Inside Dental Technology
Matching Crown Restorations in the Esthetic Zone
Material choice and communication protocol proves critical for optimal case outcome.
By Steve Hoofard, CDT, AAACD; and Edward Lowe, BSc, DMD, AAACD
With the abundance of restorative materials available today, selecting the ideal combination for a given case can sometimes be challenging.1 Clinicians and technicians must collaborate and consider all clinical and esthetic variables to meet the patient’s goals for an enhanced smile.2 Of these variables, the most difficult to manage tends to be the individual shading and coloring of the patient’s natural teeth. This is most important in the esthetic restorative process because the anterior esthetic zone is the area that patients most often want to have restored.3
Therefore, it is necessary to match restorations as closely as possible to the shading and color of adjacent natural dentition.4,5 Fortunately, given the extensive range of opacities available in the ingots, as well as the material’s strength and predictability, lithium disilicate (IPS e.max Press, Ivoclar Vivadent, www.ivoclarvivadent.com) is a proven and viable restorative option when matching restorations for placement in the esthetic zone.
Lithium disilicate provides dental professionals with a predictable and productive way to prescribe metal-free, all-ceramic restorations for highly esthetic cases. The IPS e.max product line represents a universal system that includes pressable fabrication techniques to satisfy an assortment of case demands, regardless of patient expectations and requirements for esthetics, function, or strength. Whether the restorations are placed in the anterior or posterior segment, the line delivers solutions for conventional cementation or adhesive bonding that demonstrate the esthetics and physical properties necessary for successful dental treatment.
Pressable lithium disilicate, one of the material options included in the system, demonstrates the fit, form, and function expected from pressable ceramics with enhanced strength and optimized optical properties. It is indicated for inlays, onlays, thin veneers, veneers, partial crowns, anterior and posterior crowns, three-unit anterior bridges, three-unit premolar bridges, telescope primary crowns, and implant superstructures.4,6-7
The following case demonstrates how this material was used to fabricate esthetically characterized anterior crown restorations. Of significance is the manner in which the lithium disilicate and corresponding veneering ceramic were used to create restorations that blended seamlessly with the surrounding natural dentition.
A 21-year-old man presented with concerns about his maxillary central incisors. They had chipped in a fall when he was 8 years old (Figure 1). His medical history showed no significant findings, and there were no significant intraoral soft tissue findings at the time of presentation. The patient displayed good oral hygiene practices—light supragingival calculus and stain were the only issues present. The periodontal tissues presented normal color with a slight puffiness.
The patient’s upper lip was thinner than the lower lip, his tonsils had not been removed, and the mandibular tori were present. There also was a prominent labial frenum present.
The occlusion was Class I skeletal and dental, respectively. As a result, the patient presented a maximum opening of 55 mm, with an overbite of 2 mm and an overjet of 1 mm. He also had canine rise occlusion, with contacts on teeth Nos. 6 and 27 on right lateral movement and teeth Nos. 11 and 22 on left lateral movement. The protrusive contacts were on teeth Nos. 8 and 9 and teeth Nos. 23 through 26. Palpation of the temporalis, masseter, and sternocleidomastoid muscles did not reveal any extraordinary findings. The temporomandibular joint findings were also normal with no deviations, clicking, or popping.
Upon radiographic inspection, all teeth were present with preventive composite resins in all molars. Tooth No. 8 had a Class IV mesialincisal-vestibular-lingual (MIVL) four-surface composite, and tooth No. 9 had a double Class IV mesial-incisal-distal-vestibular-lingual (MIDVL) five-surface composite (Figure 2). At the time of presentation, the width and length of tooth No. 8 was 7.8 mm and 9.6 mm, respectively. The width and length of tooth No. 9 was 8.0 mm and 8.5 mm, respectively.
The midlines were correct, and the smile was not canted. However, there was a lower lingual wire retainer on teeth Nos. 22 through 27 from previous orthodontic treatment. The teeth were mesially inclined, and the upper incisal edges followed the lower lip. The contact points and gradation of the teeth were also proper, with an ovoid arch form.
However, the gingival tissue heights over teeth Nos. 7 through 10 were low and needed to be raised. Gingival asymmetry needed to be corrected in order to better define the gingival zeniths over the lateral incisors. The facial pocket depths of teeth Nos. 7 through 10 also were measured and found to be 3.5 mm.
Treatment planning began with a composite mockup of teeth Nos. 8 and 9, after which it was determined that lithium disilicate crowns in ingot shade MO1 would be fabricated and veneered with an esthetic ceramic (IPS e.max Ceram). Soft tissue recontouring of teeth Nos. 7, 9, and 10 would be performed using a soft tissue diode laser (Odyssey Navigator, Ivoclar Vivadent) to balance the gingival levels. A frenectomy of the labial frenum between teeth Nos. 8 and 9 also was suggested.
The patient was anesthetized and the old composite restorations were removed from teeth Nos. 8 and 9. The tooth was then mocked up to full contour, and a diode laser was used to contour the tissue and complete the frenectomy. A clear polyvinyl siloxane (PVS) impression was taken of the mockup using an anterior triple tray.
The teeth were prepared for crown restorations using a coarse NTI® KS2, KS1, and a fine NTI 856-020 diamond bur system (Axis Dental, www.axisdental.com). The preparations were then polished with discs (Sof-Lex™, 3M ESPE, www.3mespe.com), and an impression was taken using full-arch trays and extra light and medium body PVS impression materials (Precision, Discus Dental, www.discusdental.com).
Acrylic provisional crowns (Luxatemp®, DMG America, www.dmg-america.com) were created from the preoperative PVS impression. Once the temporaries were fitted, they were provisionally cemented (Systemp®.link, Ivoclar Vivadent). The margins were trimmed with carbide finishing burs, and the temporaries were polished with bristle brushes (Jiffy Composite Polishing Brushes, SureDental, www.suredental.com). A light-curable, protective clear coating (G-COAT PLUS, GC America, www.gcamerica.com) was painted on the provisional restorations and cured (Figure 3).
Digital photographs were taken of the patient with the provisionals in place.8 The preparation shade was noted, along with the final shade (Figure 4). A stick bite was taken and sent to the laboratory, along with the facial analyzer record (Kois Dento-Facial Analyzer System, Panadent, www.panadent.com). In addition, a detailed laboratory prescription was completed and sent to the laboratory along with the case and patient’s records.
After the laboratory received the case, all information and records were reviewed and verified, and it was decided that stone split cast master/working models would be used (Figure 5). These were fabricated and cross-mounted along with the solid and approved provisional models using a transfer jig on an articulator.
The restorations were then waxed to full contour on the solid model (Figure 6). Once the ideal contours were established, an incisal matrix (Sil-Tech Putty, Ivoclar Vivadent) was fabricated. The patterns were transferred to the master model with removable dies and then cut back to allow room for internal effects and enamel layering, using the incisal matrix as a guide. The margins were sealed and verified.
The individual wax patterns were then sprued and invested (IPS Empress Esthetic Speed Investment, Ivoclar Vivadent). The ring was placed immediately into a pressure vessel at 20 psi and bench-sat for 30 minutes. Next, the ring was burned out for 45 minutes in a magma furnace at 1560° F.
After burnout was complete, the ring was placed in a pressing furnace (Programat EP 5000, Ivoclar Vivadent). An MO1 ingot and plunger were loaded, and the pressing cycle was completed. After proper cooling, the restorations were de-vested using a sandblaster (Basic Quattro, Renfert, www.renfertusa.com) loaded with 25-µm aluminum oxide at 4.5 bar (Figure 7).
The sprues were then removed, and the restorations were fit to the master dies. Once the fit was verified, the incisal matrix was placed on the model to verify the proper reduction needed for layering. The cutbacks were completed (Figure 8), and the restorations were removed from the dies. The restorations were then lightly sandblasted and steamed clean.
The frameworks were placed back on the master dies, and a thin layer of propylene glycol was applied to the entire surface of the restorations. Staining (Universal Stains, Ivoclar Vivadent) was completed in order to add internal character modifications. A slight amount of “blue” was brushed on the mesial and distal/incisal corners. The frameworks were then “dusted” with ceramic bleach enamel (IPS e.max Ceram Bleach, Ivoclar Vivadent). The restorations were fired to 750°C in a furnace (Programat® P500, Ivoclar Vivadent) with a 1-minute hold.
Once cooled, the restorations were placed back on the master model, and the matrix was fit onto the model over the cutback restorations to serve as a layering guide. Using a #6 brush (SmileLine USA, www.smileline-usa.com), a 50/50 mix of 040 enamel and neutral was applied to extend the mamelon structure.
Straight Essence EO2 shade was then built into the void areas of the matrix. The matrix was removed after the void areas were filled, and the incisal and incisal/facial surfaces were laterally segmentally layered in a symmetrical pattern, using neutral EO2, bleach, neutral/bleach, and OE1 to produce the desired effects.
When completed, the restorations were removed from the dies and internally filled with putty (Custom-Peg Putty™, Hankins Laboratories, www.hankinslaboratories.com). The restorations were then fired to 750°C with a 1-minute hold. A second layering was also applied using mainly neutral bleach, neutral OE2, and OE3 for an incisal halo. The restorations were then fired again to 750°C with another 1-minute hold.
The built-up and fired restorations were fitted to the master dies once again to ensure that the contacts, occlusion, and function were spotted in and achieved using articulating tape (AccuFilm®, Parkell Inc, www.parkell.com). All contours were then shaped using a variety of diamond burs (Brasseler USA, www.brasselerusa.com).9
The surface anatomy and morphology were added to make the restorations blend with the surrounding teeth (Figure 9).10 Silver surface paste (Goldfinger, Daler-Rowney, www.daler-rowney.com) was then applied in order to verify that the surface texture and contours also blended well with the adjacent dentition. The restorations were then cleaned, and the fit was verified on the solid model. They were lightly sandblasted and then steamed.
The 01/110 and 040 shade tabs in the Chromascope system (Ivoclar Vivadent) were used to verify that the desired shade matched, as depicted in the photographs that were included in the laboratory prescription. Small amounts of stain were applied where needed, and then the restorations were fired at 725°C with a 1-minute hold.
Next, a glaze firing was conducted using a fluorescent glaze (IPS e.max Fluorescence Glaze, Ivoclar Vivadent) in order to seal and protect the stain layer (Figure 10). The restorations were then fired again at 725°C with a 1-minute hold.
After cooling, the restorations were fitted back on the solid model, contacts were checked, and full embrasures were confirmed. Pumice was used to finish the surface to the desired satin luster and reflectivity (Figure 11). The internal surfaces were lightly sandblasted, and ceramic etching gel (Ivoclar Vivadent) was applied for 15 seconds. The gel was then rinsed, and the crowns were steamed and dried. After thoroughly checking to ensure all desired criteria had been satisfied, the case was carefully packaged and shipped back to the dental office for seating.
When the crowns were returned from the laboratory, they were inspected for fit and color on the models that had been previously constructed (Figure 12). Once the provisionals were removed and the preparations were cleaned with hydrogen peroxide, the crowns were placed and tried for the first time using a try-in paste (Variolink® Veneer, Ivoclar Vivadent). After the fit was verified and the contacts were checked, it was determined that the crowns would be cemented with the +2 shade on tooth No. 8 and the -2 shade on tooth No. 9 (Figure 13 and Figure 14). The restorations were then removed from the mouth and their internal aspects treated with 35% phosphoric acid for 1 minute.
After rinsing and drying, the inside of the crowns were coated with silane (Monobond-S, Ivoclar Vivadent) for 1 minute, followed by air-drying. The preparations were then cleansed with a 0.12% solution of chlorhexidine and rinsed. A 35% phosphoric acid gel was applied to the preparations for 15 seconds (Figure 15), after which the preparations were rinsed. A bonding agent (ExciTE®, Ivoclar Vivadent) was applied to the teeth for 20 seconds, and the solvent was allowed to evaporate for 10 seconds. The preparations were then cured with an LED curing light (bluephase®, Ivoclar Vivadent) for 10 seconds.
The selected resin cement was spread on the inside of the crowns, and the restorations were seated onto the teeth (Figure 16). After spot tacking the crowns in place with a 2-mm tacking tip, the contacts were flossed. By using a gum stimulator (Sunstar Americas Inc, www.jbutler.com) and micro brushes, almost all of the excess cement was removed. Glycerin was then placed around the margins to ensure curing of the oxygen inhibition layer (Figure 17).
Final curing of the crowns was completed for 10 seconds on each of the buccal, occlusal, and lingual surfaces (Figure 18). A fine 8-bladed finishing carbide (NTI® TDF-9, Axis Dental, www.axisdental.com) was used to remove excess cement around the margins. Once this was complete, the occlusion was checked with a mylar articulating tape (Madame Butterfly Silk Ribbon, Almore International Inc, www.almore.com) and the adjustments were polished with a yellow porcelain polisher (NTI® CeraGlaze, Axis Dental).
Upon completion of the treatment plan, the patient was very happy with the functional and esthetic results. Through collaboration, the clinician and technician were able to overcome all variables and challenges presented in order to meet the patient’s goals (Figure 19 and Figure 20). By using an esthetic material such as lithium disilicate, problems matching the shading and coloring of the natural dentition can be predictably resolved.
Gingival asymmetry needed to be corrected in order to better define the gingival zeniths over the lateral incisors.
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