Surveying - karary.edu.sd

transcript

Surveying

Dr. Mohamed Osman BDS, GBOI, Msc

Content :

Dental surveyor

Function (purposes )

Procedure

What is the dental surveyor :

An instrument used to determine the relative

parallelism of two or more surfaces of teeth or other

part of cast of the dental arch .

Types of dental surveyor :

Ney surveyor ( most widely used ) .

Jelenko Surveyor .

Williams Surveyor .

The Retentoscope Surveyor .

The Ticonium Surveyor .

Parts of the dental surveyor :

A. Surveying platform.

B. Vertical Column .

C. Horizontal arm .

D. Surveying arm .

E. Mandrel .

F. Surveying tool .

G. Surveying table .

Common Types of dental surveyor :

Differences between Ney & Jelenko surveyor : 1. Jelenko surveyor have movable horizontal arm while Ney surveyor

have fixed one .

2. The vertical arm in Ney surveyor retain by friction within a fixed bearing

while the vertical arm in Jelenko surveyor is spring mounted and it

retain to the top position when it is released .

Definition :

Height of contour :

Is the greatest convexity in the clinical crown determined by the

surveyor according to a certain path of insertion.

• Survey line :

A line scribed on an abutment tooth of a dental cast by

means of a dental surveyor indicating the height of

contour of the tooth according to a specific path of

insertion .

Definition :

Undercut area : area below the survey line ( retentive area ) .

Non Undercut area : area above the survey line .

Parts of the dental surveyor :

Surveying table include ball-and-socket joint , which

allows spatial reorientation of the dental cast ( tilting) .

Surveying tools :

1. Analyzing Rod :

used to determined the relative parallelism of

surfaces on dental cast.

Surveying tools :

2. Carbon Marker (+ protective sheath):

used to mark the survey line .

Surveying tools :

3. Undercut gauges :

• Used to accurately locate retentive undercut on proposed abutment

(determined the depth& position of undercut for allowing proper position

of the clasp & selection of the material and clasping system).

• Commonly supplied in 0.010 inch ( 0.25mm) , 0.020 inch (0.50mm) &

0.030 inch (0.75mm) .

Surveying tools :

4. Wax knife ( Trimming Knife ) :

used during blocking out procedures and in the construction of

surveyed restorations .

Surveying tools :

tools storage rack

What are the Path of insertion & removal :

Path of insertion ( P.I) :

Direction in which restoration\ prosthesis moves from initial point

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 .

What is the path of insertion & removal :

• Path of removal ( P.R) :

The direction of movement of the restoration\ prosthesis from it’s

resting position to the last contact with the supporting teeth .

Path of insertion :

The tilt of the cast determines the direction that the partial

denture will take during placement & removal.

In Kennedy Class I & unmodified Class II (Bounded by teeth

at one end) Variety of angles for path of insertion

Path of insertion :

In Class III, Class IV & modified Class II

the associated prosthesis will have a single path of insertion.

Minor connectors are the only components that contact the guiding planes, so they govern the path of insertion.

Functions ( purposes) of dental surveyor :

1. Surveying the diagnostic cast .

2. Recontouring abutment teeth on the diagnostic cast.

3. Contouring wax patterns .

4. Measuring specific depth of the undercut .

5. Machining cast restoration .

6. Placing intracoronal retainers .

7. Placing internal rests .

8. Surveying ceramic veneer crowns.

9. Surveying & blocking out master cast .

Function of the dental surveyor: 1. Surveying the diagnostic cast :

It’s essential for effective diagnosis & treatment planning .

Function of dental surveyor :

2. Recontouring of the abutment teeth on the diagnostic

3. Contouring the wax patterns

Function of the dental surveyor :

4. Measuring the depth of the undercut .

By undercut gauges, available in the following sizes :

0.010 inch (0.25mm) , 0.020 inch (0.50mm) & 0.030 inch (0.75mm) .

5. Machining Cast Restoration .

With dental handpiece attached to

the vertical arm with handpiece holder,

6. Placement of Intracoronal Retainers ( Internal

attachments)

The surveyor is used :

I. To select path of placement in relation to the long axes of the

abutment teeth .

7. Placing Internal Rest Seats .

A dental surveyor maybe used as

a drill press .

Internal rest seats may be carved

in the waxed pattern and further

refined with handpiece after casting

or the entire rest seat maybe cut with

handpiece in the cast restoration.

8. Surveying Ceramic Veneer Crowns

Before the final glaze the veneered portion of the abutment crowns is

checked for correct contour .

9. Surveying & blockingout the master cast .

Follows the mouth preparations to satisfy the requirements of guiding

planes, retention ,noninterference & esthetics.

Also to trim blockout material parallel to path of placement before

duplication .

Factors that determined path of placement & removal :

1. Retention

2. Interference

3. Esthetics

4. Guiding Planes

1. Retention :

retentive undercut of the abutment teeth when the cast displays a

horizontal tilt it’s essential because dislodging forces( sticky food ,

gravity ) are always perpendicular to the occlusal plane.

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,

you need to :

A. Recontouring the abutment.

B. Fixed restoration ( gold crown , PFM ).

2. Interference :

Certain structure within the oral cavity may interfere with the

insertion of the RPD ( teeth , bony prominences, soft tissue

undercuts & exostosis ).

These difficulties maybe avoided by changing the tilt or surgical

intervention .

Maxillary interferences

Palatal Torus .

Modifying the design if possible or if it’s huge we can go for surgical

intervention.

Maxillary interferences :

Exostosis & undercuts in the buccal surface .

Lead to :

i. Decrease the stability of the denture .

ii. Void between the denture base and the tissue lead to

accumulation of food .

Facially inclined ( tipping ) maxillary posterior teeth .

This lead to movement of the height of contour occlusaly which

makes positioning the buccal clasp arm difficultly for esthetics and

mechanical reason , also may cause the associate gingival tissue an

undercut.

Anterior ridge with noticeable undercut .

Tilt the cast posteriorly ( heels down) .

Mandibular interferences :

Mandibular Tori .

Mandibular lingual tori are relatively common and can produce significant

difficulties in removable partial denture therapy.

Surgical removal of mandibular lingual tori provides an improved foundation

for removable partial denture therapy.

Lingually Tilted posterior teeth .

Mandibular posterior teeth frequently display significant lingual tipping.

As a result these teeth may display no undercuts on their facial

surfaces and large undercuts on their lingual surfaces .

Lingual inclination of teeth on both sides of the mandibular arch also

may result in a major connector that stands away from the lingual soft

tissues and encroaches upon the tongue space .

As a solution for lingual tipping mandibular posterior teeth:

1. Labial bar major connector (poor acceptance due to bulkiness &

location ).

2. Recontouring the teeth .

3. Restoration .

4. Orthodontic movement .

Areas adjacent to retromolar pad area .

The areas adjacent to the pear-shaped pads also may produce

significant difficulties in removable partial denture design and

construction .

Tilting the cast is often beneficial in eliminating a unilateral undercut.

Bony prominences .

Bony prominences are often encountered at the facial surfaces of

mandibular canines and premolars , These prominences may produce

soft tissue undercuts that can interfere with the placement of denture

bases and infrabulge clasps.

Solution can be tilting the cast if it’s minor or surgical intervention.

Factors that determined placement & removal :

3. Esthetics .

To obtain optimum esthetics in removable partial denture therapy:

A. metal components must be concealed as effectively as possible.

B. prosthetic teeth must be selected ,appropriately contoured, and

properly positioned

Esthetics .

To conceal the metal components of a removable partial denture, the

practitioner must pay particular attention to the tilt of the cast.

4. Guiding Planes :

Guiding planes are parallel surfaces of abutment teeth that direct the

insertion and removal of a partial denture.

Are contacted by the minor connectors.

Guiding planes :

Help in :

1. Limit the path of insertion.

2. Stabilize the prosthesis against lateral forces.

3. Protect weakened teeth from destructive lateral forces.

Surveying procedure : Maybe divided into phases:

1. Preliminary visual assessment of the study cast .

2. Initial Survey .

3. Analysis .

4. Final surveying .

Surveying procedure :

1. Preliminary visual assessment of the study cast .

The cast is held in the hand & inspected from above (eyeballing the

cast).

2. Initial Survey .

The cast is positioned with the occlusal plane horizontal.

The teeth and ridges are then surveyed to identify undercut areas that

might be utilized to provide retention in relation to the most likely path of

placement.

3. Analysis .

The analysis of the cast continues with the occlusal plane horizontal and

the following aspects, are considered before tilting the cast:

1. Retention .

2. Interference

3. Appearance (esthetics ).

4. Guiding planes.

4. Final surveying .

After the most favourable tilt of the cast has been selected, it must be

recorded for future reference.

Tripod marks should be positioned at three widely spaced anatomic areas of the cast (Tripoding the cast or scoring the cast ).

Summary :

o Surveying is undertaken to obtain information that will allow

decisions to be made concerning the following :

The optimum path of insertion of the denture .

Design , material and position of the clasps .

Amount of mouth preparation needed .

References :

Mc cracken’s Removable partial denture 11 edition .

Stewart’s Clinical Removable partial denture 4 edition .

A color Atlas of Removable partial denture (

J.C. Davenport ,R.M. Basker , J.R. Heath , J.P. Ralph )

VanBlarcom , The glossary of Prosthodontics term J.

prosthetic Dent 1999.

Engelmeier RL. The history and Development of dental

surveyor : Part I Journal of Prosthodontic , March 2002.

Thanks for your time

Surveying - karary.edu.sd

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