Surveying

Dr. Mohamed AshourAssistant Professor of Removable Prosthodontic, Faculty of Dental Medicine, Al- Azher University

The Component Parts

of Removable

Partial Dentures

Denture BaseArtificial Teeth Supporting Rests

Retainers Direct retainersIndirect Retainers

Connectors: Major ConnectorsMinor Connectors

The Component Partsof Removable Partial Dentures

It is the procedure of locating and delineating the contour and position of the abutment teeth and associated structures before designing a removable partial denture

Surveying

Why do we survey dental casts ?and What are the objectives ?

A partial denture must be designed so that it can be easily inserted and

removed by the patient,

It should be retained against reasonable dislodging forces and have the best

possible appearance.

EssEntial tErminology

Undercut

Survey line

Guiding planes

Path of insertion and path of removal of the denture.

which is the most bulbous and convex part of the tooth, also called maximum bulge .

The Survey LineIs a line outlined on the cast by A surveyor marking the greatest prominence of tooth contour (height of contour)

Undercuts on Teeth:

Height of contour:

Is a dig or a burrow lie below the height of contour .

Definitions Height of contour

UndercutUndercut == InfrabulgeInfrabulge UndercutUndercut == InfrabulgeInfrabulge

SuprabulgeSuprabulge SuprabulgeSuprabulge

Undercut Area

Undercut: An undercut is formed when the base of an object is smaller than its top

No undercut

Survey line

Undercut Area

Types of undercuts

Tooth Undercuts (Proximal undercuts)

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

Partially edentulous mouth has many undercuts that result due toII-- Bulbous shape of the crowns of natural

teeth resulting in buccal and lingualundercuts.

2- The inclination of the long axes of teeth in relation to A vertical line

44-- Proliferation of soft tissues covering the edentulous ridge

33-- The inclination of soft tissues or bone to A vertical line

1-Desirable Undercuts 2-Undesirable Undercuts

All the Undercuts areUndesirable undercuts

Except That used for denture retention

Types of undercuts

Components of metallic removable partial dentures are all rigid, with the exception of the flexible retentive clasp arm located in an undercut area for retaining the restoration against dislodging forces Flexible clasp arm engaging tooth undercut

Path of insErtion and

Path of rEmoval of a dEnturE

The direction in which a restoration 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

The direction of movement of the restoration from its resting position to the last contact with the supporting teeth". It is the reverse of the path of insertion

Path of Insertion

Path of Removal

Selection of The Path of InsertionThe Most Favorable Path of Insertion (PI) Is That Perpendicular to the Occlusal Plane

Most Patients Tend to Seat Their Dentures Under Biting Force

If Undercuts are Present but Not Efficient at the Zero Tilt

If Displacement of the Prosthesis Is AnticipatedWith the Least Displacing Forces

Another Path of Insertion Should Be Decided

Factors Affecting Path of InsertionInterferences

-- Contouring the tooth surface

-- Retentive undercuts-- Surgery to remove interfering structures

should be equal in depth and permit the location of clasp tips in the gingival third of the tooth

-- Esthetics

-- Changing the path of insertion

Made possible with less clasp metal and less base material displayed

Guiding planes

Health of teeth used as abutment

Place the clasp on the stronger abutment

Guiding planesFlat Axial Surfaces

In an occluso-gingival direction on the proximal or lingual surfaces of teeth.

Parallel To The Path Of Insertion

Help in guiding the prosthesis during insertion and removal

Guiding planes

The functions of guiding planes Guide the prosthesis in or out of place

without exerting excessive forces against the teeth

The frictional contact of the prosthesis against these parallel surfaces, contribute to the retention of the prosthesis Provide bracing and stability when they are located on the axial lingual surface of the tooth

Lowering the Height of Contour

Guide the prosthesis in or out of place without exerting excessive forces against the teeth

Aid in Stabilizing the Prosthesis Against Horizontal Stress

It is a paralleling instrument used to determine the survey

line of teeth, identify and measure tooth undercuts and

to determine the relative parallelism of the surfaces of teeth and other areas on the

cast

THE DENTAL SURVEYOR

Parts of the Dental Surveyor

A- The Base

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 Holder

H- The Surveyor Table

M- Ball Retaining Ring

O- Storage Compartment

N- Tool Rack

Surveying Tools

3- Undercut Gauge

1- Analyzing Rods

4- Wax Trimmer

2- Carbon Marker

Analyzing Rod

ggg

Carbon Marker

XFalse survey line

Moved around the tooth and along the alveolar

ridge

Undercut Gauges

Of an inch

??? of mm.

Undercut Gauges. . 0101. . 0101 . . 0303. . 0303. . 0202. . 0202

Undercut Gauge

Excessive retention areas: Require tooth alteration to lower the height of

contour so we can keep the I-bar retention contact close to the cervical

1/3

Undercut Gauges

Wax Trimmer

Wax Trimmer

OBJECTIVES OF SURVEYING

Permit an Accurate Charting of the Required Mouth Preparations

Determine soft, bony or tooth undercuts and areas of interferences Identify and Measure Tooth UndercutsDelineate Height of Contour

Trimming Blockout Material Parallel to the Path of Placement Recording the Cast Position

Determine the relative parallelism of teeth surfaces that act as guiding planes

Determine the Most Acceptable Path of Placement and Removal

PRINCIPLES OF SURVEYING

1- Interference Features of the mouth which interfere with

easy insertion and removal of a denture

Undercut Alveolar Ridges The labial undercut here is a source of interference

Examples

Mandibular Tori

Severe Lingual Inclination Of Teeth

Recontouring the tooth surface

The prosthesis can goes smoothly into place without interference after analyzing the proximal

tooth surfaces and making the necessary alteration

The location of the undercut area can be changed by changing the tilting

The location of the undercut area can be changed by tilting the cast anteriorly or lateral

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

Cast at zero tilt. Creation of undercut by tilting cast

Without guiding planes, Clasps designed are ineffective when restoration is subject to dislodging

forces in occlusal direction.

Selection of The Path of InsertionThe Most Favorable Path of Insertion (PI) Is That Perpendicular to the Occlusal Plane

Most Patients Tend to Seat Their Dentures Under Biting Force

If Undercuts are Present but Not Efficient at the Zero Tilt

If Displacement of the Prosthesis IsAnticipated With the Least DisplacingForces

Another Path of Insertion Should Be Decided

Selection of the Path of Insertion

Place the Clasp Tips in a Better Esthetic Po.

Create Suitable Undercuts2- Tilting the Cast to

Equalize Undercuts on both Sides of the Arch

Undercut Areas Should Be Present at Both Zero Tilt and the New Tilt

Gross Inclination of the Cast to Create Apparent Undercuts Should Be Avoided

1- A Rotating or Curved Path

PROCEDURES of SURVEYING

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

1- Placement of the Cast2- Altering the Cast Position Anteroposteriorly

To Provide Parallel Proximal Surfaces That May Act As Guiding Planes by

4- Eliminate Areas of Interference by Reshaping Tooth Surfaces

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

* Tripoding or Scoring

After Selection of the Proper Path ofInsertion, the Cast Is Secured in Place

* Drawing of the Survey Line* Location of the clasp terminals

* Blocking the Undesirable Undercuts

Tripoding the Cast Scoring the Cast

Tripoding Or Scoring are Performed While theMaster Cast isStill Mounted on the Survey Table Without Changing the Tilt toPreserve the Established Cast Tilt