Dental Surveyer And Surveying Dr Shaista Afroz Associate

Dental Surveyer And Surveying Dr Shaista Afroz Associate Professor Dr Z A Dental College A M U Aligarh

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. 2

Purpose 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

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 placement 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.

Height of Contour & Undercut

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

• 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.

Types of undercuts Tooth Undercuts Soft Tissues or bony Undercuts(on lingual side of ridge) 10

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.

Direct Retainers Buccal • Retention • Composed of: – rest – retentive element – reciprocal (bracing) element – minor connector Lingual

Rule: Retentive tip should usually be designed to be placed in the gingival 1/3

Path of Insertion & Removal • Path that the prosthesis is – Placed/removed – Usually a single path

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

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 axes of teeth

Advantages of a Single Path of Insertion • Provides frictional retention

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

Guiding Planes • Where rigid components contact abutments • Proximal Plates • Bracing Arms • Rigid portions of Retentive Arms *

Effects of Guiding Planes On Retention & Stability • Minimizes need for retention

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

Effectiveness of Guideplanes • Most effective when: – Prepared on several teeth – Cover a large surface area (proximal & lingual)

Prep. Of Guiding Planes

Guiding Plane Dimensions

Guiding Plane Dimensions

If Axial Surface Already Parallel to Path of Insertion? • NO Preparation !

Retentive Areas

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)

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

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

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

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

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 • 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.

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

Optimal Path of Insertion (Esthetics) • Esthetics – Minimize display of clasps, metal components

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

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

• Surveying Table

• Surveying Arm

Surveying Tools 1 - Analyzing Rods 2 - Carbon Marker 3 - Undercut Gauge 4 - Wax Trimmer 48

• Analyzing Rod

Analyzing Rod

• Carbon Markers

Carbon Marker

. 01” Undercut Gauges . 02” . 03”

Undercut Gauge

Undercut Gauges

Undercut Gauges

Undercut Gauge

– Wax Trimmer

Wax Trimmer

Dental Surveyor 60 Ney Surveyor Prof. Dr. Jelenko Surveyor

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 Than the Other. 61 Clasp Arms

The Location of the Undercut Area Can Be Changed by Changing the Tilting

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.

4 - Eliminate Areas of Interference by Reshaping Tooth Surfaces, Surgery, Blockout, Restoration, or Change in lateral Tilt if Unilateral Interference

5 - Permits a More Esthetic Placement of Clasp Arms Than the Other.

A Cast in a Tilted Relationship Represents a Path of Placement Toward the Side of the Cast That Is Tilted Upward

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.

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

Tripoding the Cast

• 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.

References/ Suggested readings • Mc. Cracken’s Removable Prosthodontics, 11 th Edition 2005 by Mc. Givney GP, Carr AB. Chapter 11 (Surveying) • Stewert’s clinical removable prosthodontics, 3 rd edition by Rhodney D Phoenix, David R Cagna, Charles F De Freest All the text and pictures are taken from Mc. Cracken’s Removable Prosthodontics and Stewert’s clinical removable prosthodontics and internet for the sake of student’s education.