Surveying in Prosthetic Dentistry

SURVEYING IN

PROSTHETIC DENTISTRYBY

DR. FAMUREWA B.A.

OAUTHC, ILE-IFE. NIGERIA.

OUTLINE

INTRODUCTIONDEFINITION OF TERMSDENTAL SURVEYOR

HISTORICAL BACKGROUND TYPES COMPONENTS/PARTS USES OF DENTAL SURVEYOR

OBJECTIVES OF SURVEYING IN PROSTHODONTICSPROCEDURE(SURVEYING IN RPD DESIGN)CONCLUSION

INTRODUCTION

• SURVEYING IS INDISPENSABLE IN REMOVABLE PARTIAL DENTURE DESIGN.

• THE TOOL OF TRADE IS DENTAL SURVEYOR• TO MASTER THE PROCEDURE(Surveying) we

must be conversant with various parts and accessories of SURVEYOR.

• Definition of some terms will surely aid our understanding of the subject matter.

DEFINITION OF TERMS

According to Glossary of Prosthodontics Terminologies(2009)- GPT.

Surveying is the procedure of locating or delineating the contour and position of the abutment teeth and associated structures before designing RPD.

It is an analysis & comparison of the prominence intraoral contours associated with the fabrication of RPD.

DEFINITION OF TERMS

• Surveyor is an instrument used in the construction of a RPD to locate & delineate contours & relative position of abutment teeth & associated structures.

• Survey line is a line drawn on a tooth/teeth of a cast by means of a surveyor for the purpose of determining the various parts a clasp/clasps.

DENTAL SURVEYOR

• First introduced in 1918 by Dr. A.J. Fortunati.• However The Ney’s surveyor was the first

commercial ones introduced in 1923 and remains the widely used.

DENTAL SURVEYOR

TYPES

Many types of surveyors exist from a simple type to electronic e.g. Ney, Parabur, Dentagraph, Combi surveyors. More complex instruments that have attachments for milling and drilling metals(casts) are available.

TYPES• The Original Ney Surveyor Developed by NEY

in 1923. It featured a convenient palm rest on the top of the vertical arm. Designed by Weinstein and Roth,

• Ney’s Surveyor This is the currently used surveyor, designed and developed in 1937.

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• Ney Surveyor• Jelenko

Surveyor• Williams Surveyor• The Retentoscope• The Ticonium

surveyor• The Micro-

Analyzer

TYPES OF DENTAL SURVEYOR

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• Ney Surveyor• Jelenko Surveyor• Williams

Surveyor• The Retentoscope• The Ticonium

surveyor• The Micro-

Analyzer

TYPES OF DENTAL SURVEYOR

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• Ney Surveyor• Jelenko Surveyor• Williams Surveyor• The

Retentoscope• The Ticonium

surveyor• The Micro-

Analyzer

TYPES OF DENTAL SURVEYOR

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• Ney Surveyor• Jelenko Surveyor• Williams Surveyor• The Retentoscope• The Ticonium

surveyor• The Micro-

Analyzer

TYPES OF DENTAL SURVEYOR

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• Ney Surveyor• Jelenko Surveyor• Williams Surveyor• The Retentoscope• The Ticonium

surveyor• The Micro-

Analyzer

TYPES OF DENTAL SURVEYOR

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P-W rotary surveyor used to determine a hinge axis

TYPES OF DENTAL SURVEYOR

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•Intraoral surveyor

TYPES OF DENTAL SURVEYOR

Parts of Dental Surveyor

• BASE• VERTICAL ARM• HORIZONTAL ARM• SURVEYING ARM( with MANDREL)• ADJUSTABLE TABLE• ACCESSORIES/SURVEYING TOOLS

Parts of Dental Surveyor

• ACCESSORIES/SURVEYING TOOLS1.ANALYZING ROD2.CARBON(GRAPHITE) MARKER3.UNDERCUT GAUGES4.CHISEL(WAX TRIMMER)5.MILLING DEVICES(with Handpiece holder)

• Analyzing rod. This metal rod is placed against the teeth and the ridge during the initial analysis of the cast to identify undercut areas and areas of parallelism without marking the cast.

Analyzing Rod

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• The graphite marker is moved along the teeth and the alveolar ridge to identify and mark the position of maximum convexity. (SURVEY LINE)

Graphite(Carbon) marker

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A false survey line will be produced if the tip of the marker is incorrectly positioned. Below though no undercut area on the tooth incorrect surveying technique has indicated one. If this false line is used in designing an RPD, errors will arise in the positioning of components, especially clasps.

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Blatterfein Classified survey lines as Under:

1. High survey Line2. Medium Survey Line3. Low Survey line4. Diagonal Survey Line

CLASSIFICATION OF SURVEY LINES:

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found near the occlusal surface of a tooth often parallel to the gingival margin. It results from abnormal inclination of the tooth and is frequently found on the lingual surfaces of the lower teeth and buccal surfaces of the upper teeth.

High Survey Line

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It is situated across the center of the tooth and exhibits a slight occlusogingival incline from the near zone to the far zone.

Medium Survey Line

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It is situated close to and parallel to the gingival margin. It frequently occurs as a result of marked inclination of the tooth and may also occur on conically shaped tooth.

Low Survey Line

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It travels diagonally from near the occlusal surface in the near zone to the gingiva in the far zone.

Diagonal Survey Line

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Ney’S classification of survey lines

Class I: Survey line runs diagonally across the tooth surface. The type of clasp indicated is occlusally approaching cast clasp with terminal third engaging the undercut.

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Class II: Survey line also runs diagonally across the tooth surface but as a mirror image of Class I line. Here a gingivally approaching clasp arm is suggested.

Ney’S classification of survey lines:

Class III: Survey line is parallel to the occlusal surface and lies just below it.

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• They are provided to measure the horizontal undercut and are available in sizes 0.25, 0.5, 0.75.

Undercut gauge.

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

Survey line

Is A Dig Or A Burrow Lie Below The Height Of Contour, Which Is The Most Bulbous And Convex Part Of The Tooth

Line Outlined On the Model By A Surveyor Marking the Greatest Prominence Of Tooth Contour

Undercut

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Non-undercut Area

Undercut

area

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Types of undercuts

Tooth Undercuts (Proximal undercuts)

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

1-Desirable Undercuts : where used for retention

2-Undesirable Undercuts: other not useful undercut

(a) This RPD cannot be inserted in the mouth because failure to eliminate unwanted undercut on the cast has resulted in acrylic resin being processed into the area.

(b) This denture has been processed on a correctly prepared cast and, as a result, there is no interference with insertion.

BA

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Chisel(Wax Trimmer)

Trimming Knife. Wax is added to block the unwanted undercut and the wax trimmer is used to remove the excess wax.

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USES OF DENTAL SURVEYOR

SURVEYING DIAGNOSTIC & 1° CASTCONTOURING WAX PATTERNSSURVEYING CERAMIC VENEER CROWNSPLACEMENT OF INTRACORONAL

RETAINERS/INTERNAL ATTACHMENTSPLACEMENT OF INTERNAL REST SEATSMACHINING CAST RESTORATIONSSURVEYING MASTER CASTS

Objectives of Surveying

1. Locate proximal tooth surfaces that are or can be made parallel to act as guiding surfaces.

2. Locate and measure recesses or undercuts for mechanical retention.

3. Identify areas of potential hard or soft tissue interferences.

4. Determine a path of insertion/ dislodgement consistent with aesthetic requirements.

5. Determine the most advantageous path of insertion/ removal for the RPD.

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6. Delineate the height of contour of the abutment teeth and identify the areas of undercut

that must be avoided, reduced, blocked out or preserved.

7. Help in planning restorative procedures .8. Record the most ideal cast position for future reference. 9. Establish a formal plan for RPD design and

the required mouth preparation.

Objectives of Surveying

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Path of insertion

• Is 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

• This path coincides with the path of withdrawal and may or may not coincide with the path of displacement.

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Paths of insertion

• Single path of insertion• Multiple paths of insertion.• Rotational paths of insertion

Factors Affecting path of insertion

• Retentive undercuts • Interferences• Esthetics Guide planes

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Guide planes

Two or more parallel axial surfaces on abutment teeth which can be used to limit the path of insertion and improve the stability of a removable prosthesis. Guide surfaces may occur naturally on teeth but more commonly need to be prepared.

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A single path of insertion may be created if sufficient guide surfaces are contacted by the denture; it is most likely to exist when bounded edentulous areas are present.

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Multiple paths of insertion will exist where guide surfaces are not utilized, for example where the abutment teeth are divergent.

Two distinct paths of insertion will be employed for a sectional, or two-part denture.

Occasionally a rotational path of insertion can be used.

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The direction of movement of the restoration/prosthesis from its resting position to the last contact with the supporting teeth".

Path of Removal: Reverse of the Path of Insertion

This is the direction in which the denture tends to be displaced in function. The path is variable but is assumed for the purpose of design to be at right angles to the occlusal plane.

Path of displacement

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Path of Displacement

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Philosophy of Design :

• The philosophies are based on three approaches to force distribution

1. Stress equalization 2. Physiologic basing 3. Broad stress distribution

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Selection of the Path of Insertion

Place the Clasp Tips in a Better Esthetic Position.

Create Suitable Undercuts

2- 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

PROCEDURE/Surveying in RPD Design

• THIS HAS 4 DISTINCT PHASES:– 1.Preliminary visual assessment of the

cast/Eyeballing– 2.Initial survey– 3.Analysis– 4.Final survey

Preliminary visual assessment• The cast is placed on the palm and inspected

from above.• Check for the general form and arrangement

of the teeth.• This is eyeballing.

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Initial Survey.• The cast is positioned on the table horizontally

and the teeth and ridge surveyed to identify the undercut area which might be utilized for retention.

• The initial survey is done with a graphite marker.

• The amount of undercut can be judged by the Triangle of light between the graphite marker and the cervical portion of the tooth

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Initial Survey

Analysis.• A RPD can be designed so that the path of

insertion=path of removal when surveyed with occlusal plane horizontal.

• However the table can be given a tilt if the part of insertion is to be different from path of displacement

• The graphite marker is changed for analyzing rod for analysis so that various position of the teeth can be analyzed without marking the teeth.

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• The following factors must be looked at during analysis.

• The appearance.• Interference• Retention.

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This unsightly gap can be avoided by giving the cast a posterior (heelsdown) tilt so that the analysing rod is parallel with the mesiolabialsurface of the abutment tooth.

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Interference

if a bony undercut is present labially, insertion of a flanged denture along a path at right angles to the occlusal plane will only be possible if the flange stands away from the mucosa or is finished short of the undercut area. This can result in poor retention as well as a poor appearance. If the cast is given a posterior tilt so that the rod, and thus the path of insertion, is parallel to the labial surface of the ridge it is possible to insert a flange that fits the ridge accurately.

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Retention

To obtain retention, undercuts must be present on teeth relative to the horizontal survey. It is a misconception to believe that changing the tilt of the cast will produce retentive undercuts if none exist when the cast is horizontal.a) No undercuts on the tooth when the occlusal plane (OP) is horizontal.b) An apparent undercut created by tilting the cast laterally.c) Clasp arms placed in this false undercut do not provide any resistance to movement along the path of displacement. 55

• The principle of tilting the cast to enhance retention is that by so altering the path of insertion

• A rigid part of the denture can enter an area of the tooth surface or an area of the ridge which is undercut relative to the path of displacement

In this example, providing retention by engaging the distal undercut (*) of the canine may well look more pleasing than a clasp arm on the same tooth

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

Principles of Surveying

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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.

B

D

Principles of Surveying

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

Principles of Surveying

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Final Analysis

The graphite marker is exchanged with another marker and the table is tilted to either hill up or hill down position.

The cast is then surveyed.

If it is decided that the cast should be tilted, the analysing rod isexchanged for a marker different in colour from that used in the first survey, and the final survey is carried out. It will then usually be found that the teeth to be clasped have two separate survey lines which cross each other. In order to obtain optimum retention it is necessary to understand how to position the clasps correctly in relation to the two survey lines

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When guide surfaces are used to provide resistance to displacement of the denture in an occlusal direction, the retentive portion of the clasp needs only to resist movement along the path of withdrawal and therefore can be positioned solely with reference to the redsurvey line.

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If the survey lines converge mesially or distally, the tip of an occlusally approaching clasp can engage the common area of undercut to provide resistance to movement along both paths.

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It does not matter if, as in this example, the clasp engages too deep an undercut relative to the path of displacement. Movement of the denture in an occlusal direction is prevented by contact with theguide surface, therefore permanent deformation of the clasp will not occur.

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A gingivally approaching clasp positioned at the cross-over point of the survey lines resists movement along both the path of withdrawal and the path of displacement without being permanently deformed by movement along either path.

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Final Analysis

• If the cast has been tilted for the final survey, the degree of tilt

• must be recorded so that the position of the cast can be reproduced

• in the laboratory. There are two methods of recording the degree of tilt.

• This is TRIPODING the Cast

• Using the tripod method, the vertical arm of the surveyor is locked at a height that allows the tip of the marker to contact the palatal surface of the ridge in the molar and incisal regions.

• Three points are marked with the graphite marker, one on each side posteriorly and one anteriorly.

• The points will then be ringed with a pencil

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Final Analysis; Tripoding the cast

Tripoding Or Scoring are Performed While the Master Cast is Still Mounted on the Survey Table Without Changing the Tilt to Preserve the Established Cast Tilt

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• Alternatively, the analysing rod is placed against one side of the base of the cast and a line drawn on the cast parallel to the rod.

• This is repeated on the other side and at the back of the cast so that there are three widely spaced lines parallel to the path of insertion

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CONCLUSION

• Dental surveying is imperative in RPD design to obtain information for informed decisions to be made concerning:

• 1. Optimum path of insertion and removal of RPD.

• 2.Choice of clasp design

• 3.Materials for clasp design

REFERENCES

• TEXTBOOK OF PROSTHODONTICS by D.N. VEEREIYAN et al

• REMOVABLE PARTIAL DENTURE DESIGN by A.J. KROL et al

• A CLINICAL GUIDE TO REMOVABLE PARTIAL DENTURE by J.C. DAVENPORT et al

• UPDATE LECTURES IN PROSTHODONTICS by O.O. DOSUMU and O.T. ESAN

Surveying in Prosthetic Dentistry

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