Surveyors and surveying/ dentistry dental implants

SURVEYOR SURVEYOR

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SURVEYINGSURVEYINGINDIAN 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.



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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.www.indiandentalacademy.comwww.indiandentalacademy.com

• 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 ridgewww.indiandentalacademy.comwww.indiandentalacademy.com

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.www.indiandentalacademy.comwww.indiandentalacademy.com

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. www.indiandentalacademy.comwww.indiandentalacademy.com

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.www.indiandentalacademy.comwww.indiandentalacademy.com

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.www.indiandentalacademy.comwww.indiandentalacademy.com

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 devicewww.indiandentalacademy.comwww.indiandentalacademy.com

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 now www.indiandentalacademy.comwww.indiandentalacademy.com


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Surveyors and surveying/ dentistry dental implants

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