August 2012, Volume 8, Issue 8
Published by AEGIS Communications
Simplifying Cementation in “Mixed Media” Smile Makeover Cases
Adhesive and resin cement system offers a single solution for luting every available indirect prosthetic restoration.
Some of the advances in contemporary dental adhesion have opened the door to more conservative preparation forms for both restorative and elective indirect ceramic restorations. While full-coverage crowns certainly have their place in modern dentistry, conscientious practitioners recognize that with adequate adhesion to dentin, enamel, and the ceramic substrate, partial-coverage crowns and veneers permit more conservative preparations with equal or superior strength.
One challenge, however, is that modern ceramic systems vary greatly in their recommended bonding protocols, creating confusion in many dental practices. In the past, dentists have been forced to stock several different classes of adhesives and resin cements to meet the everyday demands of bonding to mixtures of dentin and enamel as well as to all-ceramic restorative materials. To further complicate matters, dentists must now decide between three modes of adhesive application: total-etch, self-etch, and selective-etch. The choice of resin cements can be equally problematic.
3M ESPE (www.3mespe.com) recently introduced RelyX™ Ultimate Adhesive Resin Cement, a novel adhesive and resin cement system that offers what may be the answer to the dilemma of stocking multiple adhesive systems and resin cements; it could in fact be the single, go-to system for luting every available indirect prosthetic restoration, in any possible clinical situation, with just two components.
The complete RelyX Ultimate Adhesive Resin Cement Kit also includes Scotchbond™ Universal Adhesive, which has been shown to yield high bond strengths to both enamel and dentin when used in the total-etch, self-etch, or selective-etch mode, with high tolerance to both dry and moist dentin. The chemistry in Scotchbond Universal Adhesive provides dentin moisture tolerance, eliminates the incidence of postoperative sensitivity in both the total-etch and self-etch modes, and forms highly stable bonds. To further this adhesive’s claim of being truly universal, silane has been added to the formulation, eliminating the need for an additional silanation step for high-glass ceramics and pressed ceramics.
RelyX Ultimate cement is a dual-cure, base-paste/catalyst-base system. It contains an innovative dark-cure activator for Scotchbond Universal Adhesive, ensuring complete polymerization in areas where the curing light may not penetrate. It is radiopaque, and ideally thixotropic for optimal handling and clean-up. Clinicians may choose to initiate light polymerization during cementation or allow the material to autopolymerize, with a total auto-cure time of 6 minutes from the start of mixing. Excess cement is removed after tack light-curing for 1 to 2 seconds. For these reasons, RelyX Ultimate cement is optimally formulated to work with Scotchbond Universal Adhesive.
A 51-year-old man presented for a cosmetic consultation with a desire for a whiter and more youthful-looking smile (Figure 1). Upon examination, it was noted that the dominantly displayed maxillary eight teeth presented with numerous rotations, crowding, large restorations, worn and chipped incisal edges, and uneven facial embrasures mixed with virgin teeth.
The treatment recommendations included aligner therapy to attempt to optimize the crowding and rotations, but the patient declined this option. Because the patient desired a significantly whiter smile, the accepted treatment plan was to treat the eight teeth most dominantly displayed in his smile with all-ceramic restorations and to bleach his mandibular arch with a take-home tray bleaching system.
After completing a minor gingivectomy on tooth No. 9 to bring the free marginal gingiva in line with tooth No. 8, the case was prepared and impressions were made. A bite registration in centric occlusion was made and provisional restorations were placed. Preoperative and clinical photographs and instructions were sent to the laboratory with a request for eight pressed lithium-disilicate restorations. The patient returned in 3 weeks for try-in and cementation.
The provisional restorations were removed, revealing highly variable preparation designs for the eight teeth to be restored. All previously existing composite restorations were removed and the preparations were extended to cover these areas in definitive porcelain. The large Class 4 restoration on tooth No. 10 required full coverage for strength and adequate bonding surface. Rotation correction was created by extension of the preparations, and minimal preparation was performed on the virgin teeth in proper alignment.
The restorations were tried in using the optional water-soluble RelyX Ultimate cement try-in pastes. After confirming fit and esthetics, the restorations were rinsed thoroughly and dried. The lithium-disilicate restorations were etched with hydrofluoric acid by the laboratory, and carefully inspected after drying.
The preparations were cleaned and rinsed thoroughly. Upon close inspection, the majority of the preparations were composed of enamel mixed with erratic portions of exposed dentin in areas where reduction was mandated by either existing restorations or rotational correction. It was determined that using RelyX Ultimate cement in the total-etch mode would provide the strongest bond to the remaining enamel and provide maximum adhesion to exposed dentin without fear of postoperative sensitivity.
Using the supplied Scotchbond Universal Etchant, all aspects of the preparations were etched for 15 seconds (Figure 2). The teeth were thoroughly rinsed for approximately 5 seconds each and lightly dried. A thin layer of Scotchbond Universal Adhesive was applied to the intaglio surface of each restoration (Figure 3), and air-dried to evaporate volatile solvents. It is imperative to not light-cure the adhesive layer placed in the restorations to ensure that no pooling of the adhesive occurs in the line angles.
While the assistant placed Scotchbond Universal Adhesive in each restoration and air-thinned, a coat was placed on the prepared teeth for 20 seconds (Figure 4). In this instance, the clinician chose to apply additional coats. Then, using a steady stream of oil and moisture-free air, the adhesive layer was thinned and solvents volatilized. Light-curing the adhesive layer on the teeth is optimal, but not necessary.
Using the tapered spiral mixing tip, each restoration was loaded with shade B.05 of RelyX Ultimate cement (Figure 5). The restorations were fully seated, and marginal and interproximal adaptation was confirmed. The restorations were cured with an Elipar™ S10 LED Curing Light (3M ESPE) for 2 seconds each. Using this technique, the residual RelyX Ultimate cement was easily peeled away using a sickle scaler and floss (Figure 6). Once all excess cement had been removed, each restoration was light-cured simultaneously from the buccal and lingual (Figure 7) to expedite complete polymerization.
As shown in the immediate postoperative view of the cemented ceramics (Figure 8), highly variable margin placement was required to conservatively treat the multiple rotations, ectopic displacements, and existing restorations to yield a harmonious smile.
The Challenges of Cementing “Mixed-Media” Cases
Due to the combination of virgin teeth, teeth with moderate-to-large existing restorations, and teeth with various rotations present, restoring cases like this with a single preparation style is not indicated. The treatment is referred to by the author as a “mixed media” case. This can be defined as blending traditional facial porcelain veneers with less conventional but also conservative preparation forms, which are dictated by the existing restorations, decay, rotations, or displacements required to create a symmetrical, balanced smile. The types of restorations often employed may include full-coverage crowns, modified three-quarters or seven-eighths crowns, so-called “taco shell” crowns, and variations/extensions of the traditional facial veneers, all of which are designed to conservatively correct the structural and esthetic concerns in a patient’s smile.
There are numerous challenges encountered in most “mixed-media” cases, including proper design of each tooth preparation, selecting the appropriate ceramic material, and achieving harmonious overall color. However, the single greatest challenge posed by these types of cases may be selecting the appropriate dental adhesive and resin cement system appropriate for each preparation design. Because “mixed media” cases often result in some preparations being exclusively in enamel, some being mostly in enamel with some shallow or intermediate dentin exposure, and others (such as full crowns) being mostly or even exclusively in dentin, the author has historically employed the use of several different adhesive and resin cement systems for optimal performance.
With the introduction of RelyX Ultimate Adhesive Resin Cement, the need for this extensive armamentarium has been eliminated. In the author’s opinion, the ability to form strong, reliable bonds to nearly every type of indirect all-ceramic and zirconia restorative material as well as both dentin and enamel in total-etch, self-etch, and selective-etch modes makes this product compelling to use, and simplifies the often-chaotic process of restoring mixed-media cases.
About the Author
Jeff T. Blank, DMD
Fort Mill, South Carolina