANDIBULAR
MOVEMENT: (2)
structures that influence the movement of the posterior portion of the mandible (TMJ)
structures that influence the movement of the anterior portion of the mandible (anterior teeth)
THE ANGLE AT WHICH THE CONDYLE MOVES AWAY FROM
A HORIZONTAL REFERENCE PLANE IS REFERED TO AS THE
CONDYLAR GUIDANCE ANGLE.
THE CONDYLAR GUIDANCE IS CONSIDERED TO BE A
“—”, SINCE IN THE HEALTHY PATIENT IT IS
UNALTERABLE
FIXED FACTOR
the anterior teeth determine how the
anterior portion of the mandible moves
as the mandible protrudes or moves laterally, the incisal edges of the manidbular anterior teeth occlude with the
lingual surfaces of the max anterior teeth
the steepness of the — surfaces determine the amount of — movement of the mandible
lingual
vertical
the anterior guidance is considered to be a
VARIABLE RATHER THAN A FIXED FACTOR
anterior guidances CAN BE ALTERED BY
PATHOLOGIC CONDITIONS
(CARIES, WEAR, ETC) OR DENTAL PROCEDURES
THE MORPHOLOGY OF THE TOOTH IS INFLUENCED BY THE
PATHWAY IT TRAVELS ACROSS ITS OPPOSING TOOTH OR
TEETH.
VERTICAL COMPONENT
supero-inferior movement
HORIZONTAL COMPONENT
antero-posterior movement
VERTICAL COMPONENT is a function of
SUPERIO-INFERIOR MOVEMENT
we want posterior teeth to pass close to, but not contact opposing teeth during
mandibular movement (occlusal harmony)
THE LENGTH OF A CUSP AND THE DISTANCE IT
EXTENDS INTO THE DEPTH OF AN OPPOSING
FOSSA DEPENDS ON: (3)
anterior controlling factor of mandibular movement
posterior controlling factor of mandibular movement
the nearness of the cusp to those controlling factors
VERTICAL DETERMINANTS:
control the function of the superior inferior movement
cusp height, fossae depth
HORIZONTAL DETERMINANTS:
influence the direction of grooves and ridges on the occlusal surfaces and the placement of the cusps in the horizontal plane
VERTICAL DETERMINANTS
these factors influence (2)
height of the cusps
depths of the fossae
vertical determinants (6)
condylar guidance (p controlling factor) anterior guidance (a controlling factor) nearness of the cusp to the controlling factor plane of occlusion curve of spee mandibular lateral translation movement
POSTERIOR CONTROLLING FACTORS (3)
fixed factors
condylar guidance
the two TMJs
at the mandible is protruded the condyle descends along the
articular eminence
the condylar guidance is the angle at which the
condyle moves away from the horizontal reference plane
when the mandible makes a lateral movement, the condylar guidance angle is greater than when the mandible makes a
protrusive movement
THE STEEPER THE EMINENCE
the more the condyle must move
inferiorly
THE STEEPER THE EMINENCE
there is a greater — movement
vertical
THE STEEPER THE EMINENCE
it allows for — posterior cusps
steeper
THE STEEPER THE ANGLE OF THE EMINENCE,
THE STEEPER THE
POSTERIOR CUSPS
anterior controlling factors (2)
anterior teeth
anterior guidance
anterior teeth
determine how the — portion of the mandible moves
anterior
anterior guidance is altered by (6)
restorations ortho extractions caries habits tooth wear
the anterior guidance is a — rather than a fixed factor
variable
anterior guidance angle
the angle formed by the intersection of the horixontal plane and the disclusive pathway of the anterior teeth
anterior guidance angle is influenced by (2)
VO
HO
HO:
: stays the same
VO:
: varies
VO overlap increases
anterior guidance angle increases
HO overlap increases
naterior guidance angle decreases
increased anterior guidance angle (2)
more vertical component
allows steeper posterior cusps
the nearer a tooth is to the TMJ, the – the joint anatomy will influence its eccentric movement and the – the anterior teeth influence its movement
more
less
other factors that influence cusp height (3)
plane of occlusion
curve of spee
mandibular lateral translation movement
plane of occlusion
an imaginary surface that touches the incisal edges of the incisors and cusp tips of the occluding surfaces of the posterior teeth
as the plane of occlusion becomes more parallel to the angle fo the eminence, the posterior cusps must be made
shorter
curve of spee
AP curve extending from the tip of the mandibular canine along the buccal cusp tips of the mandibular posterior teeth
curvature is described in terms of
length of radius of the curve
with a shorter radius, the curve will be more — than with a longer radius
acute
THE FLATTER THE PLANE OF OCCLUSION,
THE
GREATER THE CUSP HEIGHT CAN BE
If the Curve of Spee has a SHORT RADIUS:
the ANGLE at
which the mandibular teeth move away from the maxillary teeth
WILL BE LESS THAN WITH A LONG RADIUS, therefore the
CUSPS will need to be SHORTER
PLANE OF OCCLUSION
rotated more A (2)
more teeth A to perpendicular line
taller cusps
PLANE OF OCCLUSION
rotated more P (2)
more teeth P to perpendicular reference line
shorter cusps
EFFECT OF MANDIBULAR
LATERAL TRANSLATION
MOVEMENT ON CUSP
HEIGHT
BENNETT MOVEMENT
the mandibular lateral translation is a – – of the mandible during lateral movements
bodily sideshift
HOW MUCH INWARD MOVEMENT? depends on (2)
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
TM LIGAMENT very tight (3)
pure arcing movement around the rotating condyle
no lateral translation of the mandible
not common
the more medial the medial wall is from the condyle, the more
LATERAL TRANSLATION MOVEMENT
LATERAL TRANSLATION
MOVEMENT
described in (3)
amount
timing
direction
THE GREATER THE AMOUNT OF LATERAL
TRANSLATION,
THE — THE POSTERIOR CUSPS MUST BE
SHORTER
ROTATING CONDYLE
may move in a combo of movements (3)
laterosuperior
lateroinferioposterior
ect
laterosuperior movement requires
shorter posterior cusp
inferior movement allows
taller cusps
lateral translation timing
greatest influence on — morphology
occlusal
translation can occur (2)
early
late
EARLY TRANSLATION
called
immediate lateral translation (or immediate sideshift)
LATE LATERAL TRANSLATION
called
PROGRESSIVE LATERAL TRANSLATION
or progressive sideshift
IMMEDIATE LATERAL TRANSLATION
shift seen before the condyle begins to
translate from the fossa
IMMEDIATE LATERAL TRANSLATION
the more the immediate movement, the
shorter the cusps must be
Condylar Guidance (2)
Steeper the guidance
Taller cusps
Anterior Guidance (4)
Greater vertical overlap
Taller cusps
Greater horizontal overlap
Shorter cusps
Plane of Occlusion (2)
More parallel to the condylar
guidance
Shorter cusps
Curve of Spee (2)
More acute the curve
Shorter cusps
Lateral translation
movement (3)
Greater the movement
Shorter cusps
More superior movement of the
rotating condyle
Shorter cusps
Greater immediate side shift
Shorter cusps