Restoring the Aesthetic Zone Using All-Ceramic Single-Unit Restorations

With the increase in patient demand for aesthetic restorations, the all-ceramic restorations are becoming the gold standard for restoring the aesthetic zone. The usual metal-ceramic restorations provide acceptable appearance but they may cause a change of shade on the free gingival margin caused by the translucency of the gingival tissue.¹ The metal substructure causes a lack of translucency in the overall restoration due to the opacity of the material, thus resulting in a less than ideal appearance of the restoration.^2,3
A great variety of all-ceramic systems have been introduced. These include Procera (Nobel Biocare), In-Ceram (Vident), and IPS Empress 2 (Ivoclar Vivadent), among others. Material strength and biocompatibility are some of the properties of these all-ceramic restorations, as well as natural, live-looking restorations without the usual aesthetic problems caused by the metal-ceramic restorations.^4-9 The use of these all-ceramic systems requires, in many cases, tooth preparations that are different than the conventional metal-ceramic restoration preparations. Dental students should be exposed to these all-ceramic systems due to the increasing patient demand for these restorations.
This article describes the rationale and treatment in the dental school environment of a patient seeking to enhance her appearance with the use of all-ceramic restorations. The challenge of matching the all-ceramic restorations to a pre-existing metal-ceramic restoration will be part of the focus of this article.

Case Report

Figure 1. Preoperative restorations.	Figure 2. Close-up of metal-ceramic restoration.

A 48-year-old white female reported to the University of Michigan School of Dentistry with a chief complaint of aesthetic displeasure, especially with her maxillary front teeth, specifically the maxillary right lateral and central incisors, left cuspid, and the left lateral and central incisors (Figure 1). In addition, due to the extensive restorative work on these teeth, she expressed displeasure due to the roughness of the restorations. The patient expressed not wanting to replace the crown on the upper right cuspid (Figure 2). After further evaluation it was determined that the above mentioned teeth presented with carious lesions.
The patient was presented with 2 treatment options: (1) whitening of the maxillary teeth to match the shade of the maxillary right cuspid, followed by removal of all the acrylic resin restorations and carious lesions followed by new restorations with the appropriate shade; or (2) all-ceramic single-unit restorations on the maxillary right lateral incisor, right central incisor, left cuspid, left lateral incisor, and left central incisor.
The patient decided upon option 2. It was explained to the patient the difficulty in accurately matching the shade to the existing metal-ceramic restoration of the maxillary right cuspid. The patient acknowledged the possibility of the mismatch but was reluctant to change the existing restoration.
A complete medical examination was performed, as well as the review of the medical history, and there were no medical findings, which would contraindicate dental care.
Before preparing the teeth for full coverage restorations, shade selection was accomplished utilizing a Vita shade guide on the existing metal-ceramic restoration. Past experiences have taught us that metal-ceramic restorations generally have a lower value than natural teeth and all-ceramic restorations. The all-ceramic restoration permits a greater light transmission, improving color and translucency. Taking these characteristics into consideration, it was requested that the dental laboratory use intrinsic and extrinsic colorants to match the shade of the metal-ceramic restoration.
The maxillary right lateral, left cuspid, and the left lateral and the central incisors were prepared for full coverage all-ceramic fixed restorations with a moderate chamfer margin. Retraction cord “00” (Ultradent Products) impregnated with hemostatic solution (Hemodent, Premier Dental Products) was used for gingival retraction. The cord was removed and the margins were placed in a subgingival position. At this stage all the carious lesions were removed and another retraction cord “00” was placed in preparation for the final impression. The retraction cords were removed and a final complete arch impression was made with vinyl polysiloxane (Extrude low consistency and high consistency, Kerr). A lower impression with irreversible hydrocolloid (Jeltrate, DENTSPLY) was taken. The maxillary cast was then poured using a type V gypsum material (Die-Keen, Heraeus Kulzer), and the mandibular cast was poured with type IV gypsum (Microstone Stone, Whip Mix). A bite registration in centric occlusion was taken using vinyl polysiloxane (Blu-Bite HP, Henry Schein). A face bow registration was taken, attaching the bite fork of the face-bow (Denar) to the maxillary teeth, and the face-bow transfer of the maxillary cast to the upper bow of the articulator was made (Hanau Waterpik Technologies). The assembly of the face bow was placed on the articulator and the maxillary cast was mounted using plaster (Whip Mix), followed by mounting the mandibular cast with the assistance of the bite registration.

Figure 3. Final all-ceramic restorations.	Figure 4. Close-up of metal-ceramic restoration (PFM) compared to the all-ceramic restorations (note the lack of translucency of the PFM and the appearance of the soft tissue).

The tooth preparations were then digitized using the touch probe scanner (Piccolo, Procera; Nobel Biocare), and copings were fabricated in zirconia (Procera, Nobel Biocare). Zirconia was the material of choice because of its good flexural strength¹⁰ and fracture toughness.¹¹ The veneering porcelain (NobelRondo, Nobel Biocare) was applied to complete the aesthetic portion of the crowns.
The 5 Procera all-ceramic crowns were evaluated for marginal integrity, occlusal relationships, and aesthetic outcome. All margins were subgingival, and the marginal integrity was verified by tactile assessment as well as by radiographic means. The teeth were cleaned with pumice (Whip Mix) and treated with chlorhexidine (3M ESPE/OMNI Preventative Care), and the internal surfaces of the crowns were cleaned by means of alcohol. A thin coat of resin-modified glass ionomer cement (FujiCem, GC America) was added into the internal surface of the all-ceramic crowns, and were placed with finger pressure (Figure 3).
Shade matching of the all-ceramic restorations to the existing metal-ceramic restoration (which remained on the maxillary right cuspid) can be very challenging. Even though the shade of the all-ceramic restorations closely resembled the shade of the metal-ceramic restoration, the appearance of the tissue and the overall translucency associated with the all-ceramic restorations improved dramatically due to the absence of the metal substructure (Figure 4).
The patient was recalled at one week and at one month; no occlusal adjustments were needed after the cementation appointment.

References

Mr. Lipton is a student at the University of Michigan School of Dentistry. He can be reached at (248) 875-1464 or via email at dlipton@umich.edu.

Dr. Abbo is a Clinical Lecturer, Biologic and Materials Science, Division of Prosthodontics, at the University of Michigan School of Dentistry. He can be reached at (734) 763-3326 or via email at abbovan@umich.edu.