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Removable partial denture

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					Removable partial denture

        Surveying
               By
      Dr. Ashraf Gebreel
      Surveying

           This presentation describes the clinical
           objectives and procedures for surveying a
             dental cast prior to designing an RPD


Dr. Ashraf Gebreel
      Dental Surveyor

   • Definition:
         A dental surveyor 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. Ashraf Gebreel
      Principles of dental surveyor




Dr. Ashraf Gebreel
         Principles of Surveying

      • path of insertion

      • heights of contour

      • guiding planes


Dr. Ashraf Gebreel
      • Description of dental surveyor

        The most widely
        used surveyors
         are:
        Ney,
        Jelenko and
        Williams
Dr. Ashraf Gebreel
                                      Ney Surveyor
  • The principle parts of the Ney surveyor are :-
  1. Platform on which the base is move.
  2. Vertical arm that supports the superstructure.
  3. Horizontal arm from which the surveying mandrill suspend to
     carry surveyor tools.
  4. Mandrill which suspend to carry surveyor tools.
  5. Table to which the cast is attached.
  6. Base in which the table swivels.
  7. Surveyor tools;
   Analyzing rood
   Carbon marker
   Undercut gauge.(0.01, 0.02 and 0.03 inch)
   Wax trimmer.
Dr. Ashraf Gebreel
                         Jelenko Surveyor

      • The differences between Ney and
          Jelenko are:
      a. The spring-mounted paralleling tools
      b. The swivel at top of vertical arm.
      c. Undercut gauge with just one shank
          caring the 3 measures.
      d. Carbon marker without sheath.


Dr. Ashraf Gebreel
                        William Surveyor
      •    Williams surveyor has ;
      1.   Fixed base to the platform or not
           with graduated degree of tilt.
      2.   Bisected and swivel horizontal
           arm.




Dr. Ashraf Gebreel
      Different types of parallelometer




Dr. Ashraf Gebreel
                     Parallelometer




Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
 There are several different attachments that may
     be used with the surveyor:
 1. Analyzing rood
 2. Carbon marker
 3. Undercut gauge
 4. Wax trimmer




Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       1. Analyzing rod
       This metal rod is placed
       against the teeth and ridges
       during the initial analysis of
       the cast to identify undercut
       areas and to determine the
       parallelism of surfaces
       without marking the cast.
                                        Analyzing rod

Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       2. Graphite marker
      The graphite marker is moved around the
         tooth and along the alveolar ridge to
         identify and mark the position of
         maximum convexity (survey line)
         separating non-undercut from
         undercut areas.
      When surveying a tooth, the tip of the
         marker should be level with the
         gingival margin allowing the side of
         the marker to produce the survey line   Graphite marker
         as shown in the illustration.


Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       2. Graphite marker
         A false survey line will be
         produced if the tip of the marker is
         incorrectly positioned. In this
         example there is not, in fact, an
         undercut area on the tooth
         although an incorrect surveying
         technique has indicated one. If this
         false line is used in designing an
         RPD, errors will arise in the
         positioning of components,             Graphite marker
         especially clasps.

Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       3. Undercut gauge
      Gauges are provided to measure the
          extent of horizontal undercut and are
          available in the following sizes: 0.25
          mm, 0.50 mm and 0.75 mm.
      By adjusting the vertical position of the
          gauge until the shank and head
          contact the cast simultaneously, the
          point at which a specific extent of
          horizontal undercut occurs can be
          identified and marked.
      This procedure allows correct positioning    Undercut gauge
          of retentive clasp arms on the tooth
          surface

Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       4. Trimming knife
         This instrument is used to eliminate
         unwanted undercuts on the master
         cast.
         Wax is added to these unwanted
         undercut areas and then the excess
         is removed with the trimmer so that
         the modified surfaces are parallel to   Trimming knife
         the chosen path of insertion.


Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       4. Trimming knife

         When elimination of undercuts is required on a cast
         which is not to be duplicated, a material such as zinc
         phosphate cement, which can resist the boiling out
         procedure, is used. The surveyor is used to shape the
         cement before it is fully set.

Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       4. Trimming knife
      (a) This RPD cannot be inserted in
          the mouth because failure to
          eliminate unwanted undercut on
                                                              a
          the cast has resulted in acrylic
          resin being processed into the
          area.                              Trimming knife
      (b) This denture has been processed
          on a correctly prepared cast
          and, as a result, there is no                       b
          interference with insertion.
Dr. Ashraf Gebreel
      • Surveyor attachments (Tools)
       4. Trimming knife

         The trimming knife can also
         be used to prepare guide
         surfaces on wax patterns of
         crowns for abutment teeth.

                                       Trimming knife

Dr. Ashraf Gebreel
         Before discussing the functions of a surveyor in more
         detail it is necessary to explain the following terms:
      • Guide surfaces.
      • Path of insertion.
      • Path of displacement.



Dr. Ashraf Gebreel
      • Guide surfaces (or guide planes).
              Two or more parallel axial
         surfaces on abutment teeth
         which can be used to limit the
         path of insertion and improve
         the stability of a removable
         prosthesis. Guide surfaces may
         occur naturally on teeth but
         more commonly need to be          Guide surfaces
         prepared.

Dr. Ashraf Gebreel
      • Path of insertion.

         The path followed by the denture 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 of insertion.

Dr. Ashraf Gebreel
      • Path of insertion.

      A single path of insertion may
      be created if sufficient guide
      surfaces are contacted by the
      denture; it is most likely to
      exist when bounded edentulous
      areas are present.
                                       Path of insertion



Dr. Ashraf Gebreel
      • Path of insertion.

          Multiple paths of
         insertion will exist where
         guide surfaces are not
         utilized, for example
         where the abutment
         teeth are divergent.         Path of insertion



Dr. Ashraf Gebreel
      • Path of insertion.

     Multiple paths will also
     exist where point contacts
     between the saddle of the
     denture and the abutment
     teeth are employed in the
     ‘open’ design of saddle.     Path of insertion



Dr. Ashraf Gebreel
      • Path of insertion.

        Two distinct paths of insertion will
        be employed for a sectional, or two-
        part denture illustrated here by a
        diagram in the sagittal plane of a
        Kennedy Class IV denture. The
        abutment teeth on either side of the
        saddle are not shown.
                                               Path of insertion



Dr. Ashraf Gebreel
      • Path of insertion.


     Occasionally a rotational
     path of insertion can be
     used.

                                 Path of insertion



Dr. Ashraf Gebreel
      • Path of displacement.
         This is the direction in which
         the denture tends to be
         displaced in function.

         The path is variable but is
         assumed for the purpose of
         design to be at right angles     Path of displacement.
         to the occlusal plane.

Dr. Ashraf Gebreel
      Purposes of dental surveyor:

      1.    Surveying the diagnostic cast.
      2.    Contouring wax pattern.
      3.    Surveying ceramic veneer crown.
      4.    Placement of internal attachment.
      5.    Placement of internal rest seat.
      6.    Machining cast restoration.
      7.    Surveying the master cast.
Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          1. Surveying the diagnostic cast.
   The objectives are as follows:
   1) To determine the most desirable path of placement that will eliminate or minimized interference.
   2) To identify proximal tooth surfaces that are or need to be made parallel so that they act as
      guiding planes during placement and removal.
   3) To locate and measure areas of the teeth that may be used for retention.
   4) To determine whether tooth and bony areas of interference will need to be eliminated surgically,
      modification, block out or by selecting a different path of placement.
   5) To determine the most suitable path of placement that will permit locating retainers and artificial
      teeth to the best esthetic advantage.
   6) To permit an accurate charting of the mouth preparations to be made
   7) To delineate the height of contour on abutment teeth and to locate areas of undesirable tooth
      undercut that are to be avoided, eliminated, or blocked out.
   8) To record the cast position in relation to the selected path of insertion for future reference
      (Triboding
Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          2. Contouring wax pattern.

      • The surveyor blade is used as a wax carver during mouth
        preparation phase so that the proposed path of insertion
        maintained throughout the preparation of cast restorations for
        abutment teeth.
      • Guiding planes, areas of reciprocation and stabilizing components,
        location and depth of undercut areas, and position of the retentive
        clasp arm must be surveyed and carved in the surveyor to
        maintained the previously determined path of placement.
Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          3. Surveying ceramic veneer crown
      • For esthetic reasons, ceramic veneer crowns are often used
        under RPD. The surveyor is used to contour all areas of the
        wax pattern except buccal or labial surfaces so, before the
        final glaze is accomplished, the abutment crown should be
        returned to the surveyor on a full arch cast to ensure the
        correct contour of the veneered portion or to locate those
        areas that need recontouring.

Dr. Ashraf Gebreel
      4. Placement of internal attachment (intracoronal
           retainer).
    In the placement of intracoronal retainers the surveyor is used as
      follows:
   • 1) To select a path of insertion in relation to the long axes of the abutment teeth that
     will avoid areas of interference elsewhere in the arch.
   • 2) To cut recesses in the stone teeth in the diagnostic cast for estimating the
     proximity of the recesses to the pulp (used in conjunction with X-ray film) and to
     facilitate the fabrication of metal or resin jigs to guide the preparations of the
     recesses in the mouth
   • 3) To carve recesses in the wax patterns, to place internal attachment matrix or its
     tray in wax patterns, or to cut recesses in the casting with the handpiece holder.
   • 4) To place the keyway portion of the attachment in the casting before investing and
     soldering; each keyway must be parallel to the other keyways elsewhere in the arch.
Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          5. Placement of internal rest seat

      • The surveyor may be used as a drill press, with a dental
         handpiece attached to the vertical arm by a handpiece holder.
         Internal rest seats may be carved in the wax patterns and
         further refined with the handpiece after casting, or the entire
         rest seats may be cut in the cast restoration with the
         handpiece.


Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          6. Machining cast restorations.

      With handpiece holder attached, all the follows may be refined
        and improved by machining;
      • Axial surfaces of casts and ceramics.
      • Proximal surfaces of crowns and inlays, which will serve as guiding
        planes.
      • Vertical surfaces above crown ledges


Dr. Ashraf Gebreel
      Purposes of dental surveyor:
          7. Surveying the master cast.
      Because surveying the master cast follows mouth preparations, the path of insertion, the
         location of retentive areas, and the location of remaining interference must be known
         before processing of the final design of the denture framework.
      The objectives of surveying the master cast are as follows:
      • To select the most suitable path of insertion by following mouth preparations that satisfy
         the requirements of guiding planes, retention, noninterference, and esthetics.
      • To permit measurement of retentive areas and to identify the location of clasp terminals
         guided by:
           – The flexibility of the clasp arm.
           – The magnitude of the tooth undercuts.
           – The depth of the clasp terminal is placed into this undercut
      • To locate undesirable undercut areas that will be crossed by rigid parts of the restoration
        during placement and removal; this must be eliminated by blockout.
      • To trim blockout materials parallel to the path of insertion before duplication.
Dr. Ashraf Gebreel
                     SELECTING PATH of
                         INSERTION

 Factors that determine the path of insertion
 •guiding planes
 • retentive areas
 • interferences
 • esthetics


Dr. Ashraf Gebreel
     guiding
     planes




Dr. Ashraf Gebreel
                     Requirements
                          of
                       Guiding
                       Planes
Dr. Ashraf Gebreel
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Dr. Ashraf Gebreel
      Guiding plane
      angles




                      Preparation of the rest
                      always follows guiding
                      plane preparation

Dr. Ashraf Gebreel
              Only a small area of the
              guiding plane contacts metal
Dr. Ashraf Gebreel
Dr. Ashraf Gebreel
Dr. Ashraf Gebreel
Dr. Ashraf Gebreel
      Surveying procedure

      This may be divided into the following distinct phases:
      • Preliminary visual assessment of the study cast.
      • Initial survey.
      • Analysis.
      • Final survey.


Dr. Ashraf Gebreel
      Surveying procedure
      • Preliminary visual assessment of the study cast.

      • This stage has been described as ‘eyeballing’ the cast and is a
        useful preliminary to the surveying procedure proper.

      • The cast is held in the hand 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.
Dr. Ashraf Gebreel
      Surveying procedure
      • 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
        displacement.
      • 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.
Dr. Ashraf Gebreel
      Surveying procedure
      • Initial survey.



              18                              16
     Initial survey of the study cast
     shows an anterior tilt (‘heels up’)
     shows a posterior tilt (‘heels down’).
     shows the ‘triangle of light’.


Dr. Ashraf Gebreel                            17
      Surveying procedure
      • Analysis.
       • An RPD can be designed on a cast which has been surveyed with the
          occlusal plane horizontal (i.e. 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.
      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:
               1.    Appearance.
               2.    Interference.
               3.    Retention.
               4.    Guiding planes
Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      1. Appearance.
      When a maxillary cast,
      containing an anterior
      edentulous area,         is
      surveyed with the occlusal
      plane horizontal it will
      often be found that there
      are undercuts on the mesial   Fig. 19 Appearance
      aspects of the abutment
      teeth.
Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      1. Appearance.
      The mesial gap can be avoided
      by giving the cast a posterior
      (heels down) tilt so that the
      analyzing rod is parallel with
      the mesiolabial surface of the
      abutment tooth.

                                       Fig. 20 Appearance


Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      1. Appearance.

      With this posterior path of
      insertion the saddle can be
      made to contact the abutment
      tooth over the whole of the
      mesiolabial surface and a much
      better appearance results.

                                       Fig. 21 Appearance


Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      2. Interference
      While examining the cast with the occlusal
      plane horizontal, it sometimes becomes
      apparent that an undercut tooth or ridge
      would obstruct the insertion and correct
      placement of a rigid part of the denture. By
      tilting the cast, a path of insertion may be
      found which avoids this interference. For
      example, if a bony undercut is present
      labially, insertion of a flanged denture along
      a path at right angles to the occlusal plane
      will only be possible if the flange stands
      away from the mucosa or is finished short of
      the undercut area. This can result in poor       Fig. 22 Interference
      retention as well as a poor appearance.



Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      2. Interference
       If the cast is given a
      posterior tilt so that the
      rod, and thus the path of
      insertion, is parallel to the
      labial surface of the ridge it
      is possible to insert a flange
                                       Fig. 23 Interference
      that fits the ridge
      accurately.
Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      2. Interference
      Lingually tilted premolars can make
      it impossible to place a sublingual, or
      lingual, bar connector sufficiently
      close to the lingual mucosa. Such a
      problem would occur lingually to
      LR4.
      If interference from a tooth is
      present and cannot be avoided by
      selecting an appropriate path of
      insertion, consideration should be
      given to the possibility of eliminating   Fig. 24 Interference
      the interference by tooth preparation


Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      3. Guiding plans




Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      3. Retention
       To obtain retention, undercuts
      must be present on teeth
      relative to the horizontal
      survey.
       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.
                                           Fig. 25 Retention
Dr. Ashraf Gebreel
      Surveying procedure
      • Analysis.
      3. Retention
       The principle of tilting the cast
      to enhance retention is that by
      so altering the path of
      insertion;
      So a rigid part of the denture
      can enter an area of the tooth
      surface or an area of the ridge
      which is undercut relative to
                                           Fig. 26 Retention
      the path of displacement
Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
     If it is decided that the cast should be
       tilted, the analysing rod is exchanged
       for a marker different in colour from
       that used in the first survey, and the
       final survey is carried out. It will
       then usually be found that 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.        Fig. 27 Final Survey


Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey

         The aims for optimum          The former can be
         retention should be to        achieved by the use
         provide:                      of guide surfaces or
      • Resistance along the path of   clasps while the
        displacement.
                                       latter is provided by
      • Resistance along the path of
        withdrawal.                    clasps alone.

Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
     When guide surfaces are used to
      provide       resistance      to
      displacement of the denture in
      an occlusal direction, the
      retentive portion of the clasp
      needs only to resist movement
      along the path of withdrawal
      and therefore can be positioned
      solely with reference to the red   Fig. 28 Final Survey
      survey line.

Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
      It does not matter if, as in this
      example, the clasp engages too
      deep an undercut relative to the
      path       of     displacement.
      Movement of the denture in an
      occlusal direction is prevented
      by contact with the guide
      surface, therefore permanent
      deformation of the clasp will
      not occur.                          Fig. 29 Final Survey

Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
       A gingivally approaching
      clasp positioned at the
      cross-over point of the
      survey lines resists
      movement along both the
      path of withdrawal and the
      path of displacement
      without being permanently
      deformed by movement
                                   Fig. 30 Final Survey
      along either path.
Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
       If the survey lines converge
      mesially or distally, the tip
      of        an        occlusally
      approaching clasp can
      engage the common area of
      undercut to provide
      resistance to movement           Fig. 31 Final Survey
      along both paths.
Dr. Ashraf Gebreel
      Surveying procedure
      • Final Survey
   Methods of recording the
      degree of tilt:
   1. The tripod method
   2. The analyzing rod method




                                 Fig. 31 & 32 Final Survey
Dr. Ashraf Gebreel
      Summary of the clinical objectives of surveying
      Surveying is undertaken to obtain information that will
      allow decisions to be made concerning the following:
      (1) The optimum path of insertion of   (2) The design, material and
          the denture.                           position of clasps.
      The choice of a path of insertion      Decisions on these aspects of
         will be influenced by:                clasps can be arrived at from:

      •The need to use guiding surfaces      •    Measurement of the horizontal
         to achieve a pleasing                   extent of undercut on abutment
         appearance.                             teeth and

      • The need to avoid interference by    •   The identification of sites on the
         the teeth or ridges with correct        teeth to provide reciprocation
         positioning of denture                  &stabilization either from
         components.                             guiding surfaces or from cross-
                                                 arch stabilization
      • The need to use guide surfaces
         for retention.
Dr. Ashraf Gebreel
      References
      • McCracken’s Removable Partial Prosthodontics. 10th Edition (2000)

      • J. C. Davenport, R. M. Basker, J. R. Heath, J. P. Ralph, and P-O.
        Glantz (2000): A Clinical Guide to Removable Partial Denture Design
        (ISBN 0-904588-637).

      • J. C. Davenport, R. M. Basker, J. R. Heath, J. P. Ralph, and P-O.
        Glantz,(2000): Surveying; British Dental Journal ; 189: 532–541.

Dr. Ashraf Gebreel
Dr. Ashraf Gebreel

				
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