Amalgam matrix for Class II and Class V preparations connected at the proximal box
John S. Mamoun, DMD and
Mairaj K. Ahmed, DDS
 |
ABSTRACT
|
|---|
Background. The authors present a technique for placing and reinforcing an amalgam matrix around combined Class II and Class V preparations that connect at the proximal box.
Overview. First, the dentist fills the Class V aspect of the preparation, using a temporary resin-based composite wall at the line angle to support amalgam condensation. The dentist then removes the wall and places a matrix band around the tooth, internally reinforcing the band with smaller pieces of matrix band and resin-saturated cotton balls that are light-polymerized and externally reinforcing the band with fast-polymerizing vinyl polysiloxane. Finally, the dentist condenses the line angle amalgam through the proximal box and condenses the proximal box and occlusal aspects.
Conclusion. For connected Class II and Class V preparations, this matrix technique permits controlled amalgam condensation, even at the line angle aspect, where it is difficult to condense amalgam without voids or microleakage.
Clinical Implications. This technique allows dentists to provide a stable, inexpensive direct restoration for teeth with connected Class II and Class V preparations, providing an alternative for patients who do not wish to have crowns placed.
Key Words: Matrix; Class II restoration; Class V restoration; connected restoration preparations; proximal box
Sometimes, dentists must place a matrix around a multisurface Class II preparation—mesial-occlusal-buccal, distal-occlusal-buccal, mesial-occlusal-lingual or distal-occlusal-lingual—in which the buccal or lingual aspect of the preparation communicates with the proximal box and a cusp overlies the line angle where the communication occurs. Unfortunately, placing a matrix band blocks access to the Class V restoration aspect, preventing the placement of a restorative material there. In addition, if the preparation involves root surfaces, matrix adaptation is difficult owing to the irregular root surface contour. Placing a matrix that is not fully sealed or not using a matrix may compromise amalgam condensation at the line angle, resulting in overhangs, gapping or fractures. Eventually, plaque accumulation at the line angle may cause extensive caries or periodontal problems.
Dentists may use improvised, hard-to-manage methods to restore these Class II preparations. They may attempt to do a resin-based composite buildup without using a matrix, risking isolation or contact problems. They may create straight-line access to the preparation to allow for condensation by removing the cusp overlying the line angle, destroying large amounts of tooth structure and forcing the creation of a cuspal-coverage restoration. They may place a combined amalgam–resin-based composite restoration, placing resin-based composite up to the line angle, then placing a matrix and condensing amalgam in the distal-occlusal or mesial-occlusal aspect. This kind of hybrid restoration may have microleakage at the amalgam–resin-based composite interface or may be unstable owing to the different physical properties of the restorative materials.1,2
In this article, we present two approaches to placing a matrix and preparing these restorations. The dentist restores the buccal or lingual wall up to the line angle without using a matrix. After doing so, he or she places a matrix around the preparation without concern about blocking access to the Class V restoration aspect. The dentist then condenses the amalgam into the line angle by directing forces laterally through the proximal box, followed by proximal box and occlusal condensation. Condensation should be completed within five minutes of placing the Class V amalgam restoration so that the proximal box and Class V amalgam restoration bond chemically with a tensile strength at about 80 percent of maximum.3,4
|
CONDENSING AMALGAM IN COMBINED CLASS V AND CLASS II PREPARATIONS
|
|---|
Supragingival preparations involving the clinical crown only.
The following multistep procedure allows for optimal condensation of amalgam for supragingival preparations involving the clinical crown only.
Step 1.
Create a definitive Class II preparation. Ensure that the junction between the proximal box and the Class V restoration aspect allows for access of an amalgam condenser.
Step 2.
Place and cure resin-based composite at the line angle to form a temporary wall to support the Class V amalgam restoration during its condensation. Etch and bond if needed. Condense the Class V amalgam restoration and then quickly finish it (Figure 1
). Remove the resin-based composite using a sharp scaler, a no. 15 scalpel blade or a handpiece. Avoid moistening or nicking the setting amalgam.
View larger version (93K):
[in this window]
[in a new window]
|
Figure 1. Mesial-occlusal-buccal preparation with resin-based composite placed at the mesial-buccal line angle to support the portion of the amalgam restoration on the buccal surface during its condensation.
| |
Step 3.
Place a matrix band and wedge (Figure 2). If the amalgam is on the buccal aspect, position the matrix retainer from the lingual aspect, if possible, so that the matrix band adapts closely to the buccal surface. If this is not possible, position the retainer so that the matrix band disjunction is positioned along the midbuccal surface of the tooth away from the line angle. This positioning facilitates activities to reinforce the amalgam (Step 4).
View larger version (101K):
[in this window]
[in a new window]
|
Figure 2. Matrix placed around the mesial-occlusal-buccal preparation. The buccal wall is reinforced with light-cured resin-impregnated cotton.
| |
Step 4.
Reinforce the Class V amalgam restoration (Figure 2
). Place cut strips of another matrix band between the Class V amalgam restoration and the matrix band that is encircling the tooth. Then place small cotton balls saturated with unfilled resin between the cut pieces of matrix band and the matrix band around the tooth. Push the band pieces flat against the amalgam. Light cure the resin-impregnated cotton to solidify it and, thus, reinforce the Class V amalgam restoration for later use during the condensation of the proximal box (Step 6).5,6
Step 5.
Reinforce the line angle aspect of the matrix band by placing fast-set (30–60 seconds) vinyl polysiloxane (VPS) around the external surface and line angle aspect of the matrix band, using a fine syringe tip to place VPS interproximally. For additional stabilization, dentists also can place a rubber dam clamp on a neighboring tooth and envelope the clamp and the matrix retainer with VPS.7,8
Step 6.
First, condense the amalgam laterally through the proximal box to complete the Class II and Class V restoration line angle. Then condense the proximal box and the occlusal aspect.
Step 7.
Remove the VPS (if used) by sectioning it with a handpiece or a scalpel, peeling off pieces from the main body of VPS. Remove the matrix band, wedge, solidified cotton pieces and clamp.
Step 8.
Finish the restoration (Figure 3). Remove any overhangs. Inspect the amalgam for voids, particularly at the line angle. Take the marginal ridge of the restoration out of occlusion to minimize stress at the line angle.
View larger version (101K):
[in this window]
[in a new window]
|
Figure 3. Definitive mesial-occlusal-buccal restoration showing well-condensed amalgam at the line angle.
| |
Preparations involving buccal or lingual root structure.
In a combined Class II and Class V preparation involving radicular structure, the external contour of the root may have an irregular surface outline that may hinder matrix band adaptation along the root.
Follow steps 1 and 2 in the previous section, then place a matrix band and wedge. The matrix band may not completely cover the amalgam overlying the root structure or the line angle. To solve this problem, use VPS and a clear matrix band. First, loosen the matrix band slightly and place a clear matrix band strip between the band and any unsealed area at the line angle (Figures 4 and 5). Next, place VPS around the matrix retainer, clear matrix band and exposed radicular amalgam (Figure 6). The VPS will provide a stiff support for the clear matrix band and the amalgam on the buccal surface, permitting controlled condensation of the remaining amalgam. Complete the amalgam condensation, remove matrix materials and refine the restoration.
View larger version (100K):
[in this window]
[in a new window]
|
Figure 4. An accessory clear matrix band strip placed between the metal matrix and the tooth completes the seal at the line angle of a preparation involving radicular tooth structure.
| |
View larger version (102K):
[in this window]
[in a new window]
|
Figure 6. Low-viscosity vinyl polysiloxane enveloping the matrix retainer, clear matrix band and wedge for support during amalgam condensation.
| |
|
DISCUSSION
|
|---|
These techniques for placing a matrix around connected Class II and Class V preparations allow for controlled condensation of amalgam, even at the line angle. The matrices also aid in isolation, allowing for resin-based composite placement instead of amalgam. However, if isolation is difficult, the clinician should use amalgam, which is more likely to succeed in cases of moisture contamination during placement than is resin-based composite.
How thick occlusogingivally should the cusp overlying the line angle be for it to be able to withstand fracture as part of a direct Class II and Class V restoration? The cusp remainder should have enough structural support to be nonbrittle and should be free of craze lines. Studies suggest that a shell of occlusal enamel, supported by restorative material, has about one-half of the fracture resistance of enamel supported by dentin.8–10 This may imply that a cusp supported by several millimeters’ thickness of dentin (reflecting a cusp height of at least one-third of the occlusogingival tooth height) should be adequately fracture-resistant. Some researchers suggest that bonded amalgam provides more resistance to cusp fracture than does unbonded amalgam,11,12 while others dispute this.8
If the preparation involves a radicular structure, creating a flap may be necessary to provide access for the matrix materials. Also, if the definitive restoration would impinge on the periodontal connective tissue apparatus (that is, the biological width), the prepared tooth should be temporized after all caries are removed and later undergo crown-lengthening surgery or orthodontic extrusion before the definitive restoration is placed.
Finally, though a low-viscosity VPS provides a less rigid matrix support for amalgam condensation than does a high-viscosity VPS, it is easier to cut, peel off and remove than is high-viscosity VPS.13 Compound material may substitute for VPS as a matrix support.14
|
CONCLUSIONS
|
|---|
A direct amalgam restoration for teeth with a connected Class II and Class V preparation is a practical alternative for patients with new lesions or root caries that communicate with old or failing restorations or for patients who cannot afford crowns.
|
FOOTNOTES
|
|---|
Dr. Mamoun is an associate general dentist, Scotia, N.Y. Address reprint requests to Dr. Mamoun at P.O. Box 219, Green Village, N.J. 07935, e-mail "mamouno{at}hotmail.com".
Dr. Ahmed is a resident, Cleft-Craniofacial Department, Lancaster Cleft Palate Clinic, Lancaster General, Lancaster, Pa.
|
REFERENCES
|
|---|
- Fruits TJ, Duncanson MG Jr, Coury TL. Interfacial bond strengths of amalgam bonded to amalgam and resin composite bonded to amalgam. Quintessence Int 1998;29:327–34.[Medline]
- Hadavi F, Hey JH, Ambrose ER, elBadrawy HE. Repair of high-copper amalgam with and without an adhesive system: in vitro assessment of microleakage and shear bond strength. Gen Dent 1993;41(1):49–53.[Medline]
- Bagheri J, Chan KC. Repair of newly condensed amalgam restorations. Iowa Dent J 1993;79(3):13–4.[Medline]
- Hadavi F, Hey JH, Czech D, Ambrose ER. Tensile bond strength of repaired amalgam. J Prosthet Dent 1992;67(3):313–7.[Medline]
- Woodmansey KF. Replacing compound with composite resin for quick and efficient matrices. JADA 1998;129:1601–2.
- Ireland EJ. Evaluation of a new matrix band and wedge for amalgam preparations having lingual or facial extensions. Gen Dent 1985;33:434–5.[Medline]
- Mamoun JS, Cervini E. A pin amalgam or composite core foundation technique for teeth with minimal coronal structure. J Prosthet Dent 2004;91:599–602.[Medline]
- Latino C, Troendle K, Summitt JB. Support of undermined occlusal enamel provided by restorative materials. Quintessence Int 2001;32:287–91.[Medline]
- Grisanti LP 2nd, Troendle KB, Summitt JB. Support of occlusal enamel provided by bonded restorations. Oper Dent 2004;29(1):49–53.[Medline]
- Allara FW Jr, Diefenderfer KE, Molinaro JD. Effect of three direct restorative materials on molar cuspal fracture resistance. Am J Dent 2004;17:228–32.[Medline]
- Rasheed AA. Effect of bonding amalgam on the reinforcement of teeth. J Prosthet Dent 2005;93(1):51–5.[Medline]
- Zidan O, Abdel-Keriem U. The effect of amalgam bonding on the stiffness of teeth weakened by cavity preparation. Dent Mater 2003;19(7):680–5.[Medline]
- Lu H, Nguyen B, Powers JM. Mechanical properties of 3 hydrophilic addition silicone and polyether elastomeric impression materials. J Prosthet Dent 2004;92(2):151–4.[Medline]
- Harrington WG, Moon PC, Crockett WD, Shepard FE. Reinforced matrices for pin-amalgam restorations reduce microleakage. J Prosthet Dent 1979;41:622–4.[Medline]
TOP
ABSTRACT
CONDENSING AMALGAM IN COMBINED...
