1. 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 :- is the procedure of locating & delineating the contour and position of the abutment teeth and associated structures before designing R.P.D .

2. Types of Dental surveyor
**the most widely used is Ney surveyor because of it's simplicity and durability.
Types of Dental surveyor
1- Ney surveyor : with non swiveling horizontal arm.
2- Jelenko surveyor : with swiveling horizontal arm.

3. Parts of surveyor
1- plate form → it hold other parts of survey (( other parts of survey stabilized on it )) , on which base is moved.
2- vertical arm → support the superstructure .
3- horizontal arm → from which the surveyor tools suspended.
4- base → on which table is swivels
5- table → to which the cast is attached
6- mandrel→ for holding special tools
7- surveying tools → ( analyzing rod , carbon marker , undercut gauge , wax trimmer)

5. analyzing rod …… identify undercut area & determine the parallelism of surface without marking the cast.
carbon marker …… identify and mark the maximum convexity
undercut gauge …… to measure the extent of horizontal undercut
wax trimmer …… To eliminate un wanted undercuts on master cast.

7. Block out : it is elimination of undesirable undercut on master cast before duplication.
Area of block out:
a. proximal tooth surface
b. beneath all minor connector
c. beneath bar clasp
d. tissue undercut to be crossed by rigid connector

8. Relief : is the reduction or elimination of undesirable pressure or force from specific area.
Area of relief :
a. median palatal raphe or any small exostosis(when there is tours)
b. beneath major connector (area of thin tissue)
c. beneath minor connector for attaching acrylic denture base.

9. Thank you