Instruments used in operative dentistry

Question 1

what are hand instruments used for?

Answer 1

cut , plane , or cleave tooth structure during the preparation of a cavity to receive a restoration or other treatment

Question 2

what’s the purpose of an instrument formula ?

Answer 2

describe the dimensions and angulation of the instrument

Question 3

bin angled instrument =how many angles ?

Answer 3

2

Question 4

what’s the point of having a contra-angled instrument ?

Answer 4

bring the working end of the instrument within 1-2mm of the long ais of the handle for better balance

Question 5

number of angles in the shank depends on :

Answer 5

functional orientation and length of the blade

Question 6

for non-cutting instruments , the working part is termed:

Answer 6

Nib —> working surface of the nib is called the face

Question 7

explain the 3 number formula :

Answer 7

1st number is the width of the blade in tenths of a millimeter

2nd number is the length of the blade in millimeters

there third number is the angle of the blade with the long axis of the tooth

Question 8

explain the four number formula of instruments :

Answer 8

first number : width of the blade in mm
second number :angle of cutting edge with handle in degree centigrade (usually 90 is this number isn’t specified –>3 number formula )
third number indicated the length of the blade
fourth number indicates the angle that the blade makes with the handle

Question 9

what are the functions of a chisel ?

Answer 9

planning of enamel which has been undermined by carious dentin / removal of dentin

Question 10

what’s the function of an excavator ?

Answer 10

removal of soft carious dentin / shaping of the internal cavity walls

Question 11

difference between direct and lateral cutting instruments?

Answer 11

direct :
-force is applied in the same plane as that of the blade and handle
-straight blade( single plane)
-all angles in the shank are in the same plane as th handle
-used in direct and lateral cutting

+=no angle of less than 12 degree

lateral cutting :
-force is applies at right angle to the plane of the blade and handle
-curved blade (double plane )
-angles or curves are in a plane at right angle to the plane of the handle
-can only be used in lateral cutting (scrapping )

Question 12

mesial bevel:
distal bevel:

Answer 12

mesial bevel : push

distal bevel : pull

Question 13

which instrument is used to flatten the pulpal floor?

Answer 13

tripple angle chisel

Question 14

instrument used cleave or split undermined enamel:

Answer 14

straight chisel
monoangle chisel (mesial/distal)
bin-angled chisel (mesial/distal)

Question 15

modified straight chisel with slight (5 degree) curvature starting from shank up to the cutting edge without and angulations

Answer 15

wedel steadt chisel (medial/distal)

Question 16

what’s the enamel hatchet used for ?

Answer 16

-cleave enamel from cavity walls especially proximal box

Question 17

modified enamel hatchet with curved blade(right/left) and non-perpendicular cutting edge to the long axis of the blade(mesial/distal)?

Answer 17

gingival marginal trimmer .

Question 18

what are gingival marginal trimmers used for?

Answer 18

beveling of the gingival CSA and axio-pulpal line angle

Question 19

what instrument is used for the accentuation of line and point angles in cavities prepared for gold foil restorations ?

Answer 19

angle former

Question 20

an angle former is a modified ____

Answer 20

straight chisel
- cutting edge is not perpendicular to long axis of the blade
-tripple beveled
-either left or right

Question 21

describe the enamel hatchet

Answer 21

-single plane ,direct cutting instrument
-cutting edge is parallel to the plane of the shaft and perpendicular to the long axis of the blade
-either left of right

Question 22

functions of excavators:

Answer 22

-remove carious dentin
-refine the internal aspect of the preparation
-establish correct anatomical restoaration form

Question 23

difference between enamel hatchet and hatchet excavator :

Answer 23

in hatchet excavator :
-cutting edge has 2 bevels
-smaller and lighter
-used in anterior teeth for refining retention and for sharpening line and point angles

Question 24

blade with more than a 12.5 degree angle with plane of instrument (45-90 degree angle to long axis of handle )

Answer 24

hoe excavator - cutting edge of the blade is perpendicular to the axis of the handle

Question 25

what’s a hoe excavator used for?

Answer 25

planning tooth preparation walls and forming line angles (commonly used in class III and V preparations )

Question 26

spoon excavator is used in a _____ action

Answer 26

lateral scrapping

Question 27

what are spoon excavators an discoid excavators used for ?

Answer 27

carving amalgam or wax or spoon = removing caries

Question 28

what’s a cleoid excavator and what’s it used for ?

Answer 28

Sharp pointed blade in the form of a claw, with the cutting edges on two sides of the blade.
Used for carving of amalgam or wax.