A Class 2 Tooth cavity is defined as – Carious lesion present on the Occlusal Surface of the Molars and Premolars extending into the Proximal surfaces of the tooth. – By GV Black. For cavity preparation of a Class 2 Cavity in the Pre Molars or Molars it requires a certain set of instruments which change depending on the types of Restorative material being used and the depth of the Caries into the tooth. Cavity preparation is one of the most common treatment performed in a Dental Clinic and remembering the instruments used should be a must for the Dentist, Dental student, Dental Assistant, Dental Hygienist, etc.
The first step in preparing a tooth for Cavity preparation or Restoration you need to diagnose the problem to determine the treatment plan. The first step is to check with a Diagnostic X-ray to determine the extent of caries and the amount of tooth structure which is needed to be removed.
I will be dividing the instruments into various categories depending on when they will be used –
These are used in diagnosing or identifying the tooth having Caries –
Mouth mirror: There are types of mouth mirrors based on type of mirror used – Convex (regular) and Concave mirror (Magnifying mirror). The other types of mirrors are divided based on sizes – No. 2 (5/8 inch), No. 4 (7/8 inch), No. 5 (15/16 inch).
Probe (Straight, Interproximal, No. 2 Cow horn or Arch Explorer, No. 17, No. 23 Shepherds hook, Orban type explorer.
Tweezers: These are used to hold objects like cotton, haemostasis, articulating papers, adjust the position of instruments (matrix bands) etc.
These are the instruments which are used to isolate the tooth being prepared from the external structures and elements – Tongue, Cheek, Saliva, etc. These help in ease of cavity preparation and also during the restoration process, making it faster.
The instruments used are – Rubber Dam, Cotton Roll Holder, Saliva Ejector, Suction apparatus.
Instruments for Caries Removal:
This is the first step in any Class II or Class I restoration. Removal of the carious tooth structure. First is Aerator and Burs which are the primary instruments used to remove Dental Caries. Next will be the use of other hand instruments like Spoon Excavator to remove any remaining Carious tooth structure which is close to the Pulp Chamber (In deep caries).
Instruments for Shaping the cavity:
This is the step done after removal of caries, where depending on the type of Restorative material being used, the shape of the cavity is determined. Most of the shaping of the cavity is done using Aerator and Diamond cutting burs such as Round bur, Inverted Cone bur, Straight fissure bur, Tapered Fissure Bur and Tungsten Carbide Burs.
For Class II cavity preparation the burs set which is used and their functions are as follows:
Bur No: 330 – used for attaining the cavity Outline and initial pulpal depth
Bur No: 245 – Dropping the proximal box
Bur No: 169L – Used to refine the shape of the Axial wall
Bur No: 55 – Smoothening the Gingival wall
Bur No: 330 RGS – It is used to smoothen and refine the Occlusal and Proximal box to attain the Bevels and remove unsupported Enamel or Dentin.
In case of Amalgam Restoration as we need Mechanical retention, the shaping of the cavity is very important to get Primary Retention and Primary Resistance Form, all the factors such as maintaining proper Outline Form, Gingival Seat, etc. The width of the Gingival Seat should be 0.6mm to 0.8mm for premolars and 0.8mm to 1.0mm in Molars to help in distributing the masticatory forces equally. It is important that we follow all the proper rules for cavity preparation such as having proper Bevels, leaning no undermined Enamel, no unsupported enamel or dentin which can weaken the restoration.
Chisels – Used to flatten pulp floors and to remove undermined Enamel which can lead to fracture of restoration if left unattended. Hoe is used to define the Line angles and Point angles in a Cavity and most useful in Class III and Class V cavities. The types of Chisels used are – Straight chisel, Mono angle chisel, Bin Angle chisel, Triple angle chisel, Wedelsteadt chisel, Gingival marginal trimmer and Angle former.
Enamel Hatchet: It is a instrument with Bibevelled cutting edge and is single ended. It is used in Push stroke to Prepare retentive areas of Anterior Teeth, used in breaking the enamel in proximal box, smoothening of buccal and lingual walls of proximal box, smoothening of gingival seat (lateral scrapping motion) and helps in sharpening internal line angles.
Gingival Marginal Trimmer: It has the cutting edge at an angle other than a right angle to the blade, the cutting edge is parallel to the axis of the instrument. It is used to give gingival cavo surface bevel and rounding or bevelling axio-pulpal line angles.
Angle Formers: These are instruments made by grinding the bevel at an angle of 80 degrees with the shaft forming an acute angle with the long axis of the blade. It is used to exaggerate line angles and point angle to help in establishing Retention form.
Wedelstaedt Chisel: It is used to cleave undermined enamel and for shaping walls. The instrument has a curved shank and blade and it has three cutting motions – Vertical, Right and Left.
Off angle Hatchet: It is used to create and shape specific angulations for cavity walls, especially in the areas which are difficult to access. The blade is rotated by 45 degrees from the plane of the long axis of the instrument.
Triangular Chisel: Blade is triangular in shape and has a terminal cutting edge like straight chisel.
Knives: The various types of knives are Gold knives, Amalgam knives and Finishing knives. These are used in trimming excess restorative material of the gingival, lingual, proximal margins of the restorations. These are particularly useful in trimming and contouring the surface of class V restorations.
Restorative Instruments for Class II cavity:
Mixing Instruments: Cement Spatula, Agate Spatula, Mixing Glass Slab, paper mixing pad
Carrying and filling instruments – Amalgam Carrier, PFI, Titanium Nitride coated instruments – Composite Instruments (for filling and shaping)
Condensing instruments – Round condenser and Parallelogram condenser
Burnishing instruments – Ball shaped, Egg shaped and Conical shaped
Carving instruments – Hollenback carver, Diamond carver and Wards carver
Curing Instruments – Light Cure (Composite Restoration)