surveying part 2 - cden.tu.edu.iq · The surveying process is composed of several phases. Each...

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DR. LUMA NASSRAT

ASSISSTANT LECTURER, DEPARTMENT OF

PROSTHODONTICS

COLLEGE OF DENTISTRY

TIKRIT UNIVERSITY

Surveying Tools:

ANALYSING ROD:

▪ Used for preliminary survey of the cast.

▪ Assessment of degree of undercuts on hard & soft tissues.

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RPD LEC.5 | PROSTHODONTICS | 12-11-2018

Surveying Part 23RD GRADE

LEC. 5

▪ 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 visualization of the analyzing 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 GAUGES:

▪ Used to measure the location and horizontal depth of

undercuts on the analyzed and marked teeth in three

dimensions.

Stewert – o.o1”,0.015”,0.02”

McCracken-0.01”,0.02”,0.03”

▪ Same shank, only the size of the tip/bead varies.

PG. ! 1TIKRIT UNIVERSITY COLLEGE OF DENTISTRY http://cden.tu.edu.iq

http://cden.tu.edu.iq

WAX TRIMMERS:

▪ Used to trim off excessive wax while surveying the wax

patterns.

▪ To prevent overcontoured blockout of unfavorable undercuts.

▪ To demarcate the exact planned clasp arm location to be

duplicated.

Survey Process:

The surveying process is composed of several phases. Each

phase is important in successful removable partial denture therapy.

The phases are:

Identifying the most favorable tilt

• The cast is affixed to the surveying table. The ball and- socket

design of the table permits the practitioner to change the tilt of

the cast to the favorable tilt. (The tilt of the cast is described

from the viewpoint of a person looking at its posterior surface).

• If the anterior of the cast is lowered anterior tilt.

• If the posterior is lowered posterior tilt.

• If the right side is lowered right tilt.

• And if the left side is lowered left tilt

• Extreme tilts should be avoided.



There are four critical factors that must be considered when

determining the most favorable tilt of a dental cast. These factors are

in order of importance:

(1) the presence of suitable undercuts.

(2) the elimination of hard and soft tissue interferences

(3) the creation of desirable esthetics.

(4) the establishment of appropriate guiding planes.

Retentive Undercuts:• The retentive undercuts must be present on the abutment teeth

when the cast displays a horizontal tilt. This is essential because

dislodging forces are always directed perpendicular to the

occlusal plane.

!• Each abutment is examined for retentive undercuts using

analyzing rod.

• If retentive undercuts are not present, they must be created in

the mouth. Either by recontouring enamel surfaces, or by

placing fixed restorations in extensive cases. These restorations



must be carefully planned and completed prior to RPD

fabrication.

• Ideally, undercuts may be at the mesiobuccal line angle, the

distobuccal line angle, or the midfacial surface.

• In all cases, the undercut should be in the apical third of the

clinical crown.

• When the existence of retentive undercuts has been verified, the

tilt may be changed to optimize the undercut on any tooth.

• Changing the tilt to alter the position of the undercut on one

tooth will affect the positions of the undercuts on the remaining

teeth. The tilt is normally changed so that a retentive clasp will

be positioned no farther occlusally or incisally than the junction

of the gingival and middle thirds of the tooth. This produces a

more esthetic result and may decrease the torqueing forces

transmitted to the abutment.

!


Retentive Arm

Reciprocal Arm


Interferences:• Certain structures within the oral cavity may interfere with the

insertion of a removable partial denture. These structures may

include teeth, bony prominences, soft tissue undercuts, and

exostoses.

• In some instances, difficulties may be avoided by changing the

tilt of the cast on the surveying table. In other instances,

surgical intervention may be necessary to correct undesirable

contours.

• Interferences in the maxillary arch.

o Palatal Torus: Changing the tilt of the cast on the

surveying table will not solve the problem. The design of

the major connector may be altered to accommodate the

torus. If this is not possible, surgical removal of the torus

should be accomplished.

o Exostoses and undercuts are common on the buccal

surfaces of the maxillary arch Buccal exostoses and

undercuts prevent intimate contact between the removable

partial denture and the patient’s soft tissues. Surgical

correction is simple and should be accomplished to

provide an improved restorative prognosis.

o Facial tipping of posterior teeth may cause significant

difficulties. As a maxillary posterior tooth tips facially, the PG. ! 5

TIKRIT UNIVERSITY COLLEGE OF DENTISTRY http://cden.tu.edu.iq


height of contour moves toward the occlusal surface. This

makes positioning the buccal clasp arm more difficult for

esthetic and mechanical reasons.

o Undercut in the edentulous maxillary anterior ridge

• Interferences in the mandibular arch.

o Mandibular Tori: Such tori are difficult to avoid because

of the anatomy of the mandibular arch. If the delicate

tissues overlying mandibular tori must be crossed, space

must be created between these tissues and the inner

surfaces of the major connector. Surgery is a common

consideration in this case.

o Lingual tipping of mandibular posterior teeth.

o Bony prominences are often encountered at the facial

surfaces of mandibular canines and premolars.

o Soft tissue undercuts.

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Esthetics:



To obtain optimum esthetics in removable partial denture therapy:

(1) Metal components must be concealed as possible: By

choosing the appropriate tilt, they can be disguised while

maintaining the health of the associated soft tissues.

(2) Prosthetic teeth must be selected, contoured, and properly

positioned: Due to tooth migration, prosthetic teeth will have

to display smaller mesiodistal dimensions to fit into the

reduced amount of space. This may result in:

a) Esthetic compromise, particularly in anterior regions.

b) Undesirable undercuts will form.

Management could be by:

o Recontouring the proximal surfaces of teeth.

o If recontouring is not possible, then crowns or other

suitable restorations should be planned.

The surveyor is a necessity here in:

✓Determining the amount of recontouring needed to reduce undesirable undercuts.

✓Determining the final tilt of the cast should consider this problem.

Guiding Planes:

Are parallel surfaces of abutment teeth that direct the insertion

and removal of a partial denture.



Guiding planes are formed from the proximal tooth surfaces of

the teeth and are contacted by the minor connectors or other

rigid components of the partial denture.

The guiding planes are in intimate contact with the minor

connectors, help to stabilize against the lateral forces. They also

help protect weakened teeth from potentially destructive lateral

forces.

Path of Insertion

❖The tilt of a cast determines the direction that the partial denture will take during placement and removal. The resultant

pathway is termed the path of insertion.

❖ For practical purposes, the path of insertion and removal will always be parallel to the vertical arm of the surveyor.

❖Most removable partial dentures have two or more paths of insertion.

❖Tooth bounded edentulous spaces determines whether a prosthesis will have one or more paths of insertion.

❖ In unmodified Kennedy Class I & II arches, a prosthesis may enter or exit its intended position at a variety of angles.

❖ In Kennedy Class II arch with a tooth-bounded modification space on the opposite side of the arch, the modification space



will determine the path of insertion. If guiding planes have

been prepared on the proximal surfaces of abutments on the

tooth-bounded side, the prosthesis will display a single path of

insertion.

❖ In Kennedy Class III & IV arches, the existing edentulous spaces are entirely tooth bounded. So, the associated prosthesis

will usually exhibit a single path of insertion.

!

Placing Survey Lines▪ Proper placement of survey lines is essential to the design

process and must be accomplished with great care.

▪ To place survey lines, a carbon marker is positioned in the

surveyor’s mandrel, and the mandrel is tightened. The vertical

arm of the surveyor is unlocked to ensure free movement.

▪ Survey lines are transferred to the teeth by maintaining light

contact between the carbon marker and the cast. Survey lines

are transferred to soft tissue areas in a similar manner.



▪ This process is continued until the required survey lines have

been clearly marked on facial and lingual surfaces of the cast.

Locating and Marking Measured Undercuts

▪ Mechanical undercuts must be accurately located and

appropriately marked to permit correct placement of retentive

clasps.

▪ The depth and position of the desired undercut will vary with

the material and clasping system to be used. This will allow the

practitioner to choose the appropriate undercut gauge and

identify the position of the required undercut.

▪ Upon selection of the appropriate undercut gauge, the gauge is

inserted into the mandrel and locked into place. The surveying

table is then positioned so that the selected abutment tooth

contacts the shank of the undercut gauge.

▪ The vertical arm of the surveyor is raised until the head of the

undercut gauge lightly contacts the infrabulge area of the tooth.

▪ The point of contact should appear as a very light “scrape” on

the surface of the cast. The apical border of this contact should

be clearly marked using a red pencil and should appear as a

thin, horizontal line approximately 2 mm in length.

TRIPODING:



✓Once tilt has been selected for given RPD design, this tilt should be preserved, so that it can be re-established accurately to the

surveying table.

✓This procedure is termed as “TRIPODING". This helps in returning the cast to the surveyor for future reference.

METHODS FOR TRIPODING A CAST

METHOD 1: By placing widely spaced dots on the tissue surface of

the cast using the tip of the carbon marker, with the vertical arm of

the surveyor in a locked position.

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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 PG. ! 11

TIKRIT UNIVERSITY COLLEGE OF DENTISTRY http://cden.tu.edu.iq


May get smudged upon handling.

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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.



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Step by Step Procedures in Surveying a Diagnostic Cast:

Orientation of cast.

Cast tilting.

Visual analysis using analyzing 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.

For further references:

Stewart's Clinical Removable Prosthodontics, Chapter 7


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