PRINCIPLES OF SURVEYING Flashcards by sophie rosen

DENTAL SURVEYOR

• Paralleling Instrument
used in RPD fabrication

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Most common brands (2)

• Ney, Jelenko

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DENTAL SURVEYOR
COMPONENTS
(7)

• Cast Holder (A)
• Surveying Stand (B)
• Vertical
Support Post (C)
• Horizontal Arm (D)
• Analyzing Arm (E)
• Mandrel
for Surveying Tools (F)

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• Cast Holder (A)
(2)

• Surveying Table
• Allows tilt of cast

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skipped
DENTAL SURVEYOR FUNCTIONS
(5)

• Survey diagnostic cast
• Contour wax patterns
• Contour ceramic & cast restorations
• Place attachments requiring parallelism
• Survey master cast

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OBJECTIVE OF SURVEYING
DIAGNOSTIC CAST
(7)

Determine the most acceptable path of insertion
Identify proximal tooth surfaces that can function as guiding
planes
Locate & measure areas of teeth that may be used for
retention
Determine if soft or bony areas of interference (undercuts)
exist
Determine most suitable path of insertion to satisfy
esthetics
Delineate height of contour on abutment teeth
Record cast position to selected path of insertion (Tripod
cast)

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DIAGNOSTIC CAST:
SURVEY PROCEDURE
(4)

Path of Insertion Determined
Mark the Height of Contour/Survey Line
Measure/Mark Retentive Undercut
Tripod Cast

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Path of Insertion Determined
• Based on (4)

Guiding Planes, Retentive Undercut, Interferences,
Esthetics

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PATH OF INSERTION

• The direction in which the RPD is inserted &
removed from the abutment teeth.

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Exaggerated — to path of insertion avoided

tilt
• Patient unable to open mouth sufficiently to
accommodate

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PATH OF INSERTION
FOUR FACTORS

•Guiding Planes
•Retentive Undercuts
•Interferences
•Esthetics

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GUIDING PLANES

• Parallel, flattened surfaces at proximal or axial surfaces of teeth

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GUIDING PLANES
contact

minor connectors, guiding plates

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GUIDING PLANES

Greater number of GPs
• Path of insertion more

specific

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GUIDING PLANES
• Increase RPD (2)

stability & retention

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GUIDING PLANES
• Identified by tilting cast in

anterior-posterior direction until
maximum parallelism of proximal surfaces

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• Anterior-posterior tilt: as viewed from — of cast table

rear

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GUIDING PLANES
• Analyzing rod used to identify

potential
surfaces that can be converted to guiding
planes by selective grinding in occlusal 1/3-
1/2

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• Final orientation seldom — from horizontal

> 10-15°

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RETENTIVE UNDERCUT
• RPD mechanical retention provided by

clasp that engages
retentive undercut
• Resist RPD dislodging forces

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• Undercut area lies between

survey line and gingival margin

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HEIGHT OF CONTOUR/
SURVEY LINE
• Line encircling a tooth that designates its

greatest
diameter at a selected position determined by a dental
surveyor

• Height of contour will change if

the axial inclination is changed

Suprabulge Area

• Portion of tooth above
the height of contour

Infrabulge Area (3)

• Portion of tooth below the height of contour in relation to path of insertion • Retentive Undercut within this area • Only Retentive clasp tips contact tooth below the Survey line

skipped Areas of retentive undercut:

• Mesiofacial (A), Mid-facial (B), Distofacial (C) (Facial undercut preferred) • Mesiolingual, Distolingual

• Ideally, within gingival 1/3, at least --- from gingival margin

1mm

RETENTIVE UNDERCUT • Manipulate mediolateral tilt of cast to equally distribute retentive undercut to ---

abutments

• Cast tilt should not vary far from

horizontal

RETENTIVE UNDERCUT • False Undercut (4)

• Illusion of undercut due to excessive cast tilt • Will not exist clinically • Awkward path of insertion • Patient unable to place RPD

INTERFERENCES: TEETH, SOFT TISSUE, EXOSTOSES (5)

• Typical interference areas: • Lingually-inclined mandibular teeth • Buccally-inclined maxillary teeth • Bony buccal exotoses, tori • Height of contour too high, clasp placement too high • Tissue undercut area of bar clasp

INTERFERENCES: TEETH, SOFT TISSUE, EXOSTOSES • Locate & eliminate by (2)

• Alter tilt of cast/Change path of insertion • Maintain cast tilt, eliminate by surgery or recontouring of teeth

ESTHETICS • Alter mediolateral cast tilt • Allow

natural alignment of anterior tooth

• If inadequate space for natural tooth width

• Recontour proximal surfaces to restore lost dimension

HEIGHT OF CONTOUR/SURVEY LINE • Side of carbon marker indicates

survey line of abutment teeth at chosen path of insertion • Tip of marker will produce incorrect survey line

HEIGHT OF CONTOUR/SURVEY LINE • All components (rigid) of RPD, except terminal 1/3 of retentive clasp, --- survey line

above

Ideally, survey line located at

junction of middle & gingival 1/3

• Proximal --- of retentive clasp & Reciprocal clasp in middle ---, above survey line.

2/3 1/3

• Retentive terminal 1/3 in

gingival 1/3

If survey line, at chosen path of insertion, too near occlusal surface, clasp too high on the tooth (3)

• May interfere with occlusion • Increased leverage on tooth • Tooth recontoured to lower survey line.

If survey line, at chosen path of insertion, too low, no undercut exists (4)

• Survey line at or near gingival margin • No undercut exists for clasp retention • Cannot use enamoplasty to change • Requires surveyed crown

MEASURE/MARK RETENTIVE UNDERCUT • Measured with proper

undercut gauge at chosen path of insertion

Amount of undercut varies depending on

clasp type • 0.01” for Cr-Co or Ni-Cr cast clasp • 0.02” or 0.03” for wrought wire clasp

Inadequate Retentive Undercut (3)

– Enamoplasty to create undercut •“Dimple” –Addition of composite at site to create undercut –Surveyed crown

TRIPOD CAST (2)

• Record tilt of cast at chosen path of insertion • Clinician or Lab technician can re-establish path of insertion

skipped TRIPOD CAST • Method 1 (3)

• Adjust height of vertical arm: marker touches 3 widely separate tissue surface areas • In one plane • Circle each tripod mark

TRIPOD CAST • Method 2 (UMKC method) (1)

• Draw vertical lines parallel to analyzing rod on 3 sides of cast (Lines widely separated)

skipped DIAGNOSTIC CAST: RPD DESIGN (2)

1. After surveying complete, mechanical & biologic principles are applied to design the RPD. 1. The RPD design is drawn on the diagnostic cast.

Blue: (2)

- Metal framework outline - Wrought wire clasp

Red: (3)

- Indicate retentive undercut - Indicate tooth modification areas - Guiding planes, Survey line reposition, Rest seat areas

Black: (1)

-Survey line, tripod marks and soft tissue undercuts

MOUTH PREPARATION (2)

• Perform indicated tooth modifications according to RPD diagnostic cast design • guiding planes, Survey line reposition, Rests

skipped MASTER CAST • Impression for master cast after mouth preparation • Resurvey master cast (5)

• Be sure mouth preparation adequate • Align guiding planes • Mark retentive undercuts • Mark survey line • Tripod cast