Oral Health Group
Feature

Current Challenges and Definitive Solutions in Direct and Indirect Restorative Dentistry

April 1, 2013
by Jeff T. Blank, DMD


INTRODUCTION
There is no doubt that frenetic pace of advancement in contemporary adhesive technology and dental material sciences in recent years have drastically changed the face of dentistry. As dental clinicians, we are now afforded the tools and techniques to offer highly esthetic, durable direct and indirect restorations that can be delivered efficiently and predictably. However, rapid advancement in the dental profession can lead to frustration and confusion as previously held paradigms and clinical protocols become questioned. Seasoned clinicians are often reticent to quickly adapt and implement new procedures that may be foreign and more complex in fear that the “latest and greatest” may in fact no be so great.

However, many of the recent advancements in dental adhesion and restorative materials have been largely focused on reducing the complexity of everyday dental procedures and the number of technically demanding steps required to mitigate their effective use. Pursuant to this goal, a new class of adhesives labeled “universal adhesives” now permits a single product that functions in multiple modes of delivery, which reduces the need for an extensive inventory of mode-specific adhesives designed for limited applications. When combined with practical restorative techniques utilizing new and familiar products demonstrated in this article, clinicians can easily embrace and implement these current advancements with confidence.

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BRIEF REVIEW OF CONTEMPORARY ADHESIVES AND MODES OF DELIVERY
Historically, the classification of dental adhesives into “generations” led to confusion and consternation among practicing clinicians and did little to delineate the indications or modes of action of a particular product. In an effort to more accurately describe contemporary adhesives, they were initially divided into 2 categories based on their primary mode of delivery. The first is “etch-and-rinse” adhesives (often referred to as “total-etch” adhesives) which typically employ a separate phosphoric acid etching step that is rinsed away and followed by the application of primers and adhesives (multi-bottle, 3-step systems) or a primer/adhesive combination (single bottle, 2-step). The second category is the “self-etch” adhesives which employ acidic monomers to serve in lieu of phosphoric acid which are applied and not rinsed away. The “self-etch” adhesives may involve 1-3 steps which is determined by the whether the acidic monomers are applied apart from a subsequent primer then adhesive (3-step), the acidic monomers are mixed with various primers and applied independently from the adhesive (2-step), or whether the acidic monomers, primers and adhesive are all 3 combined in a single bottle (1-step).

The “self-etching” category of adhesives historically were well accepted by practicing dentists primarily because of there low incidence of post-operative sensitivity and simplified protocol for delivery. Initially, the majority of products performed well on dentin, but paled in comparison to etch-and-rinse adhesives on enamel. This prompted the inclusion of highly acidic monomers with a pH that rivaled phosphoric acid to facilitate stronger, more durable enamel bonds, and generated longer intertubular resin tags similar to total-etch products. However, the current trend in the self-etch category has been to employ the use of much milder acids that are far less robust, merely modify and reinforce the smear layer rather than removing it, and generate uniquely-shaped intertubular tags that appear to resist bond degradation better than there more acidic predecessors.

The flip side to raising the pH of self-etch adhesives is of course the ability to adequately etch enamel. While initial bond strengths seem to indicate that many of the contemporary products are comparable to total-etch products in terms of shear bond strengths, it is widely held that bonds can be improved by “selectively etching” all exposed enamel with phosphoric acid prior to application of the self-etching product. The advantages of the selective-etch technique has been well received by knowledgeable clinicians and most often utilized in posterior direct resin applications. However, depending on the chemistry of the self-etching adhesive used, the technique should be well executed such that the phosphoric acid is kept off of dentin. Inadvertent exposure of dentin to phosphoric acid is known to remove the smear layer, open dentinal tubules and demineralize both inter- and peritubular dentin and create an environment that some self-etching products cannot seal.

UNIVERSAL ADHESIVES
Historically, the majority of self-etching products are not designed to be used with a total-etch technique on dentin and doing so either intentionally or accidentally may grossly affect long-term bond stability. That said, the latest development in dental adhesives has introduced a 3rd category aptly called “Universal Adhesives” in that their chemistries are compatible on enamel and dentin when a total-etch, self-etch or selective-etch technique is utilized.

The classification of an adhesive as “universal” is predicated largely on its compatibility with the total-etch, self-etch and selective etch technique. However, truly universal adhesives are also compatible with both direct and indirect applications. The first product to be introduced in this category was Scotchbond Universal (3M/ESPE), followed by All-Bond Universal (Bisco) and more recently, Prime&Bond Elect (Dentsply/Caulk). Though each of these universal agents have unique merits, Scotchbond Universal will be discussed at length and case presentations in total-etch, selective-etch and indirect all-ceramic cementation will be demonstrated.

SCOTCHBOND UNIVERSAL ADHESIVE
This universal adhesive was the first to be released 2011 by 3M/ESPE and is a single-bottle adhesive indicated for direct restorative applications in total-etch, self-etch and selective-etch modes. More recently, 3M/ESPE released RelyX Ultimate Adhesive Resin Cement, a dual cure adhesive resin cement system that utilizes Scotchbond Universal Adhesive and is indicated for nearly every available indirect restorative material and procedure including veneers. The clinical protocol for use in both direct and indirect applications is considerably less complicated than the majority of current systems and grossly reduces the need for numerous brands of cement for limited applications.

Scotchbond Universal (3M/ESPE) shares the much of the chemical heritage with its current predecessors within the 3M/ESPE family of adhesives. Traditionally 3M/ESPE has utilized water or water/ethanol as the primary solvents as well as the Vitrebond Copolymer, a methacrylate-modified polyalkenoic acid copolymer. Both of which have been credited to provide more consistent performance to dentin under varying moisture levels. Scotchbond Universal utilizes both water and ethanol as solvents and MDP (10-methacryloxydecyl dihydrogen phosphate) as the primary acidic monomer. With a pH of ≈ 2.7, Scotchbond Universal is considered a mildly acidic self-etching formulation that is uniquely hydrophilic during application but is quickly rendered hydrophobic air volitization of the solvents and light curing. As a mild acid, MDP is has been shown to reduce the stimulation of matrix metalloproteinases (MMP’s), which are host-derived dentinal collagenolytic enzyme released hydroxyapetite in a highly acidic environment similar to the caries process. The combination of creating a hydrophobic seal and reduced potential for collagenous and inorganic degradation may facilitate more durable bonds to dentin long-term. Additionally, MDP is extremely tolerant to variable moisture levels at the bond interface and has an established history of success of forming strong ionic bonds to calcium hydroxyapatite as well as zirconium and metal
oxides. Scotchbond Universal also contains silane, a known ceramic primer that in combination with MDP, facilitates bonds to nearly every available indirect restorative material.

Since Scotchbond Universal is highly tolerant of variable moisture levels, the margin of error in determining proper levels of moisture in dentin in total-etch mode and the concern of inadvertent phosphoric acid etching of dentin during the selective-etch mode of delivery is alleviated. The high molecular weight components yield a uniform film thickness of fewer than 10 microns with a reported 85% degree of molecular conversion upon light curing. With some studies reporting less than 0.4% of post-operative sensitivity in total-etch mode and 0.06% in self-mode, it appears that Scotchbond Universal Adhesive represents a breakthrough for those who continue to struggle with post-operative sensitivity in their practices.

TOTAL-ETCH DIRECT VENEERS USING FILTEK SUPREME ULTRA UNIVERSAL RESTORATIVE AND SCOTCHBOND UNIVERSAL ADHESIVE
A 22-year-old male presented seeking cosmetic improvement of his smile. A comprehensive exam was performed including a full mouth set of radiographs. The initial findings revealed no active caries or previous restorations and minor/moderate plaque accumulation and concomitant gingivitis. The preoperative base/body shade was determined to be A3 using the Vitapan Classic Shade Guide (Vita Lumine). Numerous options including traditional and clear aligner orthodontic therapy were discussed. However, the patient’s primary concerns were the yellow appearance of his teeth and the minor rotations and irregular edge position of his maxillary incisors. The cost and duration of treatment were major concerns, so the patient elected to undergo periodontal prophylaxis/oral hygiene instruction, vital tray bleaching and direct composite veneers on the four maxillary incisors only.

A 10-day regimen of vital tray bleaching utilizing a 16% carbamide peroxide gel (Night White, Phillips/DiscusDental) was initiated and the patient was instructed to return to the office 10 days after the conclusion of bleaching to begin the direct veneer procedure. Upon presentation for treatment, the whitened body shade was determined to be A2 (Vita Lumine Shade Guide) and the patient was satisfied with using this shade as the body shade for his direct veneers.

For this case, Filtek Supreme Ultra Universal Restorative was selected as the composite restorative material for its wide range of shades and opacities, exceptionally handling, color stability, high wear resistance and 10 year track record of success. Additionally, Filtek Supreme Ultra utilizes a proprietary nanofiller technology that provides excellent strength and resistance to fracture as well as a microfill-type luster. Alternatives also used by the author would include EthetX HD (Dentsply/Caulk) and Kalore (GC America). Using the A2 body shade as the starting reference, the Filtek Supreme Ultra Shade Wheel (3M/ESPE) was to determine the corresponding body and enamel shades. For this case, Filtek Supreme Ultra A2B and A2E were selected as the restorative composite in conjunction with Scotchbond Universal Adhesive it total-etch mode.

In order to level and align the rotated and ectopic teeth and conceal the margins of the restorations within the interproximal zone, minor tooth preparations that remained within enamel were required. The author has developed the “Histological Layering Technique” which represents a simplified method of layering composite to yield vital, polychromatic direct veneer restorations with variable incisal edge translucency and this technique was utilized in this case.

Dead-soft foil (DenMat) was used to isolate tooth #8 from the adjacent teeth from the etching and bonding process and Scotchbond Universal Etchant was applied for 15 seconds and thoroughly rinsed away. A copious amount of Scotchbond Universal Adhesive was applied to the preparation for 20 seconds and the water/ethanol solvents were evaporated and the film layer was evenly dispersed with a 5 second stream of oil- and moisture-free air. Since Scotchbond Universal Adhesive is extremely moisture level tolerant, both enamel and dentin can be desiccated thoroughly prior to application without decreasing bond strength or fear of post-operative sensitivity. After light curing the adhesive layer for 10 seconds, the dead-soft foil was removed and the direct veneer was layered to full contour. Since the adjacent tooth surfaces were neither etched nor bonded with adhesive, the veneer can be built to contact without micromechanically adhering to the proximal surfaces of the adjacent teeth.

The Histological Layering Technique typically involves using only a body and enamel shade rather than more complex layering recipes and relies on grading the thickness of the base shade from thickest in the gingival 1/3 and tapering thinner as the layer approaches the incisal edge similar to the histological layer of natural intermediate dentin. When the subsequent more translucent enamel layer is applied, it is thinnest in the cervical 1/3 and thickens to full facial contour as the material approaches the incisal edge, similar to the histological tissues of enamel. This gradation of both body and enamel materials applied to biomimetically replicate the layers of natural teeth simplify direct veneers considerably and yield vital, life-like results.

In this case, Filtek Supreme Ultra A1B was dispensed and placed on a composite spatula (Hu-Friedy CCIB) and spread across the prepared surface. In keeping with the Histological Layering Technique, the body shade is brought to full facial contour in the gingival 1/3, then tapered back to the lingual as the material reaches the incisal edge. In order to biomimetically duplicate incisal translucency, a thin IPC instrument (Hu-Friedy Mini 4) is used sculpt dentin “mammelons” or lobes in the incisal 1/8 of the body material approximating the incisal edge. These erratic mammelons or lobes are present in the terminus of dentin in natural teeth, and when overlaid with a more translucent composite similar to enamel, the voids created are filled and the visual effect is equivalent to natural incisal edge translucency. Once the body layer of Filtek Supreme Ultra is morphologically correct, it is light cured for 10 seconds.

The A1E enamel material is then applied to predominantly to the incisal 1/2 to full facial contour, filling the voids of the dentin mammelons, and graded to thin to nonexistent in the gingival 1/3. The more translucent enamel material de-saturates the more chromagenic body material due to its thickness in the incisal half of the restoration, and allows more saturation in the gingival portion of the tooth where it is thinnest. Once the enamel layer is appropriately contoured, it is light cured for 10 seconds. The author often prefers to mimic the natural incisal “halo” or glowing edge of direct veneers by placing a thin ribbon of Filtek Supreme Ultra Shade WE (white enamel) on the incisal edge, however this additional step is often elective when the natural incisal halo is not dominantly displayed in the adjacent natural teeth.

The completed layered restoration is then finished with a series of composite finishing burs (Diamond Composite Finishing Kit, Komet USA) and polished with abrasive sandpaper discs (SofLex, 3M/ESPE) to the desired luster.

Note the harmonious blend of the restorations with the surrounding dentition, the incisal edge translucency, incisal halos and sustained luster of Filtek Supreme Ultra direct veneers. By utilizing the Histological Layering Technique developed by the author, the restorations were created in under 20 minutes per tooth and exhibit a vital, highly esthetic result.

CLASS I DIRECT POSTERIOR COMPOSITE UTILIZING FILTEK SUPREME ULTRAN, SCOTCHBOND UNIVERSAL ADHESIVE IN IN SELECTIVE-ETCH MODE, AND POLISHED WITH SOFLEX FINISHING WHEELS
The most commonly placed esthetic restorations in dentistry are direct posterior composite
s. For some practitioners, they also pose the most significant clinical challenge. In order to profitably place durable direct posterior composite restorations, the clinical protocol must be fast, efficient and predictable. The following technique demonstrates one method and minimal materials to accomplish that goal.

The patient presents with recurrent decay around failing composite restorations on teeth #’s 17 and 18. The restorations and recurrent caries were removed, and the prep consisted of an equal mixture of enamel and dentin. Though Scotchbond Universal Adhesive is capable of generating adequate bond strength to abraded enamel in the self-etch mode alone, like all self-etch adhesives, bond strengths are maximized by utilizing the “selective-etch” mode of adhesion.

Scotchbond Universal Etchant is ideal for the selective etch technique in that it designed to be slightly more viscous and likely to “stay put” and not inadvertently flow on to dentin. The etchant was placed on the exposed cavosurface enamel for 15 seconds and rinsed away with copious air/water spray and thoroughly dried. Scotchbond Universal Adhesive was dispensed and both the enamel and dentin surfaces were saturated for a period of 20 seconds. The water/ethanol solvents were evaporated and the adhesive layered evenly dispersed with 5 seconds of moisture/oil-free air and subsequently light cured for 10 seconds. The light dispersion afforded by the nanofilled technology utilized by Filtek Supreme Ultra predictably exhibits the chameleon-effect where the color of the surround dentin and enamel is drawn into the restoration for optimal color blending, even when a single shade is used. In this case, Filtek Supreme Ultra Shade B1B (Body Shade B1) was dispensed into the preparation in 2 vertical increments, each light cured for 10 seconds. The margins and anatomy were refined with diamond composite finishing burs (Diamond Composite Finishing Kit, Komet USA), and the rubber dam was removed and the occlusion adjusted.

Finishing and polishing posterior composite restorations can be problematic in that the undulating evaginations, pits and fissures can be difficult to access with traditional silicone points, cups and wheels or sandpaper discs. Recently, 3M ESPE has released a novel finishing and polishing system that is ideal for nearly every direct composite application and is highly suited for nanofilled composites such as Filtek Supreme Ultra Universal Restorative. The SofLex Spiral Finishing and Polishing Wheels is a 2-component system composed of elastomer impregnated spiral strands impregnated with aluminum oxide particles that represent a hybrid of traditional polishing points/cups/discs and sandpaper discs. With the flexibility and versatility of sandpaper discs, the SofLex Spiral Finishing and Polishing Wheels easily reach into tight spaces in both anterior and posterior applications, as well as fan out in higher speeds to finish and polish large flat surfaces like direct composite veneers. The darker tan-colored wheel is designed to finish the restoration and removes scratches left by more coarse finishing burs, and the lighter cream-colored wheel is designed to create a high luster. When used a lower speeds, the SofLex Spiral Finishing and Polishing Wheels are ideal for polishing posterior composite restorations like the case demonstrated here.

Figure 9 shows the use of the Step 1 Spiral Finishing Wheel to remove the residual scratches and marred finish, and Figure 10 demonstrates the use of the Step 2 Spiral Polishing Wheel to create a gloss-like luster. As seen in the 1 week post-operative view, the SofLex Spiral Finishing and Polishing Wheel system is quite capable of creating smoothly polished restorations without removing the detailed morphological features.

Using RelyX Ultimate Adhesive Resin Cement and Scotchbond Universal Adhesive in Total-Etch Mode to Cement Two 3-Unit Lava All Ceramic Anterior Fixed Bridges:

Perhaps the zenith in terms of the benefits of using Scotchbond Universal Adhesive is best represented in the recently released RelyX Ultimate Adhesive Resin Cement (3M ESPE). This system is designed to meet the specific needs of CAD/CAD and glass ceramic cementation. As mentioned earlier, Scotchbond Universal Adhesive contains MDP, an acidic monomer with a 20 year track record of durably bonding to tooth structure as well as zirconium and metal oxide. It also includes silane, an chemical known to form bonds with hydrofluoric acid-etched glass ceramics, making this system ideal for contemporary esthetic indirect applications. With above average bond strengths to these restorative substrates and tooth structure, durable color stability and natural fluorescence, combined with the versatile indications for total-etch, selective-etch and self-etch procedures, RelyX Ultimate is a practical, easy to use system for busy dental practices. Since it is a 2-component system, it requires only 2 steps compared to other brands require 3-6 steps and can be used for full crowns, inlays/onlays, and veneers. With studies demonstrating little to no post-operative sensitivity, RelyX Ultimate represents a welcomed simplification to a historically complex procedure.

A 31-year-old patient presents with the desire to replace 2 unesthetic Maryland Bridges that replace teeth #’s 7 and 10. Numerous options including implants and retreatment with more esthetic Maryland Bridges were discussed, but the patient desired correction of the black triangle and small diastema between teeth 8 and 9 and an overall color improvement. To correct these issues, 2 all-ceramic bridges with full coverage abutments and ovate pontics were prescribed.

The abutment teeth were prepped as conservatively as possible and the ovate pontic sites were create with radiosurgery using a ball-tip attachment (TCS, Whaledent). Provisional restorations were fabricated using a bis-acrylic provisional material (Protemp Plus, 3M ESPE) and the ovate pontics were trimmed and polished to support the tissues created by the ovate pontic receptor site. The patient wore these provisional restorations for 4 weeks to permit healing of the surgical areas and returned for final impressions and bite registration. Two Lava fixed bridges were fabricated and the incisal 1/3’rds of each tooth were cut-back, internally stained and layered with feldspathic porcelain were requested from the laboratory. Figure 2 illustrates the view of the prepared teeth and ovate pontic receptor sites on the day of delivery. The restorations were tried in with Shade A1 RelyX Ultimate try-in paste and the esthetics were approved the patient.

The cementation steps required by the RelyX Ultimate Adhesive Resin Cement are simple and efficient. Scotchbond Universal adhesive is dispensed in a mixing well and applied to intaglio surface of the Lava abutments. The adhesive is air-thinned to assure an evenly distributed layer while the doctor applies Scotchbond Universal Etchant to the prepared abutments for 15 seconds. The etchant is rinsed away, the preparations thoroughly dried, and the preps are thoroughly coated with Scotchbond Universal Adhesive for 20 seconds. The solvents are evaporated and the adhesive layer is evenly dispersed by 5 seconds of air spray and left uncured. The restorations were loaded with RelyX Ultimate Resin Cement (Shade A1), and firmly seated onto the abutments.

RelyX Ultimate Resin Cement is a dual-cure cement and offers the choice to allow the material to reach a gel state by an autocure reaction, or the dentist may partially polymerize the exposed material with a brief (2-3 seconds) exposure to the curing light. In this case, the author utilized the latter and Figure 10 demonstrates the brief curing light exposure. The ability to effectively remove the excess residual cement is a requisite of resin cement systems, and RelyX Ultimate Resin Cement cleans up easily and complete with an explorer or thin sickle-shaped curette. Floss is passé through the interproximal zones with a floss-threader and all residual cement in the int
erproximal zones and beneath the pontics are effectively removed.

Figure 12 depicts the 6-week post-operative result of the two Lava bridges cemented with the RelyX Ultimate Resin Cement System. Note the excellent gingival health, well-adapted ovate pontics, closure of the black triangle between teeth 8 and 9, the improved color and esthetics facilitated by this technique and cement system.

CONCLUSION
The current stat-of-the-art for dental adhesives and cements requires the flexibility to be used in total-etch, self-etch and selective-etch modes. Scotchbond Universal Adhesive and RelyX Ultimate Resin Cement represent a contemporary adhesive system capable of meeting these demands. The convenience and ease of use, durable bonds and esthetics and extreme versatility easily reduce inventory, reduce chairtime, and dramatically reduce the complexity of modern adhesion with products whose chemical lineage have a long track record of success.OH


Jeff T. Blank, DMD, Private Practice – Carolina Smile Center, Fort Mill SC and Chief Clinical Instructor – New Millennium Education, LLC.
www.carolinasmilecenter.com 
jblank@comporium.net

Oral Health welcomes this original article.