November 2008 | Dental Products Report
Techniques: NX3 Nexus Third Generation
Simplified cementation protocol
Using NX3 Nexus Third Generation resin cement and CAD/CAM for optimal predictability and customization.
By Dr. Christopher Pescatore, Danville, Calif.
| |  | • Compatible with total-etch and self-etch adhesives • Formulated for exceptional color stability and translucency • Optimal adhesion to dentin, enamel, CAD/CAM blocks, ceramic, porcelain and metal • Offered in self-cure and dual-cure modes • A light-cure based cement is available for restorations requiring unlimited working time • Cements and matching try-in gels are offered in five shades |
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Product improvements and the techniques that employ them are allowing dental professionals to provide more efficient care while satisfying the esthetic concerns of their patients. This article focuses on using a new-generation resin cement with a chairside in-office CAD/CAM restorative system, providing the ultimate in predictability and customization in a single dental visit.
One of our industry’s main growth areas is esthetic indirect restoratives, heightening the visibility of permanent resin cements with their good bond strength and improved esthetics.1 A traditional adhesive protocol requires an etching gel for the enamel and dentin, primer and adhesive components in multiple bottles or unit-dose carriers followed by an application of cement.2 Using this total-etch protocol, inlays, onlays and full-coverage all-ceramic restorations can be placed with confidence to meet the high esthetic demands of today’s dental patient.
Preparation appointment
A middle-aged woman presented with recurrent cervical decay that compromised the margins on an old porcelain-fused-to-metal (PFM) restoration on her upper-left first molar (Fig. 1). It was decided that this new restoration would be fabricated in-office with the chairside CAD/CAM restorative system, CEREC 3D® (Sirona Dental Systems). The existing restoration was removed and the presence of decay was verified with a caries detector and spoon excavator. All decay was removed from the tooth and buildups were placed to eliminate undercuts or to gain proper retention form in the resulting preparations.
Prior to the optical scanning of preparations for restoration design, the soft tissue was retracted in the subgingival areas with a putty-type retraction system, Kerr Corp.’s Expasyl (Fig. 2). A putty retraction system was chosen over a traditional retraction cord or other hemostatic agent because of the latter’s potential for tissue (epithelial attachment) damage and recession.3-5 After 2 minutes, the putty retraction material was thoroughly rinsed away with air/water spray and dried (Fig. 3). The preparation was powdered with talc-like powder (functions as a contrast medium for taking the optical impressions), and several images of the preparation were taken (Fig. 4).
Restoration fabrication
The in-office CEREC 3D® CAD/CAM restorative system, version 3.01, was chosen for this restoration because of its high success rate6 and for the esthetic properties, inherent strength and fracture resistance of the porcelain blocks used after oven glazing.7
After capturing images of the preparation, the restoration was fabricated using the CEREC 3D “database” mode. This mode allows the dentist to select the correctly shaped tooth while the computer software positions it in the arch. After the restoration was milled, it was tried in to verify fit (Fig. 5) and then stained and glazed in a porcelain oven to obtain the desired surface glaze (Fig. 6).
Preparing the internal aspect of the restoration involved…
Microabrade with a microetcher containing 50-micron aluminum oxide powder, being careful not to damage the margins, and then rinse with water and dry for approximately 5 seconds.
Apply a 9.5% hydrofluoric acid gel for 1 minute, rinse with water for approximately 20 seconds and dry thoroughly.
Apply a silanating agent and air-dry.
Because we used the total-etch adhesive technique, an unfilled resin was applied to the internal aspect of the restoration and was gently air-dried and placed in a light-protected container until insertion.
Restoration placement
After proper isolation of the area with rubber dam, the preparation was cleaned with 2% chlorhexidine, rinsed and dried, but not to the point of dessication8 (Fig. 7). The tooth was etched with 37% phosphoric acid (Fig. 8) and rinsed thoroughly. After lightly removing any excess water, the moist tooth surface was covered with OptiBond Solo Plus adhesive (Kerr Corp.) and spread over the preparation for 20 seconds (Fig. 9). A moisture-free air dryer was used to evaporate the solvent in the adhesive.
The restorations were filled with dual-cure resin cement NX3 Nexus® Third Generation (Kerr Corp.), and seated (Fig. 10). The excess resin cement was removed with microbrushes and tacked down midcervically on the buccal with a 4-mm turbo tip in a L.E.Demetron II curing light (Kerr Corp.) (Fig. 11). Flossing was done interproximally to remove as much residual uncured resin cement as possible before final curing (Fig. 12). Final curing was simultaneously performed buccally and lingually with two LED lights for 40 seconds (Fig. 13), followed by curing occlusally for 20 seconds (Fig. 14). Marginal finishing was performed with an 8-fluted carbide bur and composite points and cups. Interproximal finishing involved using medium and then fine composite finishing strips. The final result, immediately after insertion, is shown in Fig. 15.
Discussion & conclusion
Because of the high esthetic demands of our patients, dentists are performing more and more tooth-colored procedures than ever before—especially bonded porcelain restorations. For this reason, educating ourselves about the latest improvements will enhance our ability to give our patients the most advanced forms of treatment. Using the newer light-cure and dual-cure resin cements, we have the ability to place highly esthetic porcelain (or resin) restorations with predictable results, including increased longevity, reduced sensitivity and other technique-related issues.
References available upon request. E-mail tcarter@advanstar.com.
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Fig. 1 A middle-aged woman presents with recurrent cervical decay that compromised on an old PFM restoration on her upper-left first molar. | Fig. 2 The soft tissue was retracted in the subgingival areas with a putty-type retraction system. | Fig. 3 After 2 minutes, the putty retraction material was thoroughly rinsed away with air/water spray and dried. |
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Fig. 4 The preparation was powdered with talc-like powder and several images of the preparation were taken. | Fig. 5 After the restoration was milled, it was tried in to verify fit. | Fig. 6 The restoration was stained and glazed in a porcelain oven to obtain the desired surface glaze. |
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Fig. 7 After proper isolation with rubber dam, the preparation was cleaned with 2% chlorhexidine, rinsed and dried, but not to the point of dessication. | Fig. 8 The tooth was etched with 37% phosphoric acid and rinsed thoroughly. | Fig. 9 The moist tooth surface was covered with adhesive and spread over the preparation for 20 seconds. |
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Fig. 10 The restorations were filled with dual-cure resin cement and seated. | Fig. 11 The restoration was tacked down mid-cervically on the buccal with a 4-mm turbo tip in a curing light. | Fig. 12 Flossing was done interproximally to remove as much residual uncured resin cement as possible before final curing. |
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Fig. 13 Final curing was simultaneously performed buccally and lingually with two LED lights for 40 seconds... | Fig. 14 ...followed by curing occlusally for 20 seconds. | Fig. 15 The final result, immediately after insertion. |
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