DENTAL SURVEYOR The tool for perfect planning of Removable Partial Denture

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DENTAL SURVEYOR The tool for perfect planning of
Removable Partial Denture

• Dalhousie continual education
• McCrackens Removable Prosthodontics, 11th
  Edition

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Lecture Outline

• Description of Dental Surveyor
• Purposes of Surveyor
• Discussing some related terms
• Factors That Determine Path of Placement and
  Removal
• Guiding Planes
• Retentive Areas
• Interference
• Esthetics
• Step-by-Step Procedures in Surveying
  Diagnostic Cast
• Recording Relation of Cast to Surveyor

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Definition An instrument used to determine the
relative parallelism of two or more surfaces of
the teeth or other parts of the cast of a dental
arch.
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Purposes of Surveying the Diagnostic Cast

• 1. To determine the most desirable path of
  placement that will eliminate or minimize
  interference to placement and removal
• 2. To identify proximal tooth surfaces that are,
  or need to be, made parallel so that they act as
  guiding planes during placement and removal.
• 3. To locate and measure areas of the teeth that
  may be used for retention.

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Purposes of Surveying the Diagnostic Cast

• 4. To determine whether tooth and bony areas of
  interference will need to be eliminated
  surgically or by selecting a different path of
  placement.
• 5. To determine the most suitable path of
  placemen that will permit locating retainers and
  artificial teeth to the best esthetic advantage.
• 6. To permit an accurate charting of the mouth
  preparation to be made

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Purposes of Surveying the Diagnostic Cast

• 7. To delineate the height of contour on abutment
• teeth and to locate areas of undesirable tooth
• undercut that are to be avoided, eliminated, or
  blocked out.
• 8. To record the cast position in relation to the
  selected path of placement for future reference.

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Some Important Terms
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• Height of Contour Undercut

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Height of Contour (HOC)

• A line encircling a tooth, designating its
  greatest circumference at a selected position
  determined by a dental surveyor.

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• Height of contour

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• Any areas cervical to HOC used for placement of
  retentive clasp components
• Areas occlusal to the HOC used for the placement
  of nonretentive, stabilizing, or reciprocating
  components.

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Non-undercut Area
Undercut here
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Types of undercuts
Tooth Undercuts
Soft Tissues or bony Undercuts(on lingual side of
ridge)
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Angle of Cervical Convergence

• An angle viewed between a vertical rod
  contacting an abutment tooth and the axial
  surface of the abutment cervical to the height of
  contour.

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Direct Retainers
Buccal

• Retention
• Composed of
• rest
• retentive element
• reciprocal (bracing) element
• minor connector

Lingual
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Rule Retentive tip should usually be designed to
be placed in the gingival 1/3
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• Path of Insertion Removal

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Path of Insertion

• Path that the prosthesis is
• Placed/removed
• Usually a single path

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Path of Insertion (P.I)
The Direction in Which a Restoration/ Prosthesis
Moves From the Point of Initial Contact With the
Supporting Teeth to the Terminal Resting Position
Where the Occlusal Rests Are Seated and the
Denture Base Is in Contact With the Tissue
Path of Removal (P.R) Reverse of the
Path of Insertion
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Advantages of a Single Path of Insertion

• Equalizes retention

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Advantages of a Single Path of Insertion

• Bracing and Cross-arch Stabilization

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Advantages of a Single Path of Insertion

• Minimizes torque on abutments

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Advantages of a Single Path of Insertion

• Allows removal without encountering interferences

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Advantages of a Single Path of Insertion

• Directs forces along long axes of teeth

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Advantages of a Single Path of Insertion

• Provides frictional retention

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Factors Determining Path of Insertion Removal

• Guiding planes
• Retentive areas
• Interference
• Esthetics

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Guiding Planes

• Two or more vertically parallel flat surfaces of
  abutment teeth shaped to direct a prosthesis
  during
• placement and removal

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Guiding Planes

• Where rigid components contact abutments

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Effects of Guiding Planes on Retention Stability

• Maintains Retention

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Effects of Guiding Planes On Retention Stability

• Minimizes Need for Retention

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Guiding Planes Functions

• to ensure passage of the rigid parts of
  prosthesis past existing areas of interference.
• to control limit directions of movement of RPD
  as it is being inserted, removed or while in
  function.
• to ensure predictable clasp assembly function,
  including retention and stabilization

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Effectiveness of Guiding Planes

• Most effective when
• Parallel to each other
• More than one common axial surface

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Effectiveness of Guideplanes

• Most effective when
• Directly opposing each other

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Effectiveness of Guideplanes

• Most effective when
• Prepared on several teeth
• Cover a large surface area (proximal lingual)

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Prep. Of Guiding Planes
Prepare Guiding Planes First
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Use Finger Rest
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Burs
8837K-014

• Long Cylindrical Carbide or Diamond (8837K 014)

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Guiding Plane Dimensions
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Guiding Plane Dimensions
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Polish Prepared Surfaces

• Rubber wheels or points

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If Axial Surface Already Parallel to Path of
Insertion?

• NO Preparation !

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• Retentive Areas

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Retentive Areas

• Retentive arm should have a different path of
  escapement than guiding plane (path of removal),
  so retentive arm must be forced to flex over a
  convex surface during placement and removal
  (retention)

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Optimal Path of Insertion

• Retentive undercuts equalized
• Ideally, retentive arms should oppose each other
  on opposite sides of the arch with fairly even
  retention

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Retentive Areas

• To obtain fairly even retention
• --change the path of placement to increase or
  decrease the angle of cervical convergence of
  opposing retentive surfaces of abutment teeth.
• OR
• --alter flexibility of retentive clasp arm

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Optimal Path of Insertion (Interference)

• Prosthesis must be designed so that it may be
  placed and removed without encountering tooth or
  soft tissue interference

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Interference

• Bony prominences and lingually inclined premolar
  teeth are the most common causes of interference
  to a lingual bar connector

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Interference

• If the interference is bilateral, surgery or
  recontouring of lingual tooth surfaces, or both,
  may be unavoidable.
• If it is only unilateral, a change in the
  lateral tilt may prevent an area of tooth or
  tissue interference.

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Interference

• Bony undercuts
• to remove them surgically
• to change the path of placement at the expense of
  modifying or restoring teeth to achieve guiding
  planes and retention
• to design denture bases to prevent such undercut
  areas.

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Interference

• Generally, interference that cannot be eliminated
  for one reason or another will take precedence
  over the factors of retention and guiding planes.

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Optimal Path of Insertion (Esthetics)

• Esthetics
• Minimize display of clasps, metal components

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Esthetics

• Esthetics dictates the choice of path selected
  only when missing anterior teeth must be replaced
  with RPD

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Parts of a Dental Surveyor
B-Vertical Upright Column C-Cross Arm with
Spindle Housing D-The Vertical Spindle With Tool
Holder E- Screw To Lock The Spindle F- Tool
adaptor Holder G- Surveying tool holder J- Model
Clamp K- Model table lock nut L- Model rotating
ball socket M- Ball rotating ring N- Tool
Rack O- Storage Compartment P- Model lock nut
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Parts of a Surveyor

• Surveying Table

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Parts of a Surveyor

• Surveying Arm

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Surveying Tools
1- Analyzing Rods
2- Carbon Marker
3- Undercut Gauge
4- Wax Trimmer
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Parts of a Surveyor

• Surveying Tools
• Analyzing Rod

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Analyzing Rod
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Surveying Tools
1- Analyzing Rods
2- Carbon Marker
3- Undercut Gauge
4- Wax Trimmer
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Parts of a Surveyor

• Surveying Tools
• Carbon Markers

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Carbon Marker
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Parts of a Surveyor

• Surveying Tools
• Undercut Gauges

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Undercut Gauge
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Undercut Gauges
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Undercut Gauges
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Undercut Gauge
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Parts of a Surveyor

• Surveying Tools
• Wax Trimmer

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Wax Trimmer
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Dental Surveyor
Ney Surveyor
Jelenko Surveyor
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PROCEDURES of SURVEYING DIAGNOSTIC CAST
1- Placement of the Cast
2- Altering the Cast Position Anteroposteriorly
To Provide Parallel Proximal Surfaces That
May Act As Guiding Planes
3- Tilt the Cast Laterally Until Equal
Retentive Areas Exist on the Principal Abutments
4- Eliminate Areas of Interference
5- Permits a More Esthetic Placement of Clasp
Arms Than the Other.
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1- Placement of the Cast

• Position the adjustable
• table so that the occlusal surfaces of the
  teeth are
• approximately parallel to the platform

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• 2. Altering the Cast Position Anteroposteriorly
  To Provide Parallel Proximal Surfaces That May
  Act As Guiding Planes

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3- Tilt the Cast Laterally Until Equal
Retentive Areas Exist on the Principal Abutments

• By contacting buccal and lingual surfaces of
  abutment teeth with the surveyor blade, the
  amount of retention existing below their height
  of convexity may be determined.

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The Location of the Undercut Area Can Be Changed
by Changing the Tilting
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B
Cast at zero tilt. Creation of undercut
by tilting cast
D
Without guiding planes, Clasps designed are
ineffective when restoration is subject to
dislodging forces in occlusal direction.
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4- Eliminate Areas of Interference by Reshaping
Tooth Surfaces, Surgery, Block-out, Restoration,
or Change in lateral Tilt if Unilateral
Interference
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5- Permits a More Esthetic Placement of Clasp
Arms Than the Other.
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A Cast in a Tilted Relationship Represents a Path
of Placement Toward the Side of the Cast That Is
Tilted Upward
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FINAL PATH OF PLACEMENT

• The anteroposterior and lateral position of the
  cast, in relation to the vertical arm of the
  surveyor that best satisfies all four factors
  guiding planes, retention, interference, and
  esthetics.

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Recording Relation of Cast to Surveyor
Tripoding is Performed While Cast is Still
Mounted on the Survey Table Without Changing the
Tilt to Preserve the Established Cast Tilt
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Tripoding the Cast
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• All proposed mouth changes (prep. of proximal
  surfaces, reduction of buccal lingual
  surfaces, prep. of rest seats) should be
  indicated on the diagnostic cast in red pencil,
  with the exception of restorations to be done.

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References

• McCrackens Removable Prosthodontics, 11th
  Edition 2005 by McGivney GP, Carr AB. Chapter 11
  (Surveying)
• Dalhousie continual education