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After performing the laboratory/clinical exercises in this chapter, the student will be able to do the following:
1. Describe, understand, and explain the sequence of steps for the placement and carving of a dental amalgam restoration.
2. Name the instruments and materials used for placement of dental amalgam restorations.
3. Explain the rationale for amalgam finishing and polishing.
4. Recall the benefits of properly finished and polished amalgams.
5. List two indications for finishing and polishing amalgams.
6. Discuss the possible results of poor amalgam placement and carving.
7. Assess an amalgam restoration to determine whether it needs replacement or finishing and polishing.
8. Differentiate between the procedures of amalgam finishing and amalgam polishing.
9. Explain the importance of temperature control and related factors during finishing and polishing.
10. Evaluate a well-finished and polished amalgam according to the criteria provided in this chapter.
The procedures discussed in this chapter (or portions thereof) may not be included in the dental hygienist’s scope of practice in all states. Procedures that a dental hygienist may legally perform are listed in each state’s practice act.
Proper placement of dental amalgam is essential to the long-term success of the amalgam restoration. Modern amalgams are strong and hard enough to support most chewing forces and are versatile enough for restoring lesions in almost all teeth. Care must be taken and attention to detail must be observed when placing and carving these restorations. It is important not to become discouraged when following your “learning curve” to become proficient. Repetition, learning the handling characteristics, and persistence will allow you to become confident and skilled in this phase of restorative dentistry.
Amalgam finishing and polishing is an integral part of the patient’s treatment plan in the prevention of periodontal and dental disease, and it should be routinely performed by the dental hygienist. Finished and polished amalgams are less prone to plaque retention and have a greater resistance to tarnish and corrosion than unpolished amalgams. Traditionally, finishing and polishing should be performed at least 24 hours after amalgam placement. This allows the amalgam alloy to set completely before being exposed to the abrasives of polishing. Spherical fast-setting amalgams, which could be finished and polished shortly after placing and carving, are the exception. Spherical amalgams are discussed in Chapter 6, Amalgam. For previously placed amalgams, finishing and polishing may be started as soon as the procedure is indicated.
I. Procedure for Condensing Amalgam
Proper placement of an amalgam restoration results in a well adapted, void-free, and anatomically correct replacement of lost tooth structure. An example of the armamentarium for amalgam condensation and carving is shown in Table 26.1.
TABLE 26.1. Armamentarium for Amalgam Condensation and Carving
A. Matrix Band Placement
Proper amalgam condensation requires a three-dimensional “form” or box with only one surface or side open. A class II restoration has at least two surfaces open and therefore lacks the box-like shape for proper condensation. A matrix band is a thin strip of material that is placed around the tooth to establish the missing sides of the box and allows adequate condensation of amalgam (see Fig. 26.1A). The matrix retainer holds the band in a loop and tightens the band around the tooth.
FIGURE 26.1. A. Properly wedged matrix band tightened with a matrix retainer. B. An amalgam overhang that can result when a matrix band is not properly adapted.
1. Select appropriate matrix band and matrix retainer. Matrix bands are available in a variety of shapes (universal, bicuspid, molar), different thicknesses (0.002, 0.0015, and ultrathin 0.001 gauge), and flexibilities (regular or dead soft).
2. Burnish matrix band on countertop prior to placement to create a more curved/anatomical form.
3. Place matrix band and firmly wedge. Burnish the band to the adjacent tooth to assure good adaption of the proximal contact of the restoration.
4. Check the proximal box to make certain that the band is adapted with no area for the amalgam to escape, which could cause an overhanging margin (see Fig. 26.1B).
B. Mix (Triturate) Amalgam According to Manufacturer’s Specification
Mix the amalgam in the amalgamator according to the manufacturers’ directions, usually included as a package insert. Different triturators have different mixing time and speed recommendations.
C. Technique for Amalgam Condensation
1. After mixing, place the triturated material in the amalgam well.
2. Use amalgam carrier to pick up the amalgam and transfer to the preparation; see Figure 26.2.
3. Place increments and condense the material after each placement; see Figure 6.4A–D. Use the appropriately sized condenser to condense, push to compact the amalgam toward the floor of the preparation and also laterally into the line angles and proximal box. Use firm, overlapping condensing strokes (larger condensers need greater pressure); see Figure 26.3A and B.
4. Working from the floor of the preparation, continue to place and condense increments until the preparation is overfilled by approximately 1 mm. Use a larger condenser to condense the overfilled preparation. This ensures complete coverage of the margins of the cavity preparation for proper carving and to remove excess mercury.
5. Using a burnisher to precarve the overfilled amalgam as shown in Figure 26.4 will also help bring mercury to surface. Burnishing pushes and adapts the material contiguous to the margins to eliminate voids. Burnish mesiodistally and faciolingually forming the major grooves of the occlusal anatomy. The condensing phase should take approximately 2½ to 3½ minutes.
FIGURE 26.2. Placing the first increment of amalgam into the preparation with an amalgam carrier.
FIGURE 26.3. A. Condensing the first increment. B. Condensing subsequent increments.
FIGURE 26.4. Burnishing the condensed amalgam.
II. Procedure for Carving Amalgam
Carving of the amalgam begins immediately after burnishing. Use sharp instruments.
A. Marginal Ridge and Contact Area
1. Use an explorer to carve the amalgam adjacent to the matrix band forming the occlusal embrasure. Keep the tip of the explorer against the band surface and move the explorer from the buccoproximal margin toward the lingual, stopping at the center of the box. Repeat the procedure, this time from the linguoproximal margin to the center, as shown in Figure 26.5A and B.
2. Such carving defines the contact area and the marginal ridge. The marginal ridge of the restoration and the marginal ridge of the adjacent tooth should be at the same level. Usually, the contact area is in the middle of the mesial or distal surface or the restoration.
FIGURE 26.5. Carving the marginal ridge. A. Picture. B. Drawing of carving the marginal ridge.
B. Occlusal and Proximal Anatomy
1. Use the discoid/cleoid to carve the occlusal surface. Keep the edge of the carver blade perpendicular to the margins. Rest part of the blade of the carving instrument on the enamel adjacent to the restoration, and use a pulling stroke to carve with the margins of the preparation; see Figure 26.6A and B. Do not allow the tip of the carving instrument to pass the center of the prepared cavity; see Figure 26.6C. Carve occlusal margins so that there is no feathered overextension of amalgam or “step-down” at the margin, such as that shown in Figure 26.7A. Take care to create a smooth, continuous surface from the enamel to the restoration.
2. Develop occlusal grooves to complete the restoration’s anatomy. These are distinct, but not necessarily deep grooves. When an occlusal groove needs to be deepened, the side of the carver should not make contact with the amalgam at the preparation margin; see Figure 26.6D and 26.8.
3. Carving the mesial and distal pits and triangular fossa is important for correct development of the occlusal anatomy. The crest of the marginal ridge is the base of the triangle, and the facial and lingual supplemental grooves in the restoration form the two sides of the triangular fossa that meet in the mesial or distal pit. When carving the triangular ridges, keep the blade of the carver angled in harmony with slope of the cusp.
4. Refine proximal contour with a Hollenback carver or proximal carver. Use a series of shaving strokes occlusally from the cavity proximal corners. Use only minimal pressure with the shaving stroke. Blend the proximal margins to the occlusal margins. Keep part of the blade resting on adjacent enamel. At this time, the carver can be used to adjust the marginal ridge height and shape, occlusal embrasures, and the rounding of the marginal ridge. Use carvers to remove any excess amalgam from the cervical area.
5. Use the tip of a carver or explorer to remove any flash remaining in the occlusal grooves of the tooth.
6. Burnishing after carving will smooth hard to polish occlusal grooves of the restoration.
7. Examine the restoration for proper marginal adaption, anatomy, and contours; see Figure 26.9.
FIGURE 26.6. A. Carving the margin. B. The carving instrument properly rests on the tooth creating a flush margin. C. The carver does not rest on the tooth and is placed too far toward the opposite margin resulting in a step at the margin. D. The carver does not rest on tooth structure leaving flash on the occlusal surface.
FIGURE 26.7. Results of poor carving. A. Overextension or flash. B. Submarginal area. C. Open margin.
FIGURE 26.8. Accentuating the occlusal anatomy.
FIGURE 26.9. Examining for marginal discrepancies.
C. Check and Adjust Occlusion
1. To check occlusion, have the patient bring his/her teeth together lightly, check for a shiny area on the restoration and remove the premature contact with a carver.
2. Check the occlusion again with articulating paper. Have patient lightly tap teeth together, carve prematurities until any contact with the restoration occurs simultaneously with other centric contacts on the tooth and the adjacent teeth. This step may need to be repeated to get even contact.
3. Next, with articulating paper, have the patient to make lateral and protrusive movements and reduce any interferences present.
D. Examine the Restoration
Double-check the interproximal for amalgam debris, rubber dam material, or overhangs. Remove any overhangs or debris. Check interproximal contact visually to make sure that no light passes through the contact. Hold the mirror on the lingual and facial aspects of the teeth and check at different angles. Then check with dental floss, making sure there is resistance when the floss passes through the contact area.
E. Postoperative Instructions
1. Instruct patient not to chew on the new restoration for at least 2 hours.
2. If patient was given anesthesia, remind him/her to be careful not to bite a lip or tongue.
3. Inform the patient that he or she may experience postoperative sensitivity to hot or cold for a few days.
4. If the patient feels that occlusion (bite) is too high after anesthesia wears off, have him/her contact the office for occlusal adjustment.
5. Have the patient schedule a return appointment after 24 hours to finish and polish the restoration.
Summary for Condensing and Carving Amalgam
- Select and place appropriate matrix band and matrix retainer.
- Triturate amalgam.
- Use amalgam carrier to place amalgam into preparation and condense using increments until overfilled by 1 mm.
- Carve marginal ridge with explorer to establish embrasure and marginal ridge height.
- Remove matrix band.
- Carve occlusal surface using discoid/cleoid carver.
- Develop mesial/distal pits and the triangular fossa.
- Use Hollenback carver to refine the proximal and gingival margins—the Hollenback may also be used to refine or to deepen the occlusal grooves and anatomy.
- Check the interproximal contacts, the occlusion, and make any necessary adjustments.
- Give the patient postoperative instructions and dismiss with an appointment to return for polishing the restoration.
Tips for the Clinician
- Stabilize the mandible with the nondominant hand when condensing an amalgam restoration in the lower arch.
- Condense the amalgam in all three dimensions.
- Do not handle freshly mixed amalgam with bare hands.
- Make sure to properly adapt and wedge the matrix band.