Written by Douglas W. Voiers, DDS Wednesday, 01 December 2004 00:00
The integration of technology into the dental practice has provided clinicians with a means to provide their patients with enhanced care in a more efficient and frequently more aesthetic manner than in previous decades.1 In particular, chairside computer-aided design (CAD) and computer-aided machining (CAM) are achieving more widespread use in many areas of dentistry for the fabrication of all-ceramic crowns, veneers, inlays, and onlays that demonstrate improved accuracy of fit and greater strength.1 These restorations can be efficiently created without the need for clinicians to dramatically change the manner in which teeth are prepared. Conventional impressions, temporaries, and second-visit cementations are eliminated.
|Figure 1. The CEREC 3D System can be used chairside for the creation of all-ceramic restorations in an hour.|
More and more, dentists today are realizing the advantages of delivering immediate patient satisfaction by expanding their clinical skills and providing chairside fabricated all-ceramic restorations. In particular, specific technologies such as the CEREC 3D System (Sirona Dental Systems USA, Figure 1) and ProCAD all-ceramic blocks (Ivoclar Vivadent) are enabling dentists to deliver metal-free restorations with the aesthetics and physical properties that today’s patients demand.2 Other materials available for use with CEREC include Vitablocs (Vita Zahnfabrik; Distributor, Vident) and Paradigm (3M ESPE).
Unfortunately, while a growing number of dentists are embracing this technology, many are reluctant to use conventional oven staining-and-glazing techniques once the restorations are milled. In fact, in this author’s experience, most of the CEREC restorations placed today are done without the use of oven-facilitated characterization.
Historically, characterization has been achieved through the use of a 2-stage oven stain-and-glaze system, which has been cumbersome and time consuming. Typically, stain is applied first, followed by 20 minutes of oven firing. Then, glaze is applied, followed by an additional 20 minutes of firing.
|Table. Time Sequence for CEREC 3D/ProCAD Oven Stain-and-Glaze Technique.
Today, however, this author has found the use of a combined one-step stain-and-glaze application and an abbreviated 16-minute firing technique instrumental in providing one-hour (Table), aesthetically characterized restorations suit-able for placement anywhere in the mouth.3 This article presents a case in which a posterior full-coverage crown was milled in-office using the CEREC 3D and ProCAD material and outlines this particular oven stain-and-glaze technique.
|Figure 2. Occlusal preoperative view of the patient’s amalgam restorations.||Figure 3. Buccal preoperative view of the patient’s amalgam restorations.|
A 28-year-old female patient presented with a failing amalgam restoration on tooth No. 29 (Figures 2 and 3). She expressed a desire to replace the restoration with a natural-looking, durable, and metal-free restoration that could be completed and placed in one appointment.
Once the patient had been thoroughly examined, the decision was made to place a ProCAD restoration fabricated using the CEREC 3D system. ProCAD is a leucite-rein-forced glass ceramic block designed to maximize the fab-rication of CAD/CAM rest-orations. ProCAD ceramic blocks demonstrate excellent physical properties, including high flexural strength, wear compatibility similar to enamel, and high fracture resistance.4 In particular, ProCAD exhibits a coefficient of thermal expansion ranging from 17.5 to 18.5 and a flexural strength of between 120 MPa to 150 MPa. Further, ProCAD features a leucite content of between 40% and 45% volume.5 When ProCAD blocks are used in combination with the CEREC system, a one-step stain-and-glaze application, and an abbreviated firing technique, dentists have at their disposal a means to achieve greater predictability, precision, and aesthetic control in the fabrication of chairside all-ceramic restorations.6
|Figure 4. Occlusal view of the completed preparation for the anticipated ProCAD/CEREC 3D crown restoration.||Figure 5. The preparation and surrounding tooth structure was powder coated using the highly reflective titanium dioxide ProCAD contrast powder.|
The patient was anesthetized, and the failing amalgam restoration was removed. In-ternal stress fractures undermined the cuspal integrity, necessitating a full-coverage crown restoration. The tooth was prepared using a conservative, 0.8-mm chamfer margin (Figure 4). A titanium dioxide contrast powder was sprayed onto the surface of the prepared tooth and adjacent teeth (Figure 5). This powder enables the CEREC 3D infrared camera system to capture the tooth structures and soft tissue in 3-D detail.
|Figure 6. Three-dimensional image of the completely designed, full-coverage crown restoration as viewed with the CEREC 3D system.||Figure 7. The ProCAD 200 block was selected for use in this case.|
Three images of the tooth preparation were recorded and then stored into the Image Catalogue of the 3D software program. A full 3-D virtual model was created, and the 3D design process began first by tracing the preparation margins. The full crown was designed in 5 minutes using a variety of easy-to-use 3D tools (Figure 6). A size 12 ProCAD shade 200 ceramic block (Figure 7) was selected and placed into the milling unit. Within 16 minutes, the crown was precisely milled to completion.
Trying-In the Restoration
|Figure 8. The milled ceramic restoration was tried into the patient’s mouth to verify contours and fit.|
The milled ceramic crown was tried into the patient’s mouth to verify proximal contact integrity (Figure 8). The patient was instructed to close down gently, and oc-clusal contacts were checked. Adjustments were made using an occlusal diamond C899-027 and polished using a slow-speed rubber tip P30032 (Axis Prep-N-Glaze Logic Set). When trying in the restoration, it was also important to determine how final cementation would affect the shade and translucency of the restoration. This was best accomplished using Variolink II try-in paste (Ivoclar Vivadent), which is color balanced to the cured Variolink II resin cements.
Quick and Easy Stain and Glaze
After removing the milled—but uncharacterized—restoration from the patient’s mouth, it was examined to determine what effects should be added to impart a natural-looking appearance in comparison to the surrounding dentition. With the ProCAD Stain and Glaze Kits, it was possible to use a one-step stain-and-glaze application and abbreviated firing technique to create customized effects and achieve the highest level of aesthetics possible in this case.
|Figure 9. It was determined that stain should be added to the restoration to create a more lifelike appearance.|
|Figure 10. After the application of the stain, a glaze was placed over the entire restoration.|
|Figure 11. The Programat 200 Furnace was used for firing the stain and glaze together for 16 minutes.|
|Figure 12. Occlusal view of the final, characterized ProCAD crown restoration after firing under vacuum.|
|Figure 13. Buccal view of the final, characterized ProCAD crown restoration after firing under vacuum.|
First, using a fine, sable-hair brush, a slight amount of stain (ProCAD Stains, Ivoclar Vivadent) was applied at the buccal/cervical margin (eg, orange and copper) and into the pits and fissures (eg, brown) on the occlusal aspect of the crown in a conservative manner (Figure 9). Note that excessive amounts of stain are not necessary. Immediately following, the entire crown was coated with a slightly diluted glaze, brushed on with a large, sable-hair brush (ProCAD Glaze, Ivoclar Vivadent, Figure 10). Special care was taken to apply the glaze so as not to displace any of the stains. On the occlusal aspect, the goal is to provide the restoration with depth and dimension. At the cervical, the objective was for the restoration to demonstrate a natural blending that would lend itself to “invisibility” with the adjacent natural dentition.
The restoration was placed onto a firing stand and into the oven (Programat 200, Ivoclar Vivadent), which fired the restoration under vacuum for only 16 minutes (Figure 11). After firing, followed by a 2-minute cool-down period, the restoration required only minor polishing to create the desired restorative results using a Robinson bristle brush with DiaShine Ceramic Polishing Paste (VH Technologies, Figures 12 and 13).
Adhesive Placement Protocol
ProCAD restorations must be placed according to adhesive bonding techniques. Therefore, proper isolation was ensured using cotton rolls and retraction. The preparation was cleansed using 12% chlorhexidine solution, rinsed, and left semimoist. A total-etch technique was used on the enamel for 15 seconds and the dentin for an additional 10 seconds, and the preparation was cleansed appropriately. A single-component bonding agent (Excite, Ivoclar Vivadent) was placed on the preparation, lightly agitated for 10 seconds, air dried, and light cured for 10 seconds using a high-output curing light.
Simutaneously, the dental assistant etched the internal aspect of the ProCAD crown for 60 seconds using the IPS CeramicEtch hydrofluoric etchant (Ivoclar Viva-dent). The internal surface was conditioned with Monobond-S silane coupler (Ivoclar Vivadent) and let evaporate for 60 seconds. Excite bonding agent was applied to the restoration, but not cured.
|Figure 14. Postoperative occlusal view of the ProCAD crown restoration on tooth No. 29.||Figure 15. Postoperative buccal view of the final ProCAD crown restoration on tooth No. 29.|
Varliolink II translucent base and catalyst were mixed thoroughly in a 1:1 ratio and loaded into the restoration. This cement was chosen based on its high bond strength and wide shade selection. The restoration was seated, and excess cement was removed from the tooth surface using a rubber tip. Under firm finger pressure, the restoration was light cured on all surfaces. Any remaining excess cement was removed using a scaler. The aesthetic result was a natural-looking reproduction that blended into the existing dentition (Figures 14 and 15).
Chairside CAD/CAM technology and related all-ceramic materials are enabling clinicians to provide patients with aesthetic restorative dentistry in a more efficient manner.7 In this case—from start to finish—the time required to prepare the patient for the restoration and then create it, characterize it, and seat it was no more than an hour. Using the combined application of the stain and glaze and firing both for an abbreviated time of only 16 minutes greatly facilitated keeping the one-hour restoration schedule. Although this case addressed a posterior restoration, this oven stain-and-glaze technique is also suitable for anterior CEREC 3D/ProCAD restorations.
1. Samaras CD. CAD/CAM systems: a must for dentistry. Contemp Esthet Restor Pract. 2004;8:46-48.
2. Schneider O. Cerec veneers—practical procedure and case presentation. Int J Comput Dent. 2003;6:283-292.
3. Winterholler C. Advanced techniques for full-mouth reconstruction. Compend Contin Educ Dent. 2004;25:144-150.
4. Chen HY, Hickel R, Setcos JC, et al. Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed-ceramic crowns. J Prosthet Dent. 1999;82:468-475.
5. Data on file. Ivoclar Vivadent Inc. Amherst, New York.
6. Gaglio MA. Esthetic restorations designed with confidence and predictability. Compend Contin Educ Dent. 2001;22(6 suppl):30-34.
7. Posselt A, Kerschlbaum T. Longevity of 2328 chairside Cerec inlays and onlays. Int J Comput Dent. 2003;6:231-248.
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