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Dental surveyor :- is an instrument used to determine the relative parallelism of two or more surfaces of the teeth or other parts of dental arch.
Surveying
The primary purpose of surveying is to plan those modifications of oral structures necessary to fabricate a removable partial denture.
Types of Dental surveyor
The most widely used is Ney surveyor because of it's simplicity and durability
Few examples are
- Ney surveyor : with non swiveling horizontal arm.
- Jelenko surveyor : with swiveling horizontal arm.
- William‟s surveyor
- The Highriser RPD Surveyor
- The Skyscraper Surveyor
- The Therma-sculpt Surveyor Attachment
- The Tech-5
Jelenko surveyor
Ney surveyor
Components of dental surveyor :
- Base.
- Vertical arm.
- Horizontal arm. rod
- Surveying arm
- Analyzing rod is a straight metal shaft used to analyze the cast to evaluate the presence or absence of undercut.
- Spindle with tool holder. The surveying arm is capable of movement in vertical direction.
- Surveyor table, to which the cast is attached. The cast is locked in place on the table by a clamp. The table is mounted on a ball and socket joint that permit the cast to be tilted in various planes.
- other tools
- Carbon marker and reinforcing sheath, used to draw the survey line of the teeth and to delineate an undercut area of the soft tissue of the ridge.
- 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
- Undercutgauges, are used to identify the amount of the retentive undercut. It is available in three sizes; 0.01, 0.02 and 0.03 of an inch.
- Wax trimmer, used to eliminate or block out areas of undesirable undercut with wax.
Ney surveyor
USES OF A SURVEYOR
- For surveying diagnostic cast
- Measuring depth of undercut
- Contouring wax patterns
- Preparing guiding lines
- Contouring crown an cast restoration
- Placing internal attachment and rests
NOTE :
| Path of insertion | Path of displacement |
| 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. | 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 to the occlusal plane. |
Height of contour
“A line encircling a tooth and designating its greatest circumference at a selected axial position determined by a dental surveyor.” GPT definition
Ney surveyor
Portion of tooth that converges above the height of contour is called SUPRABULGE while the portion of tooth that converges apically from the height of contour is called INFRABULGE.
Guiding planes
“Vertically parallel surfaces on the abutment teeth oriented so as to contribute the direction of the path of placement and removal of removable partial denture” – GPT definition
Survey line
A line produced on a cast by a surveyor marking the greatest prominence of
contour in relation to the planned path of placement of restoration” –GPT
definition.
Blatterfein divided the abutment tooth into two halves by a vertical line through
the centre of the tooth.The area adjacent to the edentulous space was termed as
near zone and the other area was called as far zone
Survey lines are classified as MEDIUM , DIAGONAL, HIGH and LOW
Ney surveyor
| MEDIUM SURVEY LINE | Passes through middle third of tooth in near zone and gingival third in the far zone |
| DIAGONAL SURVEY LINE | Passes from near the occlusal third of the tooth in near zone to the gingival third in the far zone |
| HIGH SURVEY LINE | Placed in occlusal third in both near and far zones |
| LOW SURVEY LINE | Placed in the gingival third of both near and far zones |
Block out :
It is elimination of undesirable undercut on master cast before duplication.
Area of block out:
- proximal tooth surface
- beneath all minor connector
- beneath bar clasp
- tissue undercut to be crossed by rigid connector
Relief :
Is the reduction or elimination of undesirable pressure or force from specific area.
Area of relief :
- median palatal raphe or any small exostosis(when there is tours)
- beneath major connector (area of thin tissue)
- beneath minor connector for attaching acrylic denture base
Principles of surveying
- To study the relative parallelism or lack of parallelism of the teeth and associated structures.
- To choose a path of placing a restoration that will meet the least tooth or tissue interference.
- To determine guiding plane surfaces to direct investment and relocation of the restoration as well as to reach the best appearance possible.
Surveying procedure
STEP BY STEP PROCEDURES IN SURVEYING A DIAGNOSTIC CAST
In short
| 1- Orientation of cast |
| 2- Cast tilting |
| 3- Visual analysis using analysing rod |
| 4- Marking of survey lines /soft tissue undercuts using carbon markers |
| 5- Undercut gauges used to measure amount of available retention |
| 6- Interferences |
| 7- Wax Trimmers |
| 8- Tripoding of casts |
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 frame has been described as „eyeballing‟ the cast and is a useful preliminary, to the surveying procedure proper.
- The cast is kept in the hand and examined from above.
- The general form and arrangement of the teeth and ridge can be seen, any apparent problems noted and an idea taken as to whether or not a tilted survey should be applied.
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 utilised 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.
Analysis
An RPD can be created on a cast which has been surveyed with the occlusal plane horizontal (i.e. so that the path of placement equals the path of displacement).
Still, there are times when tilting of the cast is indicated so that the paths of insertion and displacement vary. Before deciding if the cast should be turned for the final survey the graphite marker in the dental surveyor is changed for an analyzing rod so that various positions of the cast can be examined without marking the teeth.
Following aspects, in last survey with the cast tilted, are considered:
- Appearance.
- Interference.
- Retention.
Final Survey
- If it is decided that the cast should be tilted, the analyzing rod is exchanged for a marker different in color 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.
- The former can be achieved by the use of guide surfaces or clasps while the latter is provided by clasps alone.
- Alternatively, the analyzing rod is placed against one side of the base of the cast and a line drawn on the cast parallel to the rod.
- This is repeated on the other side and at the back of the cast so that there are three widely spaced lines parallel to the path of insertion.
