surveying

* DENTAL SURVEYOR 

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.

Types of surveyors: Manual surveyors

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CAD/CAM SYSTEM. With intra oral surveing camera

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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



Main Parts of a Surveyor
Surveying Table

Surveying Arm

* Surveying Tools
3- Undercut Gauge
1- Analyzing Rods
4- Wax Trimmer
2- Carbon Marker

Surveying Tools

Carbon Markers

0.01 0.02 0.03

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Wax Trimmer

Purposes of Surveying the Diagnostic Cast
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. 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 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.

* Some Important Terms

Height of Contour (HOC)
Survey line :a line encircling a tooth, designating its greatest circumference at a selected position determined by a dental surveyor.

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Any areas occlusal to survey line used for placement of non retentive, stabilizing, or reciprocating elements
Any areas cervical to survey line used for placement of retentive clasp components



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* Types of undercuts

Tooth Undercuts
Soft Tissues or bony Undercuts(on lingual side of ridge)

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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Factors Determining Path of Insertion & Removal

Guiding planes Retentive areas Interference Esthetics

Guiding Planes

Two or more vertically parallel flat surfaces of abutment teeth shaped to direct a prosthesis during placement and removal where rigid components contact abutments *



Guiding Planes Functions
1- ensure passage of the rigid parts of prosthesis past existing areas of interference. # 2- to control & limit directions of movement of RPD as it is being inserted, removed or while in function. 3- to ensure predictable clasp assembly function, including retention and stabilization *

Effectiveness of Guiding Planes

Most effective when: A- Parallel to each other B- More than one common axial surface
C- Directly opposing each other
D- Prepared on several teeth E- Cover a large surface area(proximal & lingual)

Preperation Of Guiding Planes

Long Cylindrical Carbide or Diamond)

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)
For a clasp to be retentive, its path of escapement must be other than parallel to the path of removal of the denture itself.

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



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

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.

Interference

Bony undercuts 1- to remove them surgically; 2- to change the path of placement at the expense of modifying or restoring teeth to achieve guiding planes and retention; 3- to design denture bases to prevent such undercut areas.
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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(Esthetics)

A path of insertion should be selected to provide the most esthetic placement of artificial teeth and the least amount of visible metal on the abutment teeth. Ensure that the retentive undercut and the height of contour are not placed too far occlusally, so that the retentive clasp and that anterior proximal plates are close to the gingival contours making these components as inconspicuous as possible.

* Tripoding the diagnostic cast, so that the selected path of insertion may be easily found for future references



* H.W: DEFINE TRIPODING?