Anterior Advances
The materials driving esthetic restorations
Allison M. DiMatteo, BA, MPS
New laboratory materials designed for anterior restorations boast formidable strength and outstanding esthetics. But do they live up to the hype? Are tried-and-true materials really fading into the twilight? Inside Dentistry looks at the changing face of anterior restorations and how dentists can make the most of these material advances to achieve predictable function and optimal esthetics.
The Anterior Restoration in 2016
Since the financial crisis of 2008, dentistry has experienced a downturn in elective cosmetic procedures—including indirect veneer restorations. Concurrently, industry observers have commented that traditional porcelain veneers have lost traction in the restorative landscape due to their cost prohibitive nature. However, regardless of the introduction of direct and indirect material innovations, that phenomenon has more to do with socioeconomics than material characteristics. In fact, dentists currently have multiple material options available that cost no more than the original materials that were introduced to create ideal esthetics in veneers. Simultaneously, patient demand for preventive, functional, and minimally invasive treatments has supported more thoughtful selection of the most appropriate patient- and case-specific restorations.
“It’s not a materials question. It’s really a socioeconomic issue for the patient,” explains Michael Gaglio, DDS, senior vice president of Ivoclar Vivadent North America. “Veneers have never been covered by insurance and are considered an elective and cosmetic procedure, even though we all know that by practicing conservative, esthetic dentistry, we can restore function and esthetics with veneers and preserve tooth structure.”
Due to attrition or wear of the incisal edges, a fair number of patients could benefit from veneers, explains John Weston, DDS, director of the Scripps Center for Dental Care, so the functional discussion or rationale (ie, improving how teeth work together and protect each other) makes a very compelling argument to treat versus wait. Dentistry is following trends of more conservative treatments, and most patients would prefer not to have their teeth shaved down, he says. Coincidentally, material improvements have helped make more conservative veneer preparations—if any preparations are needed at all—a reality, enabling fabrication using thinner, stronger ceramics.
“Today, dentists and patients are looking at treatments for reconstructive needs and factors other than strictly esthetics, and veneers still provide a viable solution with the versatile range of material options available,” explains George Tysowsky, DDS, senior vice president of Technology and Research for Ivoclar Vivadent. “They can be used very effectively for strong, no-prep veneers with high edge strength; bonded to reinforce the teeth; and for minimally invasive occlusal rehabilitation with tabletops/onlays design.”
Among today’s material innovations for anterior indications are high-translucency and multi-layered zirconia options for monolithic rather than cut-back and layered restorations. At least at this point, high translucency zirconias are not quite as translucent as lithium disilicate, explains John Burgess, DDS, MS, professor and assistant dean for Clinical Research at the University of Alabama at Birmingham. However, if dentists pick their cases well and don’t require a material with very high translucency for the anterior region, then they can use these materials predictably, he says.
Economically speaking, monolithic restorations may be less expensive than fully layered porcelain, but the actual cost savings to the patient may not be as significant, explains Amanda Seay, DDS, an accredited member of the American Academy of Cosmetic Dentistry. Whether monolithic or fully layered, the same level of treatment planning and care (ie, smile design, wax preparation, tooth preparation, provisionalization) is required as part of the overall treatment delivery, she says.
The question of material selection for cost efficiency then becomes one not of choosing between one indirect material or indirect restoration, but rather of choosing between a direct versus indirect restoration based on the indication (ie, direct composite veneer versus an indirect ceramic veneer), experts suggest.
“For quite a few years, ceramic veneers were the ultimate solution for anterior esthetics. They still are beautiful, but a changing economy has had an effect,” says Jon Fundingsland, professional services manager for 3M Oral Care. “Several clinicians that I work with have told me they are doing fewer ceramic veneers and more composite veneers due to the cost differential.”
That cost differential affects patients and dentists alike, and the introduction of universal nanohybrid direct composites (ie, those that can be used in the anterior and posterior due to their esthetics, strength, smoothness, stain resistance, and polishability) represents cost savings on multiple levels, explains Jason H. Goodchild, DMD, clinical education manager for DENTSPLY Global Restorative.
“You’re achieving all of these benefits with one composite, rather than multiple products, which is everything right now in dentistry,” Goodchild explains. “We’re talking about efficiency, inventory control, less ordering, ease of use, less confusion among dental teams at the chair. Factor in characteristics like chameleon affect and blending ability, along with wear resistance and strength, and you’re definitely seeing more direct veneers and fewer indirect veneers—at least as a starting point.”
However, the challenge with choosing between a direct versus indirect restoration is that direct composite veneers are extremely difficult to create so that they replicate the anticipated esthetics, form, function, and beauty of natural teeth. It takes time, education, and practice to develop the requisite skill set—and patience—to provide these restorations, experts advise.
But for clinicians who make the investment, newer restorative materials, such as nanohybrid composites, are welcome additions to their direct anterior restorative arsenal. While resin composites may not have displaced veneers very often, improvements in composite esthetics provide a result that can be very close to ceramic veneers, observes James Lobsenz from Kerr Dental.
“In turn, this has made this type of esthetic outcome accessible to more patients. In other words, the frequency of the procedure is increasing,” Lobsenz explains. “And beyond esthetics, a direct resin veneer will also conserve more tooth structure, which both the patient and clinician view favorably.”
Increased use of direct composites to address esthetic defects may also partially explain why some dentists may be witnessing a decrease in the demand for veneers, suggests Betsy Bakeman, DDS, an accredited fellow of the American Academy of Cosmetic Dentistry. Additionally, patients seem more likely to seek out a dentist that they feel “specializes” in cosmetic restorative care, she says, as opposed to having their esthetic restorations placed by their general dentist.
While there is no recognized specialty in cosmetic dentistry, patients considering elective treatment are more inclined in recent years to seek a second option and treatment from a dentist who has extra training, skill, and credentials in the area of esthetic dentistry, observes Bakeman. These skills involve and affect evaluative decisions regarding which type of direct or indirect material to use.
“We have to combine esthetic and functional considerations with biomechanical and periodontal considerations when we develop a treatment plan and look at the patient’s risk for breakdown in all of these areas,” Bakeman elaborates. “If we outline these areas and design our treatment plan around them, we are better able to guard against the modes of failure in which the patient has greater susceptibility.”
Whether restoring teeth with direct or indirect materials, the functional discussion is important and, interestingly, teeth that are restored to proper esthetics will function better, Westin says. Principles of smile design (ie, length/width proportions, axial inclination, incisal edge design) are all based on biologic and functional parameters.
“Proper length of the central incisors will mutually protect the posterior teeth when the patient grinds forward, and proper canine lengths protect the adjacent anterior teeth, as well,” Westin elaborates.
Therefore, understanding the patient risk factors, esthetic expectations, and functional requirements can help clinicians when determining which of the newest restorative material innovations is best for specific patient treatment indications.
Indirect Anterior Restorations
Material selection for indirect anterior restorations is governed by indication and patient characteristics (ie, the individual case). Choices need to be made collaboratively by the dentist and laboratory in how to best approach a case to satisfy form, function, and esthetic requirements and ensure clinical success and patient satisfaction, says Chris Brown, owner of Aclivi Consulting/Technical Services.
“For example, if the patient is at high risk for caries or already has significant structural compromise, we may be more inclined to wrap the tooth with our restoration to reduce the risk of recurrent decay or tooth fracture,” says Bakeman. “If the patient is at increased functional risk, we lean toward stronger materials. However, neither scenario negates the need to manage the occlusion and create functional systems that do not prematurely load the teeth/restorations during function.”
Alternatively, the esthetics of a restorative material may drive the treatment decision if the patient is at high risk esthetically (eg, has a high lip line and the teeth strongly influence the patient’s appearance). The reality is that typically a combination of risks must be considered in order to individualize and design the best solutions for a particular patient, Bakeman emphasizes.
“The determinate is restoration type: veneer, crown, bridge, and/or what combination the particular case requires,” explains Jeff Stubblefield, general manager of DAL Signature Lab. “Today’s product offerings (eg, lithium disilicate, translucent zirconia) are extremely well-suited for the criteria of form following function.”
Among the newer material solutions to choose from are translucent zirconias. Created by either increasing the amount of yttria in the zirconia itself (ie, up to 9.5%), which increases the cubic polycrystal (ie, more translucent component), or by adding ions that exhibit greater translucency into the matrix, translucent zirconias are inherently weaker (ie, 600 MPa flexural strength) than their traditional high-strength zirconia counterparts (ie, 1,100 MPa flexural strength), explains Burgess.
“The concept of using monolithic materials is a better choice for longer-lasting restorations,” Weston says. “When you eliminate a material interface, you eliminate a failure point.”
However, even the more translucent zirconia materials currently available may still not be sufficiently esthetic for use as anterior veneers. They can appear monochromatic and lifeless due to differences in light transmission properties, Weston says.
While it is true that in most cases the new zirconia options won’t be as esthetic as cut-back and layered restorations, Brown says it will be interesting to see if the translucency in the incisal area can be further increased to enhance the esthetics of these materials.
“These new zirconia do offer new choices for the dental laboratory and dentist,” Brown believes. “The multi-layered zirconia materials blocks represent a definite improvement in esthetics regarding shade transitions over previous zirconia offerings.”
And, the advances in zirconia translucency have absolutely started to close the gap between layered esthetic restorations and monolithic restorations, Stubblefield observes. Because customization achieves the finest esthetics, no matter what the material is, he believes that laboratories that excel in their handling of the pre-sintered staining will maximize the esthetic value of monolithic zirconia.
Direct Anterior Restorations
A preferred option for clinical applications where minimal reduction is desired, direct restorations can be both very esthetic and durable. However, significant to achieving predictable esthetics and long-term function in less time and often with less expense to patients than indirect restorations are proper training and clinical skills, explains Westin.
Although dentists may consider direct veneers to be difficult to place in terms of achieving ideal symmetry, armamentarium are available (eg, pre-formed chairside shaping tools) to facilitate more predictable material manipulation. Then, depending on the clinician’s knowledge of the material and level of placement technique expertise, direct composite veneers are fairly easy to provide, Goodchild says.
“Considering that indirect veneers can be so expensive, require tooth reduction and two or more office visits, and require some difficult or at least some confusing material choices (such as adhesive bonding agents and cements), most dentists—if they could—would start with a direct composite veneer,” Goodchild observes. “Composite can be repaired, re-polished, reshaped, added to, and subtracted from, whereas indirect ceramic can’t be very easy. If you can’t achieve what you want with direct restorations, you always have the option to move to an indirect restoration in the future.”
Overall, advancements in the ability to bond to teeth, combined with the development and introduction of nanohybrid restorative materials, contribute to direct restorations being a permanent treatment option for many patients, explains John Cranham, DDS, acting clinical director of The Dawson Academy. In particular, for those patients without extremely high functional demands or high-risk occlusion, nanohybrid materials can enable dentists to provide long-lasting, esthetic treatments that are also conservative in nature.
“Nanocomposite or nanohybrid composite is the state-of-the-art of contemporary direct restorative materials,” Tysowsky believes. “They demonstrate optimal esthetic characteristics, strong physical properties, sculptability, and durability, and they’ve certainly brought into play many of the attributes we’ve desired from previous composites (eg, handling, polishability).”
From Seay’s perspective, nanohybrid composites represent the first time a truly universal composite that demonstrates the requisite strength and esthetic properties can be placed in both anterior and posterior areas. Previously, with conventional composites, dentists had to choose between using an anterior composite with maximum esthetics, high polishability, and lower strength, or a stronger posterior composite with limited esthetic qualities.
“Microfills are a good example for polish retention, but their limited strength has narrowed their indications. More recently, nanofill and nanohybrids have become the norm,” Fundingsland explains. “Both approaches yield excellent esthetics without sacrificing the strength and wear characteristics required for universal indications.”
Introduced in 2002, nanofill composites have demonstrated excellent polish retention after toothbrush abrasion. Today’s nanohybrids combine nano-size particles with larger particles of a traditional hybrid, notes Fundingsland. It’s been understood for years that smaller particles yield better polish retention, but every manufacturer chooses a slightly different path in translating this knowledge into products.
“Nanohybrids make it very simple, but the onus is still on the clinician to know the esthetic/color, handling, and sculptability differences among the various composite systems available,” Seay emphasizes. “Even though nanohybrids have simplified things, these materials all handle slightly differently, and proper technique still matters.”
One concern with nanohybrid materials is that the initial polish can be lost over time, explains Burgess, whose clinical trials have shown that these materials lose their polish similar to most traditional hybrids. So, although they do polish much easier than conventional hybrid materials, they still require re-polishing to achieve and maintain high esthetics. Burgess also notes that there is some question regarding the fracture toughness of these materials, adding that clinicians may see more chipping occur with large Class IV cases than they would with other direct materials.
Although some apprehension remains regarding the strength and polish retention of composites with nano-scale fillers, they have demonstrated other benefits, including more lifelike translucency and esthetics, says Lobsenz. The technological improvements reflected in these materials involve the size as well as the shape of the fillers—which can diffuse light in a manner that makes the restorative margins more difficult to detect, he adds.
Considerations for Direct Anterior Nanohybrid Composite Restorations
Because direct composite restorations tend to discolor, lose their gloss, and erode at a faster rate than ceramic restorations, they will require more surface maintenance and likely require refinishing and polishing every few years to maintain ideal esthetics.
Function must always be considered when restoring anterior teeth, whether with direct or indirect materials, and both materials will function well if placed and designed properly.
Nanohybrid composites can be used as the starting point for esthetic veneers, correcting minor rotations, closing diastemas, and repairing broken teeth, among other indications.
Patients with severe bruxism might warrant an indirect ceramic restoration with higher strength values.
Easy repairability is a future benefit. However, Burgess notes that repair strength of composite resin that has been in the mouth for some time is approximately 40% of the original value. This may be fine when repairing a low-stress margin area, but it is not ok for a marginal ridge.
Proper polishing and finishing to a submicron roughness level is critical for plaque resistance.
Finishing Up
Direct composite material characteristics are not the only factors contributing to enhanced polishability. New polisher instruments and shapes not only simplify one of the most time-consuming steps in direct anterior restorative cases, but they also contribute to procedure effectiveness for indirect restorations fabricated with newer ceramics.
Previously available ceramic finishers and polishers—which were originally intended for stackable feldspathic porcelain materials—weren’t producing quite the same luster on zirconia and lithium disilicate. They also were not able to withstand these significantly harder materials. Additionally, the more traditional, rigid polishers for ceramics and composites could potentially eliminate anatomy purposefully created in the restoration, and polishing occlusal anatomy with this armamentarium could be difficult, with points often wearing away quickly.
To resolve these issues, specific polishers for zirconia and lithium disilicate (eg, Dialite ZR for zirconia and Dialite LD for lithium disilicate, Brasseler USA, http://brasselerusa.com) have been introduced. Whereas these two-step systems quickly polish each restoration, any adjusting, cutting, or sprue removal is performed using a grinder (eg, LD Grinder), which is a rubberized epoxy stone that resists heat and minimizes the risk of microfracture.
“By essentially using the same composition as our classic system, but adjusting the binding matrix and diamond particle content, we were able to deliver two new unique systems to work with these two completely different materials—zirconia and lithium disilicate. Each system brings out the particular material’s unique qualities, while delivering an ultra-smooth surface,” explains Miranda Marchant, marketing manager, Rotary, Brasseler USA.
New flexible and versatile finger-like design polishers (eg, Dialite Feather Lite, Brasseler USA) that work well on all ceramics, including zirconia and lithium disilicate, are also options for further simplifying finishing and polishing protocol. Available in intra- and extraoral shapes, they adapt to restoration surfaces, such as the pits and fissures of occlusal anatomy, and are ideal as a final polishing step. An intraoral and composite only version (eg, Diacomp Feather Lite) can be used with all types of composite materials.
“These polishers for both ceramics and composites not only help to reduce polishing instruments, but also to restore a smooth enamel-like finish quickly, which is the ultimate desired outcome,” Marchant says. “Restorations that are finished and polished correctly have a greater potential for a longer life.”
Conclusion
Every patient has different priorities and expectations, and these factors drive material selection. Fortunately, there’s a lot of excitement from the standpoint of not only having better materials, but better ways for clinicians to be predictive about achieving the optimal outcomes for the patient, says Cranham.
“Ultimately, when we look at everything that translates into a successful direct composite or indirect all-ceramic restoration, it’s a balance of choosing the right material technology and utilizing the right clinical protocol for the indication to achieve success,” says Gaglio. “While there have been vast improvements to the physical properties of restorative materials, clinical technique remains one of the most important factors in the success or failure of the restoration.”
Functional Esthetics
Regardless of material advancements for indirect and direct restorations, a functional and stable occlusion remains the foundation of treatment success, and resolving the cause of occlusal concerns (ie, diagnosing the problem) drives the treatment decision process, not the choice of materials.
“Material choices can never resolve occlusal problems. Instead, they merely change the mode of failure,” explains John Kois, DMD, MSD, director of the Kois Center. “Even gold restorations have adverse outcomes from occlusal overload, but these failures (eg, cement fatigue/washout, restoration dislodgement, recurrent caries) do not involve the restoration itself, but rather the supporting tooth, which may actually be a worse consequence.”
Among the top three considerations when designing and establishing functional occlusal stability, Kois cites the following, noting that these principles are much easier to discuss than to actually implement:
1. The orthopedic position of the mandible
2. Equal simultaneous contact of the posterior teeth
3. An envelope of function without loading any of the teeth adversely
“I prefer to use direct restorative materials in the anterior when I’m resolving active functional issues, which enables me to create what I call training teeth to ensure that the envelope of function is managed properly,” Kois says. “If the patient still has occlusal concerns (eg, chipping, primary occlusal trauma), I can add material easily to these restorations with a traditional bonding protocol, or subtractively adjust the material with minimal consequences.”
Additionally, nanohybrid materials can be beneficial as long-term provisional restorations when patients present with a badly broken down system that requires opening of their bite prior to a full-mouth reconstruction, explains John Cranham, DDS.
“The nanohybrid materials can be placed on the occlusal surfaces of the posterior teeth to establish the ideal centric stops and posterior morphology, allowing us to be more conservative in creating ideal occlusion,” Cranham says. “Over a period of several years, those restorations can be “swapped out” for more permanent indirect restorations, which allows the patient to receive ideal treatment, without having to do it all at once.”
Assuming that occlusal problems have been resolved, different material choices can then make the difference in terms of survival probability of the restoration itself. Many of the direct and indirect options available today involve the initial status of the tooth, the environment in which the restoration is placed, esthetic concerns, fabrication modalities, and the inherent physical properties of the materials, Kois says.
When it comes to functional load, strength and fabrication modality do matter. Milled and pressed ceramics offer advantages over traditional hand stacked materials, which have more potential for human error and for complications, Kois elaborates. The material advances for indirect restorative materials that help address functional concerns (not occlusal disorders) are primarily improved strength and the opportunity to use monolithic materials (eg, lithium disilicate and zirconia).
“These materials significantly reduce some of the adverse functional events we encounter (eg, chipping) by eliminating an additional weaker and problematic interface,” Kois says. “In addition, they are strong enough even when relatively thin, providing an opportunity to preserve more tooth structure and create an ultra-conservative tooth preparation.”
