Instruments used for Cavity preparation and Restoration – Cavity preparation is one of the most commonly used and performed procedure in every dental clinic. Learning about Cavity preparation is a must for every dental student / dentist / hygienist irrespective of the branch which you might specialize in. Cavity preparation is done prior to Restoration required in cases where the tooth is affected with Dental Caries or conditions like fracture of the tooth, attrition etc.
Getting a proper cavity shape is one of the most important steps to a successful restoration. To get the perfect Cavity you need to have the proper set of instruments to prepare the cavity and to restore it using any of the following filling materials – ZOE (temporary), GIC, Composite, Amalgam etc. The Instruments used for Cavity Preparation and Restoration are required during Dental School / College in pre clinical training it self. We have divided the Instruments based of their type as Cutting Instruments, Excavators and Others.
List of Instruments used in Cavity Preparation and Restoration:
There are three types of Chisels based on the shape of their shank – Straight / Curved / Biangled / Triple angle. These chisels have three different shapes to help in reaching different location of the tooth surface which varies depending on the type of tooth. A Dental Chisel is a cutting instrument which is used to push stroke or in scrapping of the enamel, used to cleave or split undermined enamel. A Triple angle chisel is used to flatten pulpal floor.
Has straight shank and bevel on one side only. Used with both push and pull motion.
Curved chisel is called as wedelstat chisel. It has four figure formula. There is a triple angle chisel as well used to flatten the pulpal floor.
Chisels are used to
A. To cleave or split or scrapping under-mined enamel.
B. Flatten pulp also floors.
Cutting edge is parallel with long axis of the handle and beveled on one side. Cutting edge of the instrument is at right angle to the axis of blade. Enamel hatchet is a Monobeveled, Single plane, Paired instrument with the bevel on the right side called (right side) and bevel on left side (left sided). There are different types of Hatchets – Off-angle hatchet (blade is rotated by 45 degrees from the plane of the long axis of the instrument. It is used to create specific angulations for the cavity wall. Spoon Excavator is also called as Modified hatchet.
- To split under-mined enamel in buccal and lingual proximal walls (difficult to reach places).
- For placing grooves.
Gingival marginal trimmer (GMT)
It is a Enamel hatchet instrument with curved blade. The cutting edge of the instrument is parallel to the axis of the instrument. cutting edge of the instrument is at an angle other than right angle to the blade.
It has the cutting edge at an angle other than 90 degree to the axis of the blade.(4 figure formula). It is a Biangle instrument which is Monobeveled. When the 2nd figure is 90-100 it is a distal GMT. If it is 85 -75 it is Mesial GMT.
As it comes with Double plane having monobevel it has better efficiency in lateral scraping and has a better scooping effect.
- For beveling Gingival margin.
- For beveling axiopulpal line angle.
A. Ordinary hatchet:
The instrument has the cutting edge of blade directed in the same plane as that of the long axis of the handle. It is bi-bevelled.
Uses of Hatchet:
For preparing retentive areas in the anterior teeth.
For sharpening internal line angles for direct gold fillings.
Cutting edge is perpendicular to the long axis. The angle of the blade is more than 12.5 centigrade which makes it a Hoe, if the angle is less than 12.5 centigrade it is called as a mono angle chisel.
Can be used for pull and push movements.
Uses of Hoe:
- To give form to the internal parts of cavity used on enamel of posterior teeth.
C. Angle former:
Combination of GMT and chisel because it encompass the advantages of both.
Uses of Angle Former:
For sharpening line angles or obtaining retentive form in dentin.
D. Spoon excavator:
1. The cutting edge is either claw like or on a radius.
2. Circular edge is known as discoid.
3. Claw like edge is known as cleiod.
Uses of Excavator:
- For removing caries on Enamel or Dentin
- For carving amalgam
Known as finishing knives or amalgam or gold knives.
For trimming excess restorative materials like Amalgam or GIC on gingival, facial and lingual margins of a proximal restoration
It is useful in contouring the surface of class V restorations
The teeth of the instrument are designed to use the file either as a pull or push instrument.
It is used to trim excess filling material particularly on gingival margin or to smoothen overhanging restorations.
C. Discoid – cleiod instrument
The working ends of this instrument are larger than the Discoid or cleiod (claw like) end of excavator.
1. For carving on Amalgam or direct restoration
2. It is used to burnish inlay-onlay margins.
It is important to know the different types of instruments used for Cavity preparation and Restoration and when and what purpose do they serve. Using the proper instrument for it designated purpose improves the success of the restoration multiple folds and also decreases the working time.