surveyors & surveying procedures in removable partial prosthodontics

Surveyors & Surveying Procedures-67 1


SURVEYORS&

SURVEYING PROCEDURESPresented by:Dr.Kanika Manral


• Introduction• Historical Perspective• Definitions• Objectives of Surveying• Parts of a Surveyor• Surveying Tools• Survey Lines• Purposes of Surveyors• Summary & Conclusion• References

CONTENTS


INTRODUCTION• Success in the practice of Removable

Partial Dentures(RPD) – knowledgeable & guided planning of each structural detail of the prosthesis.

• Until the early 1900s most RPDs were designed by “eye balling”-a prosthesis made on the basis of educated guesses.

• The turning point-introduction of dental surveyors in 1918.


HISTORICAL PERSPECTIVE

• 1860 – Dr.J.Richardson • 1890 – Dr.W.M. Randall’s Technique• 1905 – Dr.Herman E.S. Chayes’

Parallelometer• 1918 - Dr.A.J.Fortunati - Bridge

Parallelometer• 1920 - Robinson surveyor by

Philadelphia Dental Clinic Club

• 1923 – The Original Ney Surveyor by Weinstein & Roth


• 1937 – Ney Surveyor-the Current Model

• 1929 – The Original Wills Surveyor by Noble G Wills

• 1937 – Wills Surveyor-the Current Model

• 1942 – Kings’ College Surveyor• 1944 – The Roach Surveyor


>The Electrome >The Retentoscope >The Stressograph

>Broken-arm > Pendulum Surveyor >Optical Surveyor


MICROSURVEYOR• Hand held surveyor• Establishes path of insertion by

tilting vertical arm hinged at the base/platform

• Collapsible into individual parts for easy storage


WHAT’S NEW?? - THREE DIMENSIONAL COMPUTER

AIDED SURVEYING

J Prosthet Dent 2004;92(3):408-412


• Programs were written for this technique using mathematic software (MatLab:The Math Works, Inc, Natick, Mass)

• The program identified all downward facing surface triangles on scan as –ve & upward facing as +ve, the junction being the survey line.


• Tilting the cast allows for accurate re-record of the new survey line.

• 20˚ tilt• This can then be

reproduced onto the digitally scanned tooth structure.


DEFINITIONS• SURVEY-”The procedure of locating or

delineating the contour and position of the abutment teeth and associated structures before designing a partial denture.”-GPT 8

• SURVEYING-”An analysis and comparison of the prominence of intraoral contours associated with the fabrication of a prosthesis”-GPT

• SURVEYOR-”An instrument used in the construction of a removable partial denture to locate and delineate the contours and relative positions of abutment teeth and associated structures.”-GPT 8


• SURVEY LINE-”A line drawn on a tooth or teeth of a cast by means of a surveyor for the purpose of determining the positions of the various parts of a retainer”-GPT 8

• GUIDING PLANE-”Two or more vertically parallel surfaces of abutment teeth so oriented as to direct the path of placement/removal of a removable partial denture”-GPT 8

• PATH OF INSERTION-”The direction in which a prosthesis is placed upon and removed from the abutment teeth”-GPT 8

• HEIGHT OF CONTOUR-”A line encircling a tooth designating its greatest circumference at a selected position”-GPT 8


OBJECTIVES OF SURVEYING

• To reveal favourable and unfavourable physical characteristics of the mouth that favour successful prosthesis design.

• To determine a guided path of insertion free of interferences

• To determine a design that resists unseating forces reasonably.

• To delineate unfavourable undercuts for mouth preparation.


PATH OF

INSERTION

RETENTIVE UNDERCUT

S

INTERFERENCES ESTHETICS

GUIDING PLANES

DESIGN OF THE

PROSTHESIS


PARTS OF A SURVEYOR

PLATFORM

CAST HOLDER/ SURVEYING TABLE

VERTICAL ARM

HORIZONTAL ARMMAND

REL

SURVEYING ARM


COMPARISONNEY’S

SURVEYORJELENKO’S SURVEYOR

WILLIAM’S SURVEYOR

Horizontal arm is fixed

Revolves around vertical arm

Revolves around vertical arm with a hinging joint

Surveying arm is passive

Spring loaded Spring loaded

Surveying arm secured with locking device

Spring tension holds position

Spring tension holds position

Undercut gauge-circular,beaded

Fan shaped bead, each wing differing in dimensions

Fan shaped bead, each wing differing in dimensions


SURVEYING TOOLS•Analysing Rod

•Carbon Marker

•Undercut Gauge

•Wax Trimmer


ANALYSING ROD• Used for preliminary survey of the

cast.• Assessment of degree of undercuts

on hard & soft tissues.• Assessment of angulation of teeth.• In distal extension cases, allows

judgement of whether the distal abutment undercuts are sufficient to indicate that a tilt may be beneficial.


CARBON MARKER• Basically allows visualisation of the

analysing rod’s work.• Used for drawing survey lines around

all teeth involved in clasp design or that have proximal undercuts to be eliminated

• To mark the extent of bony/soft tissue undercuts for prosthetic mouth preparation if required.

• Light pressure without erosion.


UNDERCUT GAUGE• Used to measure the location and

horizontal depth of undercuts on the analysed and marked teeth in three dimensions

• Stewart-0.01”, 0.015”. 0.02”• McCracken-0.01”, 0.02’, 0.03”• Same shank, only the size of the

tip/bead varies(except Neys).


WAX TRIMMER• Used to trim off excessive wax while

surveyin the wax patterns.• To prevent overcontoured blockout of

unfavourable undercuts.• To demarcate the exact planned

clasp arm location to be duplicated.• To create a gap/self cleansing area

using a 25. trimmer.


SURVEY LINES• Survey lines primarily stand for the

height of contour of abutment teeth marked by a carbon marker during surveying in a particular horizontal plane.

• 1916-Prothero’s Cone Theory• 1955-DeVan-Suprabulge & Infrabulge


• Classified as:HighMediumLowDiagonal

Based on Louis Blatterfein’s division of abutment teeth into NEAR ZONE(NZ) & FAR ZONE(FZ)

J Prosthet Dent 1956;6(3):386-404


• HIGH SURVEY LINE: From occlusal 1/3rd in NZ to occlusal 1/3rd in FZ

• MEDIUM SURVEY LINE: From occlusal 1/3rd in NZ to middle 1/3rd in FZ.

• LOW SURVEY LINE: From cervical 1/3rd in NZ to cervical 1/3rd in FZ

• DIAGONAL SURVEY LINE: From occlusal 1/3rd in NZ to gingival 1/3rd in FZ


Angle of Cervical Convergence

J Dent 2007;4(1): 15-20


PURPOSES OF A SURVEYOR

• Surveying of diagnostic cast• Tripoding of cast• Surveying the master cast• Contouring of wax patterns• Placement of Internal Rest Seats• Machining of cast restorations


SURVEYING OF DIAGNOSTIC CAST

• To determine the most desirable path of placement.

• To identify proximal tooth surfaces that need to be made parallel as that they act as guiding planes during placement and removal.

• To locate and measure areas of teeth that may be used for retention.


• To determine whether tooth and bony areas of interference will need to be eliminated surgically(mouth preparation) or those that need to be blocked out.

• To identify the height of contour

• To record the cast position in relation to the selected path of placement for future references


STEPS BY STEP PROCEDURES IN

SURVEYING A DIAGNOSTIC CAST• Orientation of cast

• Cast tilting• Visual analysis using analysing rod• Marking of survey lines /soft tissue undercuts

using carbon markers• Undercut gauges used to measure amount of

available retention• Interferences• Wax Trimmers• Tripoding of casts


Orientation of Cast• Casts oriented such that the anterior

part is always toward the vertical member of surveyor and away from the operator

• Position for description is fixed for either cast.

• Can be attached to the holding table via:o Soft plasticine or waxo Locking screws engaging the sides of

modeloMagnetised iron cast into base of model


Cast Tilting• Tilting is changing the position of the cast, which

thus changes the long axis of each tooth relative to the horizontal plane.

• Alters the contour, positions, location & depth of undercut relative to the new plane.

• Allows:– The most advantageous path of insertion– Increase in desirable and decrease in undesirable

undercuts– Distribution of available undercuts to produce more

uniform retention throughout the available teeth & tissues– Establishes parallelism & improvises upon esthetics.


• Dislodging forces primarily to occlusal plane.

• Hence, HORIZONTAL or 0. TILT most common(Not>10˚).

• Other tilts:oAnterioro Posterioro Lateral


Visual Analysis using Analysing Rod

• Primarily responsible for “eyeballing” of the cast.

• Once orientation & tilt is established, allows for a general tangential analysis of undercuts, tooth angulations, etc.

• Also aids the establishment of relative parallelism of various planar surfaces.


Marking of Survey Lines /Soft tissue Undercuts using Carbon

Markers• Analysis by the analysing rod is

visualised via the carbon marker.• 5H pencil graphites secured with

metal reinforcement sheath


Undercut Gauges used to measure amount of Available

Retention• These gauges are used to identify the specific amount and location of desired retentive undercut on the surface of the abutment tooth.

• Two types:– Ney– Jelenko

• The undercut is best viewed against light passing through a triangle bounded by surfaces of abutment tooth, surveyor blade ,apex being the point of contact at the height of convexity and base of triangle being the gingival tissues.


• Undercut utilisationo 0.01 → cast retainerso 0.02 → wrought wire retentiono 0.03 → rarely used

• If no retentive undercuts are present, they must be created by:o Gold Crownso Retentive Restorationso Creating an undercut by tooth modification


Interferences• Seen in both maxilla & mandible• Maxilla:

o Torus Palatinus-surgical removal advised, tilting does not provide relief

oBuccally Tipped Teeth-Tilting+Recontouring• Mandible:

o Torus Mandibulariso Lingually Tipped Teeth

Labial Bar


Wax Trimmers• Once unfavorable undercuts are

blocked, to prevent overcontouring, wax trimmers are used.

• In case of distal extension cases, to create a gap/self cleansing area under the saddle, a 25. trimmer is used in conjunction.

• Wax patterns for casting can also be carved accordingly.


Tripoding of Casts• Once all this is done,

the final cast position must be recorded so that the cast may later be repositioned precisely. This procedure is referred to as TRIPODING.

• Seven primary methods. J Prosthet Dent

1976;35(4):267-269


• METHOD 1– Three cross marks (each line

3mm wide) / dots on the tissue portion of the cast, lingual to the teeth, at widely apart points with vertical arm of the surveyor maintained at fixed position

– Marks encircled with coloured pencil for easy identification.

– Marker tip to be trimmed at 45.

– Not to include areas involved in framework design.


• METHOD 2– Scour 2 sides and the

dorsal aspect of the base of the cast with a sharp instrument/ marking pencil held against the surveyor blade.

– Marks don’t interfere with the design

– Easy duplication– May get smudged

upon handling


• METHOD 3– A hole about 10 mm in diameter

and 10 mm deep is prepared in the lingual land area of the mandibular cast with a large acrylic finishing bur.

– The pin is locked in the vertical spindle and lowered to the bottom of the hole.

– The vertical spindle with the pin is then locked in this position and the hole is filled with dental plaster.

– Once the plaster is set, vertical spindle is released from cemented pin.


• METHOD 4– An instrument

reproduces the tilt of a cast on a surveyor using protractor

– Flat metal strip 5mm wide and 3cm long, one end of which bend upward at 90˚

– Metal rod is attached to the end of the flat part of the strip which serves to fit the instrument to the surveyor J Prosthet Dent 1965;34(3)465-471


• A hole is tapped and threaded in the middle of the bent part of metal strip through which a protractor is screwed

• The protractor can rotate around the metal rod, acting as a pointer.

• After determining the path of insertion, the protractor instrument is mounted on the surveyor in place of analyzing rod

• 3 divergent points are marked, with readings recorded at each tilt


• METHOD 5– Make a hole in the

tongue space on mandibular cast 4-6mm in diameter

– Hole should create undercut but should not perforate the base of the cast

– Following normal surveying procedures, a parallel shanked straight handpiece bur is suspended. J Prosthet Dent 1981;41(3):352-354


• With the bur in place, fill the hole with autopolymerizing acrylic resin

• For reorientation, reposition the bur in autopolymerizing resin for a parallel tripod record.


• METHOD 6– Wax deposited on

side of cast at 3 widely separated points

– Analyzing rod used to create imprints of wax

– This can be transferred by duplicationJ Prosthet Dent 1991;61(5):378-380


• METHOD 7– Make a universal tray

on a cast after adapting 2 thickness of baseplate wax over the teeth.

– Make a platform with a cylinder over the tray and insert analyzing rod into cylinder.

– Move the tray to and fro vertically during setting of the material to make a smooth vertical perforation in cylinder. J Prosthet Dent 1997;72(1):104-107


• Tray loaded with elastic impression material, the cylinder is attached to the rod and locked

• After establishing tilt, an impression is made

• Reorientation can later be done by placing the impression on cast and the tilt at which the stylus can enter the cylinder locks the prior position


Surveying the Master Cast• Surveyed as a new cast• Prepared proximal guiding plane surfaces

will indicate the correct anteroposterior tilt• Any remaining interferences after mouth

preparation must be eliminated with block out.

• Survey lines marked


Surveying in Confined Areas

J Prosthet Dent 1991;61(5):378-380


• Orthodontic wire can be used as a horizontal "feeler gauge“ in combination with the vertical analyzing wire to estimate the adequacy of the retentive undercut.

• Dimensions of the wire allow for finer measurements.


Contouring of Wax Patterns•Surveyor blade – used as wax carver•Proposed path of placement maintained throughout preparation of cast restorations for abutment teeth.•Surfaces of restorations that provide reciprocation for clasp arms have to be contoured to permit their location well below occlusal surfaces and on non retentive areas


BLOCK OUT• After the establishment of path of insertion and

the location of undercut areas on the master cast, the areas that shall be crossed by the rigid parts of the denture must be blocked out.

• Roach carver or No.7 spatula used to adapt the blocking wax.

• Four types:o Parallel Blockouto Shaped Blockout/Ledge Blockouto Arbitrary Blockouto Relief


• Parallel Blockout:– Performed:

oOn interproximal surfaces to be used as guiding planes(0/2/6˚ taper)

oBeneath all minor connectorsoOn tissue undercuts to be crossed by rigid

connectorsoBeneath bar clasp arms to gingival crevices

–Materials Used:oHard baseplate waxoHard inlay waxoOil based modelling clay

– Thickness-Only undercut remaining gingival to contact of surveyor blade with tooth surface


• Shaped/Ledge Blockout:– Performed:

oOn buccal & lingual surfaces to locate plastic or wax patterns for clasp arms

–Material:oHard Baseplate Wax

– Thickness: Ledges for location of reciprocal clasp arms to follow height or convexity so that they may be placed as cervical as possible without becoming retentive


• Arbitrary Blockout:– Performed:

oOn all gingival crevicesoOn gross tissue undercuts below areas involved in

framework designoOn tissue undercuts distal to cast framework oLabial & buccal tooth undercuts not involved in

denture design–Material:

oOil Based Modelling ClayoHard Baseplate Wax

– Thickness:Enough to just eliminate gingival crevice, levelled arbitrarily with a wax spatula


• Relief– Provided:

oBeneath lingual bar connectors or the bar portion of linguoplates

oOn areas in which the major connector will contact thin tissue

oBeneath framework extensions onto ridge areas for attachment of resin bases

–Material:oAdhesive waxoHard Baseplate Wax

– Thickness:o32 gauge wax(universally)o20 gauge wax for resin base attachment relief


Placement of Internal Rest Seats• Large box shaped metallic extensions

that function as intracoronal extensions.

• Carved in wax patterns and refined further with hand piece after casting.


Machining of Cast Restorations• Rotary instruments can be attached

to the surveyor via a handpiece holder for trimming/machining of restorations.

• Surveying arm can then be rotated around the restoration to trim excess crown material.


SUMMARY & CONCLUSIONTreatment planning of a removable

partial denture with the use of a dental surveyor helps in the analysis & planning of the denture design and accomplishment of tooth modifications (preparation) and delineates proper clasp placement that is critical for optimum stability and retention and are strongly necessary for successful favourable fabrication of the prosthesis.


REFERENCES• Brown DT, Carr AB. McCracken’s Removable Partial

Prosthodontics. 12th ed. St.Louis: Mosby; 2011• Lammie GA, Osborne J. Partial Dentures. 4th ed.

Michigan: Blackwell; 2009• Miller EL. Removable Partial Prosthodontics. 6th ed.

Baltimore: Wilkins; 2006• Cagna DR, DeFreest CF, Phoenix RD. Stewarts

Clinical Removable Partial Prosthodontics. 4th ed. Toronto:Quintessence;2008

• Engelmeier RL. The History and Development of the Dental Surveyor: Part I. J Prosthodont 2002;11(1):11-18


• Engelmeier RL. The History and Development of the Dental Surveyor: Part II. J Prosthodont 2002;11(1):122-130

• Engelmeier RL. The History and Development of the Dental Surveyor: Part I. J Prosthodont 2004; 13(1): 195-202

• Jerome R. Tabbot MK. Three dimensional computer aided surveying. J Prosthet Dent 2004;92(3):408-412

• Matthews CL, Philip R. Survey lines in removable partial denture design. J Prosthet Dent 1956;6(3):386-404

• Eghlim L, Geramy A. The Influence of Angle of Convergence. J Dent 2007; 4(1): 15-20

• Jerard P, Simmons RS. Transfer of survey record to multiple casts. J Prosthet Dent 1976;35(4):267-269


• Prentiss AL, Vockhardt M. Technique for maintaining cast relation to surveyor for reproduction of record. J Prosthet Dent 1965;34(3):465-471

• Jacob BS. Acrylic Bead Method for reorientation of Master Casts. J Prosthet Dent 1981;41(3):352-354

• Arthur JM. Reinstating techniques for tripoding. J Prosthet Dent 1991;61(5):378-380

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