CLINICAL TECHNIQUE

For all procedures involving bonding of any nature, the authors recommend placement of a rubber dam in order to obtain proper isolation. However because these types of lesions are often subgingival, a split dam technique may be required.

First, application of a rubber dam or comparable isolation system is performed. Next, the interproximal decay is removed from either a buccal or lingual approach, depending on which allows easier access. Typically, these lesions are found within 1-2 mm of the cementoenamel junction (CEJ)¹ (Figure 1) and will extend the entire buccal-lingual width of the tooth. The finished preparation will usually resemble a half circle once completed (Figures 2 and 3).

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Once the decay has been removed, the preparation is conditioned using Cavity Conditioner (20% polyacrylic acid, GC America, Alsip, IL, USA). This is placed in the preparation for 10 seconds and then rinsed with water. The excess water is then removed using a single puff of air, leaving the preparation slightly moist. Next, a Tofflemire band (Henry Schein, Melville, NY, USA) is placed around the tooth making sure that the band extends past the gingival margin of the lesion to healthy tooth structure. Either a number 1 or a number 2 band will be used depending on how far gingivally the lesion is located. The band is trial fitted and a scratch mark is placed at the desired access location using a bur (Figure 4). The band is then removed from the mouth and a hole is made using a small bur, in this case, a 330 carbide bur (Brasseler USA, Savannah, GA, USA). This hole should be between 2.5 and 3 mm in diameter. This is just large enough to allow the tip of the glass ionomer syringe to pass through (Figure 5).

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At this point, the band is reinserted (Figure 6). A wedge may be placed in order to ensure proper adaptation of the band to the gingival margin. Often, the wedge is inserted only to the point of passive binding. Forcing the wedge into place can cause the band to bulge into the cavity preparation, leaving the final restoration with a less than ideal anatomic form.

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Fuji IX GP Extra (GC America) is then activated and triturated for 10 seconds at ±4000 rpm and immediately placed into the applicator. The tip of the syringe is placed just into the opening in the matrix band, and the material is discharged aggressively until it begins to extrude from the hole (Figure 7). When syringing the material, do so forcefully to allow the material to spread into the preparation and become well adapted. Wait about one minute and then begin to clean up the excess material while it is still in the gelatinous phase, particularly around the access hole. Removing the excess at this point helps to minimize finishing once the material is set and will ensure that the matrix does not get locked into place. Often, excess material will creep occlusally along the inside of the band, and cleanup will likely be required adjacent to the marginal ridge as well. This is easily done with the tip of an explorer.

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Once the material is set (in the case of Fuji IX GP Extra, around 3 minutes after trituration), the band is removed and an ET-6 bur (Brasseler USA) is used to remove any remaining flash. The restoration is then coated using G-Coat Plus (GC America) to protect the glass ionomer from moisture fluctuations, as well as to give it a smoother surface finish. The final restorations should have proper anatomic contour and have a shiny surface finish (Figures 8 and 9). Bitewings of completed restorations can be taken to confirm excellent results.

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DISCUSSION

According to the 2010 census, the number of people over the age of 62 years in the United States increased 21% over the past 10 years. As the average age of the population increases, so does the number of geriatric patients who require dental care. Older patients have several challenges to overcome regarding the maintenance of their oral health. These patients are often on multiple medications that can cause them to produce less saliva, which increases the likelihood of caries formation. Likewise, older patients tend to have gingival recession and exposed root surfaces. These surfaces are more prone to decay than the enamel covered coronal portion of the tooth. When compounded with reduced manual dexterity and the inability to properly manipulate floss, these patients are more likely to form interproximal root surface decay.²

Root surface lesions can often be difficult to restore. Typically, they are found at the level of the gingiva and often extend subgingivally. Interproximal lesions offer an even greater challenge since they often cannot be easily accessed. Sometimes accessing these lesions from the occlusal is the only way to restore them. However, this method requires removing large amounts of what is often healthy tooth structure, which is less than ideal. When the caries can be accessed and removed by direct access from the buccal or lingual, the challenge is then finding the best material and method of isolation in order to restore it.

When choosing a restorative material for these lesions, one must take into account the strengths and weaknesses of each potential material and how they will affect the longevity of any restoration. When accessing interproximal root surface lesions from the buccal or lingual, it can be difficult sometimes to position the bur and handpiece in such a way as to create the proper mechanical retentive features required to place an amalgam restoration. Likewise, the banding of these lesions to create a proximal wall against which an amalgam can be condensed is extremely challenging. When the band is in place, the cavity cannot be accessed. Placing composite would address the problem of needing mechanical retention in the preparation; however, the proximity to the gingiva and the inability to isolate the preparation from moisture would create problems with bond strength and restoration longevity.³ Likewise, the bonding effectiveness of today's bonding systems on cementum is unpredictable at best.⁴

Conventional glass ionomer restorative materials are, by the nature of their composition, self-adhering.⁵ These materials form a chemical bond with the mineral content of the tooth and only require minimal conditioning of the tooth.⁶ Studies have shown that conditioning with 20% polyacrylic acid prior to placing Fuji IX GP Extra increases the bond strength.⁷ These materials also release fluoride in significant enough quantity and longevity to drastically reduce the incidence of recurrent caries. Conventional glass ionomer has also been shown to possess the ability for the fluoride reservoir to be “recharged” by means of topical application of fluoride gels or pastes.⁸ Root surface lesions are often found at or below the level of the gingiva, making isolation from moisture difficult. Glass ionomers are hydrophilic materials that actually require water as part of the acid/base setting reaction that they undergo.⁹ Therefore, if moisture contamination occurs during placement of your restoration, it will not be as catastrophic as it would be for a composite restoration. Furthermore, conventional glass ionomer has shown excellent biocompatibility¹⁰ and gingival response to restorations placed subgingivally.¹¹ A downside of this material is its lack of overall strength.¹² However, this is of little consequence interproximally where the restoration will be subject to minimal stress. Likewise, the relative poor esthetics of these materials should not be a factor due to the location of these lesions.

Fuji IX GP Extra was the material used for this technique. Directly after trituration, the material has a slightly flowable viscosity, which allows it to be syringed into the preparation and adapted to the internal walls. It is important to syringe the material quickly after trituration to ensure it is still in this slightly flowable state. If allowed to begin setting up, it will not adapt as well and voids may form. Because this technique relies on the pressure of the material against the walls for adaptation, it is important to initially syringe more material than can fit into the preparation. This back fill pressure will help get excellent adaptation of the material into the cavity preparation but will also cause some overflow of the material past the margins. This overflow typically occurs within the band in an occlusal direction and is easily removed with an explorer tip while the material is setting. Good adaptation of the band along the gingival portion of the preparation limits movement of excess material in this direction. Being able to band these lesions actually reduces the amount of finishing required compared to freehand placing of these restorations. Furthermore, having the band in place assures the material only bonds to the intended tooth and not the adjacent tooth as well.

Advantages of this technique include, most importantly, preservation of tooth structure. By providing a good technique to restore interproximal lesions, practitioners no longer have to access these lesions through the marginal ridge in order to be able to place a matrix band. This preserves the strength of the tooth while still being able to provide a sound restoration. Another positive outcome associated with this technique is the lack of finishing required. Often the gingival margins require no finishing at all due to tight adaptation of the band to the tooth at this point. Since no condensation force is placed on the glass ionomer after it is syringed, the material stays within the confines of the matrix band. The flash that is produced is in areas that are easily accessible and is simple to remove.

There are several potential problems associated with this technique. In some parts of the mouth, interproximal root surface lesions cannot be accessed directly. For example, individuals with third molars can sometimes get these lesions on the distal root surfaces of the second molars. In these instances, it may be easier to access the decay from the occlusal with a class II type preparation. Another difficulty with this technique involves placement of the band. It can sometimes be difficult to ensure that your band is seated gingival to the margin of the cavity preparation because this area cannot be visualized as directly as it can be when doing a class II restoration. It is imperative that the gingival margin of these restorations be smooth, not only for the health of the tissue in that area, but also for the longevity of the restoration. An uneven, subgingival margin can be mistaken for calculus by dental hygienists who can end up chipping or dislodging these fillings with scalers during prophylactic appointments.