Oral Health Group
Feature

PRODUCT PROFILE: It’s Not Your Father’s PFM

November 1, 2000
by Robert G. Ritter, DMD


When tooth-coloured restorative materials were first introduced to the field of dentistry, it was apparent that a revolution was in the making. The word “cosmetic” was uttered in the same sentence with “filling,” and everyone took notice, from dentists and manufacturers to staff members and patients. But just how far could it go? Generation after generation of materials have come and gone, and new versions are perpetually in development as manufacturers, clinicians, and laboratory technicians alike strive to duplicate nature in both appearance and function.

Many argue that porcelain materials provide the best-possible aesthetics while alloys offer the required strength and durability to hold up under the stresses inherent in the oral cavity. The ultimate goal, of course, is a successful marriage between both characteristics-that is, aesthetics and function. Everyone would agree that there is no value in a beautiful restoration that fails when exposed to normal stress.

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Porcelain-fused-to-metal (PFM) restorations have been widely accepted as an option that closely merges desired aesthetics with functional requirements. While conventional PFM systems do generally meet the functional needs of modern restorative dentistry, overall they lack the fluorescence, reflection, and translucency inherent to natural dentition. In fact, these restorations generally exhibit murkiness and opacity where they should scatter light from within to accurately mimic natural teeth. While the addition of metal oxides to conventional feldspathic porcelains creates brightness and diffuses reflective light, it does so at the expense of translucency and vitality.

A relatively new metal ceramic system (IPS d.SIGN, Ivoclar North America) addresses these issues in a unique way. It is a Fluorapatite-Leucite glass ceramic–i.e., it is made up of a combination of Fluorapatite and Leucite crystals-that replicates the crystalline structure found in natural teeth, imitating inherent optical properties by dispersing light throughout the material in a manner typical of natural dentition. The material offers a high degree of bright, luminous reflection as well as exceptional translucency; both are achieved without the addition of conventional opaquing agents. In other words, the crystals scatter light within the material in such a way that a significant amount of translucency can be achieved without losing value or brilliance.

As is the case for other metal-ceramic systems, indications for IPS d.SIGN include metal framework veneering for single- and multiple-unit restorations, as well as metal-free veneer applications utilizing refractory die or platinum foil techniques. The system provides consistent shade matching and ideal aesthetic control and it adjusts and grinds easily to provide optimal density, polishability, and surface smoothness for long-term function and stability. The glass ceramic also provides shade stability, lifelike fluorescence, and wear characteristics similar to those of enamel, and it is exceptionally kind to opposing dentition.

The case presented here involves two PFM bridges and four PFM crowns, all created with the IPS d.SIGN system. In addition to highlighting the restorative system, the case demonstrates the importance of treatment planning and laboratory communication.

CASE STUDY

A woman in her mid- to late-50s presented with an existing maxillary partial denture replacing teeth 1-5, 1-4, 2-4, and 2-5. She also exhibited superficial vertical fractures in teeth 1-2, 1-1, and 2-1, as well as existing PFM crowns on teeth 1-6 and 2-6. When asked if she would be interested in fixed rather than removable restorations, the patient answered affirmatively. Thus, with the goal of restoring form and function and enhancing aesthetics, the treatment plan called for fixed bridges spanning from tooth 1-6 to tooth 1-3 and from tooth 2-3 to tooth 2-6, along with PFM crowns on teeth 1-2, 1-1, 2-1, and 2-2.

Preliminarily, complete examinations were conducted on both hard and soft tissues, and evaluations were made of the muscles and the TMJ. Using a vinylpolysiloxane (VPS) material, preliminary impressions were taken. Along with the impressions, a face bow, a stick bite, and a full series of slides were taken and sent to the laboratory. Following receipt of the communication materials, the laboratory technician created a diagnostic wax-up, which was sent to the dental office for additional treatment planning purposes.

PREPARATION & TEMPORIZATION

The patient was painlessly anesthetized through a procedure using 4% Citanest Plain topical anesthetic (Astra Pharmaceuticals) followed by a carpule of 2% Lidocaine. After anesthetization was achieved, crowns 1-6 and 2-6 were sectioned off, existing amalgam build-ups were removed, caries detector was applied, and decay was removed. With Clearfil Liner Bond 2V (J. Morita USA, Inc.) and core paste, core build-ups were fabricated for teeth 1-6 and 2-6.

Teeth 1-6, 1-3, 1-2, 1-1, 2-1, 2-2, 2-3 and 2-6 were then prepared for the PFM restorations. A uniform reduction of 1.5 mm was accomplished circumferentially, in addition to 2 mm occlusal reduction on teeth 1-6 and 2-6 and 2 mm incisal reduction on teeth 1-3 through 2-3. Number 9 Siltrex retraction cord (Pascal) was soaked in Hemodent hemostatic agent (Premier Dental Products) and placed around teeth 1-6, 1-3, 1-2, 1-1, 2-1, 2-2, 2-3 and 2-6, and a full-arch impression was taken using Take 1 light/heavy body impression material (Kerr). Clinician’s note: By placing a thin retraction cord at the preparation stage, the user helps to create a quality impression and prevents any recession from occurring.

Following the impression, a bite registration was taken using Vanilla Mousse (Discus Dental), a stick bite was taken to help align the incisal edge position of the restorations, and a face-bow transfer was accomplished using the Stratos 200 articulator (Ivoclar). In addition, photographs were taken of the preparations to relay information to the laboratory technician.

To create temporary restorations, Gluma desensitizer (Heraeus Kulzer) was applied to the preparations, followed by a coat of OptiBond primer (Kerr) on the gingival margins of all prepared teeth. Using a Sil-Tech putty matrix (Ivoclar) of the wax-up, Luxatemp (Zenith/Foremost) shade A1 was injected into the matrix and then seated onto the prepared teeth. This was allowed to sit for two minutes, after which the matrix was carefully removed. Excess flash was trimmed away, and the temporaries were adjusted for occlusion, including excursions. Final contouring of the temporaries was accomplished, as was a final polish.

All information-including incisal edge position, length of central and final desired shade-was recorded. A VPS impression was made of the approved provisionals, and the patient was instructed on how to care for her temporary restorations. All of the detailed information was then sent to the laboratory.

LABORATORY FABRICATION

Standard framework design and alloy preparation principles were followed in the laboratory fabrication process. For maximum bond strength, appropriate IPS d.SIGN alloy oxidation procedures were followed according to manufacturer specifications. Six different ceramic alloys are offered with the IPS d.SIGN system, including high gold, reduced-gold, palladium-based, palladium-silver, cobalt-chromium, and nickel-chromium. The system-specific alloys are specially formulated to create an ideal interface with opaquer materials.

The restorations were opaqued, adjusted, characterized, and fired. Requiring a lower firing temperature than most conventional ceramics (900C and below), IPS d.SIGN allows users to prescribe a wide range of alloys. In addition, the material’s low firing temperature paired with the system-specific alloys negates the need for long-term cooling.

RESTORATION SEATING

The Luxatemp temporaries were sectioned and removed, and the PFM restorations were tried in. During the try-in phase, a final check was made of occlusion, excursions, and aesthetics. Following approval from the patient, bi-la
teral dry angles and cotton rolls were placed to isolate the teeth.

The prepared teeth were then disinfected with Consepsis (Ultradent Products, Inc.), after which they were rinsed and dried. A hybrid ionomer system (ProTec CEM, Ivoclar Vivadent) for conventional cementation was selected for the case. ProTec CEM conditioner was applied to the preparations and then air-thinned with a warm-air dryer. The internal aspects of the restorations were micro-etched, and the porcelain shoulders were treated with phosphoric acid, washed, and dried. This was followed by the application of a silane coupling agent, which was allowed to air dry for one minute.

ProTec CEM was mixed and then loaded into the crowns and bridges. All of the restorations were seated, and the patient bit down on Aidaco bite sticks (Temrex Corp.). After approximately three minutes, excess cement was removed from the crown margins, and a floss threader was used to clean under the bridges.

Final checks were made of occlusion and excursions, and final adjustments and polishing were accomplished. The patient was very pleased with her fixed restorations, which demonstrated exceptional aesthetics paired with ideal form and function.

This material truly replicates the structure of natural teeth. By combining the optical properties of natural dentition with outstanding brightness, translucency, and vitality, the system has eliminated the problems of metal show-through and opacity. So, to those who were wondering way back when, just how far we could go with tooth-coloured restorations, the answer is clear: All the way.

Acknowledgements

The author gratefully acknowledges the outstanding laboratory work by Mr. Lee Culp and Ms. Paula Moore of Mosaic Studios as well as the work of the entire team at the Studio of Esthetic Dentistry.

Dr. Robert Ritter operates a private practice–The Studio of Esthetic Dentistry–in Palm Beach Gardens, FL. He is Clinical Director for The Institute for Oral Art and Design in Sarasota, FL, with Master Ceramist Lee Culp, CDT. In addition, Dr. Ritter is an instructor at the Pacific Aesthetic Continuum (P.A.C.-Live) and on the faculty at The University of The Pacific School of Dentistry. He is also a founder of The Advanced Education in Aesthetic Dentistry Study Club.

Oral Health welcomes this original article.