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7 Nomenclature and Instrumentation bonding restorative materials to enamel and dentin was not available to Black, his steps of cavity preparation are generally Instrumentation as appropriate today as they were when he formul...

7 Nomenclature and Instrumentation bonding restorative materials to enamel and dentin was not available to Black, his steps of cavity preparation are generally Instrumentation as appropriate today as they were when he formulated them: Hand instruments 1. Establish outline form. Outline form is based primarily on the Black2 organized not only the classification of cavity prepara- location and extent of the caries lesion, tooth fracture, or tions and their parts but also the naming and numbering of erosion. In carious teeth, the outline form is established after hand instruments. Cutting instruments, which he also called penetration into carious dentin and removal of the enamel excavators, were to be used in shaping the tooth preparation. overlying the carious dentin. The extent of carious dentin All other hand instruments are grouped into the noncutting should be a primary determinant of the outline form of the category. preparation; the final outline is not established until the cari- ous dentin and, usually, its overlying unsupported enamel Metals have been removed. For many years, carbon steel was the primary material used 2. Obtain resistance form. Resistance for the remaining tooth in hand instruments for operative dentistry, because carbon structure and for the restoration must be designed in the steels were harder and maintained sharpness better than stain- preparation so that the restoration will be resistant to dis- less steels. Stainless steels, which are more corrosion resistant placement and both the tooth and the restoration will be than carbon steels, are now the preferred materials for hand resistant to fracture during function. instruments, because all instruments must be sterilized with 3. Obtain retention form. Retention may be obtained through steam or dry heat between patients and because the properties mechanical shaping of the preparation to retain the restora- of stainless steels have improved. There are literally hundreds tion and/or via bonding procedures that attach the restor- of formulas for stainless steels,3 all based on iron and incorpo- ative material to tooth structure. rating a significant amount of chromium, some carbon, and 4. Obtain convenience form. Convenience form allows adequate very often nickel. Chromium imparts corrosion resistance and observation, accessibility, and ease of operation during brightness to the metal; carbon imparts hardness. preparation and restoration of the tooth. Convenience form that involves the removal of sound, strong tooth structure Cutting instruments should be limited to that which is necessary. Before rotating instruments were available, dentists could cut 5. Remove remaining carious dentin. Removal of remaining well-shaped cavity preparations using sharp hand instruments carious dentin applies primarily to that in the deepest part alone. The process was slow. The advent of the dental hand- (pulpally) of the preparation. Other carious tooth structure piece in 1871,4 first attached to a foot-operated engine, allowed was removed when the outline form was established. Caries increased speed of tooth preparation. Most tooth preparation removal may necessitate a modification of the outline form. today is accomplished with rotary instruments, but hand cut- 6. Finish enamel walls and cavosurface margins. For indirect ting instruments are still important for finishing many tooth restorations (those requiring the making of an impression preparations. Few preparations involving a proximal surface and fabrication of a stone duplicate of the preparation or can be completed properly without the use of hand cutting the creation of a digital image), finishing involves making instruments. It is crucial that hand instruments used for cutting the walls relatively smooth. For direct and indirect restora- tooth structure or carving restorative materials be sharp. tions not utilizing bonding, finishing involves removing any unsupported, weak, or fragile enamel and making the Design. Hand cutting instruments are composed of three parts: cavosurface margin smooth and continuous to facilitate handle (or shaft), shank, and blade2 (Fig 7-15). The primary finishing of restoration margins. For bonded resin composite cutting edge of a cutting instrument is at the end of the blade restorations, enamel that is not supported by dentin and is (called the working end), but the sides of the blade are usually not going to be exposed to significant occlusal loading is beveled and also may be used for cutting tooth structure (Fig frequently allowed to remain in place and is reinforced by 7-16). The shank joins the blade to the handle of the instrument bonding to its internal surface. However, weak, fragile, or and is angled to keep the working end of the blade within 2 unsupported enamel should be removed to prevent fracture to 3 mm of the axis of the handle (Fig 7-17). This angulation is due to polymerization shrinkage. intended to provide balance, so that when force is exerted on 7. Clean the preparation. Black referred to this step as “perform- the instrument it is not as likely to rotate, which would decrease ing the toilet of the cavity.” It includes washing or scrubbing the effectiveness of the blade and could possibly cause dam- away any debris in the preparation and drying the prepara- age to the tooth or soft tissue. Figure 7-17a illustrates an instru- tion. Afterward, the cavity is inspected for any remaining ment that has a single angle at the junction of the blade and debris, fragile enamel, and demineralized tooth structure the shank. Because the working end of the blade is not aligned and altered if necessary; then the restoration is placed. with the handle, the instrument is said to be out of balance. Such an instrument may still be useful in tooth preparation. Its blade will usually be relatively short, and it will usually be used 160  Instrumentation 7 Shank Handle Blade (or shaft) Face Fig 7-15 Components of a hand instrument. Although the handle is also called Face a shaft, that designation is little used. Secondary Side bevel Secondary cutting cutting edge edge Primary cutting End bevel edge (working end) Fig 7-16 Blade bevels. Most hand cutting instruments not only have a bevel on the end of the blade but also have bevels on the sides. Although most of the work of a hand cutting instrument is accomplished with the end of the blade, the sides may also be used to plane or scrape walls and margins. (In the illustration on the right, the blade is lying face down.) a b c a b Fig 7-17 The shanks of instruments have multiple angles to keep the working Fig 7-18 Instrument handle configurations. Instrument handles are available end of the instrument within 2 to 3 mm of the long axis of the handle. (a) The from most manufacturers in a variety of designs and diameters. (a) Standard working end of this instrument is not close to the long axis of the handle, and the stainless steel handle with a diameter of approximately 6.4 mm. (b) Padded instrument is therefore not balanced. (b) The shank of this instrument has two handles are available; the diameter of the illustrated padded handle is approxi- angles in it so that the working end is brought near (within 2 mm) to the long axis mately 8 mm. (c) Handles with larger diameters are said to be more ergonomic; of the handle; this provides balance to facilitate control of the instrument during the diameter of the one illustrated is approximately 9.5 mm. the application of force. The instrument is said to be contra-angled. with minimal force. Figure 7-17b shows a shank that has two round and have knurled areas for improved grip. The standard angles to bring the cutting edge into near alignment with the metal handle has a diameter of approximately ¼ inch (6.4 mm). long axis of the handle to provide balance. Although little research support can be found, handles with A variety of handle configurations are available (Fig 7-18). larger diameters, such as the 3/8-inch (9.5-mm) diameter handle Padded handles (Fig 7-18b) are said to increase operator illustrated in Fig 7-18c, are said to be more ergonomic and comfort and grip during use. Most metal handles today are less likely to contribute to the development of carpal tunnel 161 7 Nomenclature and Instrumentation a b c d e a b a b Fig 7-19 Instruments classified by the number of angles in Fig 7-20 (a) Binangle hatchet. (b) Binangle Fig 7-21 (a and b) Monangle hatchets (left- the shank: (a) straight; (b) monangle; (c) binangle; (d) triple- spoon. A double-ended hatchet or spoon would cutting). angle; (e) quadrangle. have a left-cutting end and a right-cutting end (see Fig 7-22). vators, and he referred to instruments as hatchet excavators, spoon excavators, etc. The term excavator is still applicable, but in the day-to-day language of operative dentistry, it is little used. In catalogs of instruments, however, cutting instruments are often indexed as excavators. Black combined the name of each instrument with a desig- nation of the number of angles in the shank of the instrument. Shanks may be straight, monangle (one angle), binangle (two angles), triple-angle (three angles), or quadrangle (four angles) (Fig 7-19). The term contra-angled refers to a shank in which a b two or more angles are necessary to bring the working end into near alignment (within 2 to 3 mm) with the axis of the handle Fig 7-22 End view of binangle hatchets, paired: (a) right- (see Fig 7-17b). cutting; (b) left-cutting. A double-ended binangle hatchet has left-cutting and right-cutting ends. Hatchet. In a hatchet (also called an enamel hatchet), the blade and cutting edge are on a plane with the long axis of the han- dle; the shank has one or more angles (Figs 7-19e, 7-20a, 7-21, and 7-22). The face (see Fig 7-16) of the blade of the hatchet will be directed either to the left or the right in relation to the syndrome. A handle with an intermediate diameter (5/16 inch or handle, and the instrument is usually supplied in a double- 7.9 mm) is also available. The larger diameters are encouraged ended form. Therefore, there are left-cutting and right-cutting primarily for dental hygienists, who spend a large part of their ends of the double-ended hatchet. day using hand instruments. A drawback to the use of larger handles in operative dentistry is the space they consume in an Chisel. A chisel has a blade that is either aligned with the instrument tray. handle (Figs 7-19a, 7-23, and 7-24d), slightly angled (Figs 7-19b, 7-24a, and 7-24b), or curved (Fig 7-24c) from the long axis of Nomenclature. The terminology organized by Black2 in the the handle, with the working end at a right angle to the handle. early part of the last century is still used today, with minor mod- ifications. Most names Black assigned to cutting instruments Hoe. A hoe has a cutting edge that is at a right angle to the were based on the appearance of the instrument, such as handle, like that of a chisel. However, its blade has a greater hatchet, hoe, spoon, and chisel. For an instrument that did not angle from the long axis of the handle than does the chisel; its have the appearance of a commonly used item, Black based the shank also has one or more angles (Figs 7-15, 7-19c, and 7-25). name on the intended use (eg, gingival margin trimmer). Black A general guideline for distinguishing between a hoe and a called all cutting instruments used for tooth preparation exca- chisel will be given later in the chapter. 162  Instrumentation 7 a b a b c d Fig 7-23 Straight chisel with bevels on the Fig 7-24 Chisels: (a) binangle; (b) monangle; (c) Wedel- Fig 7-25 Hoes: (a) monangle; (b) binangle. sides of the blade, to give secondary cutting staedt; (d) straight. The blades for a, c, and d are slightly The blade of a hoe has an angle from the long edges, as well as on the end (primary cutting rotated to visualize the face as well as the side bevel. axis of the handle of greater than 12.5 centi- edge). grades (45 degrees); in contrast, the blade of a chisel will have an angle from the long axis of the handle of 12.5 centigrades (45 degrees) or less (see Figs 7-33 and 7-34). a b c a b c a b Fig 7-26 Spoons: (a) triple-angle discoid Fig 7-27 End view of gingival margin trimmers, paired: Fig 7-28 (a) Left-cutting mesial gingival margin spoon; (b) binangle spoon (or regular spoon (a) right-cutting, (b) left-cutting. A double-ended gingival trimmer. (b) Left-cutting distal gingival margin or banana spoon); (c) binangle discoid spoon. margin trimmer has both left-cutting and right-cutting trimmer. (c) Right-cutting binangle hatchet. Spoons are used in tooth preparation for remov- ends, but there must be two double-ended gingival mar- ing (or “spooning out”) carious dentin. gin trimmers to complete a set, one double-ended mesial gingival margin trimmer and one double-ended distal gingival margin trimmer. Spoon. The blade of a spoon is curved, and the cutting edge at its junction with the shank; these are called discoid spoons (Figs the end of the blade is in the form of a semicircle (Figs 7-20b 7-26a and 7-26c). and 7-26b); this gives the instrument an outer convexity and an inner concavity that make it look somewhat like a spoon. Gingival margin trimmer. A gingival margin trimmer is similar Like the hatchet, the spoon has a cutting edge at the end of its to an enamel hatchet, except that the blade is curved and the blade that is parallel to the handle of the instrument; therefore, bevel for the cutting edge at the end of the blade is always on there are left-cutting and right-cutting spoons. The shank of the outside of the curve; the face of the instrument is on the some spoons holds a small circular, or disk-shaped, blade at its inside of the curve (Figs 7-27 and 7-28). Gingival margin trim- end, and the cutting edge extends around the disk except for mers, like hatchets and spoons, come in pairs (left cutting and 163 7 Nomenclature and Instrumentation a b Fig 7-29 (a) Gingival margin trimmer being used Fig 7-30 Bi-beveled cutting edge. These instru- in a proximal box of a Class 2 preparation with a ments are useful in placing retention points in horizontal (left or right) stroke to scrape (plane) some direct gold (gold foil) preparations but have a gingival wall and margin. (b) Gingival margin little use in any of the preparations described in trimmer being used with a vertical, or chopping, this book. stroke to plane a facial or lingual wall and margin. A hatchet could be used in a similar way. right cutting) (see Fig 7-27), but there are also mesial gingival is designated as left cutting. In a double-ended hoe, in addition margin trimmers and distal gingival margin trimmers (see Fig to allowing vertical or chopping strokes, one end is intended 7-28). Thus, a set of gingival margin trimmers is composed of for pulling strokes (beveled end or end with distal bevel) and four instruments: left-cutting and right-cutting mesial gingival the other is intended for pushing strokes (contrabeveled end margin trimmers and left-cutting and right-cutting distal gingi- or end with mesial bevel). val margin trimmers. Because these are usually double-ended The cutting edges of most hand cutting instruments used instruments, one instrument is a mesial gingival margin trim- today are single beveled, as are all of those described here (see mer (with left- and right-cutting ends), and the other is a distal Fig 7-16). Double-beveled, or bi-beveled, cutting edges are also gingival margin trimmer (with left- and right-cutting ends). Fig- available but have limited application in contemporary opera- ure 7-28a illustrates a mesial left-cutting gingival margin trim- tive dentistry (Fig 7-30). These instruments usually have narrow mer. Figure 7-28b illustrates a distal left-cutting gingival margin blades and are used for tasks such as adding mechanical reten- trimmer. Contrasted with these is a right-cutting hatchet (see tion points in areas of preparations that cannot be reached by Fig 7-28c). Gingival margin trimmers have many uses in addi- a bur. tion to trimming gingival margins (Fig 7-29). Numeric formulas. The configuration of the shanks combined Off-angle hatchet. Black’s instrument names apply to instru- with the appearance of the blade or the use of the instrument ments that have cutting edges that are either parallel or at a produces names such as straight chisel, monangle chisel, right angle to the handle. Instruments have been developed binangle hoe, and triple-angle hatchet. These are descriptive that have blades rotated 45 degrees from the plane of the long terms, but they are imprecise because they do not indicate axis of the handle; these are called off-angle hatchets. sizes or angles. For more complete identification of hand cutting instruments, Black2 developed a system of assigning Usage. Hand cutting instruments are, for the most part, made numeric formulas to instruments (Figs 7-31 and 7-32). The in pairs, and, as with the gingival margin trimmers, most instru- formulas make use of the metric system. For designating the ments used today are double-ended and will have one of the degree of angulation, centigrades are used. Centigrades are pair on each end (see Figs 7-15, 7-22, and 7-27). A cutting instru- based on a circle divided into 100 units (Fig 7-33), as opposed ment may be used with horizontal strokes, in which the long to the 360-degree circle ordinarily used to designate angles. In axis of the blade is directed at between 45 and 90 degrees to a centigrade circle, a right angle has 25.0 centigrades. the surface being planed or scraped (see Fig 7-29a), or with ver- tical or chopping strokes, in which the blade is nearly parallel to Three-number formula. For instruments in which the primary the wall or margin being planed (see Fig 7-29b). For horizontal cutting edge (at the end of the blade) is at a right angle to the (scraping) or vertical (chopping) strokes, the acute angle of the long axis of the blade, Black developed a formula that has three cutting edge is intended for use. The acute angle is the junc- numbers (see Fig 7-31). The first number is the width of the tion of the face of the blade with the bevel; in other words, the blade in tenths of a millimeter; the second is the length of the bevel is on the back of the blade, not the face of the blade. A blade in millimeters, and the third is the angle (in centigrades) double-ended hatchet, gingival margin trimmer, or spoon will made by the long axis of the blade and the long axis of the have one end that is designated as right cutting and one that handle (Fig 7-34). 164  Instrumentation 7 8 mm m m 7 95 c 14 c m 14 c m m m 1.3 1 10-7-14 13-95-8-14 Fig 7-31 Black’s three-number formula for instruments that have a primary cut- Fig 7-32 Black’s four-number formula for instruments that have a primary cut- ting edge (working end) that is at a right angle (90 degrees) to the long axis of ting edge (working end) that is not at a right angle to the long axis of the blade: the blade: The first number is the width of the blade in tenths of a millimeter; the The first number is the width of the blade in tenths of a millimeter; the second second number is the length of the blade in millimeters; and the third number is number is the cutting edge angle, the angle the primary cutting edge makes with the blade angle, the angle the blade makes with the long axis of the handle, in the long axis of the handle, in centigrades (c); the third number is the length of centigrades (c). The complete name of the instrument illustrated would be binan- the blade in millimeters; and the fourth number is the blade angle, the angle the gle hatchet, 10-7-14. The formula would be the same if the blade were rotated 90 blade makes with the long axis of the handle, in centigrades. Illustrated is the degrees on the shank to form a hoe, but the name would be different. Assuming right-cutting end of a distal gingival margin trimmer, 13-95-8-14. the instrument illustrated is double-ended, the right-cutting end is shown. 95 0 5 90 10 85 15 80 20 75 25 70 30 65 35 60 40 0 50 45 95 5 90 10 85 15 80 20 75 25 70 30 65 35 60 40 55 45 50 Fig 7-33 Centigrade scale. The circle is divided into 100 units. Fig 7-34 Centigrade scale inset to show angulation indica- tor of 16.0 centigrades for the blade angle of this hoe (three- number formula). The vertical axis (0.0 centigrades) is the axis of the instrument’s handle. If the blade of the instrument were 1.4 mm wide and 10.0 mm long, the formula for the instrument would be 14-10-16. 165 7 Nomenclature and Instrumentation of the blade toward the handle is said to be beveled, or to have a distal bevel (see Figs 7-24a to 7-24c); a blade with its primary cutting edge (and its face) on the side of the blade away from 95 0 5 the handle is said to be contrabeveled, or to have a mesial bevel 10 15 (see Fig 7-19c). 20 25 Recommended instrument kit. Black recommended a long 30 35 set of 96 cutting instruments, a university set of 44 cutting 55 50 45 40 instruments, or a short set of 25 cutting instruments. Because bonding technology and high-speed handpieces were not available, the dental materials of the time were more limited, 90 95 0 5 and a primary restorative material was direct gold; the lon- 85 gevity of restorations depended on the retention and resis- 80 20 tance form developed with hand cutting instruments. 75 25 70 30 With access to advanced materials and technology, current 65 35 use of hand cutting instruments is greatly diminished. The kit 40 recommended in this chapter (Box 7-1) has only 12 hand cut- ting instruments (six double-ended instruments). Because it is now recognized that there is no need to plane walls and floors of cavity preparations to smoothness with hand instruments for a restoration to perform well, hand cutting instruments play only a small, albeit important, part in cavity preparation. If burs alone were used for shaping proximal preparations, excessive sound tooth structure would have to be removed from the tooth being restored or the bur would damage the adjacent Fig 7-35 Centigrade scales inset to show angulation indicators of 7.0 centi- grades for the blade angle and 95.0 centigrades for the cutting edge angle of tooth. Hand cutting instruments enable the dentist to shape this gingival margin trimmer (four-number formula). The vertical axis (0.0 centi- and refine small proximal boxes without damaging adjacent grades) is the axis of the instrument’s handle. If the blade were 1.5 mm wide and teeth. 10.0 mm long, the formula for the instrument would be 15-95-10-7. Hatchets, hoes, chisels, and gingival margin trimmers have straight cutting edges and are designed to plane enamel and dentinal walls and margins in shaping cavity preparations, Four-number formula. For instruments in which the cutting especially in areas of the preparation that cannot be reached edge at the end of the blade is not at a right angle to the with a bur. Spoons, on the other hand, have rounded cutting long axis of the blade, such as gingival margin trimmers, edges; their intended use is the removal of carious dentin. Black designed a four-number formula (see Fig 7-32). The first Although slowly rotating round burs are most useful in remov- number is the width of the blade in tenths of a millimeter; the ing carious dentin, a spoon gives more tactile sensation and is second number is the angle (in centigrades) that the primary preferred by many operators for evaluating the hardness and cutting edge (working end) makes with the axis of the handle penetrability of dentin in tooth preparation. (Fig 7-35); the third number is the length of the blade in mil- limeters; and the fourth number is the angle (in centigrades) Noncutting instruments that the long axis of the blade makes with the handle. In margin Non–tooth-cutting hand instruments are similar in appearance trimmers, a cutting edge angle of greater than 90 centigrades is to cutting instruments, except that the blade used for tooth intended for distal gingival margins (see Fig 7-32); an angle of preparation is replaced with a part that has a totally different 85 centigrades or less is intended for mesial gingival margins. use. In noncutting instruments such as burnishers and con- densers, the blade is replaced by a nib or point.2 The flat end of Chisel versus hoe. Although Black defined a chisel as having a the nib of a condenser is called the face. Amalgam carvers have blade that is aligned with the handle or slightly curved from it, carving blades instead of tooth-cutting blades. terminology has evolved so that a chisel may also have a blade Condensers, carvers, and burnishers are used to place dental that is angled from the handle up to 12.5 centigrades.5 A chisel amalgam and, to a certain extent, resin composite restorative with a blade angled more than 3.0 or 4.0 centigrades from the materials. Plastic filling instruments are used to place resin axis of the handle must be binangle for the instrument to be composite and glass-ionomer materials, provisional restorative balanced. materials, and sometimes cavity-basing materials into tooth If the blade is angled more than 12.5 centigrades, the instru- preparations. Spatulas may be necessary for mixing cavity- ment is defined as a hoe. In a curved or angled chisel or a hoe, lining and cavity-basing materials, provisional restorative mate- a blade with its primary cutting edge (and its face) on the side rials, and cements for luting inlays, onlays, and crowns. 166  Instrumentation 7 Box 7-1 Suggested operative dentistry instrument kit A compact assembly of hand instruments that will satisfy Therefore, instrument sequence in the kit proceeds most operators’ needs during any amalgam, resin com- from the mirror and explorer for examination, to the posite, glass-ionomer, ceramic, or cast gold restorative plastic instrument used to facilitate dam placement as procedure is presented here. This kit is especially useful well as for placement of materials, to tooth preparation for dental schools and large group practices. Dental stu- instruments, to restoration placement instruments. The dents, residents, and practitioners have used the kit, and, kit uses a 26-slot tray with a small well (open, boxlike sec- although another instrument may have to be added for tion) from American Eagle. American Eagle has this tray a specific situation from time to time, the kit will more and others available with customizable color-coded tabs than suffice for most procedures. The kit was designed to facilitate replacement of similarly color-coded instru- with the sequence of most operative procedures in mind. ments into the correct positions in the tray. In slots (in this order, from left to right, with the open well Clipped to lid of tray: to the rear): Hemostat, mosquito, 5-inch curved Mirror, no. 5 with handle Scissors, Quimby Explorer–periodontal probe, XP23/QOW Cotton forceps (college, with serrations) Sterilized separately and available for each operative pro- Plastic instrument, no. 1-2 cedure: Spoon, discoid, 11½-7-14 Hatchet, 10-7-14 Anesthetic syringe Hoe, 12-10-16 Rubber dam kit (forceps; punch; frame; 1 each of clamps Gingival margin trimmer, 10-80-7-14 W2A, 27, and 212SA; and 2 W8ASA clamps [Hu-Friedy]) Gingival margin trimmer, 10-95-7-14 Brasseler bur block (no. A600) with burs arranged in the Wedelstaedt chisel, 10-15-3 following order: Applicator/spatula (American Eagle or Miltex) – Friction-grip burs, no. 1/8, ¼, 1, 2, 33 ½, 56, 169L,170, 329, Condenser, SA1 (American Eagle or Miltex) 330, 7404, OS1F, 7803, 7901, ET9F Condenser, SA2 (American Eagle or Miltex) – Latch burs, no. 2, 4, 6, 8 Condenser, SA3 (American Eagle or Miltex) – Mandrel for pop-on disks Burnisher, beavertail-ovoid, 2/30 Burnisher, PKT3 Sterilized separately and available for occasional use: Barghi no. 1 (paddle-shaped for composite) (American Eagle) Condenser, SA4 Carver, cleoid-discoid, UWD5 Hemostat, mosquito, 5-inch straight Carver, Walls no. 3 Mirror, no. 2 (on handle) Carver, Hollenback no. ½ Proximal contact disks (Thierman Products or Centrex) Carver, interproximal (IPC) (see chapter 8) Carver, no. 14L Rubber dam clamps, 00, W1A, W8A Articulating paper forceps Scaler, McCalls, SM13s-14s Carrier, amalgam, medium/large Spatula, no. 24 (or 324) In well of tray: Scalpel handle, no. 3, flat Sharpening stone, flat, Arkansas or ceramic Tofflemire retainer, straight Tofflemire retainer, contra-angle Amalgam well, stainless steel, small (American Eagle or Miltex) 167 7 Nomenclature and Instrumentation a a b b c d Fig 7-36 Amalgam carriers: (a) regular; (b) large. Amalgam carriers are usually Fig 7-37 Condensers with round faces: (a) SA1, with 0.5- and 0.7-mm-diameter supplied as double-ended instruments. They are available in several different faces; (b) SA2, with 0.7- and 1.0-mm faces; (c) SA3, with 1.5- and 2.0-mm faces; diameters; for example, mini is 1.5 mm; regular (medium) is 2.0 mm; large is 2.5 (d) SA4, with a 2.5-mm face on the binangle end and a 1.5-mm face on the triple- mm; and jumbo is 3.0 to 3.5 mm. These are the approximate inside diameters angle or back-action end. of the cylinders of amalgam carriers and may vary slightly from manufacturer to manufacturer. Amalgam carriers. For dental amalgam restorations, amalgam with the largest condenser face that will fit into the area. Firm is placed into the preparation with an amalgam carrier, an pressure will push the condenser into the increment of com- instrument with a hollow cylinder that is filled with amalgam posite and risks forming a void in the restoration. (Fig 7-36). A plunger operated with a finger lever pushes the amalgam out of the carrier into the preparation. Carvers. Carvers are used to shape amalgam and resin com- posite and other tooth-colored materials after they have been Condensers. Condensers are used to compress amalgam or to placed in tooth preparations. Figure 7-38 shows the shapes of push resin composite or glass-ionomer materials into all areas the blades of a cleoid-discoid carver. Figure 7-39 illustrates six of the preparation. The working ends, or nibs, of condensers commonly used carvers. In general, when a convex amalgam may be any shape, but usually they are round with flat ends contour is being carved, a concave-shaped carver facilitates the (faces). Figure 7-37 shows four round condensers of different shaping or carving. Likewise, a convex carver facilitates carving sizes and configurations. Other commonly used condenser nibs of a concave shape. A convex carver may be used to carve a are triangular, rectangular, or diamond shaped. Amalgam is convex surface; the surface is carved tangentially, with multiple condensed by pushing the condenser directly into the prepara- strokes. Whether a carver is used to carve amalgam or resin tion and confining the amalgam between the condenser face composite, it is important that the blade be sharp. and the preparation floor through vertical pressure (vertical The cleoid-discoid (or discoid-cleoid) carvers shown in Figs condensation). The amalgam is condensed against the vertical 7-39a and 7-39b are used primarily for occlusal carving in amal- walls of the preparation (lateral condensation) by angling the gam restorations. The Walls no. 3 carver (see Fig 7-39c) is useful nib and using the end for condensation or by lateral, or side-to- for carving occlusal surfaces; the end that is shaped like a hoe is side, movements of the condenser, using the sides of the nib to also useful for shaping cusps and for carving facial and lingual condense the amalgam. surfaces of large amalgam restorations. The Hollenback no. ½ The condensation pressure applied to the amalgam with a carver (see Fig 7-39d) is useful for occlusal, proximal, and axial condenser depends on the size of the face and the amount of (facial and lingual) surfaces; several larger Hollenback carvers, force used by the operator. For small condensers, such as the with the same general shape, are also available. The inter- SA1 condenser (see Fig 7-37a), little force is needed. The nibs of proximal carver (IPC) (see Fig 7-39e) has very thin blades and the SA1 condenser are 0.5 and 0.6 mm in diameter. For larger is extremely valuable for carving proximal amalgam surfaces condensers, such as the SA3 (see Fig 7-37c), with nib diameters near the interproximal contact area, as well as those surfaces of 1.5 and 2.0 mm, a significant amount of force (6 to 8 lbs) mentioned for the Hollenback carver (occlusal, proximal, axial). gives optimum condensation. Other uses for this instrument include placing and shaping When condensers are used in placing resin composite or resin composite and glass ionomer and pushing retraction cord glass-ionomer materials, the resin material is not actually con- into a gingival sulcus. The no. 14L carver (see Fig 7-39f) can be densed but is pushed or patted into all areas of the preparation used to carve proximal surfaces, or it may be used for carving 168  Instrumentation 7 a b Fig 7-38 (a) Cleoid-discoid carver: (top) cleoid end; (bottom) discoid end. This type of carver is a double-ended instrument. Cleoid means claw shaped. Both shapes are useful in carving occlusal surfaces of amalgam restorations. The point of the cleoid carver is used to carve the bases of grooves in the occlusal amalgam, and the tip is usually very slightly rounded so that the grooves it carves will not be sharp. (b) Cleoid (top) and discoid (bottom) ends of the cleoid-discoid carver. a a b c b d e c f Fig 7-39 Amalgam carvers: (a) large cleoid-discoid (Tanner no. 5 [5T]) carver; Fig 7-40 Burnishers: (a) PKT3 (rounded cone-shaped) burnisher, designed by (b) small cleoid-discoid (UWD5) carver; (c) Walls no. 3 carver; (d) Hollenback Peter K. Thomas as a waxing instrument but useful in placing direct restorations no. ½ carver; (e) interproximal carver (IPC); (f) no. 14L sickle-shaped carver. as well; its rounded end and cone shape allow it to serve most functions that a small ball-shaped burnisher would serve, plus others; (b) beavertail (no. 2) burnisher; (c) football or ovoid (no. 30) burnisher. The ovoid burnisher, available in various sizes (eg, 28, 29, and 31), can be used for final condensation of amal- gam and the initial shaping of the occlusal anatomy in amalgam. The beavertail and ovoid burnishers are useful for burnishing margins of cast gold restorations. convex facial and lingual surfaces of very large amalgam resto- Burnishers. Burnishers are used for several functions. The word rations. The no. 14L carver has a very strong, hollow-ground tri- burnish is defined as “to make shiny or lustrous, especially by angular blade, so it can be used to remove amalgam overhangs rubbing; to polish” and “to rub (a material) with a tool for com- from completely set amalgam. pacting or smoothing or for turning an edge.”6 Burnishing is Although most of the shaping of resin composite restora- probably used in all of these ways in dentistry. Two frequently tions should be completed before the material is polymer- used double-ended burnishers are illustrated in Fig 7-40. ized and most operators prefer to use rotary instruments for One use of burnishers is to shape metal matrix bands so post-polymerization shaping, several amalgam carvers are that they impart more desirable contours to restorations. Large also useful for carving resin composite. The discoid carvers burnishers are used with considerable force to pinch off freshly are especially useful for lingual concavities of anterior teeth; condensed amalgam at the margins, or, in other words, to cleoid and discoid carvers and the hoe-shaped end of the Walls impart some condensation and to begin shaping the occlusal no. 3 carver are useful for occlusal surfaces of posterior resin surfaces of amalgam restorations. After the amalgam has been composite restorations. Another carver very useful for resin carved, a burnisher may be used with a gentle rubbing motion composite restorations is a disposable scalpel blade (no. 12 or to smooth the surface. The PKT3 (P. K. Thomas no. 3) burnisher no. 12B blade) mounted in a scalpel handle. (see Fig 7-40a) and some other burnishers are also useful for 169 7 Nomenclature and Instrumentation b a c Fig 7-41 (a) The Almore Gold Microfil instrument is very useful for placing and contouring large, anterior resin composite restorations or veneers. (b) The no. 1-2 plastic instrument, made of stainless steel, is useful for placing a rubber dam, placing and shaping resin composite and other tooth-colored restorative materials, and packing gingival retraction cord into the sulcus around a crown or abutment preparation before an impression is made. Some cord-packing instruments are similar to the no. 1-2 plastic instrument but may have serrated ends to provide better control of the cord. (c) A plastic instrument made of hard plastic, rather than metal, is preferred by some operators for placing resin composites. sculpting occlusal anatomy in posterior resin composite resto- 7-39e), for instance, is preferred by some operators for packing rations prior to polymerization of the resin. knitted cord and placing and shaping resin composite. Burnishers are used to “bend” cast gold near the margin to These instruments are now available in both hard plastic narrow the gap between the gold and the tooth. This closing of and metal, and metal instruments are available with several a marginal gap is best accomplished with a narrow burnisher, different coatings on blades or nibs to prevent resin materials such as the side of a beavertail burnisher, used with heavy force from sticking to them. The original rationale for using an instru- in strokes parallel to the margin but about 1.0 to 1.5 mm away ment made of plastic (Fig 7-41c) was to eliminate abrasion of from it. If burnishing is accomplished directly on a thin gold metal by the quartz in resin composites, which caused gray- margin, the gold can be bent severely and may break. ness in the tooth-colored material. Because of changes in the inorganic fillers used in many of today’s resin composites, the Plastic instruments. Plastic instruments (or plastic filling instru- problem of metal abrasion and graying is unusual and material- ments) are so named because they were originally designed to specific, so even a stainless steel instrument functions well to use with plastic restorative materials, such as acrylic resins, or carry and shape resin composite. other nonmetal restoratives, such as the silicates, used in the middle of the 20th century. The name does not refer to the Cement spatulas. A variety of materials in operative dentistry material from which the instrument itself is constructed. They require mixing, some on a glass slab, others on a paper pad. are currently used to carry and shape tooth-colored restor- Several spatulas are available, and they vary in size and thick- ative materials, such as resin composites and glass-ionomer ness (Fig 7-42). The larger cement spatulas were originally restorative materials. Many specially designed instruments are designed for mixing luting cements and the smaller spatulas available, in a myriad of shapes and sizes, for contouring resin for cavity liners, but since the advent of resin luting cements, composite and resin-modified glass ionomer prior to curing. A the smaller spatulas are frequently used for mixing small plastic instrument with a large, slightly curved, paddle-shaped amounts of those materials. The thinner spatulas are flexible; blade (eg, Almore Gold Microfil Instrument, Almore; Fig 7-41a) the thicker ones are rigid. Selection of a rigid or flexible cement is very useful for placing and contouring large, anterior resin spatula is dependent on the desired viscosity of the cement composite restorations or veneers. and personal preference. A commonly used plastic instrument is the no. 1-2 (Fig 7-41b). The double-ended instrument has a nib or blade on Sharpening of hand instruments each end, one at a 90-degree angle to the other. Other double- To assess sharpness, the user of the instrument should look at ended plastic instruments have a blade-type nib on one end the cutting edge in bright light; the presence of a glint indi- and a condenser nib on the other. The bladed plastic instru- cates that the edge is dull or rounded (Fig 7-43). Alternatively, ments have many uses in operative dentistry in addition to the dentist can pull the instrument across hard plastic, such as carrying and contouring restorative materials. The IPC (see Fig the handle of a plastic mouth mirror or an evacuator tip. A dull 170  Instrumentation 7 a b c a b Fig 7-42 Spatulas: (a) no. 24, a flexible spatula, is used for luting cements such Fig 7-43 (a) The glint from the cutting edge of this hoe indicates that the blade as zinc phosphate and glass ionomer; (b) no. 24A is thicker, for more rigidity; (c) is quite dull. (b) After sharpening, no glint is noticeable. no. 313 is used for cavity liners, such as calcium hydroxide liners. a b Fig 7-44 The sharpness-testing stick is a hard plastic stick used for testing the sharpness of instruments. To test sharpness, the blade should be applied to the stick at an angle that is similar to that applied during use and pulled or pushed in a direction that is similar to the direction of its intended use. (a) Testing the sharpness of a monangle chisel. (b) Testing the sharpness of the discoid end of a Walls no. 3 carver. blade will slide across the plastic; a sharp blade will cut into the face of the blade, the blade should make a 45-degree angle the surface, stopping movement. A specially made, sterilizable, with the surface of the sharpening stone (Figs 7-46 and 7-47). sharpness-testing stick is also available (Fig 7-44) (Dalron Test When spoons, discoid carvers, and cleoid carvers are sharp- Stick, American Eagle or Miltex). ened, the instrument is rotated as the blade is advanced on Sharpening is performed in different ways for different the flat stone (Fig 7-48). The bevel is at 45 degrees, or slightly hand instruments. When chisels, hatchets, hoes, and margin more or less, to the face, and the instrument is advanced on trimmers are sharpened, the cutting-edge bevel is placed flat the stone with the bevel against the surface of the stone and against a flat stone on a stable surface, and the instrument the cutting edge of the instrument perpendicular to the path is pushed or pulled so that the acute cutting angle is moved of advancement. When a blade with a rounded edge is being forward, with fairly heavy force on the forward stroke and with sharpened, the handle cannot simply be twirled to achieve the little or no force on the back stroke (Figs 7-45 and 7-46). Usu- desired rotation but must actually be swung in an arc to keep ally, unless the instrument has been badly neglected, only two the cutting edge of the blade perpendicular to the direction of or three forward strokes are required. Because the bevels of the stroke and the bevel parallel with and against the surface these instruments should usually make a 45-degree angle with of the stone. 171 7 Nomenclature and Instrumentation a a b b Fig 7-45 Sharpening the two ends of a double-ended Wedelstaedt chisel: (a) Fig 7-46 Sharpening the two ends of a double-ended binangle hoe: (a) sharp- sharpening the contrabevel end (inside or mesial bevel); (b) sharpening the ening the bevel end (outside or distal bevel); (b) sharpening the contrabevel end bevel end (outside or distal bevel). The end bevel (for the primary cutting edge (inside or mesial bevel). The primary bevel is always flat against the stone; the or working end) of each blade is placed flat on the stone; the blade will make face of the blade is up. a 45-degree angle with the stone. In the primary sharpening stroke, the cutting edge is moved forward. Unless the instrument is very dull, only two or three fairly heavy forward strokes will be necessary to sharpen the cutting edge. Blunt Correct Steep (45-degree bevel) Fig 7-47 Bevels of sharpened cutting instruments. Working-end bevels of chis- Fig 7-48 Sharpening a cleoid carver. The handle is swung in an arc to rotate els, hatchets, and hoes, as well as the bevels of amalgam carvers, should be at the blade as the bevel is pulled forward on the stone. This movement is used to approximately 45 degrees to the face of the blade. The cutting edge at the left is keep the cutting edge perpendicular to the direction of the stroke. too blunt, the center blade has a correctly angled cutting edge, and the cutting edge at the right is too acute and will dull rapidly. 172  Instrumentation 7 a b Fig 7-49 Sharpening a discoid spoon with a rotat- Fig 7-50 (a) Front-surface mirror. Any object touching the mirror, such as the tips of the cotton forceps, will ing sharpening stone. A discoid spoon may also appear to be touching itself. (b) Mouth mirrors: (top) no. 2 (5/8-inch diameter); (middle) no. 4 (7/8-inch diameter); be sharpened on a flat stone; the blade is rotated (bottom) no. 5 (15/16-inch diameter). as it is pulled with the cutting edge forward. If the face is ground with a rotating stone, the blade will be thinned and could be more likely to break dur- ing use. The discoid carver and spoon may be sharpened with a con- Mirrors. For every procedure performed in the mouth, the den- tinuous rotation of the blade; the shank moves clockwise from tist must have clear and distinct vision of the field. Wherever the 9 o’clock position to the 3 o’clock position in one motion. possible, the field should be viewed with direct vision. When For the cleoid carver, however, the rotation begins with the needed, the mouth mirror allows the operator to visualize areas shank in the 9 o’clock position and continues clockwise only of the mouth that he or she would not otherwise be able to see. until the bevel just next to the point is ground (see Fig 7-48); to It also allows the operator to maintain a body position that will sharpen the other side of the cleoid, the rotation begins with reduce health problems associated with poor posture. the shank at the 3 o’clock position and continues counterclock- Almost as important as its allowing indirect visualization of wise to the point. If sharpening both sides of a cleoid carver obscure areas of the mouth is the mirror’s function as a reflec- creates a sharp point at its tip, the junction of the bevels at the tor of light into the area being examined or treated. A mirror point should be slightly rounded. that is positioned properly allows the operator to visualize the The blade of a discoid spoon may be sharpened by grinding field of operation in the mirror and, at the same time, reflects the face of the blade with a rotating stone (Fig 7-49). This meth- the operating light into that area. To accomplish this, the light od of sharpening also thins the blade, and care must be taken should be positioned behind and directed just to the side of the to avoid rendering the blade so thin that it could easily break. operator’s head and into the mirror. Sharpening machines are available. A slowly rotating sharp- The mouth mirror can also serve as a retractor of soft tissue ening wheel is employed by one type of machine; an oscillat- (tongue, cheeks, or lips) to aid access and visualization. ing flat stone, or hone, is used by another. These machines are For clarity of vision, the reflective surface of the mirror useful for sharpening instruments between patients and before should be on the external surface of the glass. This type of sterilization. mirror is called a front-surface mirror (Fig 7-50a). Mouth mirrors When instruments are sharpened during an operative pro- are usually round and come in a variety of sizes (Fig 7-50b). cedure, they should be sharpened with a sterile stone. When The most widely used sizes for adults are the no. 4 and no. 5. a stone is sterilized, it should not have oil in or on it, because For constricted areas in posterior regions of the mouth, when the oil may thicken during the sterilization process and form a a rubber dam is in place, a smaller mirror, such as a no. 2, is shellac-like coating that will prevent the abrasion needed for helpful. sharpening. A good substitute for oil is water. Stones lubricated with water should be washed well or cleaned in an ultrasonic Explorers. Explorers are pointed instruments used to feel tooth cleaner after use to remove the metal filings prior to steriliza- surfaces for irregularities and to determine the hardness of tion. A flat, white Arkansas stone or fine synthetic sharpening exposed dentin. The explorer that is used most often is the stone should be made a part of the operative dentistry instru- shepherd’s hook, or no. 23, explorer (Fig 7-51a). Another useful ment kit so that it is available during each procedure. shape is a cowhorn explorer, which provides improved access for exploring proximal surfaces (Fig 7-51b). The no. 17 explorer Mirrors, explorers, periodontal probes, and forceps is also useful in proximal areas (Fig 7-51c). Mirrors, explorers, periodontal probes, and forceps are basic instruments that will be needed during each appointment for Periodontal probes. Periodontal probes are designed to detect diagnosis or treatment. and measure the depth of periodontal pockets. In operative 173 7 Nomenclature and Instrumentation 10 9 8 7 a 5 3 2 1 3 6 9 b 12 a b 1. 5 8. 5 5. 5 c c 3. 5 Fig 7-51 Dental explorers: (a) no. 23 explorer (shepherd’s hook); (b) 3CH Fig 7-52 Periodontal probes: (a) QOW probe (Michigan O probe with Williams explorer (cowhorn or pigtail); (c) no. 17 explorer. markings); (b) PCP12 probe (Marquis markings); (c) PSR (periodontal screening and recording) probe. a b a Fig 7-53 Cotton forceps: (a) College (no. 17); (b) Meriam (no. 18). a b b Fig 7-54 Articulating paper forceps: (a) Forceps handles provide a spring that Fig 7-55 Hemostats: (a) Halstead mosquito straight, 7-inch; (b) Halstead mos- keeps the jaws closed together; they are opened (as shown) by squeezing the quito curved, 5-inch. handle. (b) The entire length of the piece of articulating paper or tape is sup- ported by the jaws of the forceps. 174  Instrumentation 7 Fig 7-56 Two-handed instrumentation. The use of both hands can make refine- Fig 7-57 Pen grasp. The pen grasp is not actually the way a pen is held for ment of a preparation more precise. The right hand is thrusting and rotating the writing. The instrument is held between the index finger and thumb, and the instrument while the index finger of the left hand guides and assists the motion middle finger is placed atop the handle or shank, nearer the working end of the of the working end to refine a proximal margin of a Class 2 preparation. A similar instrument, to provide more force, or thrust, directed toward the working end of dual-handed action is useful for condensing amalgam; it allows increased con- the instrument. densation force to be controlled. a b Fig 7-58 (a) Pen grasp used in a chopping (downward) motion. The ring finger is resting on the incisal edges of the anterior teeth. During the use of any instrument in the mouth (with the exception of the mirror), a firm rest must be achieved on teeth or attached gingival tissue. (b) Pen grasp as the instrument is used more posteriorly and with a side-to-side or scraping motion. The small finger and ring finger are resting on the facial and occlusal surfaces, respectively. dentistry, they are also used to determine dimensions of instru- Instrument grasps ments and of various features of preparations or restorations. The operator should master two basic instrument grasps, the There are many periodontal probe designs; the differences are pen grasp, which provides more flexibility of movement, and in the diameters, the position of the millimeter markings, the the palm or palm-thumb grasp, which provides limited move- configuration of the markings (eg, whether they are notched ment but controlled power. Usually only one-handed grasps or painted), and the design of the tip. Three commonly used are used, but occasionally two-handed instrumentation is probes are illustrated in Fig 7-52. needed to make refinement of a preparation more precise (Fig 7-56). Forceps. Forceps of various kinds are useful in operative den- tistry. Cotton forceps are used for picking up small items, such Pen grasp. This is the most frequently used instrument grasp in as cotton pellets (small cotton balls), and carrying them to the operative dentistry. The pen grasp is actually different from the mouth (Fig 7-53). Other forceps useful in operative dentistry way one would grasp a pen (Fig 7-57); the handle of the instru- include articulating paper forceps (Fig 7-54) and hemostatic ment is engaged by the end, not the side, of the middle finger; forceps (hemostats) (Fig 7-55). A hemostat locks tightly, so this provides more finger power. The pen grasp is initiated by it is often helpful in placing or removing items used to con- placement of the instrument handle between the thumb and fine amalgam for condensation. Articulating paper forceps are index finger; the middle finger engages the handle near the designed to carry an inked tape to the mouth to mark the con- shank or on the shank itself (Figs 7-57 and 7-58). The ring finger tacts of teeth in opposing arches during closure. is braced against the teeth to stabilize instrument movement (see Fig 7-58). 175 7 Nomenclature and Instrumentation Fig 7-59 Palm-thumb grasp. The instrument is grasped much nearer to its Fig 7-60 The palm-thumb grasp is used frequently when a hand cutting instru- end than in the pen grasp so that the thumb can be braced against the teeth to ment, such as a gingival margin trimmer, is used in Class 3 preparations that provide control during movement of the instrument. have lingual access. The thumb is resting on the incisal edges of the teeth. The palm-thumb grasp is also used frequently with the Wedelstaedt chisel, usually for facial access in posterior and anterior operations, and occasionally for lingual access. Palm or palm-thumb grasp. In this grasp, the thumb serves as millimeters of the long axis of the handle of the handpiece to a brace (Fig 7-59). Side-to-side, rotating, or thrusting move- provide balance. ments of the instrument by the wrist and fingers are controlled There are two types of contra-angle handpieces, which are by the thumb, which is firmly in contact with the teeth (Fig 7-60). classified by their speed potential. Low-speed contra-angle handpieces have a typical free-running speed range of 500 to Instrument motions 15,000 rpm; some are able to slow to 200 rpm, and others are The following are some of the many motions used with hand able to achieve speeds of 35,000 rpm. High-speed handpieces instruments: can achieve a free-running speed greater than 160,000 rpm, and some handpieces attain free-running speeds up to 500,000 Chopping (in the direction of the working end of the instru- rpm.7 In the United States, most dentists are accustomed to air- ment or parallel to the long axis of the blade) turbine high-speed handpieces. The speed of these handpieces Pulling (toward the operator’s hand) during tooth preparation is 180,000 rpm and lower, depending Pushing (away from the hand) on the application pressure and the power of the handpiece. Rotating For air-turbine handpieces, speeds during tooth preparation Scraping (with the blade directed at an angle between 45 and are significantly less than their free-running speeds. 90 degrees to the surface being scraped and moved side to Electric handpieces (powered by an electric motor instead side or back and forth on the surface) of an air-turbine) have been used for some time in Europe, and Thrusting (forcibly pushing against a surface) their use is rapidly growing in the United States. Most electric handpieces achieve free-running speeds of 200,000 rpm, an ideal speed for cutting enamel. Electric handpieces are very Rotating instruments efficient in preparing teeth. High-speed techniques are generally preferred for cutting Handpieces enamel and dentin. Penetration through enamel and exten- In dentistry, two basic types of handpieces are used: the sion of the cavity outline are more efficient at high speed. straight handpiece (Fig 7-61) and the contra-angle handpiece Small-diameter burs should be used in the high-speed hand- (Fig 7-62). In the straight handpiece, the long axis of the bur piece. High speed generates considerable heat, even with is the same as the long axis of the handpiece. The straight small-diameter burs, and should be used with air and water handpiece is used more frequently for laboratory work but is coolant sprays8 and high-efficiency evacuation. For refining occasionally useful clinically. preparations, a high-speed handpiece may be slowed consid- The primary handpiece used in the mouth is the contra- erably and used with only air coolant and a gentle brushing or angle handpiece. As with hand instruments, contra-angle indi- painting motion in which each application of the bur to the cates that the head of the handpiece is angled first away from, tooth is brief. This technique allows visualization and prevents and then back toward, the long axis of the handle. Also as overheating.9 with hand instruments, this contra-angle design is intended to Low-speed contra-angle handpieces, with round burs rotat- bring the working point (the head of the bur) to within a few ing very slowly, are used for removal of carious dentin. Low- 176  Instrumentation 7 Fig 7-61 Straight handpiece. This handpiece Fig 7-62 Contra-angle handpiece. This is a high-speed contra-angle hand- is used occasionally in the mouth, but it is more piece, which is used with small-diameter burs for rapid cutting of tooth structure frequently used extraorally, for tasks such as or restorations. A low-speed contra-angle is also useful for removal of carious making adjustments to removable prostheses or dentin, with a slowly rotating round bur, and for shaping and polishing with abra- adjusting and repolishing a cast gold or ceramic sive disks and impregnated rubber polishers. Some operators also prefer the restoration prior to insertion. The bur installed in low-speed contra-angle for refining tooth preparations. this handpiece is a tree-shaped denture bur. a ø 2.35 mm (2.33 – 2.35 mm) 31.7 mm (27.9 – 35.8 mm) b ø 2.35 mm (2.33 – 2.35 mm) 13.2 mm (10.6 – 13.9 mm) c ø 1.59 mm (1.59 – 1.60 mm) 12.7 mm (10.2 – 13.8 mm) Fig 7-63 Typical dimensions (and ANSI/ADA standard dimension tolerances), in millimeters, of the three common bur designs: (a) straight handpiece bur; (b) latch-type bur for latch-type contra-angle handpiece; (c) friction-grip bur for friction-grip contra-angle handpiece.10,11 speed contra-angle handpieces are also used for various finish- ry in 1871 and the electric engine in 1872.4 The most significant ing and polishing procedures that use abrasive disks, points, advancement, which has made present-day high-speed cutting or cups. possible, is the tungsten carbide bur, which became available There are two types of contra-angles based on their bur- in 1947.10 locking, or chucking, mechanisms for the low-speed handpiece: Burs have three major parts: the head, the neck, and the a friction-grip chuck and a latch-type chuck. The shanks of the shank (Fig 7-64). For the different types of handpieces or hand- burs that fit into each of these types of contra-angle chuck are piece heads, there are burs with different designs and dimen- shown in Fig 7-63. The high-speed handpiece will receive only sions (see Fig 7-63). the friction-grip bur. The head of a bur is the portion that cuts. The cutting action is produced by blades on the head, and the blades are pro- Burs duced by cuts made into the head. The angle of the cutting Hand-rotated dental instruments are known to have been used edge of a blade (edge angle) is usually not acute; the angle is in since the early 1700s. The foot engine came into use in dentist- the range of 90 degrees to provide strength to the blade and 177 7 Nomenclature and Instrumentation Fig 7-64 Parts of a rotary cutting instrument (bur). Head Neck Shank Inverted Straight Tapered Pear- Round cone fissure fissure shaped Direction of rotation Cutting edge Clearance face Clearance angle Rake face Edge angle Rake angle Fig 7-65 Typical bur head, viewed from the end of the bur nearest the handpiece.5,10 Fig 7-66 Basic bur head shapes for tooth preparation. Most burs used for tooth preparation are modifications of these burs. The primary modifications are lengthening of the bur heads and rounding of ends or corners to allow preparations to be cut without sharp line angles. longevity of cutting efficiency of the bur. A cross section of a that time.10 That system has been modified and expanded as typical six-bladed bur is shown in Fig 7-65; the names of the new burs have been developed. The American National Stan- faces and angles of the blades are also shown. The bur in Fig dards Institute/American Dental Association (ANSI/ADA) speci- 7-65 has a negative rake angle, as do most burs used in den- fication11 provides standard characteristics for dental burs; this tistry.10 The negative rake angle increases the life expectancy specification lists both the US numbers and the International of the bur and provides for the most effective performance in Standards Organization (ISO) numbers for dental burs. low- and high-speed ranges. Prior to the advent of high-speed handpieces, it was found A positive rake angle would produce a more acute edge that additional cuts across the blades of a dental bur increased angle. Positive rake angles may be used to cut softer, weaker cutting efficiency; these cuts were called crosscuts. Today, with substances, such as soft carious dentin. If a blade with a posi- high-speed handpieces, crosscut burs are not normally of any tive rake angle were used to cut a hard material, such as sound benefit. enamel or dentin, it would dig in, leaving an irregularly cut Table 7-1 shows diagrams, US bur sizes, and the head surface, and the cutting edges of the blades would chip and diameters of many available regular carbide tooth-preparation dull rapidly. burs. ISO sizes for each type of bur can be calculated from the The basic shapes of tooth-preparation burs used in opera- diameter: A bur with a diameter of 0.8 mm will have an ISO size tive dentistry are shown in Fig 7-66. Many other shapes are of 008; a diameter of 1.0 mm will have an ISO size of 010. The available; most are modifications of these five. Numbering ISO sizes are combined with the shape of the bur, so an ISO systems have been introduced to describe the shapes of den- inverted cone 006 is an inverted cone bur with a 0.6-mm major tal burs. The original system, introduced by SS White Dental diameter; from Table 7-1, it can be determined that an ISO Manufacturing, had nine shapes based on the burs available at inverted cone 006 corresponds with a US no. 33½ bur. 178  Instrumentation 7 Table 7-1 Shapes and diameters of regular carbide burs used for tooth preparation (US designations*) Round Bur size 1 ⁄16 1 ⁄8 1 ⁄4 1 ⁄2 1 2 3 4 5 Diameter (mm) 0.3 0.4 0.5 0.6 0.8 1.0 1.2 1.4 1.6 Bur size 6 7 8 9 11 Diameter (mm) 1.8 2.1 2.3 2.5 3.1 Inverted cone Bur size 331⁄2 34 35 36 37 39 40 Diameter (mm) 0.6 0.8 1.0 1.2 1.4 1.8 2.1 Straight fissure† Bur size 551⁄2 56 57 58 59 60 Diameter (mm) 0.6 0.8 1.0 1.2 1.4 1.6 Straight fissure, rounded end (straight dome)† Bur size 1156 1157 1158 Diameter (mm) 0.8 1.0 1.2 Straight fissure, crosscut† Bur size 556 557 558 559 560 Diameter (mm) 0.8 1.0 1.2 1.4 1.6 Straight fissure, rounded end, crosscut (straight dome crosscut) Bur size 1556 1557 1558 Diameter (mm) 0.8 1.0 1.2 Tapered fissure† Bur size 168 169 170 171 Diameter (mm) 0.8 0.9 1.0 1.2 Tapered fissure, rounded end (tapered dome)† Bur size 1169 1170 1171 Diameter (mm) 0.9 1.0 1.2 Tapered fissure, crosscut† Bur size 699 700 701 702 703 Diameter (mm) 0.9 1.0 1.2 1.6 2.1 Pear† Bur size