PRINCIPLES OF SURVEYING Flashcards
DENTAL SURVEYOR
• Paralleling Instrument
used in RPD fabrication
Most common brands (2)
• Ney, Jelenko
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)
• Cast Holder (A)
(2)
• Surveying Table
• Allows tilt of cast
skipped
DENTAL SURVEYOR FUNCTIONS
(5)
• Survey diagnostic cast
• Contour wax patterns
• Contour ceramic & cast restorations
• Place attachments requiring parallelism
• Survey master cast
skipped
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)
DIAGNOSTIC CAST:
SURVEY PROCEDURE
(4)
- Path of Insertion Determined
- Mark the Height of Contour/Survey Line
- Measure/Mark Retentive Undercut
- Tripod Cast
- Path of Insertion Determined
• Based on (4)
Guiding Planes, Retentive Undercut, Interferences,
Esthetics
PATH OF INSERTION
• The direction in which the RPD is inserted &
removed from the abutment teeth.
Exaggerated — to path of insertion avoided
tilt
• Patient unable to open mouth sufficiently to
accommodate
PATH OF INSERTION
FOUR FACTORS
•Guiding Planes
•Retentive Undercuts
•Interferences
•Esthetics
GUIDING PLANES
• Parallel, flattened surfaces at proximal or axial surfaces of teeth
GUIDING PLANES
contact
minor connectors, guiding plates
GUIDING PLANES
Greater number of GPs
• Path of insertion more
specific
GUIDING PLANES
• Increase RPD (2)
stability & retention
GUIDING PLANES
• Identified by tilting cast in
anterior-posterior direction until
maximum parallelism of proximal surfaces
• Anterior-posterior tilt: as viewed from — of cast table
rear
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
• Final orientation seldom — from horizontal
> 10-15°
RETENTIVE UNDERCUT
• RPD mechanical retention provided by
clasp that engages
retentive undercut
• Resist RPD dislodging forces
• Undercut area lies between
survey line and gingival margin
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)
- After surveying complete, mechanical & biologic principles
are applied to design the RPD. - 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
