1) Surveying involves marking the height of contour and infrabulge on teeth to determine the path of insertion and areas for retention. Guide planes are then prepared parallel to this path to restrict movement. 2) Analysis determines if the initial survey line provides sufficient retention and whether tilting the cast is needed. 3) The final survey line is marked, selecting retentive undercuts opposing the path of displacement. Guide planes are prepared to further limit movement to a single path.

1. SURVEYING, PATH OF INSERTION,
GUIDING PLANES
Dr. Razan Al-Mghawich

2. DEFINITIONS
• SURVEY LINE is a line produced on a cast by a surveyor
or scribe marking the greatest prominence of Height of
contour in relation to the selected & planned path of
insertion of a restoration
The survey line divide the tooth to suprabuldge occlusaly and
infrabuldge cervically
The infrabulge is the undercut
These undercuts are where the retentive tip is placed to retain the
prostheses from displacement
Uses of the survey line:
Determine the position of the clasps and the retentive areas
Determine the position of the reciprocal arm
Determine the position of the guiding planes and the proximal plates

3. PATH OF INSERTION
• The path followed by the prosthesis from its first contact with the teeth until it is fully seated. This path
coincides with the path of withdrawal and may or may not coincide with the path of displacement
• There may be a single path or multiple paths
multiple path exists for example :
where the abutment teeth are divergent
or where point contacts between the
saddle of the denture and the abutment teeth.
multiple single

4. SELECTING THE PATH OF INSERTION
• How to find it ? Where is it ? How to determine it ? which one we want?
• Usually the dentist selects the path of insertion
• imagine how the patient will put in the prostheses
• How the prosthesis is seated in its final position

5. SELECTING THE PATH OF INSERTION
• We usually assume the path of insertion is rotational with an end position almost at right angle
or perpendicular to the plane of occlusion;10 degrees more or less
Path of
insertion
Occlusal
plane
Path of insertion

6. PATH OF DISPLACEMENT
This is the direction in which the
prostheses tend to be displaced or
dislodged from its position during
function.
As the path of insertion this path
is variable but is assumed for the
purpose of design to be at right
angles to the occlusal plane.

7. SINGLE PATH OF INSERTION
AND DISPLACEMENT
• Our goal is to have a single path of insertion & displacemnt :
• It helps in equalizing retention
• It directs forces along long axes of teeth
• It aids in bracing and cross-arch Stabilization
• Helps to Minimizes torque on abutments
• Allows removal without encountering interferences
• Provides frictional retention

8. SINGLE PATH
• The way to restrict the denture to a single path of placement and displacement is to prepare
the teeth ; creating guide planes on them
• These guide planes will restrict the prosthesis to be placed in and dislodged in only a single
path and they will prevent the movement of the denture in any other path
• That’s why they should be parallel to each other and parallel to the selected path of placement
and displacement , which is usually almost at right angle with the occlusal plane
Guiding planes guiding
the prosthesis to be
Guiding planes on the teeth seated
parallel and opposing each other

9. SURVEYING PROCEDURE
• This may be divided into the following distinct phases:
• • Preliminary visual assessment of the study cast.
• • Initial survey.
• • Analysis.
• • Final survey.
• Preliminary visual assessment of the study cast this stage has been described as ‘eyeballing’
the cast and is a useful before the initial surveying. The cast is held in the hand, checked and
inspected from above. The general form and arrangement of the teeth and ridge can be
observed, any obvious problems noted and an idea obtained as to whether or not a tilted
survey should be employed

10. 1- INITIAL SURVEY
• The cast is positioned with the occlusal plane relatively horizontal.
• This is called the zero tilt surveying
• The teeth and ridges are then surveyed
• Place analyzing rod against abutments
• Contact point is Height of Contour
• Below is infrabulge the retentive undercut that we want
• Above is suprabulge

11. A- As we said the survey line is parallel to a line that is at right angle with the occlusal plane which
ideally would be the path of insertion and the path of displacement
B- If we prepare guide planes according to the initial survey line in assumption that it’s a good fit for
the design, this will make this survey line at right angle with the path of insertion
C- And if we engaged the undercuts created by it with retentive arms they will retain the RPD from
being displaced in this path, which will make the survey line at a right angle with a path of
displacement
•From points A, B , C we accomplished a survey line that defined the guiding planes and the retentive
undercuts and we restricted the path of insertion and displacement to one
•But what if there is no enough undercuts for retention what should we do ??
• that is why we need to analyze this initial survey line to see if it will help us to get a good design for
the RPD

12. 2- ANALYSIS
• So after creating the initial survey line on the teeth and associated tissues ,it should be inspected
• The position of the survey lines and the variations in the horizontal extent of undercut associated
with them should be noted
• The amount of undercut can be judged approximately from the size of the ‘triangle of light’
between the marker and the cervical part of the tooth, or measured more precisely by using an
undercut gauge.
• An assessment can then be made as to whether the horizontal extent of undercut is sufficient for
retention purposes

13. 2- ANALYSIS
• An RPD can be designed on a cast which has been surveyed with the occlusal plane horizontal (ie
so that the path of insertion equals the path of displacement).
• However, there are occasions when tilting of the cast is indicated so that the paths of insertion
and displacement differ.
• Before deciding if the cast should be tilted for the final survey the graphite marker in the surveyor
is changed for an analyzing rod so that various positions of the cast can be examined without
marking the teeth.
• The analysis of the cast continues with the occlusal plane horizontal and the following aspects,
one or more of which might necessitate a final survey with the cast tilted, are considered:
• • Appearance.
• • Interference.
• • Retention.

14. 3- FINAL SURVEY LINE
• So the tilt of the cast is modified in certain cases to get a different survey line (the final survey
line)
• We use a different color marker
• The final tilt is rarely more than 10 degrees from the horizon
• It should be noted that usually the teeth to be clasped have two separate survey lines which
cross each other. In order to obtain optimum retention it is necessary to understand how to
position the clasps correctly in relation to the two survey lines

15. • 1- Modify tilt if necessary
• Esthetics is a problem
• Minimize display of clasps, metal components

16. FINAL SURVEY LINE
• Modify tilt :
• to obtain maximum parallelism
• Heights of contour are at relatively same
position occluso-gingivally
• Equal amounts of undercut for retention

17. • Modify tilt if necessary
• Soft tissue interferences
• Minimize severe tooth & soft tissue interferences

18. TRIPODING IS MARKING THE CAST IN 3
DIFFERENT POSITIONS TO DETERMINE THE TILT
USED

19. SELECTING THE RETENTIVE UNDERCUTS
• After the final survey line, and determining the path of displacement
• Retentive undercuts should be selected in relative to this path
• The retentive undercuts should be equalized in size and angle
• Retentive arm has a different path of escapement than guiding plane, so it must flex during
removal
• Ideally, retentive arms should oppose each other on opposite sides of the arch
• Retentive tip should usually be designed to be placed in the gingival 1/3

20. OPTIMAL PATH OF INSERTION
• Definition :Two or more parallel axial surfaces on abutment teeth which can be used to limit
the path of insertion and improve the stability of RPD.
• Note: Guide surfaces may occur naturally on teeth parallel to ath of insertion ,in this case no
preperation is needed
• but more commonly need to be prepared, and the should be:
• Flat surfaces parallel to path of insertion
• Control & limit movement of RPD
• Initial contacts for RPD
• Stabilizing the RPD against the retentive clasp

21. IDEAL GUIDE PLANES
• parallel to each other
• directly opposing each other
• Prepared on several teeth
• Cover a large surface area

22. GUIDING PLANE PREPARATION
• We also prepare Where rigid components contact
abutments
• Proximal Plates
• Bracing Arms
• Rigid portions of Retentive Arms

23. GUIDING PLANE DIMENSIONS
1/3 of the bucco-lingual width
Around 2-4 mm from the marginal ridge cervically
Round
Axial Line
Angles
2-4 mm
1/2-1/3
height
4 mm
2-

24. EFFECTS OF GUIDING PLANES ON
RETENTION & STABILITY
• Minimize the need for retention
• Maintains Retention
• Stabilizing Teeth
Use short guideplanes on Class I & II
Use long guideplanes on Class III & IV

25. ASSESSING GUIDING PLANES
Proximal
View
Facial
View
Carbon
Markings
IIddeeaall AAcccceeppttaabbllee Too
Divergent
Divergent
Too
Too
Short
Ideal Ideal Too
Short

26. PREPARING GUIDE PLANES INTRA-ORALLY
Use Surveyor to Align Bur Intra-orally
Long Cylindrical Carbide or Diamond (8837K 014)
Polish Prepared Surfaces with Rubber wheels or points
8837K-014

27. OTHER USES OF A SURVEYOR
• Blocking out undesirable undercuts
• Ensures the framework is not cast in an undercut

28. ABUTMENT MODIFICATIONS
• After the final survey ,RPD Designed ,and preparing the Guide planes, there
might be areas that has no undercuts or the guide planes that we have are not
satisfactory, so we can alter the axial contour in 2 ways :
• Lower heights of contour to eliminate interferences & improve esthetics
• Create undercuts if absolutely necessary (raising heights of contour)

29. MODIFICATION OF ABUTMENTS
• Lowering Heights of Contour
• Rigid elements contacting
abutments
• Improve esthetics
• Prepare guiding planes - most
efficient method to lower

30. MODIFICATION OF ABUTMENTS
• Raising Heights of Contour
• Insufficient retention in gingival 1/3 (undercut
must be least 1mm from gingiva)
• Preparing an undercut using a bur
• Adding composite above to create undercut

31. PREPARING RETENTIVE UNDERCUT
• Axial surface of the preparation must be parallel to the path of insertion
• Follows the shape, design and path of the selected retentive tip
• Axial surface must be close to parallel the path of insertion
X

32. PARTS OF A SURVEYOR
• Surveying Table

33. PARTS OF A SURVEYOR
• Surveying Arm

34. PARTS OF A SURVEYOR
• Analyzing Rod

35. PARTS OF A SURVEYOR
• Surveying Tools
• Carbon Markers

36. UNDERCUT GAUGES

37. PARTS OF A SURVEYOR
• Surveying Tools
• Wax Trimmer