Surveyors and surveying/ dentistry dental implants

SURVEYORSURVEYOR
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SURVEYINGSURVEYING
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
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DENTAL SURVEYOR:
It has been defined as 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.

Dr. A.J. Fortunati is thought to be the first person
to employ a mechanical device to determine the
relative parallelism of tooth surfaces. The first
such device to be produced commercially, the Ney
instrument, remains the most widely used
surveyor in the dental field. The Wills surveyor by
Jelenko is second most widely used.

The aims and objectives of surveying are as
follows:
• To determine the most advantageous path of
insertion/ removal for the RPD.
• To locate proximal tooth surfaces that are or can
be made parallel to act as guiding surfaces.

•To locate and measure recesses or undercuts for
mechanical retention.
•To identify areas of potential hard or soft tissue
interferences.
•To determine a path of insertion/ dislodgement
consistent with esthetic requirements.

•To delineate the height of contour of the abutment
teeth and identify the areas of undercut that must
be avoided, reduced, blocked out or preserved.
•To help in planning restorative procedures .

•To record the most ideal cast position for future
reference.
•To establish a formal plan for RPD design and the
required mouth preparation.

The parts of dental surveyor are :
• A level platform that is parallel to the bench top
and on which the cast holder is moved.
• A vertical arm that supports the superstructure.
• A horizontal arm that extends at a right angle
form the vertical column from which extends the
other part of the superstructure, the surveying
arm.. www.indiandentalacademy.comwww.indiandentalacademy.com

In the Ney surveyor the horizontal arm is fixed,
whereas in the Wills instrument it may revolve
horizontally around the vertical column.
• A surveying arm drops vertically from the
horizontal arm. The surveying arm is capable of
movement in a vertical direction. In the Wills
surveyor the surveying arm is spring loaded

• A cast holder, or surveying table, to which the
cast to be studied is attached. The table equipped
with a clamp to lock the cast in place, is mounted
on the ball and socket joint that permits the cast
to be oriented in various horizontal places so that
the axial surfaces of the teeth as well as other
areas of the cast can be analyzed in relation to the
vertical plane.

• An analyzing rod or paralleling tool. This tool
contacts the convex surface of the object being
studied in the same way a tangent contacts a
curve. In this way, the parallelism of one surface
to another may be determined.

• Additional tools that may be attached to vertical
surveying arm and used in conjunction with the
surveyor
a) Undercut gauges: These gauges are used to
identify the specific amount and location of
desired retentive undercut on the surface of the
abutment tooth.

b) Wax knife: This instrument is used in late
stages of removable partial denture construction
to eliminate or block out areas of undesirable
undercuts with wax on the cast before the
framework is made.
c) Carbon marker: The marker may be used to
scribe the survey line and to delineate an
undercut area of the soft tissue or ridge

Diagnostic survey :
The diagnostic cast must be surveyed before the
treatment plan for the patient can be formulated.
Soft tissue contours must also be studied to
determine what effect they may have on the partial
denture that is being planned. Undercuts in the
soft tissue areas may require surgical removal
before the prosthesis will go to place in the mouth.

The position of the cast being studied can be
changed on the surveying table to allow the
designer to analyze what effect this changing the
tilt will play on the relative parallelism of the
structures.

The surveyor is also used to scribe the survey line
on the teeth after the final tilt of the cast has been
determined. The significance of the survey line is
that all rigid components of the partial denture
must be kept occlusal to it. Normally only the
terminal third of the retentive clasp arm is placed
gingival to the survey line.

The procedures to be followed during diagnostic
survey are as follows:
a). The cast is placed on the surveying table with
the occlusal surface parallel to the horizontal
plane.
b). The analyzing table is initially given an
anteroposterior tilt, then left and right lateral tilt
and analyzed in each position.

c). The degree of tilt is altered while the operator
looks for the maximum number of parallel surfaces
which may act as guides during insertion of the
denture, yet at the same time offer resistance to
displacement of the denture during function.
d). Once analysis is complete, a note is made of the
results of the various possible tilts and the
analyzing rod is exchanged for an undercut gauge.

e). The teeth and tissue are re-analyzed using an
undercut gauge.
f). Final analysis is carried out bearing in mind the
principle of denture design. Once the path of
insertion has been decided the surveying table is
locked in position.
g). Finally tripoding is carried out on the diagnostic
cast.

Tilt:
Tilt is referred to as ‘changing the long axis of each
tooth relative to the horizontal plane’.
Tilting is used to obtain the most advantageous
path of insertion. Tilting may be used to increase
desirable undercuts and to decrease undesirable
undercuts.
Tilting can also be used to distribute available
undercuts to produce more uniform retention
throughout the available teeth.

Tilting is also used to develop a path of insertion
that will permit the most effective use of an
anterior space for replacement. Tilting can also
minimize unfavorable undercuts both on the teeth
and soft tissues to facilitate better position of
major and minor connectors. It should be
remembered that if a cast does not have usable
undercuts, tilting in it would not produce them.

Survey Line :
It is the line which is marked on the
abutment tooth by the surveyor spindle to indicate
its greatest circumference in a given horizontal
plane. Significance of the survey line is that all
rigid components of the partial denture must be
kept occlusal to it. Normally only the terminal third
of the retentive clasp arm is placed gingival to the
survey line. www.indiandentalacademy.comwww.indiandentalacademy.com

The survey line also helps to locate areas of
undesirable tooth undercut that must be avoided
or eliminated by contouring or placing restorations
on the teeth. Survey line divides the tooth into
Supra bulge and Infra bulge area. The area
occlusal to the survey line is supra bulge area
and the area gingival to the survey line is infra
bulge area.

Blockout
After the establishment of the path of
placement and the location of the undercut areas
on the master cast, any undercut areas that will be
crossed by rigid parts of the denture (which is
every part of the denture framework but the
retentive clasp terminals) must be eliminated by
block out.

In the broader sense the term blockout includes
not only the areas crossed by the denture
framework during seating and removal, but also
those areas not involved that are blocked out for
convenience.
Ledges on which clasp patterns are to be placed.
Relief beneath connectors to avoid tissue
impingement, and Relief to provide for later
attachment of the denture base to the framework.

Ledges or shelves (shaped block out) for locating
the clasp patterns may or may not be used.
However, this should not be confused with the
actual blocking out of undercut area that would
offer interference to the placement of the denture
framework. Only the latter is made on the
surveyor, with the surveyor blade or the diagnostic
stylus being used as a paralleling device

Tripoding:
After the final tilt of the cast has been
selected, it must be recorded so that the cast may
later be repositioned precisely. This procedure is
referred to as Tripoding.

The simplest method consists of placing 3 cross
marks on the tissue position of the cast, lingual to
the remaining teeth at widely separated points
while the cast and the vertical arm of the surveyor
are held at fixed position. This will establish 3
points on the same horizontal plane.

Surveying the master cast:
After the surveying of the diagnostic cast
mouth preparation is done and the master cast is
obtained. The master cast is placed on the
surveyor table. The 3 points selected from the
diagnostic cast must be identified with the
analyzing rod held at the fixed vertical position; the
cast is tilted in various ways until the tip of the
analyzing rod contacts the points on the same
horizontal plane. The tilt of the diagnostic cast and
the master cast will be same nowwww.indiandentalacademy.comwww.indiandentalacademy.com

Surveyors and surveying/ dentistry dental implants

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