CHAPTER 4

OPERATIVE DENTISTRY

INTRODUCTION

Operative dentistry is the area of dental practiceconcerned with the prevention and treatment of defectsin tooth enamel and dentin. Since many patients needtreatment that is provided in operative dentistry, this iswhere most of the dental assistants are assigned.Operative dentistry includes the treatment andrestoration of carious teeth with metallic andnonmetallic dental materials. These materials areusually amalgam, composite resins, and glass ionomerrestorations.

PURPOSE

Operative dentistry provides treatment to restore apatient’s dental condition to a healthy, functional, andesthetically (pleasing to the eye) acceptable level.Operative dentistry primarily is responsible for therestoration of decayed or fractured teeth. This chapterprovides information and procedures that you may berequired to perform in operative dentistry.

AREAS OF OPERATIVE DENTISTRY

You must be aware that each operative proceduremay not be performed in the same manner. Basicprocedures are usually performed during eachoperative appointment. Some of these procedures arealso used in other dental specialties. The areasdiscussed in this chanter are as follows:

Identification of operative instruments

Miscellaneous instruments, materials, andequipment

Four-handed dentistry

Basic dental procedures

Operative procedures

Supply procedures

IDENTIFICATION OF OPERATIVE

INSTRUMENTS

Because of the many hard to reach areas in thehuman mouth and various functions required,

operative instruments come in a wide variety of sizesand shapes. To be an effective dental assistant, youmust be able to understand why, where, and when thedentist will use them. We will discuss hand cuttinginstruments, amalgam instruments that consist ofcondensers, carvers and burnishers, and composite(resin) instruments.

HAND CUTTING INSTRUMENTS

Many dental procedures require the use of handinstruments with sharp cutting edges. This cuttinginstrument group used in operative dentistry includesexcavators, chisels, hatchets, hoes, and gingivalmargin trimmers. They are used in the cavitypreparation of both amalgam and composite (resin)restorations.

Spoon Excavators

The spoon excavator is a double-ended instrumentwith a spoon, claw, or disk-shaped blade. Spoonexcavators are used primarily to remove debris fromtooth cavities. Their tips and sides are designed forcutting action. The most common sizes are the smalland the large (fig. 4-1) spoon extractors.

Chisels

Dental chisels are commonly referred to asminiature chisels. Chisels are used to cleave (split)tooth enamel, to smooth cavity walls, and to sharpencavity preparations. The two most common types usedin operative dentistry are the Wedelstaedt and bianglechisels (fig. 4-2). The Wedelstaedts have slightlycurved shanks and are used primarily on anterior teeth.The biangle chisels have two distinct angles—one atthe shank, and one at the working end. This designallows access to tooth structures that would not bepossible with straight chisels.

Hatchets

A dental hatchet (fig. 4-3) resembles a camper'shatchet, except much smaller. Like dental chisels,some have single cutting ends, and others have cuttingedges on both ends of the handle. Hatchet blades are set

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Figure 4-1.—Small and large spoon excavators.

Figure 4-2.—Wedelstaedt and biangle chisels.

Figure 4-3.—Hatchet.

at a 45- to 90-degree angle from the shank. Theseinstruments have different lengths and widths ofblades. Hatchets are used on the wall of the cavitypreparation to cleave enamel and cut dentin so therewill be a sharp cavity outline.

Hoes

Dental hoes (fig. 4-4) look like a miniature gardenhoe. They are used with a pulling motion to smooth andshape the floor and sides of cavity preparations. Hoeblades are set at a 45- to 90-degree angle from theirhandle.

Gingival Margin Trimmers (GMTs)

The gingival margin trimmers (GMTs) (fig. 4-5)are modified hatchets that have working ends withopposite curvatures and bevels. As the name implies,GMTs are used to trim, smooth, and shape the gingivalfloor of a cavity preparation. GMTs are available indouble-ended styles and are used in pairs, such as the#26 and #27. This is because the working ends of theeven-numbered instruments are designed for use onthe distal surfaces, and the odd numbered are used onthe mesial surfaces.

AMALGAM RESTORATIONINSTRUMENTS

The instruments discussed in this section are usedwhen the dentist elects to use an amalgam or atemporary dental material to restore a tooth.

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Figure 4-4.—Hoe.

Figure 4-5.—Gingival margin trimmers (GMTs).

Condensing Instruments

To deliver the amalgam to the cavity preparationand properly condense (pack) it, the dentist will use avariety of instruments. Amalgam carriers andcondensers are used for this purpose.

completed, eject any remaining a: nalgam alloy fromthe carrier into the amalgam well The carrier is nolonger serviceable when the amalgam is allowed toharden in the carrier.

CONDENSERS. —Amalgam condensers, oftencalled pluggers, are instruments used to condense or

AMALGAM CARRIERS.—Amalgam carriers(fig. 4-6) transport the freshly prepared amalgamrestorative material to the cavity preparation. Thesecarriers have hollow working ends, called barrels, intowhich the amalgam is packed for transportation. Bothsingle and double-ended carriers are available with avariety of barrel sizes including: mini, large, andjumbo. When the lever (located on the top of thecarrier) is depressed, the amalgam is ejected into thecavity preparation. Normally, two carriers are usedduring the amalgam placement procedure. This savestime for the dentist who is ejecting or condensing acarrier load while you are refilling the carriers. Apoorly packed carrier of amalgam handed to the dentistmay fall out before it is ejected into the cavitypreparation. It is your responsibility to ensure that allcarriers are properly packed before the transfer to thedentist. After amalgam material placement is

pack the amalgam filling materials into the cavitypreparation. The hammer-like working end is largeenough to compress the soft amalgam without sinkinginto it. Condensers come in single- and double-endeddesigns. They have various shaped and sized workingends, which may be smooth or serrated as shown infigure 4-7.

Carvers

After the amalgam is condensed, it must then becarved to approximately the same original toothstructure. Carvers have sharp cutting edges that areused to shape, form, or cut tooth anatomy into amalgamrestorations. Figure 4-8 illustrates these instruments thatcome in assorted shapes and sizes in double-endeddesigns. Many carvers were designed for carvingspecific tooth surfaces. The Interproximal and #1/2Hollenback were designed for carving proximal (inbetween) tooth surfaces; whereas, the discoid-cleoid #89/92 and Tanner #5 are used on occlusal surfaces.Carvers shaped similar to Vignon or Frahm #2/3 (also

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Figure 4-6.—Amalgam carriers.

Figure 4-7.—Amalgam condensers.

called acorn carvers) are used to quickly carve thebasic anatomy on occlusal surfaces. As withcondensers, dentists also have favorite carvers thatthey use routinely. You must know the dentist'spreference so that you can have the desired instrumentready when it is needed.

Burnishers

When the carving is complete, the dentist may use

burnishers to smooth and polish the restoration, and to

remove scratches left on the amalgam surface by a

carving instrument. Burnishers have smooth rounded

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Figure 4-8.—Carvers.

working ends and come in single- and double-endedtypes. Some of the more commonly used burnishersare shown in figure 4-9.

COMPOSITE RESIN INSTRUMENTS

A variety of double-ended instruments make upthis instrument group. They are used to transport andplace dental cements, resins, temporaries, andinsulating and pulp-capping materials. The workingends on composite resin instruments range fromvarying small cylinders to assorted angled, paddle-likeshapes. Figure 4-10 illustrates the Woodson #3, #W3,and #11 (also know as Stellite), which are some of thecommonly used instruments in this category.

Other types of composite resin instruments aremade of plastic. Plastic instruments can be heatsterilized and used on composites and cements. Theyeither come included in the kit of resin material fromthe manufacturer or, in some cases, can be ordered as aset as shown in figure 4-11. Some advantages to usingplastic instruments are that they won't discolor orcontaminate the composite restoration, and compositeresin material will not cling to the instrument. Figure 4-9.—Burnishers.

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Figure 4-10.—Composite and cement instruments.

Figure 4-11.—Plastic composite instrument set.

Another instrument frequently used with etchingand bonding procedures associated with compositeresins is a disposable brush with a reusable handle. Anexample is shown in figure 4-12. Single-use disposalbrushes are being used more frequently, aiding in goodinfection control practices.

CEMENT AND INSULATING BASEINSTRUMENTS

The instruments in this group are used for mixingand handling restorative resin, and various temporaryrestorative, insulating, and pulp-capping materials.

Spatulas

Three different spatulas are available for mixingrestorative materials, as shown in figure 4-13. Some ofthese spatulas can cause discoloration in the materialbeing mixed. The selection of a mixing spatula is notcritical except when preparing a permanent anteriorcomposite restoration. Some composite restorationmaterial discolors easily, so use the spatulas providedby the manufacturer when working with it. The single-ended #322 and #324 are suitable for mixing othermaterials other than composites. A smaller version forthe #324 is the #313 spatula. The #313 is used formixing small quantities of cement.

Insulating Base Instruments

Insulating base instruments have a small metal ballat the working end and are often referred to as calciumhydroxide instruments. They are used to mix, carry,and place insulating bases, and are available as a

Figure 4-12.—Disposable brush and handle. Figure 4-13.—Spatulas.

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single-ended instrument or as a double-endedinstrument, shown in figure 4-14.

MISCELLANEOUS INSTRUMENTS,MATERIALS, AND EQUIPMENT

A number of miscellaneous instruments,materials, and equipment are used in operativedentistry. Instruments such as dental mirrors,explorers, and cotton forceps are called a basic dentalset (BDS) and are usually used in all dental specialties.

ASPIRATING SYRINGE

This syringe is used in dentistry to inject a localanesthetic. The aspirating syringe differs from mostsyringes in that it is designed to inject anesthetic from acarpule (fig. 4-15). The parts of an aspirating syringeconsist of a threaded tip where the needle attaches, abarrel where the carpule is placed, a piston rod(plunger) with a harpoon attached that embeds itselfinto the rubber stopper of the carpule, a finger grip, anda thumb ring (fig 4-16). The harpoon allows the dentistto aspirate (draw back) the injection site to see if theneedle tip is located in a blood vessel before injectingthe anesthetic solution. Once the harpoon is engagedinto the rubber stopper of the anesthetic carpule, thedentist can apply inward or outward pressure on the

Figure 4-14.—Double-ended calcium hydroxide instrument.

Figure 4-15.—Anesthetic carpule.

stopper by exerting pressure on the thumb ring. Pullingthe thumb ring outward also pulls the plunger outwardproducing an aspirating effect; whereas, pushinginward forces the anesthetic solution through theneedle.

ASPIRATING SYRINGE NEEDLE

The aspirating syringe needles used in dentaltreatm ent arrive sterile and are disposable. They aredesigned for a single use, and are available in differentgauges and lengths (fig. 4-17). The gauge of a needlerefers to the diameter of the hollow shaft of the needle.The larger the gauge, the smaller in diameter theneedle. The lengths of the needles vary, and areclassified as long (L) or short (S).

Each needle has either a plastic or metal hubdesigned to screw onto the threaded end of the syringe(fig. 4-18). This hub is positioned to permit the needleto extend inward to penetrate the rubber seal portion ofa loaded anesthetic carpule.

The plastic caps covering the sterile needle areeasily removed from both ends. When placing theneedle onto the syringe, remove only the cap thatcovers the syringe end on the needle. This maintainsthe sterility of the needle portion used to inject thepatient.

Normally, you prepare the anesthetic syringe witha short needle (13/16 inch in length) for maxillaryinjections, and a long needle (17/8 inches in length) formandibular injections. The tip of the needle has abeveled angle, which is turned toward the alveolus toaccurately deposit the solution.

RUBBER DAM INSTRUMENTS

Rubber dam instruments include the rubber dampunch, clamps, clamp forceps, and frame. Theseinstruments prepare and maintain the position of thinsheets of latex rubber (rubber dam material). Therubber dam itself is used to isolate a designated tooth orteeth in the mouth before certain operative, endodonticand preventive dentistry procedures are performed.The rubber dam provides a clean, dry field of operationand improves the dentist’s view of the operating site. Italso keeps fluids, tissues, and the tongue away from theoperating site and prevents the patient fromaccidentally swallowing or aspirating debris.

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Figure 4-16.—Parts of an aspirating syringe.

Figure 4-17.—Different gauges and lengths of aspiratingsyringe needles.

Rubber Dam Punch

The rubber dam punch is used to make necessaryspaced holes in the rubber dam material. The workingend is designed with a plunger on one side and a wheelon the other side (fig. 4-19). This wheel has differentsized holes on the flat surface facing the plunger.These features let the operator select and adjust the

Figure 4-18.—Parts of the aspirating syringe needle.

wheel to punch the desired diameter hole in the rubberdam.

Figure 4-19 also illustrates the recommendedholes on the wheel to use. The largest hole is used onthe tooth that your clamp will go on. The last fiveremaining holes correspond to the teeth that areincluded in the isolation.

Rubber Dam Clamps

After the required number of holes are punched inthe rubber dam, it is stretched to fit over each designedtooth. To maintain a snug fit around the neck of the

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Figure 4-19.—Two styles of rubber dam punches.

tooth, a rubber dam clamp is used. These clamps aremade of spring steel in various sizes (fig. 4-20) to fitthe general contours of the different teeth. You willneed to know some of the commonly used clamps andtheir area of use, which are shown in table 4-1.

Clamps commonly used in pediatric dentistryinclude the #2, #4, #8A, and #14A. Clamps with "W"prefixes, such as the #W8A or W3, indicate that theclamps are without wings on the outer portionsopposite the holes.

Table 4-1.—Commonly Used Rubber Dam Clamps and

Their Area of Use

Clamp # Area of use in the mouth

0 Primary teeth

2 Small bicuspids

W3 Bicuspids and small molars

7 Mandibular molars

W8A Partially erupted molars

9

2 1 2

Anterior teeth

Anterior teeth

Figure 4-20.—Rubber dam clamps.

The space between the gripping edges of the clampis narrower than the diameter of the correspondingtooth. Thus, to place the clamp around the tooth, it isnecessary to spread the gripping edges wider than thetooth's diameter. To spread the gripping edges, rubberdam clamp forceps are used.

Rubber Dam Forceps

The rubber dam clamp forceps (fig. 4-21) aredesigned to spread the two working ends of the forcepsapart when the handles are squeezed together. The

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Figure 4-22.—Adult rubber dam frame.

Figure 4-21.—Rubber dam clamp forceps.

working ends have small projections that fit into twocorresponding holes on the rubber dam clamps. Thearea between the working end and the handle has asliding lock device. This sliding lock device locks thehandles in positions while the provider moves therubber dam clamp around the tooth.

Rubber Dam Frame

To place and clamp a rubber dam around the toothis not enough. The dentist still needs something to holdthe loose outer edges of the rubber dam sheet so that thearea is visible, and provides access to the tooth beingtreated. The need is met with an instrument called therubber dam frame. Most of the rubber dam frames usedtoday are U-shaped. One of the most popular is theYoung frame, which is available in adult (fig. 4-22)and pediatric sizes. When the edges of the rubber damare connected to the small, sharp projections on thisU-frame, there is adequate access to, and visibility ofthe area of treatment.

RUBBER DAM APPLICATION

The use of the rubber dam is an important part ofquality dental treatment and infection control. To savevaluable chairside time, place the rubber damfollowing the administration of local anesthetic (asdirected by the dentist). To place the rubber dam, you

will need the rubber dam material, frame, punch,clamps, and clamp forceps.

Preparation

The first step in applying the rubber dam is tocheck the contact areas of the teeth to be isolated. Use apiece of dental floss to do this. The next step is todetermine which tooth the rubber dam clamp will beplaced upon. Once this is determined, select a rubberdam clamp for a trial placement.

CAUTION

To prevent the patient from aspirating orswallowing the rubber dam clamp, always tiedental floss (ligature) on the bow of the clampbefore placing it in the patient’s mouth.

A simple and secure method is put both ends of apiece of floss together and place them on a flat surface.This forms a looped end where the floss is folded inhalf. Place the clamp over the floss with the bow of theclamp facing up. Now, place the two loose endsthrough the looped end and carefully pull the looseends through the loop until the floss is secured tightlyover the bow of the clamp (fig. 4-23). You should now

Figure 4-23.—Ligature on rubber dam clamp.

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have a securely placed ligature on the clamp. You arenow ready to place the clamp on the rubber damforceps.

Hold the clamp with the bow facing upward andaway from the forceps. Place the small projections onthe working ends of the rubber dam forceps into thecorresponding holes on the rubber dam clamp.Squeeze the handles of the forceps together to alignprojections with the corresponding holes on the clamp.Once the clamp is placed on the forceps, tilt the forcepsupright and slide the locking device on the forcepsdownward to lock the handles in position. Locking theforceps handles is necessary to continue the tensionrequired to keep the clamp attached to the forceps.Now the clamp is ready for trial placement.

Pass the rubber dam forceps, with the working endcovered, with the palm of your hand and the clamppointed toward the placement position of the tooth. Besure to hold on to the ligature while the clamp ischecked for proper fitting. Normally, the clamp shouldfit near or slightly below the cementoenamel junction.To stabilize the clamp, all the tips of the clamp must bein contact with the tooth to establish a facial lingualbalance. Exercise care to ensure that the clamp tips donot impinge on the gingival tissues. If it does, it willcause the patient to experience pain. If the clamp is notplaced properly, it may spring off the tooth and causeinjury. Caution is advised to stabilize the clamp firmlyon the tooth before the clamp forceps are loosened.Once the trial placement is complete, remove theforceps and attach the clamp until final placement.

To prepare the rubber dam material, you need therubber dam punch to make the appropriate number ofholes of varying sizes. The punch has an adjustablewheel with holes of varying sizes. By adjusting thewheel, holes of different sizes are produced in thematerial when the cutting tip strikes the hole in thewheel. The holes in the rubber dam material must bepunched firmly and cleanly. A ragged hole or tag willtear easily as the dam is placed over the crowns of theteeth. A ‘ragged hole also may cause leakage ofmoisture around the tooth.

Ideally, the rubber dam material is marked (fig.4-24) with predetermined markings of an average archusing a rubber dam stamp and ink pad. This makespunching the rubber dam material easier because youhave a pattern to follow with the normal shape of thearch and spacing alignment of the teeth. Beforepunching the material, always check the oral cavity forany missing, misaligned, or extra teeth. You will needto make adjustments from the standard pattern for

these items. Punch the hole for the tooth to be treatedfirst. Then, determine what additional holes must bepunched. Normally, you will punch holes for the twoanterior and at least one tooth posterior to the toothbeing treated. An exception to this is root canaltherapy when only the involved tooth is exposed. Afterthe holes are punched, apply a slight amount of watersoluble (brushless shaving cream) lubricant to the backof the material over the crowns and contact areas of theexposed teeth. Now the rubber dam is ready forplacement into the oral cavity.

Placement

The rubber dam material and clamp can be placedusing several methods. The first method usuallyrequires assistance. Place the rubber dam frame on theoutside of the dam with the bow of the frame facingout. Stretch the dam material from side to side tosecure the corners of the dam on the four projections atthe corner of the frame. The rubber dam materialshould appear baggy on the frame rather than tight toallow easier placement in the oral cavity. Pass therubber dam and attached frame to the dentist forplacement in the oral cavity. As the dentist stretchesthe rubber dam material over each tooth to be isolated,the assistant uses floss to slip the septum (rubber dammaterial between the holes) between the teeth withouttearing the material. Always place the floss on thetooth, never directly on the rubber dam itself.Placement of the floss upon the tooth assists inbringing a single thickness of the dam through the

Figure 4-24.—Marked rubber dam material.

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proximal contact when the floss is carried through.Floss placed on the rubber dam itself tears the dam andrequires the passing of two thicknesses of the damthrough the contact. Once the floss passes the contactof the teeth, release the lingual end of the floss. Loopthis end toward the opposite end and floss through thecontact again. Now, gently remove the floss by pullingit from the side horizontally, rather than attempting topull the floss back up through the contact vertically.Continue using the floss to invert the inter-proximalseptum, mesially and distally as well. Inversion of therubber dam turns the edges of the dam inward or under,around the isolated teeth, to provide a seal. After this iscompleted, pass the rubber dam clamp forceps andattached clamp to the dentist for final placement on thetooth. Adjustment of the rubber dam material on theframe can be made at this time to ensure a smooth andstable fit. Wrap the ligature attached to the clamparound a projection on the side of the frame. Thisprevents the clamp from becoming a dangerousprojectile if it should spring off the tooth. Pass a dullinstrument, such as a stellite instrument, to theprovider for inversion of the rubber dam on the facialand lingual areas of the exposed teeth. Dry the exposedteeth with air from the three-way syringe as needed toassist in the inversion.

The second method places the rubber dam clampon the tooth first. Then slip the rubber dam materialover the clamp. Next, in either order, attach the frameand expose the remaining teeth through the holes.Secure the clamp ligature to the frame. Then invert themesial and distal septum with floss, and the facial andlingual areas with a dull instrument accompanied withair from the three-way syringe.

In the third method, the clamp is held in the rubberdam forceps and the rubber dam placed over the bow ofthe clamp. Holding the edges of the rubber dam withyour fingers, use the forceps to carry the dam andclamp into the patient’s mouth. Place the clamp on thetooth and remove the forceps. Continue the placementas in the second method. The last two methods ofrubber dam placement are valuable when a rubber dammust be placed by one individual rather than two.After the restoration is placed, remove the rubber dam.

Removal

Before the rubber dam is removed, use the watersyringe and high-volume evacuator (HVE) to flush outall debris that collected during the procedure. Ratherthan pulling the septa through the contact of a newlyplaced restoration, the septa is cut. Stretch the rubber

dam material outward in the facial area of the isolatedteeth. This pulls the septa facially to provide access forcutting. Use a pair of small blunt-nose scissors to cuteach septum of the rubber dam from the facial aspect(fig. 4-25). When all the septa are cut, gently pull thedam lingually to free the rubber dam completely fromthe interproximal spaces. Use the clamp forceps toremove the clamp. Simultaneously, remove the clampligature from the frame. Set the clamp forceps andclamp aside. Now, remove the dam with the frameattached. Wipe the patient's mouth, lips, and chin witha tissue or gauze. Carefully inspect the dam on a flatsurface for missing pieces. If a fragment of the rubberdam is missing, check the corresponding interproximalarea of the oral cavity with a mirror and explorer.Pieces of the rubber dam left under the free gingivacause severe gingival irritation. Use dental floss toremove any material stuck between the teeth. Rinsethe patient’s mouth with the water syringe and HVE toremove all debris from the oral cavity.

MATRIX RETAINERS

Matrix retainers are used to hold the matrices(metal bands or strips) firmly in place around a tooth.Matrix retainers and metal bands are used incombination for a temporary mold while the fillingmaterial is being packed into place. The Tofflemireretainer (or matrix retainer) is available in threedifferent designs: the universal straight, contra-angle,and contra-angle junior (pedodontic) shown in figure4-26. These retainers are practically maintenance free.They can be heat sterilized along with other dentalinstruments. Your part in maintaining matrix retainersis to check them periodically and replace those withbadly worn screw threads. You are also expected toattach the correct matrix band to the appropriateretainer in anticipation of the dentist’s needs.

Figure 4-25.—Cutting rubber dam septum.

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Figure 4-26.—Matrix retainers.

Figure 4-27.—Amalgam matrix bands. A: Precontoured.

B: Junior (Pedodontic #15 with aprons). C: Wide #2 withaprons. D: Junior #13 (Pedodontic). E: Universal #1.

Amalgam Matrices

Amalgam matrices are made of very thin flexiblestainless steel available in either roll form or in bands.At times, the standard packaged matrix bands do not

provide the necessary length, width, or shape for aparticular cavity preparation. When this is the case, thedentist can cut the metal matrix strips to form theneeded band. Bands used with the Tofflemire retainerscompletely encircle the tooth. Matrix bands come inassorted sizes and shapes, as shown in figure 4-27. Themost commonly used band is the Universal or Straight#1 size. The Junior #13 is the smaller pedodonticversion of the #1 Universal. The Wide #2 and Junior#15, (which have extensions known as “aprons”) areused when additional length is needed for a preparationextending below the gingiva. A dentist usually preferscertain types of these bands over others. With practice,you should become very proficient in having thepreferred band on the appropriate retainer.

ASSEMBLING MATRICES

When multiple surfaces of the tooth are removedduring the cavity preparation, a matrix is used toapproximate the original surface and hold therestorative material in proper form and position until itsets. The type of matrices used depends on the type ofrestorative material placed. You will need to have theright type of matrix available and assembled ready foruse during the procedure.

Amalgam matrices are made of very thin, flexiblestainless steel available in either roll form or bands.The matrix band, retainer, and wedge are used incombination to form a temporary mold while thefilling material is being packed.

The matrix is assembled and placed before theamalgam is mixed. After the amalgam has beenpacked, the matrix and wedge must be removed beforethe final carving can be accomplished.

The most commonly used retainer is the universalstraight Tofflemire. Its components are shown infigure 4-28.

Figure 4-28.—Components of the matrix retainer.

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To assemble the matrix, hold the retainer in onehand with the slots in the guide posts and locking visef a c i n g u p w a r d . T u r n t h e l a r g e i n n e r n u tcounterclockwise to position the locking vise close tot h e g u i d e p o s t . T u r n t h e s m a l l o u t e r n u tcounterclockwise until the rod is not visible in thelocking vise slot. In your other hand, grasp the bandwith the ends placed evenly together. Place the edge ofthe band with the larger circumference (occlusal edge)into the diagonal slot at the vise end of the retainer.With the. band placed in this manner, the largercircumference is toward the occlusal surface and thesmaller circumference toward the gingiva, as shown infigure 4-29. Continue to ease the band through theinner guide post slot. As figure 4-30 shows, positionthe band through the left guide post for teeth on themandibular right or maxillary left quadrants. For teethin the mandibular left or maxillary right quadrants,position the band through the right guide posts. Turnthe outer nut clockwise until the rod tip presses firmlyagainst the band in the lock vise to secure the band.Turn the inner nut counterclockwise to increase thesize.

When the assembled matrix is placed over theprepared tooth, the slot opening of the retainer and thesmall circumference of the band are positioned toward

Figure 4-29.—Large and small circumferences of the band.

Figure 4-30.—Positioning the band to the right or left for theappropriate quadrants.

the gingiva, and the retainer is placed along the facialsurface of the tooth. The handle of the retainer extendsout of the oral cavity at the corner of the lips. Thedentist gently manipulates the matrix band into theinter-proximal space on either side of the tooth. Thedentist then places an index finger or thumb over theocclusal surface to hold the band in place and tightensthe band by turning the inner nut clockwise to fitsnugly around the tooth. At this time, the dentist maydecide to place a wedge along the side of the matrixband.

Wedges

Wedges are small, tapering, triangular pieces ofwood or clear plastic about 1/2 inch in length. Wedgesare available in various sizes, which may be colorcoded. They are either plain (straight) or anatomicallyshaped (fig. 4-31). Clear plastic anatomical wedgesare designed for use with light-cured materials.

material to the confines of the prepared cavity marginsand the band itself.

matrix band around the tooth may not always produce asnug fit. This leaves space through which condensedrestorative material can be pushed out to create anundesirable overhanging restoration. The dentist useswedges to force the matrix band or strip tightly againstirregular tooth surfaces to prevent these spaces. Thissnug fit then restricts the firmly condensed restorative

Since the general shape oftooth crowns varies, the

Matrix Removal

Because new restorations fracture easily, useextreme care when removing the matrix band. Toremove the matrix band and retainer, the dentist, first

Figure 4-31.—Wedges.

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gently manipulates the point of an explorer around theinside edge of the band. This contours the marginalridge of the restoration and removes the excessamalgam around the matrix band. The assistant willpass the dentist hemostats or cotton forceps to removethe wedge if one was placed. With the thumb or fingerover the occlusal surface of the restoration and matrixband , the ou te r and inne r nu t s a re tu rnedcounterclockwise to loosen the retainer from the band.After the retainer is removed, the remaining band iscarefully removed. A loose end of the band is graspedwith the hemostats or cotton forceps and gently rockedback and forth until the band comes out of theinterproximal space. Remove the band from the otherinterproximal space in the same manner.

PIN AMALGAM SET

Extensive decay or a cusp fracture results in theloss of a major portion of the tooth structure. Torestore such a tooth to its former healthy condition, thedentist may choose to rebuild the tooth. If the tooth is aposterior one, the dentist may use the pin amalgamtechnique. For a pin amalgam restoration, the dentistuses specif ic instruments. The pin amalgaminstruments are packaged in kits in which pin burs(drills), self-threading pins, and pin (hand) wrenchesare precision matched. It is extremely important tokeep the set together since there are a large variety oftypes and sizes. The pins are placed with a handwrench in the tooth preparation to anchor the amalgamor restorative material in place (fig 4-32). A pinbender is frequently used to bend or slightly adjust theposition of inserted pins. Follow the manufacturer'sinstructions before handling these materials.

FOUR-HANDED DENTISTRY

The goal of four-handed dentistry is to allow thedentist and assistant to function as a team in a seated

position with maximal efficiency and minimal strain.Four-handed dentistry, as it has been developed, notonly increases productivity, but also reduces stress andfatigue on the provider and assistant. Four-handeddentistry can be used in all of the specialty areas, and inoperative dentistry. It is discussed here becauseinstrument exchanges in operative dentistry requireyou to perfect this task. To be an effective dentalassistant in four-handed dentistry, you must know thecorrect zones and positions that you are in and whereyou are in relation to the patient and dentist. Alsocorrect passing and receiving of instruments andmaterials to the dentist is a task that must be practicedto work efficiently with the dentist.

ZONES AND POSITIONS

The position of the patient is determined by theprocedure to be performed. Most dental treatment isprovided with the patient in the supine position. Oncethe patient has been seated, the dentist and the assistantshould place themselves in the proper positions fortreatment. These positions are best understood byrelating them to a clock. In the clock concept, animaginary circle is placed over the dental chair, withthe patient’s head at the center of the circle. The circleis numbered like a clock with the top of the circle at 12o'clock. The clock, as shown in figure 4-33, is dividedinto four zones of operation:

Static zone

Assistant's zone

Transfer zone

Operator's zone

The use of these zones is the key to the efficientimplementation of the principles of four-handeddentistry. For right-handed dentists, seated to theright of the patient, the operator's zone is between 8and 11 o'clock, and the assistant's zone is between 2

Figure 4-32.—Using a hand wrench to place pins in a toothpreparation.

Figure 4-33.—Zones of operation for four-handed dentistry.

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and 4 o'clock. For left-handed dentists, seated to theright of the patient, the operator's zone is between 1and 4 o'clock position and the assistant's zonebetween 8 and 10 o'clock. Whenever the treatment siteis on the lingual surfaces of anterior teeth, the dentist(right or left-handed) generally uses the 12 o'clockposition.

The transfer zone is from 4 to 8 o'clock.Instruments and materials are passed and received inthis zone over the chest and at the chin of the patient.All instruments and materials are located in theassistant's zone.

The static zone, from 11 to 2 o'clock, is a non-traffic area where equipment, such as nitrous oxide,can be placed with the top extending into the assistant'szone. When an object is heavy, or material or aninstrument is objectionable if held near the patient'sface, you may pass or hold it in the static zone. As anexample, anesthetic syringes are sometimes passed tothe dentist in this area so that the patient will not bealarmed at the sight of the syringe. Part of this area canalso be used when the provider is positioned in the 12o'clock position as previously mentioned.

Dentists and dental assistants should sit with theirback straight and head relatively erect. This helpsprevent curvature of the spine. The patient should belowered to a position that places the treatment site asclose to the dentist's elbow level as possible. When thepatient is properly positioned, the dentist's eyes shouldbe 14 to 16 inches from the treatment site.

As the assistant, you should sit as close as possibleto the back of the patient's chair with your feet directedtoward the head of the chair. This position lets youreach the treatment site, hose-attached instruments,and instruments and materials from the mobile cart orinstrument tray without leaning, twisting, oroverextending your arms. In this position you are alsoable to observe the patient’s responses throughout theprocedure. Adjust your stool so that your eye level is 4to 6 inches above the dentist's eye level. Like thedentist, the assistant should sit in an erect position. Theassistant's chair may have a curved, movable armrest.This armrest may be adjusted in front to support thebody just below the rib cage. Using this armrest as abrace, you are able to lean slightly forward from thehips only. Place your feet firmly on the foot-supportring at the base of the assistant chair so that your feetare parallel to the floor. The mobile cart or instrumenttray should be placed toward the head of the patient'schair, and positioned to allow you easy access to theneeded instruments and materials.

PASSING AND RECEIVINGINSTRUMENTS AND MATERIALS

To increase production while reducing stress andfatigue of the dentist and the assistant, you and thedentist will need to work together as a team. You mustbe able to anticipate the dentist’s needs and fulfill thoseneeds without unnecessary delay. To accomplish this,you must know the sequence of the treatmentprocedure and have the required instruments andmaterials ready at the proper time. When you assist infour-handed dentistry, you must also irrigate with airand water as well as aspirate with the high-volumeevacuator throughout the procedure. To enable you topass and receive items efficiently during theprocedure, we will begin with instrument transfers.

Instrument Exchange

Instrument exchange between the dentist andassistant takes place in the transfer zone near thepatient's chin. As the assistant, you must anticipate thedentist's needs, and be ready when signaled by thedentist to pass the next instrument and receive the usedone in a smooth motion. An alert assistant does notneed a verbal command to make the exchange, butshould be constantly ready when the exchange signaloccurs . Idea l ly , the ins t rument t r ans fe r i saccomplished with a minimum of motion involvingmovement only of your fingers, wrist, and elbow.During the transfer, the dentist should not move thefinger rest or eyes from the treatment site. When theexchange is completed, the dentist pivots the workinghand back to the working position.

You should arrange the instrument setup in anorderly fashion. Usually the instruments are set upfrom left to right, in the sequence in which they are tobe used. You should return them to their originalposition following use in case they need to be reused.

Let's assume that you are assisting a right-handed dentist and, therefore, are seated on the leftside of a patient. Since your right hand is busyaspirating, you must learn to transfer instrumentswith your left hand. The one-hand instrumentexchange is discussed next.

ONE-HAND INSTRUMENT EXCHANGE.—The actual instrument transfer is divided into fourstages—working, signal, pre-transfer, and mid-transfer.

In the working stage, pick up the next instrumentto be used from the instrument tray with your left

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hand. Grasp the instrument between your thumb and

first two fingers by the end opposite from the working

end as shown in figure 4-34 (step A). Hold the working

instrument close to the treatment area and parallel to

the instrument being used. Extend your little finger to

receive the instrument being used by the dentist as

shown in figure 4-34 (step B). finger.

The signal stage takes place when the dentistsignals for the next instrument by slightly raising theinstrument from the tooth. During this stage, thedentist maintains his/her fulcrum (finger rest) and,with a pivotal action, rotates the working hand awayfrom the patient's oral cavity. This positions the usedinstrument so that vou can grasp it with vour little

Figure 4-34.—Instrument exchange (steps A through D).

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In the pre-transfer stage, grasp the used instrumentfirmly using the little finger as shown in figure 4-34(step C). Sometimes, you may prefer to use the last twoor even three fingers to receive the used instruments.Immediately following this action, you carry out themid-transfer stage.

In this stage, place the next instrument into thedentist's hand with the working end positioned towardthe treatment site, as shown in figure 4-34 (step D).When the treatment site is located on the maxillaryarch, point the working end of the instrument up.Likewise, when the treatment site is on the mandibulararch, position the working end down. Do not releaseyour grip of the new instrument until the dentist hasfirmly grasped the instrument. If the instrumentsbecome tangled during the exchange, this is usuallycaused by failure to parallel the handles before theexchange. The exchange of all instruments is donewith firm, deliberate movements to give both thedentist and the assistant the feeling of confidence andto eliminate lost time and motion. Return the usedinstrument to its original position on the instrumenttray and prepare to repeat the procedure with the nextinstrument required.

Refer to figure 4-35 for an overhead view (left-handed) of an instrument exchange during patienttreatment. When you assist from the right side of the

Figure 4-35.—Overhead view of instrument exchange.

patient, use your right hand in the same mannerdescribed for the left hand.

O T H E R I N S T R U M E N T E X C H A N G ETECHNIQUES.—Other instrument exchangetechniques may have to be used depending on whattype of instrument is being exchanged. These othertechniques have been described in "Oral SurgeryAssistance," Volume 2, chapter 5.

Handpiece and Bur Exchange

The dental handpiece can be exchanged foranother instrument in the same manner described inthis section. If two handpieces are exchanged, exercisecaution to avoid tangling the hoses during theexchange.

During the operative procedure, the dentist holdsthe handpiece firmly over the patient's upper chest inthe transfer zone, and then the assistant will loosen andremove the bur. The assistant next retrieves the burthat was selected by the dentist and places it into thedental handpiece and secures it. Always give the bur agentle tug to ensure that it is firmly seated in thehandpiece. If the dentist uses a different instrumentbetween bur exchanges, change the bur outside thetransfer zone, usually over the tray setup.

If the dentist changes handpieces and requires anexchange of burs in the returned handpiece, be sure touse the lock-out toggle switch for the handpiece beforeattempting to change burs. If you fail to do this, youcould cause harm to yourself when the provider stepson the foot control to activate the other handpiece.

Preparing and Passing Materials

Dental materials are exchanged at the patient'schin in the transfer zone. This prevents materials frombeing dropped on the patient’s face. Small amounts ofdental materials may be mixed and passed on a glassslab, paper pad, or dappen dish.

As a dental assistant, you must prepare dentalmaterials at the proper time during the procedure. Amaterial mixed too soon does not allow sufficienthandling time. Knowing when to mix is equally asimportant as knowing how to mix. As withinstruments, knowing the routine of the procedure letsyou anticipate when the dentist will need the specificmaterial. You should have the mixing equipmentready and the material in position and in place slightlybefore the time it is needed. Begin mixing only whenyou know the dentist is ready.

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When you are assisting during an amalgamrestoration, load the amalgam into the carrier and passthe loaded carrier to the dentist. You may sometimesuse two or more amalgam carriers, which lets you fillthe barrel of one while the dentist is using the other.You must also add into this sequence of filling andrefilling the amalgam carriers the passing ofcondensing instruments to the dentist during theamalgam restoration process.

During the use of cements, most dentists preferthat you leave the mixed cement on the glass slab ormixing pad and then hold the pad or slab in your handnear the treatment site. The dentist can select theamount desired. In your other hand, you can hold theair syringe to dry the area for application andplacement of the material. With the use of somematerials, you may need to hold a gauze sponge in yourhand (rather than the air syringe) to wipe excessmaterial from the application instrument.

The overall idea in passing and receiving dentalinstruments and materials is to have the needed item atthe right place, in the right position, at the right time. Indoing this, the dentist is then free to concentrate moreon the area of treatment.

BASIC DENTAL PROCEDURES

Some basic dental procedures, such as admini-stration of local anesthetic, irrigation, aspiration, andretracting of tissues, are performed in nearly all aspectsof all clinical dentistry. Others such as rubber damapplication and assembling of matrices are performedin operative procedures. Except for the administrationof local anesthetic, you must be able to perform theseprocedures. When administration of local anesthetic isrequired, you need to prepare all the items used for thisprocedure.

LOCAL ANESTHETIC

Before doing a possibly painful dental procedure,the dentist will give the patient a local anesthetic tomake the treatment site insensitive to pain. You mustbe knowledgeable of the various techniques used toprepare for the correct type of injection. Thesetechniques such as topical, infiltration, and blockinjections have been discussed in Volume I, chapter 7,"Oral Pharmacology."

Pre-Injection Items

Before giving a local anesthetic, the dentist mayuse the following pre-injection items to prepare theinjection site:

Antiseptic solution

2 x 2 inch gauze sponges

Cotton tip applicators

Topical anesthetic

The dentist may have the patient use an antisepticmouthwash to rinse the oral cavity before applying atopical anesthetic. The gauze sponges are used to drythe injection site mucosa before applying the topicalanesthetic. The topical anesthetic, usually supplied inan ointment, is applied with a cotton tip applicator toreduce the pain associated with the injection of theneedle.

Injection Items

The items used to give local anesthetics are anaspirating syringe, needle, and carpule. It is alsoimportant to know the different types of anesthetic andhow to assemble and disassemble the aspiratingsyringe properly for the dentist's use.

You'll find many types of anesthetic carpules inNavy dentistry. As discussed in Volume I, chapter 7,"Oral Pharmacology," the two most common localanesthetics used in dentistry are 2% lidocainehydrochloride and 2% mepivacaine. Each type ofanesthetic is sealed in a 1.8-cc glass carpule. Theneedle end of each carpule is sealed with rubbermembrane held in place by a metal band. The other endhas a different colored rubber stopper. Each type ofanesthetic has a different colored rubber stopper.

Assembling An Aspirating Syringe

Based on the patient's health history and theprocedure to be performed, the dentist will inform youwhich type of anesthetic (including vasoconstrictorcontent), needle length, and needle gauge to use toprepare the syringe. You will become familiar witheach dentist's preference and various procedures forneedle length and gauge. However, always verify thetype of anesthetic solution. Assemble the syringe outof the patient's view to reduce unnecessary patientapprehension. Assembly can be done while the dentistadministers the topical anesthetic.

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First, always check the carpule for cracks orsuspended articles floating in the solution. If you findany, discard the carpule and notify the dental anddental supply to ensure other batches of anesthetic areusable. Disinfect the rubber diaphragm on the carpulebefore loading it in the syringe. Do not touch therubber diaphragm after you disinfect it. Placing thecarpule end in the aspirating syringe is fairly easy. Usethe following steps:

Use the thumb ring to pull the plunger backagainst the syringe body.

Place the cartridge into the barrel of the syringewith the rubber stopper end in first, positioned towardthe plunger.

Break the seal on the needle container andremove only a small portion of the plastic needle cover.

Insert the needle into the syringe and screw thehub onto the syringe.

ring with your other hand.

Engage the harpoon into the rubber stopper of thecartridge by holding the body portion of the syringewith one hand while lightly tapping the end of the thumb

CAUTION

Do not tap the thumb ring with too much force;

this might cause the glass carpule to shatter.

Make a quarter turn with the thumb ring toensure that the harpoon is firmly engaged in therubber stopper. If it is, the thumb ring will rotateback to its original position.

Force a small, but visible amount ofanesthesia through the needle to expel air.

Loosen the needle cap, but keep the plasticneedle covering in place until you pass the syringe tothe dentist to guard against possible contamination.

The plastic needle cover must be removed tocheck the syringe's operation and during theinjection.

Passing and Receiving the Syringe

The dentist will be ready to administer the localanesthetic after the topical anesthetic is applied. Theassistant passes the syringe with the needle cover inplace. Hold the barrel of the syringe in your hand.Place the thumb ring of the syringe over the dentist'sthumb and the finger grip between the dentist's index

and middle fingers. While you are still holding thesyringe by the barrel, use the other hand to remove theneedle cap.

After the dentist gives the injection, carefullyremove the syringe by grasping the barrel and liftingthe syringe out of the dentist's hand. Remember toexercise extreme caution when grasping the barrel ofthe syringe because the needle is exposed andcontaminated. DO NOT attempt to recap the needlewhile the syringe is in the dentist's hand. If it isnecessary to recap the needle, it must be done usingsome type of mechanical device or the one-handedscoop technique discussed in Volume I, Chapter 9,"Infection Control."

Disassembling the Aspirating Syringe

After the patient is dismissed, the syringe must bedisassembled safely. It is vitally important to preventneedle sticks from the contaminated needle. It isadvisable to first remove the carpule with the needleremaining in place. This provides an air vent toprevent the glass carpule from shattering. To unloadthe carpule, pull the piston rod back as far as possible todisengage the harpoon from the rubber stopper withoutpulling the stopper from the carpule. The carpule canthen be easily removed from the syringe. Remove theused needle and dispose of it into a puncture-resistantcontainer according to established infection controlstandards.

IRRIGATION AND ASPIRATION

Immediately after the dentist administers the localanesthesia, you will irrigate and aspirate the injectionsite. This is necessary because the anesthetic solutionproduces a bitter taste in the patient's mouth.Additionally, you are required to irrigate and aspirate(drawn by suction) often throughout the treatmentprocedure to maintain a clean treatment site.

Irrigation

The dentist expects you, as the dental assistant, toirrigate the oral cavity when necessary. By applyingwater or saline solutions to the treatment site in the oralcavity, small tooth particles, dried blood, and otherdebris are flushed from the area and removed byaspiration. Handpieces with water spray systemsprovide some irrigation, but additional irrigation isalways necessary. At times, the dentist may decide notto use the water spray system on the handpiece for aparticular procedure. During routine operativeprocedures, you will use the three-way syringe on the

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dental unit to irrigate the treatment site with water orwater spray. The tip of the three-way syringe rotateseasily to direct the water, spray, or air at the specifictreatment sites. The tip disconnects to allow forsterilization.

When you irrigate treatment sites during surgicalprocedures, you will use a sterile saline solution orsterile water as the irrigation solution. Sterile saline orsterile water is applied by using a bulb-type or Luer(piston-barrel) syringe. The main purpose forirrigation during surgical procedures is to keep a cleantreatment site. The cleansing is not complete until theirrigating solution is aspirated from the mouth.

Aspiration

Aspiration is necessary to remove blood, pus,saliva, and debris from the treatment site and oralcavity. This is done by using the high-volumeevacuator (HVE) or saliva ejector. Figure 4-36illustrates the reverse palm grasp and modified pen.grasp that should be used when you are using the HVE.As the dental assistant, you must assure that a sterile ordisposable tip is in place for each patient. When usingeither of these, always place the tip in the uprightposition before turning the aspiration off. This helpsprevent materials from dripping out or clogging thehoses. You must also clean and maintain theevacuation system as instructed in the manufacturer'soperation and maintenance instructions.

Figure 4-36.—Reverse palm grasp and modified pen grasp

using an HVE.

OPERATIVE PROCEDURES

Operative dentistry strives to restore decayed orfractured teeth to their original functional ability andesthetic quality of healthy dentition. In general,procedures include the following:

Determining the procedure to be done

Administering anesthesia

Placing a rubber dam

Preparing the cavity or cavities to be filled

Placing filling material into prepared cavitypreparations

Carving and finishing restorations

Smoothing and polishing restorations

As an assistant in operative dentistry, you willperform many of the basic clinical proceduresdiscussed earlier, such as:

Preparing the dental treatment room (DTR)

Performing proper infection control procedures

Wearing appropriate personal protectiveequipment

Selecting and arranging instruments andmaterials required for the procedure

Receiving and preparing the patient

Preparing local anesthetic

Irrigating and aspirating throughout theprocedure

Retracting tissue to maintain a clear field ofvision

Preparing and assisting with the placement of therubber dam

Preparing, passing, and receiving instrumentsand materials

Figure 4-37 illustrates a typical selection andarrangement of instruments for a routine operativeprocedure. Items should be arranged in sequentialorder of the procedure to proceed smoothly withoutdelay.

TERMINOLOGY AND CLASSIFICATIONOF CAVITIES

For the necessary treatment procedures to proceedsmoothly and without delay, you need to understandsome basic terminology and classification of cavities.

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Figure 4-37.—Typical operative dentistry instrument tray setup.

A cavity preparation is a mechanical procedurethat removes caries or existing restorative materialsand a limited amount of healthy tooth structure toreceive and retain restorative materials in the cavitypreparation. A cavity wall is a side or surface of thecavity preparation that aids in enclosing the restorativematerial. You should already be familiar with theterms used to describe the various tooth surfaces, suchas mesial, distal, lingual, facial, incisal, and occlusal.A bevel is a slanting of the enamel margins of the tooth

preparation cut at an angle with the cavity wall. Thereare numerous types of bevels, such as full, long,chamfer, and dovetail.

Cavities can occur on one or more surfaces, andcan be of various sizes, ranging from very small tothose that include all five surfaces of the tooth. Simply,cavities are those which occur on one surface of thetooth. When two surfaces of the tooth are involved, thecavity is called a compound cavity. A cavity is

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considered a scomplex cavity when three or moresurfaces are involved. Compound and complexcavities may include one or both of the proximalsurfaces as well as portions of the facial and lingualsurfaces. When caries attack the proximal surfaces ofposterior teeth, the cavity preparation must alsoinclude preparation of the occlusal surfaces.

Cavities may be classified according to thelocation where the carious lesion begins. Cariesfrequently start in the developmental pits and fissuresof the teeth. These areas are deeper than thesurrounding tooth substance and are nearly impossibleto clean thoroughly, creating ideal conditions forbacterial plaque formation. Locations of pit andfissure caries can be located in any of the followingareas:

Lingual pits of maxillary incisors

Lingual grooves and pits of maxillary molars

Occlusal surfaces of posterior teeth

Facial grooves and pits of mandibular molars

Pits occurring in areas because of irregularitiesin the formation of enamel

Smooth surface cavities can be found on all teethon the proximal surfaces, and gingival one-third of thefacial and lingual surfaces.

STEPS IN CAVITY PREPARATION

After the dentist decides which tooth or teeth torestore, the anesthesia is administered and the rubberdam placed. If you are well prepared, the steps in thecavity preparation should proceed smoothly withoutdelay, and the patient will be more at ease andconfident. Watch closely during the procedure and beready to irrigate and aspirate as needed, as well as, passthe instruments and material to the doctor whenneeded. The initial cavity preparation generally isdone using the high-speed handpiece and a variety ofrotary instruments.

Cavity Design

The design of the cavity preparation for either atooth with initial caries or replacement restoration isbased on the location of the caries, the amount andextent of the caries, the amount of lost tooth structure,and the restorative material to be used.

Some basic principles should be considered whenpreparing a cavity preparation. The dentist must

establish an outline form, which determines theoverall shape of the preparation along the cavitymargins of the restoration and the tooth surfaces. Theoutline form is determined by the size and shape of thecarious lesion and by the need for a suitable design thatwill hold a restoration firmly in place. Usually, thedentist is able to visualize the shape of the completedcavity before cutting the preparation by viewing theextent of the caries on the radiograph and examiningthe tooth and soft tissues.

Removal of Remaining Caries

Carious dentin not removed during the design ofthe cavity preparation is removed by using either roundburs or spoon excavators. When the dentin has a firmfeel with the explorer, removal of the tooth structureshould cease, even if stained dentin remains.

Finishing the Enamel Walls and Margins

The last cutting step in the preparation of the cavityis finishing the enamel walls. This is a process ofangling, beveling, and smoothing the walls of thecavity preparation to achieve the best marginal sealpossible between the restorative material and toothstructure. The dentist may use burs, diamond stones,or hand-cutting instruments (chisels, hoes, hatchets,and gingival margin trimmers) to complete the wallsby removing loose or unsupported enamel to create thestrongest possible enamel wall.

Cleansing the Cavity

The final step in cavity preparation is cleansing thecavity. This includes the removal of accumulateddebris, drying the cavity, and final inspection beforeplacing restorative materials. All debris must beremoved from the cavity, especially on the margins,because deposits left on them subsequently dissolve,resulting in a leak that invites recurrent caries.

Irrigating the cavity preparation with warm waterusually removes all debris. Stubborn particles of

debris may be removed with a small cotton pelletdampened with water or hydrogen peroxide.Following irrigation and aspiration to remove thedebris, the cavity must be dried thoroughly withpressurized air from the 3-way syringe or dry cottonpellets.

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Placement of Restorative Materials

After the cavity preparation is completed, yourattention as the assistant is especially critical. Youmust rapidly anticipate each step in the procedure tohave the necessary material ready at the proper time.You must prepare and pass restorative materials, mixthem at the right time, and follow the manufacturer'sinstructions. More instruments are needed to place therestoration than to prepare the tooth; therefore, moreinstrument transfers are necessary and occur morerapidly than in cavity preparation. Once the restorativematerials have been placed in the oral cavity, thedentist then begins to finish the restoration.

C A V I T Y L I N E R S A N D B A S E S .—Mostdentists use some type of cavity liner or base in almostall cavity preparations. They are used primarily toprotect the pulp and to aid the pulp in recoveringfrom irritation resulting from cavity preparation.Liners and bases are placed when the cavitypreparation is completed, just before insertion of therestorative material.

Glass ionomer cements and dentin bonding agentsare used primarily to seal the dentin and protect thepulp from bacterial invasion. Calcium hydroxide canbe used in extremely deep areas as an antibacterialagent and/or as a pulp capping material.

Most bases are applied best when the assistantwipes the instrument clean between each smallapplication. You will hold a gauze sponge in thetransfer zone and quickly wipe the end of theinstrument as the dentist moves toward the base mix. Ifthe dentist inadvertently gets the base on the enamelwalls of the cavity preparation, you will pass aninstrument for removal of the material.

Cavity varnish is a liner used to seal the dentinaltubules to help prevent microleakage and is placed in acavity to receive amalgam alloy after any bases havebeen placed. Cavity varnish is being used less and lesswith amalgam restorations, and dentin bonding agentsare replacing cavity varnish as the liner of choice.Cavity varnish has an organic solvent of ether orchloroform that quickly evaporates, leaving the resinas a thin film over the preparation. This varnish shouldbe slightly thicker than water. If it becomes very thick,discard it. Cavity varnish is not used with compositessince the varnish retards the set of composites andinterferes with the bonding of composites.

A small cotton pellet held by cotton forceps isdipped into the varnish just enough to wet the pellet.

The cavity varnish is applied to the pulpal area, wallsof the cavity preparation, and onto the edge of themargins of the preparation. Any excess varnish can beremoved from the enamel with a fresh cotton pellet. Asecond application of cavity varnish is placed over thefirst to thoroughly coat the surfaces of the dentin andfill any voids from bubbles created when the firstapplication dries. After liners and bases are placed intothe cavity preparation, the tooth may be restored withmaterials, such as amalgam, composite resin, or glassionomer.

AMALGAM RESTORATIONS.—Amalgam isused as a restorative material on the surfaces of bothpermanent and primary teeth. Amalgam also isaesthetically acceptable for distal restorations of thecuspid when the restoration is not readily visible.Amalgam can also be used to prepare a sound base for atooth before the preparation of a full artificial crown.This is commonly referred to as an amalgam buildup.

When multiple surfaces of the tooth are removedduring the cavity preparation, a matrix is required toapproximate the original wall and hold the restorativematerial in proper form and position until it sets.During the final stages of the cavity preparation, if notsooner, you should acknowledge the need for thematrix band and assemble it. While the liner and basematerials set, the dentist places the assembled matrixband and retainer around the tooth, along with wedgesif needed. Figure 4-38 illustrates a properly contouredand wedged matrix band.

While the dentist makes the final adjustments tothe matrix, you will need to ensure the precapsulatedamalgam is placed securely in the amalgamator andready to tr i turate (mix). The operat ion andmaintenance of the amalgamator is discussed inchapter 11, Volume 1, under Dental Equipment. Waitfor a signal from the dentist to begin mixing the

Figure 4-38.—Properly contoured and wedged matrix band.

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amalgam. When the amalgamator stops, remove theamalgam capsule for the amalgamator, open thecapsule, and empty the mixed amalgam into theamalgam well. Use caution with the amalgam mixbecause any moisture contamination causes thefinished restoration to expand. Load the amalgam intothe amalgam carrier (fig. 4-39). Some dentists permitthe assistant to dispense the amalgam into the cavitypreparation. Other dentists prefer to have you pass theloaded amalgam carrier and dispense the amalgamthemselves. In either case, you must pass the amalgamcondenser to the dentist. The dentist uses thecondenser to pack the amalgam firmly into all the areasof the prepared cavity. During the condensingprocedure, the dentist indicates when a change ofcondensers is needed. As you gain experience, youwill know wh en a change is needed by observing thestage of completion. The exchange of amalgam carrierand condensers continues until the cavity preparationis slightly overfilled. When the condenser is used forthe last time, the dentist may use a burnisher and or anexplorer on the restoration before removing the matrixband.

The dentist uses a burnisher to bring any excessmercury from the amalgam placed to the top of therestoration. Next the explorer is used to slightlycontour the restoration between the tooth and the bandbefore removal of the matrix and retainer. For dentistswho choose to initially carve the occlusal anatomy intothe restoration before removal of the matrix, have anamalgam carver ready to pass when you receive theexplorer. You will also need to have the cotton forceps

Figure 4-39.—Loading amalgam into the amalgam carrierfrom amalgam well.

or hemostat ready to pass when the dentist is ready toremove the wedge, retainer, and matrix band.

The dentist uses an interproximal carver to smooththe gingival margin of the amalgam restoration at theinterproximal area. Only the excess amalgam isremoved near the gingival margin to allow theproximal contact to be retained. The dentist continuescarving the proximal surfaces to conform to thecontour of the inter-proximal area of the tooth. Thedentist uses another carver, such as the discoid-cleoid,to carve the primary grooves on the occlusal surfaceand remove excess amalgam. You may need to haveanother carver ready to pass to the dentist to carve thefacial and lingual margins of the amalgam, ifapplicable. In addition to passing and receiving avariety of carvers to the dentist, you will need the high-volume evacuator (HVE) tip in your other hand toaspirate the shavings from the carving procedure atvarious times. When carving the amalgam restorationis completed, remove the rubber dam. Irrigate andaspirate the patient’s mouth and check the occlusion ofthe new restoration for any needed adjustments.

Have the articulating paper ready for use byplacing it into a hemostat or articulating paper holder.Pass this to the dentist to check the occlusion of therestoration. The articulating paper is placed in theteeth of the opposing quadrant and the patient isinstructed to gently close the teeth together. If thepatient closes the teeth together too suddenly or withtoo much pressure, the new amalgam restoration willfracture if it is too high. Have an amalgam carver readyto pass to the dentist to reduce any high spots on theamalgam restorations. The restoration is checked withthe articulating paper and carved until the properocclusion is obtained. Have a burnisher, such as a ballor ovoid, ready to pass to the dentist to burnish theamalgam restoration. When the restoration iscompleted, the oral cavity is irrigated and aspiratedusing the water syringe. Use the HVE to removeamalgam shavings resulting from the occlusaladjustment. Before dismissal, ensure the patient isgiven the postoperative instructions and understandsthem.

MERCURY CONTROL PROGRAM FORDENTAL TREATMENT FACILITIES.—Alldental personnel will follow BUMEDINST 6260.30because of the health hazard potential of mercury. Thisinstruction discusses control procedures for thehandling and disposal of amalgam or mercury-contaminated items and is discussed in Volume I,Chapter 11, "Dental Safety and Equipment."

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FINISHING AND POLISHING AMALGAMRESTORATIONS. —When amalgam restorationsare placed in the tooth, finishing and polishing of therestorat ions general ly take place at anotherappointment. The appointment should be at least 24hours after the placement of the amalgam. Polishingthe amalgam smooths the surface so that plaque doesnot adhere to it readily and makes the restoration lookmore attractive. The dentist checks the margins andproximal contacts of the restoration initially. A metalfiling strip can be used to remove any roughness oroverhand of the restoration in the proximal area. Thedentist may use finishing burs or stones in thehandpiece, followed by discs and abrasive points.Before use, discs may be coated with a lubricant, or insome cases, wet with water. The abrasive pointsprogress from a more-abrasive to a less-abrasive pointuntil a smooth mirror-like surface is obtained on theamalgam restoration. Extra-fine pumice and dry tinoxide, or commercial silicone-mounted polishingcups, may be used for a final polishing.

COMPOSITE RESIN RESTORATIONS.—The restoration of tooth surfaces that are normallyeasily visible are restored with tooth-coloredrestorative materials for an esthetic appearance. Oneof the most commonly used tooth-colored restorativematerials is the composite resin. The three types ofcomposite resins available are

macrofilled,

microfilled, and

hybrid.

The classification of each composite resin dependson the particle size of its inorganic filler. Themacrofilled and hybrid resins have higher amounts ofinorganic fillers and lower amounts of organic resinthan the microfilled resins. This provides the strengthneeded for proximal-incisal restorations. Theserestorations may be prepared with or without the pinretention technique. On the other hand, becausemicrofilled resins have a smaller particle size, they areeasier to polish than macrofilled resins. Many of therecently developed hybrids achieve good polishabilityand esthetics—one reason for their increasedpopularity.

Composite resin materials are available in self-curing two-paste systems and light-curing single-paste systems. Some brands offer several colorselections; whereas, others are supplied in a universalshade. The shade must always be selected before the

teeth are allowed to dry because dehydration results inlighter shades.

The restorative material is retained in the cavitypreparation by mechanical retention. Chipped orfractured teeth rely mostly on acid-etch enamel forretention of the restorative material. Acid-etching theenamel portion of cavity preparations with a 35 to 50percent solution of phosphoric acid results in improvedretention for resin restorations. A celluloid matrix maybe placed before the acid-etching procedure to protectthe adjacent teeth. The phosphoric acid is applied tothe enamel surface of the cavity preparation and isallowed to be in contact with the enamel for 1 minute.Then the area is rinsed thoroughly with water anddried. The etched enamel surface, when dried, appearschalky white because of a slight dissolving of thesurface enamel that leaves microscopic undercuts(retention). After etching the tooth, a bonding agent isapplied.

The dentist may need an instrument to pack thecomposite resin material into the cavity preparationand to avoid formation of air bubbles. When thecomposite resin material is applied to the etched andbonded surface, the resin invades the surface void,undercuts, and irregularities. When surfaces in theproximal area are restored, the dentist will place acelluloid matrix that will assist in preventing thecomposite material from adhering to adjacent teeth andalso acts as a form to properly place the material (fig 4-40). If using a light-cured system of composite resin,the light source is positioned near the restoration andexposed according to the manufacturer's instructions.These light-curing systems are discussed in Chapter11, Volume I, "Dental Safety and Equipment." Thedentist, assistant, and the patient should wearprotective glasses during the light exposure.

Once the resin material cures, a mechanical bondforms. This type of surface union between therestorative material and the enamel improves theretention qualities and provides a smoother cavity

Figure 4-40.—Using a celluloid matrix for a proximalcomposite restoration.

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margin, improving the esthetics of the restoration. Inaddition, less marginal leakage is likely to occurbecause of the improved union of the enamel andrestoration.

To finish the restoration, the matrix is removed andany rough areas are smoothed with composite-typefinishing burs. If the restoration involves proximalsurfaces, abrasive strips similar to those shown infigure 4-41 are used to smooth these surfaces. Ifapplicable, the gingival margin of the restoration ischecked to remove any excess composite material.The surface of the restoration is smoothed further witha fine and an extra-fine disc of silicon carbide andzirconium silicate. These smooth surfaces preventretention of food debris or plaque. If a higher gloss ofthe facial surface is desired, a coating of sealantmaterial is placed over the finished restoration. Aftercompletion of the restoration, the rubber dam isremoved and oral cavity irrigated and aspirated. Ifnecessary, the dentist checks the occlusion and makesadjustments.

GLASS IONOMER RESTORATIONS.—Usually, the gingival areas on the facial aspect of themaxillary anterior teeth are restored with one of thetooth-colored restorative materials for an estheticappearance. Restorations located on the gingival thirdof the tooth may be necessary because the tooth iscarious or because it has been worn away or abraded byincorrect brushing habits. Since glass ionomercements bond directly with enamel, dentin, andcementum, they may be used for such restorationswhere minimal preparation of the tooth is desired, orwhere the fluoride release from the cement is desired toresist recurrence of caries. During placement of theglass ionomer cement restoration, the cavity area mustbe kept totally dry because moisture will cause afailure of the restoration.

SUPPLY PROCEDURES

A competent dental assistant can increase theefficiency, productivity, and reduce the operational

Figure 4-41 .-Using an abrasive strip to finish a proximalsurface.

costs in a DTR by using proper supply procedures. Itcosts time and money to run out of necessary items. Itis also wasteful and expensive to order and store itemsthat are never used.

You will use a supply catalog to order supplies.Some facilities make up a catalog for local use, listingfrequently ordered items.

To order an item, look it up in the catalog and thenfill out the appropriate "request for issue" form. Theseforms may vary slightly in format but they all requirethe same basic information. It is important that you fillout the form accurately and completely. It is importantto know item nomenclature, identification, anddistribution data.

When your supplies arrive, check the items againstyour order form to ensure you receive the items andquantities that you ordered. Also check broken seals orloose parts. If you discover anything out of theordinary, notify your supervisor. After supplies havebeen checked, store them in a manner consistent withthe manufacturer's instructions to prevent spoilage ordamage.

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