As composites became more popular for posterior class II fillings, there were more and more interproximal food traps, causing patients a frustration that enticed them to floss more, at least in that area. If they didn’t floss, there were more and more areas of pocketing. Even with the increased use of the bitine ring, tight contacts are still somewhat elusive and do not always prevent food impaction interproximally. This has always been a frustration and still is to most dentists.
A more positive system of wedging has been developed that supplements the standard procedures and guarantees contacts so tight that they might even need to be loosened. It is recommended to try this procedure on a bicuspid before going to a molar.
CAVITY PREPARATION
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| Figure 1. Mirror image of tooth No. 21 with small DO preparation. |
A change in conventional thinking concerning class II preparations, even for the latest composite preparations, is a prerequisite to this new method. Proximal caries should require the smallest preparation one can make, extending from the proximal ridge gingivally to include only the decay and any decalcified enamel (Figure 1). A No. 1157 or a No. 1557 carbide bur should be the largest bur used. These burs have rounded ends, and all composite preps should have rounded corners. Hand instruments, like a mesial or distal margin trimmer, should then be used to remove any undermined enamel on the buccal and lingual walls and the gingival floor of the preparation.
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| Figure 2. Using the Fissurotomy Bur (SS White) to remove stain in mesial pit of occlusal of No. 21. |
A fissurotomy bur (SS White) is then used to remove any stain and/or decay from the occlusal grooves (Figure 2). It is most advantageous not to weaken the tooth by going across the isthmus and cutting a dovetail preparation since it is not necessary for retention of the composite filling. Stain in the occusal groove is indicative of decay that penetrates the enamel 75% to 80% of the time, so it should always be removed when doing this type of restoration. A small round bur is used to remove any remaining decay in the dentin. The tip of the fissurotomy bur is then used to place a small groove in the gingival floor, right up against the axial wall. The same bur is then used in like manner on the buccal and the lingual walls, right next to the axial wall, extending all the way to the occlusal surface.
MATRIX PREPARATION
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| Figure 3. Metal matrix band, wedge, and bitine ring placed on No. 21. |
Use a metal matrix as you would use for an alloy filling instead of a plastic matrix. This will become obvious later. Place the matrix and wedge tightly. Place the bitine ring. Be sure the matrix band is touching the adjacent tooth (Figure 3).
PLACING THE RESTORATION
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| Figure 4. Placing flowable composite. |
Apply the etchant and then the bonding liquid, or use self-etching bonding over the entire preparation, including the occlusal grooves, and cure thoroughly. Next, apply a thin coating (1 mm or less) of flowable composite over the entire preparation, including the occlusal grooves (Figure 4). This will guarantee you the best seal at the interface of the cavity and the restoration and guarantee little or no flash gingivally or on the buccal or lingual aspects. Drag an explorer slowly through the flowable composite to remove any bubbles that may have been trapped in the corners of the prep. Cure thoroughly. Add additional layers of flowable composite no more than 2 mm thick to fill the proximal box to no more than halfway. The height is determined by a step that is explained in the next paragraph.
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| Figure 5. Cured balls of posterior composite. |
The next series of steps are the most critical to obtain a very tight contact. Your assistant will make a little ball of material of posterior composite by rolling it on the bracket table cover with a nonpowdered gloved finger, then cure it. Actually, she should make 2 or 3 of these balls of slightly different sizes, approximately the mesio-distal width of the proximal box, so that you have a choice of the size that fits best (Figure 5). This little ball should be egg-shaped, which will provide a wedging action when pressed tightly into the proximal box space by a plugger. It should not reach the cured layer of flowable composite in the box when pressed tightly apically, or the wedging action will not produce a tight contact. The concept is to put pressure between the axial wall and the metal matrix band, thus forcing the metal band tightly against the proximal tooth and separating the 2 teeth. A plastic matrix would deform easily and the proximal contours would not be smooth. In addition, a metal matrix is thinner. Now check the fit of the ball by holding it with cotton pliers, then place it back on the bracket table.
Place another layer of flowable composite into the proximal box. If you prefer to use a posterior composite, then you should paint the surface of the cured composite in the proximal box with a thin layer of bonding agent as a wetting agent. Do not cure. Place a composite of your choice into the cavity so that it is within approximately 1 mm of the proximal ridge. The uncured composite should be high enough to engage the cured ball of composite when pressed into the cavity. Before placing the ball of cured composite, you should paint the uncured surface with a thin layer of bonding agent unless you are using more of the flowable composite instead.
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| Figure 6. Cured ball picked up by small amount of flowable composite on end of plugger. | Figure 7. Using the plugger to force the ball of composite into the proximal box. |
Next, place a small amount of flowable composite on the tip of the plugger and use that to pick up the cured composite ball (Figure 6). Use a plugger to force the ball into the cavity and into the uncured composite, thereby forcefully separating the teeth (Figure 7). Press firmly and hold while the assistant cures the composite material. The ball will bond directly to the other composite, and this addition of a ball of cured composite will reduce the overall shrinkage of the restoration. Release the pressure and remove the plugger once you feel the material has been cured adequately enough to hold the ball in place. Fully cure this layer. Add additional restorative material as necessary to fill the preparation. A thin coating of bonding agent between layers of any posterior composite will give a better bond and ensure that no bubbles are trapped.
FINISHING AND POLISHING
Remove all the paraphernalia from the tooth except the wedge. You will notice that the matrix band is difficult to remove because of the tight contact. This is good since this is what we are trying to achieve. Cure additionally from the buccal and lingual aspects once the band has been removed. If the wedge is left in place, there will be little or no bleeding (bleeding renders curing ineffective since the color red blocks out most visible light rays). Adjust the occlusion and return the original contours of the tooth.
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| Figure 8. Bard-Parker 12B scalpel used to contour the proximal ridge. | Figure 9. Using the Fissurotomy Bur to contour and smooth the interproximal surfaces. |
A Bard-Parker 12B scalpel is very useful in removing flash from the buccal and lingual interproximal surfaces of the tooth. It is also very useful for rounding the marginal ridge to the contact area (Figure 8). Palm grasp the handle, using your thumb for guidance, and place the convex cutting surface on the proximal ridge. Using pressure directed apically, shave off the sharp corners and round over the marginal ridge while preserving the sought after contact. Use a fissurotomy bur to contour and smooth the buccal and lingual surfaces (Figure 9).
Floss the contact with ribbon floss before trying to smooth the contact. Smooth the contact with the smoothest fine diamond strip (yellow tipped) available. If floss is not used first, it is almost impossible to get the diamond strip into the contact area. Only 1 or 2 swipes with the diamond strip is necessary. Don’t overdo or you may lose the much desired contact! Polish the remainder of the restoration and then remove the wedge. If needed, shave any flash interproximally with the Bard-Parker and you are done.
Dr. Karst maintains a private practice in Salem, Ore. He has served as an associate clinical instructor at the Oregon Health Sciences University, and as a product innovator, he has developed such products as the Stainbuster air polishing device and the Bite-Tray Plus impression tray for his company, Emery Dental. He can be reached at (503) 378-0523.
