Restorative Instruments and Techniques
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TREATMENT PLAN SEQUENCE
The treatment linked to the greatest need is completed first. A prioritization of treatment plan items can be grouped as:
- Urgent/Acute phase – symptomatic problems addressed.
- Control phase – active oral disease and infection addressed.
- Re-evaluation phase – allows for resolution of inflammation and time for healing.
- Definitive phase – treatment completed.
- Maintenance phase – personalized recall and ongoing treatment to maintain health.
G.V. BLACK CLASSIFICATION
The G.V. Black classification is widely used to describe cavity preparations.
Class I
- A single surface of a tooth.
- The occlusal surface of a premolar or molar tooth (pit and fissure).
- The buccal or lingual surface of a premolar or molar tooth (pit and fissure).
- The lingual pit of an anterior tooth.
- All other classes refer to smooth surface lesions.
Class II
- Two surfaces of a tooth.
- The proximal (mesial or distal) surfaces of a premolar or molar tooth.
- Examples are MO, DO, MOD, MODB.
Class III
- Two surfaces of a tooth.
- The proximal (mesial or distal) surfaces of an incisor or canine.
- Examples are MB, ML, DB, DL.
- Does not involve the incisal line angle.
Class IV
- Three or four surfaces.
- The proximal (mesial or distal) surfaces of incisors or canines involving the incisal line angle.
- Examples are MIB, MIBL, DIB, DIBL.
Class V
- One surface.
- The gingival (cervical) third of the facial or lingual surfaces of any tooth.
Class VI
- One surface.
- The incisal edge of an anterior tooth or the cusp tip of a posterior tooth.
HAND CUTTING INSTRUMENTS
Instrument categories include cutting (excavators, etc.), and non-cutting (explorers, amalgam condensers, mirrors, probes). For non-cutting instruments the part equivalent to the blade is called the nib. It is the working end and can be used for condensing material, burnishing, inserting, or for finishing the restoration. The end of the nib (working surface) is known as the face. The amount of force needed to compact a direct filling gold is largely influenced by the surface area of the condenser.
Hand instruments consist of three components:
- The handle (also known as the shaft) which can be single or double ended.
- The shank connects the blade to the handle, it can be straight or angled.
- The blade is the functional component, called the cutting edge or nib.
There are 4 types of excavators: The hatchet excavator, hoe excavator, angle former and spoon excavator.
The G.V. Black instrument numbering system is used to convey information about the instrument. There are 3 or 4 numbers separated by dashes or spaces, for example 15-85-8-12. In a three numbering system the first number indicates the width of the cutting edge in tenths of a millimeter, the second number the length of the cutting blade in millimeters, the third the angle the blade makes with the long axis of the instrument (clockwise). The instrument is positioned so that this number is always 50 or less.
In a four numbering system the first number also refers to the width of the cutting blade in tenths of a millimeter. The second number indicates the primary cutting edge angle, measured clockwise against a line parallel to the long axis of the instrument, as a percentage of the full 360 degree rotation (e.g. 85 means 85% of 360 degrees, or 306 degrees). The instrument is positioned so that this number always exceeds 50. The third number is the blade length in millimeters, and the fourth number is the blade angle relative to the long axis of the instrument. The instrument is positioned so that this number is always 50 or less.
CUTTING EDGE WIDTH – CUTTING EDGE ANGLE – BLADE LENGTH – BLADE ANGLE
The instruments can also be classified by four divisions: Order, Suborder, Class, and Subclass.
- Order – the purpose of the instrument. Excavators are cutting instruments intended for removal of caries and to refine preparations.
- Suborder – the position and techniques.
- Class – the form and shape of different cutting instruments.
- The chisel family’s cutting edge makes a 90 degree angle with the plane of the blade and has a blade with one sided bevel. They are used to plane and cleave enamel. They include Chisels, Hoes, Angle formers, Discoid and Cleiod.
- The hatchet family’s cutting edge is parallel with the plane of the instrument and has a blade that ends in a cutting edge in the plane of the handle. They include Hatchets, Excavators, Gingival marginal trimmers (trim/plane gingival cavo surface margins and axio-pulpal line angles).
- Subclass – the angle of the shank, can be straight, mono, bin, or triple angle.
The cutting instruments are used to cut hard or soft tissues of the mouth, excavators to remove caries and refine internal parts, chisels for cutting enamel (mainly). Other hand cutting instruments, such as the file, knife, and discoid-cleoid instrument, are used for carving and trimming restorative material. Having defined but rounded occlusal anatomy also helps provide sluiceways for food to escape the occlusal table during mastication. The facial and lingual areas can be carved with a Hollenbeck carver once the matrix band is removed. Hand instrument techniques include the modified pen grasp, inverted pen grasp, palm-and-thumb grasp, modified palm-and-thumb grasp.
POWERED CUTTING INSTRUMENTS
Three speed ranges are generally recognized
- low or slow speeds (below 12,000 rpm).
- medium or intermediate speeds (12,000 to 200,000 rpm).
- high or ultrahigh speeds (above 200,000 rpm).
Laser equipment has been around for a while, but they are expensive and don’t seem to be overtaking low and high speed handpieces. Lasers are commonly used for soft tissue management. Air motors are being superseded by electric motor units because of their size, reduced noise, and constant torque. Rotary cutting instruments consist of three parts: a shank, neck and head. Dental burs are rotary cutting instruments that have either bladed cutting heads or diamond abrasive heads, and they come in all shapes and sizes. There is a general intended purpose for each shape but it quickly becomes subjective when in the hands of operators.
Carbide bur blades have two sides and three important angles. The rake face contacts the tooth surface and faces the direction of rotation. The clearance face is the surface that faces away from the direction of the rotation. The rake angle is made between the line connecting the edge of the blade to the axis of the bur and the rake face. It can be a positive or negative angle. Soft materials are preferentially cut with a positive angle burs, while hard or brittle materials are cut with negative rake angle burs. Increasing the number of cutting blades decreases the cutting efficiency but leaves a smoother surface. The edge angle is the angle the bur blade makes between the rake face and the clearance face. The clearance angle is the angle formed between the clearance face and a tangent to the rotational vector. The greater the clearance angle, the less friction generated. Heat generated by friction can cause pulpal damage and is mitigated by increased dentin thickness, lowering the pressure on the bur while cutting, using a coolant (water preferred over air), and bur sharpness.
Diamond burs are likely more popular now because of their compatibility with resin bonding systems, leaving a rough surface to bond to. A metal blank head is coated with powdered diamond abrasive held in place by a bonding material. Like sandpaper, the particle size, spacing, and uniformity dictates how aggressively it will cut. Diamond particle size is commonly categorized as coarse, medium, fine, and very fine. Air or water spray is used during treatment to prevent increases in temperature due to friction. Care must be taken not to damage the pulp, the closer you get the more likely heat generation, desiccation or pulpal exposure. Care must also be taken not to cause soft tissue damage, proper retraction and visualization, careful technique, and finger rests.
Eye protection is necessary as part of PPE. Rotary instruments may require ear protection due to noise. They also generate aerosol spray which requires the use of PPE and adherence to high cross infection control standards. Rubber dam and high volume suction will catch aerosols, particles, and vapors during amalgam removal and monomers from composite or acrylic removal.
