Dr. Waseem Bahjat Mushtaha Specialized in prosthodontics SURVEYING Dr. Waseem Bahjat Mushtaha Specialized in prosthodontics

Definitions: Dental surveyor: A paralleling instrument used in the fabrication of a removable partial denture. Surveying: The procedure of analyzing and delineating the contours of the abutment teeth and associated structures before designing a removable partial denture. Path of insertion (placement): The specific direction in which a prosthesis is placed upon the abutment teeth.

Components of dental surveyor : 1- Base. 2- Vertical arm. 3- Horizontal arm. 4- Spindle with tool holder. The surveying arm is capable of movement in vertical direction. 5- 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

6- Surveyor tools : a-Analyzing rod is a straight metal shaft used to analyze the cast to evaluate the presence or absence of undercut. b-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. c-Undercut gauges, 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. d-wax trimmer, used to eliminate or block out areas of undesirable undercut with wax.

Uses of dental surveyor 1- Determination of the most acceptable path of insertion and removal. Whenever possible, the path of insertion should be selected while the cast is placed horizontally with its occlusal plane parallel to the base of the cast. 2- Identifying the proximal tooth surfaces that may be used as guiding planes. The guiding planes are the proximal tooth surfaces that are prepared to be parallel to each other and to the path of insertion. These planes contribute to the stability of the partial denture

3- Locating and measuring undercut areas of the teeth that may be used for retention. An undercut area is that portion of a tooth lies gingival to the survey line (height of contour). 4-Determination of the most suitable path of insertion for retention and esthetic. 5-Detetmination of tooth and bony areas interference that would be eliminated surgically or by selecting a different path of insertion . 6-Aid in determining mouth preparation and restorative procedures (e.g. the preparation of proximal tooth surfaces to provide guiding planes and the reduction of excessive tooth contour to eliminate interference).

7-Drawing the survey line (height of contour) on the abutment tooth 7-Drawing the survey line (height of contour) on the abutment tooth. The survey line is a line encircling a tooth at its greatest circumference at a selected cast position 8-Location of undesirable undercuts which should be blocked out before duplication. 9-Recording the cast position in relation to the selected path of placement for future reference. This may be done by locating three parallel lines or three dots in the same horizontal plane on the cast (tripodization).

Factors that determine path of placement and removal: The factors that determine the path of placement and removal are guiding planes, retentive areas, interference, and esthetics. Tilting the cast on a surveyor during the determination of the path of placement and removal will help in: 1- Aligning the proximal guiding planes to be more favorable to the path of insertion

2- Redistribution of the retentive undercuts in both sides of the arch 3- Elimination of soft tissue interference. 4- Selecting the most suitable path of placement for esthetic, by development of symmetrical embrasure spaces and placing the clasp terminals in areas with less metal display.

Procedures for surveying the study cast: 1-Determining tire path of insertion: a-The cast is attached to the surveyor table with the occlusal plane parallel to the base of the surveyor. b- The analyzing rod is placed in the tool holder and the surveying table is moved until the analyzing rod contact the occlusal third of the proximal surfaces of the abutment teeth. c-The proximal walls usually determine the path of insertion and may require some tooth preparation to be parallel. 2-Determining the undercut areas: a-The analyzing rod is used to locate the undercut areas. The amount of undercut is measured by undercut gauges. b- The undercuts can be redistributed on various abutments by tilting the cast. c-The location of the undercuts must be suitable for the function and esthetics of the clasp. The abutment teeth may have to be: modified or restored, to obtain proper contour. d- Tissue undercuts that may act as interference for the RPD should be determined on the diagnostic cast. e- The adjustable table is then locked in the selected position.

3-Drawing the survey line: The analyzing rod is replaced with a carbon marker. The height of contour is marked on the abutment teeth and other tissue prominence 4- Tripodizing the cast: The cast position on the surveyor table is recorded for future reference to the selected path of insertion by marking it with three widely separated dots or lines.