Written by Robert Lowe, DDS Thursday, 10 May 2012 08:56
Often times, when presented with a single- tooth edentulous space, we "automatically" think of either a 3-unit fixed partial denture (bridge), or an implant and crown. Yet, there are still some situations that are best treated with direct resin.
Many years ago, I was introduced to a direct resin bridge technique called "the Georgia Bridge," as demonstrated in a 1986 lecture by Dr. John Savage from Atlanta. Dr. Savage described a "freehanded" bonding technique to use direct composite resin as a pontic, utilizing adhesive dentistry and undercuts in the enamel surface of the abutment teeth to help retain this "pontic" between the edentulous span. Facial and proximal surfaces of the abutment teeth were prepared minimally, as if for direct labial veneers. Horizontal groves were then made in these surfaces for auxiliary retention of the restorative material. Next, a "composite bridge" was fabricated using light-cured resin across the edentulous area between the abutment teeth.
Dr. Savage described this Georgia Bridge as "the bridge of choice" when replacing single anterior missing teeth when: (1) the patient could not afford a conventional fixed bridge, (2) the patient did not wish to prepare "virgin" abutment teeth required for a fixed bridge replacement, (3) the edentulous ridge was inadequate for placement of an implant, and (4) the patient chose not to have an implant placed.
Since the time that the original article on the Georgia Bridge was written, many advances in adhesive dental technology and composite resins have occurred that make this technique even a better long-term solution for some of the aforementioned clinical situations. This article will feature a modification of the Georgia Bridge technique using a modern composite resin to close an edentulous space left by the extraction of a mandibular incisor.
Diagnosis and Treatment Planning
A 76-year-old female patient presented with a missing mandibular left lateral incisor that had been recently extracted because of severe root caries on the distal surface that had made the tooth unrestorable (Figure 1).
Upon clinical and radiographic examination, it was noted that there was not enough remaining bone in the labial-lingual direction to consider an implant. Also, the teeth adjacent to the edentulous space, aside from having some crestal bone loss, were unrestored. The crown-to-root ratio and mesiodistal root diameter at the gingival crest of the mandibular left central incisor were not favorable due to the alveolar bone loss, making it a questionable abutment for a fixed partial denture. The other restorative "choice," a single-tooth removable "flipper" appliance, would have been a poor solution due to the amount of plastic to replace "one missing tooth"; and the probable lack of patient compliance to wear such an appliance long term. It was decided that the most conservative approach for this patient would be to "suspend" a pontic between the abutment teeth using adhesive technology and fiber reinforcement.
Since the pontic would be layered in a similar fashion to the way a ceramist would make a bridge, the plan was to use an opacious dentin as the first layer replicating the internal dentin structure of the natural tooth. Next, the "universal" VITA shade would be layered over the initial material to recreate the "bulk" of the remaining dentin. Finally, an incisal shade would be used to recreate translucency in the incisal third of the tooth and complete the incisal edge.
A universal nanocomposite resin (Kalore [GC America]) was chosen as a material that would be well-suited for this task. In recent years, advances in composite resin technology have been largely on the filler side—changes in particle size, particle shape, or filler type—to try to maximize the aesthetic potential of the material while maintaining the physical properties necessary to enable the material to withstand the stresses of masticatory forces in the oral environment. With Kalore, the manufacturer reports an innovation in monomer technology. A DuPont monomer (DX-511) is used, which has a long rigid core with flexible arms. It is believed, with this new monomer formulation, that the polymerization shrinkage challenge may be solved by removing the shorter chain methacrylate matrix, providing the potential for reducing such clinical challenges as marginal gap formation, microleakage, stain, and secondary caries while enhancing aesthetics and wear resistance.
|Figure 1. A facial preoperative view of a 76-year-old female patient who presented with a missing left mandibular lateral incisor.||Figure 2. This is a photo of the Kalore Shade Guide (GC America). Its unique design allows for individual shade selection in 3 different opacities, and gives the "recipe" for layering to create the "Vita Spectum" of shades for difficult anterior shade matches.|
|Figure 3. The shades of the nanocomposite resin (Kalore [GC America]) were chosen for this patient's restoration.||Figure 4. This photo demonstrates the difference in the "new" Kalore Unitip (top) from the original design (bottom). Note the difference in the size of the tip opening that allows for easier extrusion of the nanocomposite material.|
Kalore also has a unique shading system that offers opaque, universal, and translucent shading that provides the dentist the opportunity to "stack" a composite resin in the same fashion as a lab technician to create internal beauty and lifelike aesthetics. Most of the time, the universal shade alone will provide excellent shade blending with natural tooth structure. The simplified shade system offers the dentist the "recipe" to produce beautifully aesthetic anterior restorations; for example, in Class IV situations, neutralizing the darkness of the oral cavity presents a challenge for even the most experienced clinician.
Figure 2 shows the shade guide of corresponding hues and opacities required to recreate "nature's blueprint" in composite resin. Note also that there are 3 cervical shades: cervical (CV), cervical dark (CVD), and cervical translucent (CVT). In this case, these shades will be helpful to recreate the exposed root structure seen on the adjacent natural teeth (Figure 3).
In addition, for ease of use, the manufacturer recently improved the extrusion of this noncomposite material by slightly increasing the size of the unitip (Figure 4) and slightly decreasing the filler content. The combined effect is improved flow. This tiny decrease in filler content also had no effect on other physical properties.
After the patient had been given local anesthesia, horizontal grooves were prepared into the lingual surfaces of the abutment teeth, teeth Nos. 22 and 24 (Figure 5). These grooves were placed just incisal to the cingulum areas of the lingual surface, at a depth of about 1.0 to 1.5 mm. Next, a self-etching adhesive (G-aenial Bond [GC America]) was applied to the prepared surfaces, both the enamel and dentin, and left undisturbed for 10 seconds (Figures 6 and 7). After air-thinning and evaporation of the solvent, the adhesive was light-cured for 20 seconds (Figure 8). A piece of 1.0 mm diameter fiberglass ribbon (Connect [Kerr]) was cut and fit into the slots on the lingual surfaces spanning across the edentulous area. This ribbon should fit perfectly into the slot, not being too long that the fibers are doubled up and completely obliterating the space, or not so short that there is not enough length to the ribbon to provide mechanical rigidity. Once the fit was verified, a flowable composite resin (G-aenial Universal Flo [GC America]) was placed into the slot to "wet" the internal surface of the preparations; the ribbon was placed using a cotton forceps, to full depth, and then the ribbon was completely covered with G-aenial Bond to the cavosurface margins (Figures 9 and 10). Next, the flowable composite was light-cured for 20 seconds (Figure 11).
|Figure 5. A lingual view shows the abutment teeth that were prepared with a slot cut in the lingual surfaces to contain the imbedded fiber reinforcement to provide the "framework" to freehand the nanocomposite resin pontic in the edentulous space.||Figure 6. G-aenial Bond (GC America), a seventh-generation self-etching bonding agent, was dispensed into a disposable |
|Figure 7. The bonding agent was applied to all prepared surfaces using a microbrush.||Figure 8. The bonding agent was then light-cured for 20 seconds.|
|Figure 9. The flowable composite resin (G-aenial Universal Flo) with an applicator tip applied to the end of the syringe; the long, narrow cannula makes precise placement very easy.||Figure 10. G-aenial Universal Flo was syringed into the preparations in a thin coat. The fiber reinforcement was placed into the floor of the preparations, and they were then filled with flowable composite to the cavosurface margins and light-cured.|
|Figure 11. Next, the flowable composite was placed on the stabilized fiberglass fiber (Connect [Kerr]) to wet the surface between the teeth with composite resin. It was then light-cured for 20 seconds.||Figure 12. This facial view shows the composite-reinforced fiberglass reinforcement in place.|
|Figure 13. Kalore AO3 was used to begin building a pontic on the fiber between the abutment teeth.||Figure 14. A plastic instrument (Goldstein Flexithin Mini 4 [Hu-Friedy]) was used for shaping A3.5 as the base dentin for the pontic. Kalore CV (B5) was used to simulate a root form similar to the adjacent teeth.|
Once the fiber was anchored in place, an additional layer of flowable composite was placed to completely cover the exposed fiber and effectively "splint" the abutment teeth together (Figure 12). The next step was to begin to "sculpt a tooth" on the fiber. The first layer of the pontic was sculpted and cured directly to the fiber using Kalore A3 opaque composite (Figure 13). Notice about 2 mm of space was left incisally for addition of an incisal shade later. Also, space was left in the cervical area for simulation of the root surface with cervical shades.
Once completed, the cervical area was sculpted with Kalore CV, while universal shade A3.5 was added to build facial contour to the initial opaque increment giving the "illusion" of depth (Figure 14). A Goldstein FlexithinMini 4 (Hu-Friedy) was then used to sculpt the nanocomposite resin. A fine sable brush (Keystone No. 4 Flat [Patterson Dental]) was used to add texture and refine contour (Figure 15). The incisal edge was added using Kalore Dark Translucent (DT) (Figure 16), blended with the sable brush, and then light-cured for 20 seconds.
Final contour was accomplished using an 8-fluted composite finishing diamond (ET No. 9 [Brasseler USA]), followed by flexible discs (Optidisc [Kerr]). Note the "back side" of the disc has the abrasive on it so it can be flexed across the proximal facial line angles to create "reflective angles" and proper triangular form for the facial surface of this mandibular incisor (Figure 17). The polishing phase is stated using a rubber abrasive polishing disc (Jiffy Polishers [Ultradent Products]) (Figure 18). The edge of the rubber disc was oriented vertically, then moved across the facial surface of the composite in the horizontal direction to create surface texture and create natural luster. The final luster on the surface of the restoration was created using a polishing cup with impregnated bristles (Occlubrush [Kerr]) (Figure 19).
Figures 20 to 23 are finished views of the completed direct composite bridge replacing tooth No. 23. In some cases, the clinician may want to use a gingiva colored composite; if so, one could use Gradia Gum (GC America).
|Figure 15. A sable brush (Keystone No. 4 Flat [Patterson Dental]) was used to create surface texture and refine anatomic form.||Figure 16. Kalore DT was used to create incisal translucency.|
|Figure 17. After initial contouring with an 8-fluted carbide composite finishing bur, contouring was completed using abrasive discs (Optidisc [Kerr]).||Figure 18. A yellow disc (Jiffy Disc [Ultradent Products]) was then used to polish the labial surface, and to refine the reflective angles and surface texture.|
|Figure 19. A polishing cup with impregnated bristles (Occlubrush [Kerr]) was used as the final instrument to create surface |
luster and shine.
|Figure 20. Facial view of the completed fiber-reinforced direct nanocomposite resin bridge.|
|Figure 21. Patient smiling with the completed direct composite bridge. Note the natural appearance of the restoration, as compared to the patient's natural teeth.||Figure 22. One-month postoperative photo of the direct composite bridge. Note the beauty of the natural aesthetics that was created.|
|Figure 23. A close-up view from the facial aspect of the direct composite pontic. The cervical shade created a natural appearing root form that simulated the patient's natural teeth.|
A technique has been demonstrated using a direct universal nanocomposite resin to construct a fiber-reinforced 3-unit fixed bridge. It is important to consider the direct resin restorative option for a single-tooth edentulism when clinical and economical circumstances preclude an implant or fixed partial denture as a treatment choice. The direct composite bridge can be a very aesthetic and functioning dental restoration when used in the appropriate clinical circumstance. It is important to also remember that if this appliance should ever require repair or replacement, it is much easier to do since the substrate is composite rather than porcelain. For the clinical patient presented in this article, as for many like her, the direct composite bridge will satisfy her restorative need for years to come!
Disclosure: Dr. Lowe lectures for Kerr and GC America.
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