Download Guiding plane and Occlusal rest seat Design

Guiding plane and Occlusal
rest seat
Design & Preparation
Dr.Emad Hanbali
Guiding planes :
two or more vertically parallel
surfaces of abutment teeth, so
shaped to direct a prosthesis
during placement and removal.
Functions :
. To provide for one path of placement
and removal of the restoration.
. To ensure the intended actions of other
components of the RPD.
. To eliminate gross food traps .
Width :
1/2 the width of the distance between the
tips of adjacent buccal and lingual cusps.
1/3 the buccal lingual width of the tooth.
Height :
2/3 of the length of the enamel crown
portion from the marginal ridge cervically.
Surveying
at the
selected
path of
insertion
and
removal of
the RPD.
Zero tilt survey line
Insertion tilt survey line
F
Follow the buccolingual contour
during the
preparation. Do
not slicew
Length of
guiding
plane 2-3
mm.
Occlusal rest seat
Design &
Preparation
Rest
A rigid component resting in a recessed
preparation on the occlusal, lingual or
incisal surface
Provides vertical support
Occlusal Rest Seat Form
Conventional Form: rounded triangle
Occlusal Rest Seat Form
Rounded triangular shape
– Apex near center of tooth
Occlusal rest seat 3D:
- Mesio - distally.
- Bucco - lingually.
- Occluso - gingivally
Dimensions:
Mesio – distally :
premolars 1 / 3
molars 1 /4
Occlusal Rest Seat Form
Base of triangle should be one third the
bucco-lingual width of the tooth
Occluso-gingivally ( depth )
Occlusal Rest Seat Form
Marginal ridge must be lowered and
rounded 1-1.5mm
– Bulk of metal to prevent fracture
Occlusal Rest Seat Form
Floor inclined towards the center
Angle formed by rest and minor connector
should be less than 900
Occlusal Rest Seat Form
Deepest portion is central
Occlusal Rest Seat Form
Floor should be concave or spoon shaped
ball-&-socket joint
Prevents horizontal stresses & torque
Occlusal Rest Seat Form
Directs the occlusal forces along the long
axis of the tooth
Prevent orthodontic movement
Result of force applied when angle is greater than 90 degrees .
Preparation of Rest Seats
Occlusal Rest Seats
– Diamonds
8801- 014
38006 -135
– Medium round carbide
burs
#2, #4
8801- 014
Preparation of Rest Seats
Keep in enamel
No anesthesia
Rounded triangle
Deepest part
of rest seat
Marginal
ridge
reduction
1.5 mm
SAUSER SHAPE
GP
Molar occlusal
rest seat
Modified Occlusal rest seat
Occlusal Rest Seat Form
Adjacent Tooth
– Rest not flared to facial line angle
– Lingual flared more - space for minor
connector
Double Embrasure Rest Seat
Form
Adjacent teeth, the form is also modified
Flared more dramatically on facial and
lingual line angles
Double Embrasure Rest Seat Form
Provides space for the retentive & bracing
arms
Ensure all line angles are smoothed
Preserve the contact between the adjacent
teeth
Interproximal Occlusal Rest
Seats
Care must
be exercised
to avoid
violation of
contact
point.
E
N
J
O
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