Re: Considerations When Restoring a Nonvital Tooth

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Next, a size 3 anatomically-formed retraction cap was carefully placed over the preparation with the scalloping on the working or preparation end, facing mesial distal (Figure 12). Proper selection and placement of the retraction cap is important to ensure that the hemostatic paste is gently guided into the sulcus and stays in place during the waiting period. The patient was asked to gently bite down on the cap for 4 minutes. Combined with proper placement of the hemostatic retraction paste into the sulcus, the retraction cap provides essential hydrostatic pressure on the tissue to help accomplish the necessary hemostasis and retraction for accurate impressions.

After 4 minutes, the retraction cap was removed. Figure 13 shows the excellent hemostasis and retention of the Traxodent that was achieved in and around the tooth. Next, the hemostatic retraction paste was thoroughly rinsed using an air-water syringe and a suction tip, leaving an open, retracted sulcus (Figure 14).

Before making the impression, the preparation margins were evaluated to ensure there was access for the impression material to all the margin areas. In this case, a posterior T-LOC Triple Tray (Premier Dental Products) was selected for making the impression. This type of tray is wide enough to ensure that it does not impinge on the alveolar process. Its thin, flexible mesh allows adequate closing into occlusion without distortion, and it has retentive features built into the tray rim to stabilize and retain the impression material.

A heavy-body impression material (Imprint 3 Penta Heavy Body [3M ESPE]) was chosen because it offers adequate working time in addition to a short setting time, which minimizes the time the material needs to be in the mouth, adding to patient comfort. The light-body material (Imprint 3 Quick Step Light Body Impression Material [3M ESPE]) was extruded around the prepared tooth and margin areas, while the heavy-body material was loaded into the tray. The heavy body material was "overloaded" on both sides of the tray. The tray was then placed in the mouth, and the patient was instructed to close into her maximum interocclusal position for 2.5 minutes.

Upon removal, the impression was evaluated to verify all of the margins could be identified (Figure 15). With the use of the dual-arch tray, the preparation, the opposing arch, and the bite registration were captured simultaneously, saving time and improving patient comfort. At this point, if the restoration is slated to be fabricated by a dental laboratory, the impression is disinfected and sent to the lab.

A temporary crown was fabricated using a bis-acryl, light-cured, temporary composite material placed inside a putty impression matrix of the unprepared tooth. After trimming the margins, adjusting the occlusion, and polishing, the temporary was seated and cemented with a noneugenol temporary cement.

Because in this case the treatment plan included the in-office fabrication of the permanent restoration and the patient had opted for 2 shorter appointments, the impression was taken in order to create a physical model to use for creating the restoration between visits.

In-Office CAD/CAM System to Fabricate the Final Restoration
In my practice, I like to take advantage of new technology to enhance patient outcomes, comfort, and convenience. Using chairside CAD/CAM allows us to utilize new adhesive and ceramic technologies and provide high-strength aesthetic restorations in a single visit, while preserving natural tooth structure. It also enables the use of preparations that are more defect-oriented than material-oriented. I have used chairside CAD/CAM since 1998 in various forms, and the E4D (D4D Technologies) clinically as a beta tester since 2007.

The E4D system is designed for same-day delivery of restorations as well as for cases where there may be a need to separate the procedure into 2 visits. The E4D system can be used to scan, design, and mill all-ceramic restorations. Virtual models are used to create the appropriate crowns, veneers, inlays, onlays, and laboratory fabricated ceramic bridges, while incorporating the opposing dentition, a wax-up, or scans of a provisional or preoperative condition. With E4D, clinicians can scan both hard and soft tissue, pre- or post-preparation, and record bite registrations. The E4D is the only digital CAD/CAM system with the ability to scan in the mouth, directly on the impression, or on a model without using contrast agents or opaquing mediums. As of the writing of this article, the E4D (launched in 2008) cannot be used to fabricate bridge restorations, but soon, digital scanning (impression making) and sending a virtual restoration to the laboratory will be possible.

The final restoration for this case was fabricated using a lithium disilicate block (IPS e.max CAD; HT block, shade A2 [Ivoclar Vivadent]) (Figure 16). The preparation side of the dual-arch impression was directly scanned. Then the dual-arch impression was poured up and articulated according to the bite recorded in the triple tray. After the stone had set up, a bite registration was recorded from the model and scanned into the E4D system. The restoration was designed utilizing the bite information from the neighboring teeth and the occlusion, ensuring a highly accurate restoration.

After milling, the ceramic CAD glass block, or "blue block," was tried on the model and adjustments were made. IPS e.max stains and glaze were applied, and then the restoration was subsequently crystallized to its final hardness. The chameleon effect and higher strength of the lithium disilicate material provides excellent aesthetics while providing adequate strength and resistance to functional forces.

Final Restoration Delivery
When the patient returned for final delivery of the restoration, the temporary was removed and the preparation was pumiced to remove any temporary cement residue for optimal bonding. After try-in of the milled restoration to check for shade, fit, contacts, and proper occlusion, any necessary adjustments were made with fine diamonds at medium speed before it was polished. A rubber dam (Ivory brand 6×6 latex rubber dam [Heraeus Kulzer]) was applied to ensure an absolutely dry field. If there is any seepage in the marginal tissue, Traxodent can be applied for 2 minutes.

Before final seating, the restoration was etched with 5% hydrofluoric acid (IPS Ceramic etching gel [Ivoclar Vivadent]) for 20 seconds, then rinsed and dried thoroughly. Next, a universal primer (MonoBond-S [Ivoclar Vivadent]) (conventional silane can also be used on lithium disilicate) was applied to the internal surfaces of the crown to promote adhesion of the composite resin cement to the restoration. After being left to react for 60 seconds, the universal primer was air-dried.

The restoration was seated using a transparent shade of a universal self-etching luting composite (MultiLink [Ivoclar Vivadent]). This dual-cure material is designed to be used with a wide variety of indirect restoration materials, sets quickly, and has demonstrated high-strength bond strength values and long-term stability. After mixing the enamel-dentin A/B primer in a 1:1 ratio in a mixing well, it was applied to the tooth surface with a microbrush and scrubbed vigorously for 15 seconds. The tooth surface was then gently air-dried. Using the Multilink automix syringe with tip in place, the material was expressed directly into the crown. After ensuring the crown was fully seated, the material was light-cured for only 2 seconds at each line angle to achieve a gel state. Excess cement was immediately removed with an explorer. Contacts were flossed to remove excess cement interproximally. Polymerization of the cement was then completed by curing the tooth for 20 seconds each from the buccal, lingual, and occlusal.
After using finishing and polishing strips in the proximal regions to ensure that all the cement was removed, and after final confirmation of proper occlusion, the patient was dismissed with postoperative instructions. The patient was pleased with the final result and the excellent aesthetics achieved (Figures 17 and 18).

CLOSING COMMENTS
Two of the most critical factors impacting the quality of an impression and the resulting restoration are accomplishing the hemostasis and retraction necessary to accurately record the preparation margins. With the excellent new materials available to the practitioner, excellent hemostasis and tissue retraction can be accomplished in a few minutes, while minimizing patient discomfort. Clinical excellence and predictability, ensured by using reliable products and techniques, will ensure success of your final outcome.