7: Preliminary Considerations for Operative Dentistry


Preliminary Considerations for Operative Dentistry

Lee W. Boushell, Ricardo Walter and Aldridge D. Wilder, Jr.

This chapter addresses routine chairside pre-operative procedures (before actual tooth preparation). Primarily, these procedures include patient and operator positions and isolation of the operating field.

Preoperative Patient and Dental Team Considerations

In preparation for a clinical procedure, it is important to ensure that patient and operator positions are properly selected, that instrument exchange between the dentist and the assistant is efficient, that proper illumination is present, and that magnification is used, if needed.

Patient and Operator Positions

Efficient patient and operator positions are beneficial for the welfare of both individuals. A patient who is in a comfortable position is more relaxed, has less muscle tension, and is more capable of cooperating with the dentist.

The practice of dentistry is demanding and stressful. Physical problems may arise if appropriate operating positions are neglected.1 Most restorative dental procedures can be accomplished with the dentist seated. Positions that create unnecessary curvature of the spine or slumping of the shoulders should be avoided. Proper balance and weight distribution on both feet is essential when operating from a standing position. Generally, any uncomfortable or unnatural position that places undue strain on the body should be used only rarely.

Chair and Patient Positions

Chair and patient positions are important considerations. Dental chairs are designed to provide total body support in any chair position. An available chair accessory is an adjustable headrest cushion or an articulating headrest attached to the chair back. A contoured or lounge-type chair provides complete patient support and comfort. Most chairs also are equipped with programmable operating positions.

The most common patient positions for operative dentistry are almost supine or reclined 45 degrees (Fig. 7-1). The choice of patient position varies with the operator, the type of procedure, and the area of the mouth involved in the operation. In the almost supine position, the patient’s head, knees, and feet are approximately the same level. The patient’s head should not be lower than the feet; the head should be positioned lower than the feet only in an emergency, as when the patient is in syncope.

Operating Positions

Operating positions can be described by the location of the operator or by the location of the operator’s arms in relation to patient position. A right-handed operator uses essentially three positions—right front, right, and right rear. These are sometimes referred to as the 7-o’clock, 9-o’clock, and 11-o’clock positions (Fig. 7-2, A). For a left-handed operator, the three positions are the left front, left, and left rear positions, or the 5-o’clock, 3-o’clock, and 1-o’clock positions. A fourth position, direct rear position, or 12-o’clock position, has application for certain areas of the mouth. As a rule, the teeth being treated should be at the same level as the operator’s elbow. The operating positions described here are for the right-handed operator; the left-handed operator should substitute left for right.

Right Front Position

The right front position facilitates examination and treatment of mandibular anterior teeth (see Fig. 7-2, B), mandibular posterior teeth (especially on the right side), and maxillary anterior teeth. It is often advantageous to have the patient’s head rotated slightly toward the operator.

Right Position

In the right position, the operator is directly to the right of the patient (see Fig. 7-2, C). This position is convenient for operating on the facial surfaces of maxillary and mandibular right posterior teeth and the occlusal surfaces of mandibular right posterior teeth.

Right Rear Position

The right rear position is the position of choice for most operations. The operator is behind and slightly to the right of the patient. The left arm is positioned around the patient’s head (see Fig. 7-2, D). When operating from this position, the lingual and incisal (occlusal) surfaces of maxillary teeth are viewed in the mouth mirror. Direct vision may be used on mandibular teeth, particularly on the left side, but the use of a mouth mirror is advocated for visibility, light reflection, and retraction.

General Considerations

Several general considerations regarding chair and patient positions are important. The operator should not hesitate to rotate the patient’s head backward or forward or from side to side to accommodate the demands of access and visibility of the operating field. Minor rotation of the patient’s head is not uncomfortable to the patient and allows the operator to maintain his or her basic body position. As a rule, when operating in the maxillary arch, the maxillary occlusal surfaces should be oriented approximately perpendicular to the floor. When operating in the mandibular arch, the mandibular occlusal surfaces should be oriented approximately 45 degrees to the floor.

The operator’s face should not come too close to the patient’s face. The ideal distance, similar to that for reading a book, should be maintained. Another important aspect of proper operating position is to minimize body contact with the patient. A proper operator does not rest the forearms on the patient’s shoulders or the hands on the patient’s face or forehead. The patient’s chest should not be used as an instrument tray. From most positions, the left hand should be free to hold the mouth mirror to reflect light onto the operating field, to view the tooth preparation indirectly, or to retract the cheek or tongue. In certain instances, it is more appropriate to retract the cheek with one or two fingers of the left hand than to use a mouth mirror. It is often possible, however, to retract the cheek and reflect light with the mouth mirror at the same time.

When operating for an extended period, the operator can obtain a certain amount of rest and muscle relaxation by changing operating positions. Operating from a single position through the day, especially if standing, produces unnecessary fatigue. Changing positions, if only for a short time, reduces muscle strain and lessens fatigue.1

Operating Stools

A variety of operating stools are available for the dentist and the dental assistant. The seat should be well padded with smooth cushion edges and should be adjustable up and down. The backrest should be adjustable forward and backward as well as up and down.

Some advantages of the seated work position are lost if the operator uses the stool improperly. The operator should sit back on the cushion, using the entire seat and not just the front edge. The upper body should be positioned so that the spinal column is straight or bent slightly forward and supported by the backrest of the stool. The thighs should be parallel to the floor, and the lower legs should be perpendicular to the floor. If the seat is too high, its front edge cuts off circulation to the user’s legs. Feet should be flat on the floor.

The seated work position for the assistant is essentially the same as for the operator except that the stool is 4 to 6 inches higher for maximal visual access. It is important that the stool for the assistant have an adequate footrest so that a parallel thigh position can be maintained with good foot support. When properly seated, the operator and the assistant are capable of providing dental service throughout the day without an unnecessary decline in efficiency and productivity because of muscle tension and fatigue (Fig. 7-3).

Instrument Exchange

All instrument exchanges between the operator and the assistant should occur in the exchange zone below the patient’s chin and a few inches above the patient’s chest. Instruments should not be exchanged over the patient’s face. During the procedure, the operator should anticipate the next instrument required, and inform the assistant accordingly; this allows the instrument to be brought into the exchange zone for a timely exchange.

During proper instrument exchange, the operator should not need to remove his or her eyes from the operating field. The operator should rotate the instrument handle forward to cue the assistant to exchange instruments. Any sharp instrument should be exchanged with appropriate deliberation. The assistant should take the instrument from the operator, rather than the operator dropping it into the assistant’s hand, and vice versa. Each person should be sure that the other has a firm grasp on the instrument before it is released.

Magnification and Headlamp Illumination

Another key to the success of clinical operative dentistry is visual acuity. The operator must be able to see clearly to attend to the details of each procedure. The use of magnification facilitates attention to detail and does not adversely affect vision. Magnifying lenses have a fixed focal length that often requires the operator to maintain a proper working distance, which ensures good posture. Several types of magnification devices are available, including bifocal eyeglasses, loupes, and surgical telescopes (Fig. 7-4). The use of such magnification devices also provides some protection from eye injury. To further improve visual acuity, headlamps are recommended in operative dentistry. Their greatest advantage is the light source being parallel to the clinician’s vision, eliminating shadows at the operating field. Current headlamps use light-emitting diode (LED) technology and produce whiter light than conventional tungsten halogen light sources.

Isolation of the Operating Field

The goals of operating field isolation are moisture control, retraction, and harm prevention.

Goals of Isolation

Moisture Control

Operative dentistry cannot be executed properly unless the moisture in the mouth is controlled. Moisture control refers to excluding sulcular fluid, saliva, and gingival bleeding from the operating field. It also involves preventing the spray from the handpiece and restorative debris from being swallowed or aspirated by the patient. The rubber dam, suction devices, and absorbents are variously effective in moisture control. Generally, the rubber dam is the recommended technique for moisture control. Raskin et al. and Fusayama have reported, however, that achieving effective isolation is more important than the specific technique used.2,3

Harm Prevention

An important consideration of isolating the operating field is preventing harm to the patient during the operation.4,5 Excessive saliva and handpiece spray can alarm the patient. Small instruments and restorative debris can be aspirated or swallowed. Soft tissue can be damaged accidentally. The same devices used for moisture control and retraction contribute not only to harm prevention but also to patient comfort and operator efficiency. Harm prevention is achieved as much by the manner in which the devices are used as by the devices themselves.

Rubber Dam Isolation

In 1864, S.C. Barnum, a New York City dentist, introduced the rubber dam into dentistry. Use of the rubber dam ensures appropriate dryness of the teeth and improves the quality of clinical restorative dentistry.6,7 The rubber dam is used to define the operating field by isolating one or more teeth from the oral environment. The dam eliminates saliva from the operating site and retracts the soft tissue.

Advantages

The advantages of rubber dam isolation of the operating field are (1) a dry, clean operating field; (2) improved access and visibility; (3) potentially improved properties of dental materials; (4) protection of the patient and the operator; and (5) operating efficiency.

Improved Properties of Dental Materials

The rubber dam prevents moisture contamination of restorative materials during insertion and promotes improved properties of dental materials. Amalgam restorative material does not achieve its optimum physical properties if used in a wet field.6 Bonding to enamel and dentin is unpredictable if the tooth substrate is contaminated with saliva, blood, or other oral fluids.9,10 Some studies have concluded that no difference exists between the use of the rubber dam and cotton roll isolation as long as control of sources of contamination is maintained during the restorative procedures.2,1113

Protection of the Patient and the Operator

The rubber dam protects the patient and the operator. It protects the patient from aspirating or swallowing small instruments or debris associated with operative procedures.14 A properly applied rubber dam protects soft tissue from irritating or distasteful medicaments (e.g., etching agents). The dam also offers some soft tissue protection from rotating burs and stones. Authors disagree on whether the rubber dam protects the patient from mercury exposure during amalgam removal.15,16 However, it is generally agreed that the rubber dam is an effective infection control barrier for the dental office.1719

Disadvantages

Rubber dam use is low among private practitioners.2022 Time consumption and patient objection are the most frequently quoted disadvantages of the rubber dam. However, the rubber dam usually can be placed in less than 5 minutes. The advantages previously mentioned certainly outweigh the time spent with placement.

Certain situations may preclude the use of the rubber dam, including (1) teeth that have not erupted sufficiently to support a retainer, (2) some third molars, and (3) extremely malpositioned teeth. In addition, patients may not tolerate the rubber dam if breathing through the nose is difficult. In rare instances, the patient cannot tolerate a rubber dam because of psychological reasons or latex allergy.12,23 Latex-free rubber dam material is, however, currently available (Fig. 7-5). Jones and Reid reported that use of the rubber dam was well accepted by patients and operators.24

Materials and Instruments

The materials and instruments necessary for the use of the rubber dam are available from most dental supply companies.

Material

Rubber dam material (latex and nonlatex), as with all rubber products, deteriorates over time, resulting in low tear strength. The dam material is available in 5 × 5 inch (12.5 × 12.5 cm) or 6 × 6 inch (15 × 15 cm) sheets. The thicknesses or weights available are thin (0.006 inch [0.15 mm]), medium (0.008 inch [0.2 mm]), heavy (0.010 inch [0.25 mm]), and extra heavy (0.012 inch [0.30 mm]). Light and dark dam materials are available, and darker colors are generally preferred for contrast. The rubber dam material has a shiny side and a dull side. Because the dull side is less light reflective, it is generally placed facing the occlusal side of the isolated teeth. A thicker dam is more effective in retracting tissue and more resistant to tearing; it is especially recommended for isolating Class V lesions in conjunction with a cervical retainer. The thinner material has the advantage of passing through the contacts easier, which is particularly helpful when contacts are tight.

Retainer

The rubber dam retainer consists of four prongs and two jaws connected by a bow (Fig. 7-7). The retainer is used to anchor the dam to the most posterior tooth to be isolated. Retainers also are used to retract gingival tissue. Many different sizes and shapes are available, with specific retainers designed for certain teeth (Fig. 7-8). Table 7-1 lists suggested retainer applications. When positioned on a tooth, a properly selected retainer should contact the tooth in its four line angles (see Fig. 7-7). This four-point contact prevents rocking or tilting of the retainer. Movement of the retainer on the anchor tooth can injure the gingiva and the tooth, resulting in postoperative soreness or sensitivity.25 The prongs of some retainers are gingivally directed (inverted) and are helpful when the anchor tooth is only partially erupted or when additional soft tissue retraction is indicated (Fig. 7-9). The jaws of the retainer should not extend beyond the mesial and distal line angles of the tooth because (1) they may interfere with matrix and wedge placement, (2) gingival trauma is more likely to occur, and (3) a complete seal around the anchor tooth is more difficult to achieve.

Table 7-1

Suggested Retainers for Various Anchor Tooth Applications

Retainer Application
W56 Most molar anchor teeth
W7 Mandibular molar anchor teeth
W8 Maxillary molar anchor teeth
W4 Most premolar anchor teeth
W2 Small premolar anchor teeth
W27 Terminal mandibular molar anchor teeth requiring preparations involving the distal surface

Wingless and winged retainers are available (see Fig. 7-8). The winged retainer has anterior and lateral wings (Fig. 7-10). The wings are designed to provide extra retraction of the rubber dam from the operating field and to allow attachment of the dam to the retainer before conveying the retainer (with dam) to the anchor tooth, after which the dam is removed from the lateral wings. As seen in Figure 7-10, the anterior wings can be cut away if they are not wanted.

The bow of the retainer (except the No. 212, which is applied after the rubber dam is in place) should be tied with dental floss (Fig. 7-11) approximately 12 inches (30 cm) in length before the retainer is placed in the mouth. For maximal protection, the tie may be threaded through both holes in the jaws of the retainer because the bow of the retainer could break. The floss allows retrieval of the retainer or its broken parts if they are accidentally swallowed or aspirated. It is sometimes necessary to re-contour the jaws of the retainer to the shape of the tooth by grinding with a mounted stone (Fig. 7-12). A retainer usually is not required when the dam is applied for treatment of the anterior teeth except for the cervical retainer for Class V restorations.

Punch

The rubber dam punch is a precision instrument having a rotating metal table (disk) with holes of varying sizes and a tapered, sharp-pointed plunger (Fig. 7-13). Care should be exercised when changing from one hole to another. The plunger should be centered in the cutting hole so that the edges of the holes are not at risk of being chipped by the plunger tip when the plunger is closed. Otherwise, the cutting quality of the punch is ruined, as evidenced by incompletely cut holes. These holes tear easily when stretched during application over the retainer or tooth.

Anchors (Other Than Retainers)

Besides retainers, other anchors may also be used. The proximal contact may be sufficient to anchor the dam on the tooth farthest from the posterior retainer (in the isolated field), eliminating the need for a second retainer (see Step 13 of Procedure 7-1). To secure the dam further anteriorly or to anchor the dam on any tooth where a retainer is contraindicated, waxed dental tape (or floss) or a small piece of rubber dam material (cut from a sheet of dam) or a rubber Wedjet (Hygenic, Akron, OH) may be passed through the proximal contact. When dental tape is used, it should be passed through the contact, looped, and passed through a second time (Fig. 7-16, A). The cut piece of dam material is first stretched, passed through the contact, and then released (see Fig. 7-16, B). When the anchor is in place, the tape, floss, dam material, or Wedjet should be trimmed to prevent interference with the operating site.

Hole Size and Position

Successful isolation of teeth and maintenance of a dry, clean operating field largely depend on hole size and position in the rubber dam.26 Holes should be punched by following the arch form, making adjustments for malpositioned or missing teeth. Most rubber dam punches have either five or six holes in the cutting table. The smaller holes are used for the incisors, canines, and premolars and the larger holes for the molars. The largest hole generally is reserved for the posterior anchor tooth (Fig. 7-17). The following guidelines and suggestions can be helpful when positioning the holes:

image (Optional) Punch an identification hole in the upper left (i.e., the patient’s left) corner of the rubber dam for ease of location of that corner when applying the dam to the holder.

image When operating on the incisors and mesial surfaces of canines, isolate from first premolar to first premolar. Metal retainers usually are not required for this isolation (Fig. 7-18, A). If additional access is necessary after isolating teeth, as described, a retainer can be positioned over the dam to engage the adjacent nonisolated tooth, but care must be exercised not to pinch the gingiva beneath the dam (see Fig. 7-18, B and C).

image When operating on a canine, it is preferable to isolate from the first molar to the opposite lateral incisor. To treat a Class V lesion on a canine, isolate posteriorly to include the first molar to provide access for placement of the cervical retainer on the canine.

image When operating on posterior teeth, isolate anteriorly to include the lateral incisor on the opposite side of the arch from the operating site. In this case, the hole for the lateral incisor is the most remote from the hole for the posterior anchor tooth. Anterior teeth included in the isolation provide finger rests on dry teeth and better access and visibility for the operator and the assistant.

image When operating on premolars, punch holes to include one to two teeth distally, and extend anteriorly to include the opposite lateral incisor.

image When operating on molars, punch holes as far distally as possible, and extend anteriorly to include the opposite lateral incisor.

image Isolation of a minimum of three teeth is recommended except when e/>

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Jan 9, 2015 | Posted by in Operative Dentistry | Comments Off on 7: Preliminary Considerations for Operative Dentistry
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