1. No category

Today
• AM - Seminar - 3157
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Get Casts from Marjorie
Survey Class I & II Casts (no preps)
Tripod Casts
Get Heads & Mounts ready for PM
• PM - Clinic
– Prepare guiding planes on Class I & II Typodonts
(last sheet Course Sched)
– Formative
– Marking sheets
– Diagnostic Casts Mark Sheets - Hand in
Surveying, Path of Insertion,
Guiding Planes
Definitions
• Height of contour
• Undercut =
Infrabulge
• Suprabulge
Definitions
• Height of contour
• Undercut =
Infrabulge
• Suprabulge
Rule: Retentive tip should usually be
designed to be placed in the gingival 1/3
Path of Insertion
• Path that the prosthesis is
–Placed/removed
–Usually a single path
Advantages of a Single Path of
Insertion
• Equalizes retention
Advantages of a Single Path of
Insertion
• Bracing and Cross-arch Stabilization
Advantages of a Single Path of
Insertion
• Minimizes torque on abutments
Advantages of a Single Path of
Insertion
• Allows removal without encountering
interferences
Advantages of a Single Path of
Insertion
• Directs forces along long axes of teeth
Advantages of a Single Path of
Insertion
• Provides frictional retention
Selecting a Single Path of Insertion
• Use a dental surveyor to
–Select path
–Prepare guiding planes
Guiding Plane Preparation
• Where rigid components contact abutments
• Proximal Plates
• Bracing Arms
• Rigid portions of Retentive Arms
Other Uses of a Surveyor
• Blocking out undesirable undercuts
–Ensures the framework is not cast in an
undercut
Parts of a Surveyor
• Surveying Table
Parts of a Surveyor
• Surveying Arm
Parts of a Surveyor
• Surveying Tools
–Analyzing Rod
Parts of a Surveyor
• Surveying Tools
–Carbon Markers
Parts of a Surveyor
• Surveying Tools
–Undercut Gauges
. 01”
. 02”
. 03”
Undercut Gauges
Parts of a Surveyor
• Surveying Tools
–Wax Trimmer
Selecting a Path of Insertion
• Orient cast relatively
horizontal
–Final tilt rarely more
than 10° from horizontal
Selecting a Path of Insertion
• Place analyzing rod against
abutments
– Contact point is Height of Contour
- Below is infrabulge
- Above is suprabulge
Selecting a Path of Insertion
• Tilt cast to obtain
maximum parallelism
– Heights of contour are at
relatively same position
occluso-gingivally
– Equal amounts of
undercut
Altering Path of Insertion
• Proximal surfaces similar
undercuts
• Retentive areas similar
undercuts
Selecting a Path of Insertion
• Modify tilt if necessary
– Soft tissue interferences
Selecting a Path of Insertion
• Modify tilt if necessary
–Esthetics
Once Path Selected
• Instructor:
–Approves path
–Demo:
- Mark heights of contour with
carbon marker
- Tripod
Selecting a Path of Insertion
• Lock cast position & tripod
Tripoding
Optimal Path of Insertion
• Retentive undercuts
equalized
–Retentive arm has a
different path of
escapement than
guiding plane, so it
must flex during
removal
Optimal Path of Insertion
• Retentive undercuts equalized
– Ideally, retentive arms should
oppose each other on opposite
sides of the arch
Optimal Path of Insertion
• Minimize severe tooth & soft
tissue interferences
Optimal Path of Insertion
• Esthetics
–Minimize display
of clasps, metal
components
Optimal Path of Insertion
• Prepare Guiding Planes
–Flat surfaces parallel to path of
insertion
–Control & limit movement of
RPD
–Initial contacts for RPD
Guiding Planes
• Stabilization
Effectiveness of Guideplanes
• Most effective when:
–Parallel to each other
–More than one common axial
surface
Effectiveness of Guideplanes
• Most effective when:
–Directly opposing each other
Effectiveness of Guideplanes
• Most effective
when:
–Prepared on
several teeth
–Cover a
large surface
area
Assessing Guiding Planes
Proximal
View
Facial
View
Carbon
Markings
Preparing Guiding Planes
• Select path of insertion
• Design Partial Denture *
• Select number & position of
guiding planes
• Prepare guiding planes
Use Surveyor to Align Bur
Intraorally
FINGER REST!
Burs
8837K-014
• Long
Cylindrical
Carbide or
Diamond
(8837K 014)
Guiding Plane Dimensions
2-4
2-4 mm
mm
1/2-1/3
1/2-1/3
height
height
Round
Round
Axial
Axial Line
Line
Angles
Angles
Axial Surface Already Parallel to
Path of Insertion
• NO Preparation !
Polish Prepared Surfaces
• Rubber wheels or points
Prepare Guiding Planes First
Effects of Guiding Planes On
Retention & Stability
• Maintains
Retention
Effects of Guiding Planes On
Retention & Stability
• Minimizes Need for Retention
Effects of Guiding Planes On
Retention & Stability
• Stabilizing
Teeth
Use
Use short
short guideplanes
guideplanes on
on Class
Class II &
& IIII
Use
Use long
long guideplanes
guideplanes on
on Class
Class III
III &
& IV
IV
Other Alterations of Axial Contours
• Lowering Heights of
Contour
– Rigid elements contacting
abutments
– Improve esthetics
– Prepare guiding planes most efficient method to
lower
Other Alterations of Axial Contours
• Raising Heights of Contour
– Insufficient retention in
gingival 1/3 (at least 1mm
from gingiva)
– Prepare undercut
– Add resin above to create
undercut
Preparing Retention
• Axial surface must be close to
parallel the path of insertion
X
Retentive Preparation Shape
• Follows the path of designed
retentive tip

X
X
Creating Undercuts with Bonded
Resins
• Axial surface must be close to
parallel the path of insertion
X
Summary of Abutment
Modifications
• After RPD Designed
– Guideplanes
– Lower heights of contour to
eliminate interferences &
improve esthetics
– Create undercuts if absolutely
necessary (raising heights of
contour)
– Rest seat preparation