restorative instruments*

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GENERAL
The Restorative Section is the element of a dental service in which decayed or fractured teeth are rebuilt or repaired by artificial materials in the form of amalgam restorations, composite resins, or crowns. In some clinics, the restorative section is divided into two services: operative, where restorations are placed, and fixed, where crowns and fixed partial dentures are fabricated, fitted, and cemented into place. Endodontic treatment, the treatment of dental pulps, and the filling of root canals, is sometimes performed in the restorative section. See Lesson 4 for discussion of the dental assistant in endodontics.


CLASSES OF CAVITY PREPARATIONS
Cavity preparation is the term used to describe the process of preparing a tooth to receive a restoration. It includes the removal of decayed material, the necessary cutting and shaping of remaining tooth structure, and the cleaning of the prepared area. Certain basic principles of cavity preparation, first advanced by the American dentist, Dr. G. V. Black, in the early part of this century, still serve as standards. These principles provide for convenience in placing the restoration, retention of the restoration, sufficient bulk and strength of restoration and remaining tooth structure, and prevention of further dental caries. The design of the cavity preparation must take into account the location and size of the cavity, the stresses to which it will be subjected, and the type of restorative material to be used. Cavity forms are classified according to the tooth surfaces involved.
a. Class I cavity preparations (pits and fissures) are one-surface preparations which involve the occlusal surfaces or the occlusal two-thirds of the facial or lingual surfaces of a posterior tooth or the lingual pits of maxillary anteriors.
b. Class II cavity preparations are those that involve the proximal surfaces of posterior teeth.
c. Class III cavity preparations are one-surface preparations that involve the proximal surfaces of anterior teeth.
d. Class IV cavity preparations are those that involve the proximal surfaces and the incisal angle of anterior teeth.
e. Class V cavity preparations are one-surface preparations that involve the gingival third of the labial, buccal, or lingual surfaces of any teeth.
f. Class VI cavity preparations are those that involve areas not normally affected by dental caries such as the incisal edges of anterior teeth and the cuspal tips of posterior teeth. This class is in addition to
Dr. G. V. Black's original five classes.

FACILITATING PATIENT TREATMENT
In the age of fourhanded, sit-down dentistry, a well-trained assistant is an integral part of a restorative procedure. Part of your responsibility will be to anticipate the dentist's next move and have the instruments ready when he needs them. To do this efficiently, you must have a thorough working knowledge of a variety of restorative instruments. Your knowledge, combined with practice, will add to the efficiency of the dentist and the comfort of the patient, by helping treat the patient much more quickly.

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EXAMINATION AND DIAGNOSTIC INSTRUMENTS
The examination and diagnostic instruments described in Lesson 1 are used in all treatment areas of the dental service. Mouth mirrors, explorers, cotton pliers, disposable saliva ejector, periodontal probe, gauze pads, and cotton rolls or cotton dispensers are the first instruments set out before any dental procedure is begun

LOCAL ANESTHETIC INSTRUMENTS
Local anesthesia is used extensively in restorative dentistry to reduce the pain associated with these procedures. The instruments and techniques used in administering a local anesthetic and the duties performed by a dental assistant .

RUBBER DAM )
Moisture presents a problem in the performance of many dental operations. Dryness of the operative field is essential to the success of restorations and endodontic procedures. The use of the rubber dam is the best method of maintaining a dry field. Rubber dam equipment is listed and illustrated in figure 2-1



SALIVA EJECTORS (MOUTHPIECE, SALIVA EJECTOR, DENTAL)
Saliva ejector mouthpieces are made to attach at one end to the saliva ejector tubing on the dental unit. The other end rests in the mouth for the evacuation of saliva, blood, water, or debris during dental procedures.

MOTOR DRIVEN ROTARY INSTRUMENTS USED FOR CAVITY PREPARATION
a. Burs
(1) Characteristics. In discussing the preparation of a cavity for restoration in a modern clinic, it is essential that we talk about the many different kinds of burs available to the dentist. Regardless of the procedure being done, the burs will probably be used in preparing the cavity for restoration. They are manufactured in different sizes and shapes suited to the various types and forms of the cavity preparation desired. You will be expected to know four different things about the burs that you are given: The shape (name) of the working end, the series number of the bur, the material of which it is made, and in which hand piece each type of bur may be used. Series numbers and bur shapes are associated with each other: A round bur is in the ten series, an inverted cone bur is in the thirty series, a straight crosscut fissure bur is in the five hundred series, and the tapered fissure bur is in the seven hundred series. Burs may be made of one of two materials: A stainless steel bur will have a smooth shank, and a tungsten carbide alloy, bur will have a ring, a set of parallel rings, or possibly a ring of X's around the shank. Tungsten carbide burs will stay sharp longer than stainless steel burs, and they may be used repeatedly without marked reduction in cutting efficiency. There are three different hand piece attachments for the burs. The slow-speed straight hand piece (SHP) uses a friction grip attachment and accepts a bur with a long shank. This means that the end of the bur that goes into the hand piece is smooth and is held in the hand piece by friction. The shank of the straight hand piece bur is not only longer but also larger than the other burs. The bur that goes into the slow-speed contra-angle hand piece (AHP) is almost as large around as the straight handpiece bur, but it is much shorter and has a notched end with a groove opposite the working end that fits into the latch attachment on the angle hand piece. The bur for all high-speed hand pieces (HSHP) is smaller and shorter than the other burs; it also has a friction grip attachment (that is, the end is smooth). The Midwest Quiet-Air hand piece accepts the friction grip bur, but the hand piece is designed with a chuck that must be tightened on the bur. Burs are an essential part of the setup for the dentist performing a restorative procedure. They are the rotary cutting instruments that replace many of the hand instruments used in a cavity preparation procedure. You will be required to know four identifying characteristics about dental burs.



(a) The first type is a description of the shape of the working end as illustrated in figure 2-2.




The first letter of each bur type is underlined. These four letters, in order, spell RIST. This key word will help you learn the burs in increasing numerical sequence.



(b) The second identifier is the number:
10 series--(Round bur) 30 series--(Inverted cone bur) 500 series--(Straight crosscut fissure bur) 700 series--(Tapered fissure bur)

(c) The third is composition.

(d) The fourth is the hand piece attachment. Burs are attached to one of three hand pieces. To establish which hand piece a bur is used in, you may look at the end away from the working end, as illustrated in figure 2-3.
(e) Any of the independent factors describing burs may be combined when designing a bur. Obviously, the use and series numbers correspond with the name or shape of the bur. However, any shape bur may be made of either of the two materials, and it may be made to fit into any of the three types of hand pieces.

(2) Availability. Available stainless steel burs include the following for both AHP and SHP except as noted: round burs numbers 1/2, 2, 4, 6, and 8; inverted cone burs numbers 33 1/2, 35, 37, and 39 (39 is available for AHP only); straight crosscut fissure burs numbers 557, 558, 559, and 560 (560 is available for AHP only); and tapered crosscut fissure burs numbers 700, 701, 702. Angle hand piece steel burs numbers 4, 35, and 558 are available in either the standard or short-neck lengths. Tungsten carbide burs are available for the AHP in the same sizes except for numbers 1/2 and 560. An end-cutting tungsten carbide bur is available as number 901. The tungsten carbide burs function best at high-speed operations; they are harder than stainless steel burs. See figure 2-4. Available friction grip tungsten carbide burs include the following for high-speed angle hand pieces: round burs. Numbers 1/2, 2, 4, and 6; inverted cone burs numbers 33 1/2, 34, and 35; straight, crosscut fissure burs number 557 and 558; straight, plain fissure bur number 57; tapered, crosscut fissure burs number 699, 700, and 701; and tapered, plain fissure bur number 170L.





b. Diamond Stones and Wheels Diamond stones and wheels (figure 2-5) are used to cut enamel and are manufactured in various sizes and shapes. These instruments create heat during use and require water or air-cooling if used for any length of time.





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HAND INSTRUMENTS USED FOR CAVITY PREPARATION
a. General. Hand instruments are used extensively in cavity preparation. A number of instruments of different designs are used for performing different tooth cutting and caries-removing procedures on various surfaces of different teeth and in different parts of the mouth.
b. Spoon Excavators (EXCAVATOR, DENTAL). Spoon excavators (figure 2-6) are used in removing debris and decayed dentin from cavities. Paired instruments are used. These include Darby-Perry instruments numbers 5, 6, 21, and 22, and black instruments numbers 63, 64, 65, and 66.





Figure 2-6. Spoon excavators.
c. Enamel Chisels. Chisels (figure 2-7) are hand instruments used in cavity preparation. They are designed to cleave enamel along the lines of the enamel rods and to prepare the walls and accessible margins of a cavity. Straight chisels have single bevels and straight shanks. Bin-angle chisels have single bevels and two bends in their shanks. Wedelstaedt chisels have single bevels and curved shanks. Enamel chisels include Wedelstaedt numbers 41 and 42, and Black numbers 81, 83, 84, 85 and 86.





Figure 2-7. Chisels.
d. Enamel Hatchets (EXCAVATOR, DENTAL). Hatchets (figure 2-8) are instruments designed to cleave enamel along the lines of enamel rods and to prepare the walls and accessible margins of a cavity preparation. They include Black numbers 8, 17, 23, 51, 52, 53, and 54.





Figure 2-8. Hatchets.
e. Gingival Margin Trimmers. Gingival margin trimmers) (figure 2-9) are used to bevel the enamel at the cervical seat of the cavity preparation. They include black numbers 77, 78, 79, and 80.



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MATRIX RETAINERS AND BANDS
A matrix confines the restorative material in the cavity preparation. It also establishes proper contours in restorations replacing missing walls of the tooth.
a. Matrix Retainers. Matrix retainers (figure 2-10) are used to hold and adjust matrix bands on the teeth. These include Ivory retainers numbers 1 and 9 and the contra-angle Tofflemire retainer that comes in adult and junior sizes.




Figure 2-10. Tofflemire matrix retainer.
b. Matrix Bands and Band Material. Matrix bands (figures 2-11, 2-12, and 2-13) are used to form missing walls of prepared teeth. They shape and confine restorative materials and wax to areas prepared to receive restorations. These include Ivory matrix band sets, Tofflemire matrix band sets, a cervical set, plastic celluloid strips, and metal matrix strips. Related materials include a celluloid matrix wedge and a crown form set. Celluloid crown forms are designed for specific teeth and are used as matrices for Class IV restorations




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