Determinents of occlusion morphology /certified fixed orthodontic courses by Indian dental academy

Determinants of
occlusal
morphology
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

• Posterior controlling factors.
(condylar guidance)
• Anterior controlling factors.
(anterior guidance)

Effect of plane of occlusion on
cusp height

Effect of curve of spee on
cusp height

HORIZONTAL DETERMINANTS OF
OCCLUSAL MORPHOLOGY
DIRECTION OF GROOVES AND RIDGES

Gnathological Objectives
• To obtain a stable centric relation of the
mandible and have the teeth intercusp
maximally at this mandibular position
• All centric stops should hit equally and
simultaneously and the stress of closure
should be directed, as nearly as possible,
down the long axis of the posterior teeth.

• To have a harmonious glide path of
anterior teeth working against each other
to separate or disclude the posterior teeth
immediately, but gently , as soon as the
mandible moves out of centric closure.

• The glide path provided by the anterior
teeth must be in harmony with the way in
which the mandible moves through
border excursions. If there is immediate
shift of the mandible, there must be a
concavity in the lingual surfaces of the
maxillary anterior teeth to accommodate
the side shift movement , or the anterior
teeth will be stressed.

• The cuspids should be the main gliding
inclines on lateral excursion and the six
maxillary anterior teeth should articulate
with the six mandibular anterior teeth and
the mandibular bicuspids(first bicuspid in
non-extraction cases)so that the
protrusive load is spread over 14 teeth.

Ideal tooth positioning
 Lower incisors at the cephalometric goal-
+1 to A-Po
 Tips of the upper incisors 2-2.5mm below
the lip embrasure of the upper and lower
lips , when the lips are closed with no lip
strain
 No more than 1mm of attached gingiva
showing upon full smile

• Approx. a 2.5mm overjet-overbite
relationship to the lower incisor(the lower
incisor has .0005” clearance with the
lingual surface of the upper incisor
• A level or nearly level occlusal plane at
the end of appliance therapy that would
return to a 1-1.5mm curve at its deepest
point after appliance removal and setting
of the occlusion

• The curve of Wilson that would allow
seating of centric cusps but clearance
upon excursions
• As much divergence as possible of the
occlusal plane from the angle of the
eminence for excursive clearance.

• Lower incisors aligned contact point-to-
contact point with the roots in the same
plane , when observed from the occlusal ,
and a mesioaxial inclination of 2 degrees
• Lower cuspid crowns angulated mesially
5 deg with the incisal tip 1mm higher
than the incisal edge of the lateral
incisors.

• The lower bicuspids should be up righted
1 deg from their normal mesial
inclination and should have a slight distal
rotation
• The lower molars should be up righted
1deg from their normal 2 deg mesial
inclination and should have a slight distal
rotation.

• The lower buccal segment should have
progressive torque close to Andrew’s
measurements for establishing the curve
of wilson and there should be no rotations
or spaces
• The upper six year molars should have
sufficient distal rotation,mesio axial
inclination,and buccal root torque; the
same would follow for the upper second
molars.

• The upper bicuspids should be uprighted
to 0 deg from their normal 2 deg mesial
inclination with no rotation.
• The upper cuspid must have its contact
points adjacent to the contact points of
the upper bicuspid and lateral incisor ; it
should have 11- 13 deg of mesial crown
tip and mesial rotation of 4 deg on an
extraction case.

• The upper lateral and central incisors
should be almost equal in incisal edge
length ,with no more than 0.5mm height
differential; they should have 9 deg and
5deg mesioaxial inclination resp. and
there should be sufficient torque.
• There should be no rotations ( other than
those of overcorrection ) or spaces in the
upper arch and the buccal segments from
the cuspids distally should have 14 deg
nonprogressive buccal root torque.

• The arch form should be a modified
catenary curve consisting of five separate
radii- one for front of the arch form, one
for each cuspid bicuspid area, and one
each for buccal segment from the first
bicuspid distally

• The widest point of the lower arch would
be at the mesiobuccal cusp of the mand.
First molars and at the first bicuspids
• The widest point of the maxillary arch
would be at the mesiobuccal cusps of the
first molars.

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Determinents of occlusion morphology /certified fixed orthodontic courses by Indian dental academy

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Determinents of occlusion morphology /certified fixed orthodontic courses by Indian dental academy