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Current Thinking on Composites & Adhesion
Dentists know that newer does not always mean better. A hard look at long-term data and operator experience over time are key ways to assess what materials and techniques are truly worth adopting. Inside Dentistry gathered expert clinicians, researchers, and manufacturers to discuss what we know about composites and adhesion now, as well as what trends to expect for the future.
Gary Alex, DMD, AAACD
“For the new “universal” adhesives, in the case of placing indirect restorations, some manufacturers give the option of curing or not curing the adhesive once it is placed on the tooth and the volatiles evaporated. In my opinion, the adhesive should always be light polymerized for both direct and indirect restorations. Film thickness should not be a problem if the adhesive was properly placed, dried, and light cured."
Dr. Alex is an accredited member of the American Academy of Cosmetic Dentistry and practices in Huntington, New York.
Gerard Kugel, DMD, MS, PhD
“ If you are happy with the bonding agent you are using, then don’t switch. Don’t assume that the next generation of the system you are using now will be an improvement. We have found in many cases the older product is significantly better than the new. You can search PubMed or visit the AADR/IADR website and search any abstracts with data related to the new product. At the end of the day, the only real test will be if the new product works in your hands.
Dr. Kugel is associate dean for research at the Tufts University School of Dental Medicine and practices in Boston, Massachusetts.
Robert C. Margeas, DDS, FAGD
“For me to change my adhesive protocol, I have to have the utmost confidence in the manufacturer and the people who are doing the research. I depend on clinical studies and correspondence with my colleagues from major universities for their input. I have had such excellent results with the etch-and-rinse systems that I have not changed to the all-in-one self-etch materials. I do use them, but if I have enamel, I etch it even if the manufacturer says it is not necessary."
Dr. Margeas is an adjunct professor in the department of operative dentistry at the University of Iowa College of Dentistry and practices in Des Moines, Iowa.
INSIDE DENTISTRY (ID): Is the new generation of bonding systems significantly better or just easier to use?
DR. KUGEL: The new self-etching bonding agents are easier to use when used as one-step systems. Easier for the dentist doesn’t always translate into better for the patient. In our studies, we have noted that many of the new bonding systems will sacrifice enamel bond to make them more user friendly. They do well on dentin, but we sacrifice our enamel bonds unless we incorporate a selective etch. This idea simply means doing abbreviated enamel etch prior to using our self-etching product. We have found this to be very beneficial. I might add this requires little additional time.
DR. MARGEAS: The newer generation of adhesives are getting much easier to use, but that does not mean they are getting better in bond strength. Bond strength to dentin is quite good, but to unetched, uncut enamel, the bond strengths are not as strong as etching enamel. The manufacturers are gearing their materials to a one-bottle, multi-use material. The materials can be used in three different ways. A self-etch, selective-etch, or total-etch technique can be employed depending on the clinical situation. Some of the one-bottle systems still require a separate dual-cure activator to be mixed with the single bottle to allow optimum adhesion. This is due to the pH of some of the newer generation adhesives. The goal of the one-bottle systems is to provide a hydrophilic material on priming that becomes hydrophobic on polymerization. This will allow the hybrid layer to prevent water from penetrating through to the composite.
Some of the self-etch systems offer two separate bottles—a primer and a separate adhesive. These still are not acidic enough to actually etch the enamel as well as phosphoric acid. There is no doubt the materials are getting much better and easier to use, but most long-term bond strength studies still favor the three-step systems of total etch-and-rinse. I do feel we will soon be able to use a one-bottle system for all adhesive situations, but I am not 100% committed.
DR. ALEX: If you asked me that question a year ago, my answer would be they are just simpler to use and quite frankly not as good as many of the earlier systems. That would include most of the so-called 7th generation systems that, while easy to use, I am not a particular fan of. However, there are some new systems being marketed as “universal” adhesives that have very innovative chemistries, the potential to bond to a variety of substrates, and the ability to be used in total-, self-, and selective-etch modes, that do have my attention. I have seen some impressive in vitro studies for some systems including, at least for one system (All-Bond Universal®, Bisco, Inc.), stable bond strength values after 1-year water storage (most systems show significant decreases after long-term water storage). While I think it’s too early to say these systems are “better,” they are certainly easier to use then many earlier systems and could represent the next evolution in adhesive dentistry (even if they turn out to be “at least as good as” earlier systems). Independent short- and long-term clinical studies are needed to objectively evaluate these new systems.
ID: What are the clinical indications for the use of glass ionomers, and what liners, if any, should be used with composites?
DR. MARGEAS: True glass ionomers are chemical cured and are somewhat difficult to handle. The resin-modified glass ionomers (RMGIs) can be light cured. I use some true glass ionomers for restoration of root caries and pediatric teeth. The RMGIs can be used for noncarious cervical lesions with great success. The 5-year survival rate in many clinical studies is as good as composite resins. If I have a deep restoration that is close to the nerve, I prefer to use an RMGI liner. Most of my cementable crowns are seated with RMGI cements. Some of the newer materials allow you to light cure these materials for ease of clean-up.
DR. KUGEL: RMGIs are a good choice as a liner under a posterior composite especially in a high-caries-risk patient. RMGIs chemically bond to dentin and are placed prior to employing a total-etch technique. This helps to seal the dentin and could decrease sensitivity caused by improper bonding technique. They have decreased shrinkage and their coefficient of thermal expansion mimics tooth structure. This could result in a better seal. The introduction of the new “bioactive” liners has gotten attention recently. Some of these new materials are a combination of RMGI and resin with bio-available calcium, phosphate, and fluoride. These could prove to be a significant addition to our liner options.
DR. ALEX: There is no question that many clinicians have had good success using glass ionomers (open or closed sandwich technique) as basically a dentin replacement layer prior to placing composite restorations. I personally am still a fan of using RMGI liners such as VitreBond™ (3M ESPE) and Fuji Lining™ LC (GC America) under moderate to large direct composite restorations. RMGI liners have many positive attributes, including that they are self-adhering to tooth structure, are simple to mix and place, set on command (self- and light cure), release high sustained levels of fluoride, have significant antimicrobial properties, evidence very low solubility, and exhibit a favorable modulus of elasticity and coefficient of thermal expansion and contraction (similar to that of dentin). I also like to use RMGI liners to fill in voids, irregularities, and undercuts when necessary in crown and other indirect restoration preparations.
ID: Do low-stress composite materials provide a true clinical benefit?
DR. KUGEL: Shrinkage stress development is a multi-factorial phenomenon involving a contribution of modulus, volumetric shrinkage, reaction kinetics, and cavity dimensions. Many of the restorative techniques aiming at reducing stress have been shown to limit applicability, and their efficiency varies depending upon the materials used.
The low-shrinkage composite has demonstrated lower contraction stress than microhybrid and nano-filled composite; however, the first generation of these materials has met with limited clinical success. Ideally, non-shrinking resins would represent the ultimate solution to overcome polymerization contraction and stress-related issues, but the composite material must still be easy to handle, polish, and not require a special bonding agent.
DR. ALEX: This is an interesting question. Indeed, dentists are bombarded with marketing campaigns promoting “low shrinkage composites” and there are a number of composites that demonstrate less than 2% volumetric polymerization shrinkage at this point. I think it important for clinicians to understand that low shrinkage does not necessarily mean low stress. Photo polymerization is complex and other factors, such as as modulus of elasticity, rate of polymerization and polymerization kinetics, degree of conversion, initiator chemistry, gel point, and type of filler and monomer, all have an effect on stress development and intensity. It is very possible to have a composite that may shrink less than another but still induce more stress because of the factors mentioned above. Dentists also have to be very wary of claims made by some manufactures in terms of “low stress.” It is very easy to make any composite “low stress”—just don’t cure it very well. The degree of polymerization conversion will have a direct effect on polymerization shrinkage stress. So when looking at numbers relating to polymerization shrinkage stress, it is also important to look at the degree of polymerization conversion. One of the reasons that techniques like “pulse curing” demonstrate less stress at the adhesive interface is that the final conversion rate tends to be lower than a composite that is polymerized by continuous light delivery.1 The “Holy Grail” of composites would be one that is self-adhering, biocompatible, and bioactive, has excellent physical and esthetic properties, can be cured very quickly in thick layers with a high degree of conversion (at both top and bottom), and have very low or no polymerization shrinkage stress. We are clearly not there yet but are getting closer. My advice is to be cautious but open-minded regarding many of the newer materials and techniques (such as bulk fill) now being advocated. It is important to read the literature, take continuing education programs, talk to colleagues, examine your own failures and successes, and become as knowledgeable as you can in the constantly evolving field of adhesive and composite dentistry.
Harald O. Heymann, DDS, MEd
“Studies demonstrate that no difference exists in sensitivity between the etch-and-rinse and self-etch adhesives if they are properly placed. Because self-etch primers do not typically open the dentinal tubules when applied to dentin, low sensitivity may be easier to achieve with self-etch adhesives."
Dr. Heymann is a professor in the department of operative dentistry at the University of North Carolina School of Dentistry in Chapel Hill, North Carolina.
Jorge Perdigao, DMD, MS, PhD
“Most adhesives are more effective if applied dynamically with a scrubbing motion, rather than leaving the adhesive on the dentin surface. In fact, some dental manufacturers recommend active application for their dental adhesives. An active application may result in better dentin hybridization, improving dentin sealing.
Dr. Perdigao is a professor in the department of restorative sciences at the University of Minnesota School of Dentistry in Minneapolis, Minnesota.
Byoung I. Suh, PhD
“The application of a calcium silicate liner such as TheraCal® LC on deep dentin can eliminate postoperative sensitivity due to its ability to seal dentin and act as a thermal insulator. TheraCal LC’s high pH and its inherent antimicrobial properties eliminate bacteria and may add to the observed decrease in sensitivity when used.
Dr. Suh is the founder and president of Bisco Dental Products, Inc. With a background in research and chemistry, his focus at Bisco is on dental materials research and product development.
ID: Prior to bonding, should an anti-microbial agent be used on the dentin, and does that vary by different generations of bonding systems?
DR. HEYMANN: For years, it has become accepted practice among many dentists to apply some type of antimicrobial agent prior to placing a direct resin-bonded restoration. This approach has been based in part on work by Brännström, whose recommendations for cavity disinfection with benzalkonium chloride were part of his regimen for dentin densitization.2 By disinfecting the cavity preparation, release of noxious bacterial endotoxins, which reportedly can contribute to tooth sensitivity, are negated.
Although this theoretical approach likely has clinical merit, it is largely based on empiricism. Little direct clinical data exist to support the use of antimicrobial agents for disinfection of cavity preparations purely to kill remaining bacteria from dental decay. In fact, clinical studies exist that demonstrate that if the final restoration is well-sealed, remaining bacteria become inactive and any potential caries activity is arrested, owing to deprivation of bacterial nutrient supply.3 Nonetheless, the use of most disinfecting agents under bonded restorations may have some beneficial value, and most do not adversely affect bonding.
More recently, the use of chlorhexidine (CHX) has been advocated for cavity treatment prior to bonded resin composite restorations because of its potential to negate the potentially deleterious effects of MMPs (matrix metalloproteinases) on collagen.4,5 Treatment of acid-etched dentin with a 30 to 60 second application of 2% CHX appears to stabilize the hybrid layer and inhibit MMP activity, thereby better preserving the resin-dentin bond. However, these results are based only on short-term data up to 14 months, and it remains to be seen if CHX improves long-term durability of these bonds.
DR. PERDIGAO: There is not enough evidence to back the use of antimicrobial agents prior to bonding. Below is a summary of the existing evidence.
Phosphoric acid gels have intrinsic antibacterial properties, not only from their extremely low pH (0.0 to 0.6), but also due to their osmotic characteristics.6,7 A study8 tested the antibacterial inhibition produced by eight commercial phosphoric acid etchants against bacteria commonly found in the oral cavity: Streptococcus mutans, Streptococcus salivarius, and Actinobacillis actinomycetocomitants. All etchants resulted in antimicrobial activity, which raised the question of whether antimicrobial agents are necessary in dentin adhesion.
Phosphoric acid gels used in dentistry are hypertonic—the osmolarity of 37% phosphoric acid is 6070 mOsm/kg compared with isotonic saline at 290 mOsm/kg.7 S mutans, for example, does not have osmotic tolerance.9
Glass-ionomer cements (GICs), widely used as bases or liners, also have antimicrobial properties as a result of both low pH and fluoride release.10-12 Therefore, the use of an antimicrobial agent prior to placing a GIC based or liner would be redundant. Vitrebond (3M ESPE), a resin-modified GIC, has strong antibacterial properties against S mutans, Streptococcus sobrinus, and Actinomyces viscosus.13
CHX has been used as an antibacterial agent in restorative dentistry for more than 30 years. Tubulicid Red Label (Dental Therapeutics AB) was one of the first liners to include CHX.14 Aqueous solutions of CHX, such as Cavity Cleanser™ (Bisco Inc.) and Consepsis® (Ultradent Products, Inc.), have also been used since the 1990s as antibacterial agents prior to bonding. More recently, CHX has been used integrated into the composition of phosphoric acid etchants and dental adhesives.15,16 CHX digluconate (2% aqueous solution) is currently used as an inhibitor of dentin MMPs to prevent the degradation of the resin-dentin interface. Although studies have demonstrated the potential of CHX to stabilize the resin-dentin interface in vitro, clinical trials are not abundant. A recent 18-month clinical study showed no difference in clinical behavior of two adhesives, a self-etch and an etch-and-rinse adhesive, with and without the application of CHX prior to bonding.17
Other antimicrobial agents, such as the quaternary ammonium methacrylate 12-methacryloyloxydodecylpyridinium bromide (MDPB),18 are currently used in the composition of dentin adhesives. Clearfil™ Protect Bond (Kuraray Noritake Dental, Inc.) was the first commercial dentin adhesive to incorporate MDPB in its composition. This adhesive is currently available as Clearfil™ SE Protect.
DR. SUH: Yes, dentin should always be cleaned prior to bonding. Eliminating as many microorganisms as possible allows the tooth a fresh start to recovery and may prolong the restoration.
When using a total-etch (etch-and-rinse) adhesive, applying an etchant with BAC benzalkonium chloride (BAC), for example, would eliminate the need for a separate antimicrobial agent. BAC has been shown in vitro to kill bacteria and inhibit MMP to preserve the dentin bonded interface without compromising immediate bond strengths.
When using a self-etch adhesive, application of an antimicrobial such as 2% CHX or glutaraldehyde-containing solutions will disinfect the dentin, and may also inhibit MMPs, which is still yet to be proven in vivo. MMPs are inactive enzymes in dentin that are activated by acid, which may degrade the hybrid layer over time. MMPs are inhibited by endogenous inhibitors, such as 2% CHX or BAC.
Of more importance is selecting a hydrophobic adhesive that minimizes water content and is less acidic (pH > 3). Many of the current self-etch dentin adhesives are too hydrophilic and absorb too much water, which will plasticize and hydrolyze faster, and ultimately produce a less durable bond.
ID: The all-in-one adhesive that can be used for everything: does it exist?
DR. PERDIGAO: No, it does not.
One-bottle self-etch adhesives contain water that unables them to ionize and slightly etch dentin. One-step self-etch adhesives result in water permeability in dentin,19,20 as well as osmotic blistering in enamel, which may affect clinical durability.21 Residual water has been associated with degradation of collagen and resin within the resin-dentin interface.22,23
All-in-one adhesives are not compatible with chemically-cured composite resin materials,24 due to the residual acidity on the surface of the adhesive after curing. Therefore, their use with buildup composite materials and resin cements is limited to light-activated resin materials.
All-in-one adhesives perform better if used as two-step self-etch adhesives. In fact, when all-in-one adhesives are used as two-step self-etch adhesives their clinical performance improves significantly.25 The application of an extra coat of a hydrophobic bonding resin over the cured all-in-one adhesive improved the 18-month clinical retention rates of two all-in-one adhesives in noncarious class V lesions.25
DR. HEYMANN: Maybe, but only time will tell. A number of new self-etch adhesives have been introduced, some of which are very “universal” in their ability to bond to multiple substrates, including enamel, dentin, and some even to various ceramics. However, most of these new “all-in-one” adhesive systems are so recent that clinical trials that are of sufficient duration to adequately validate their efficacy long-term simply do not exist. And, with most, it is still very important that they be used in conjunction with a total-etch or selective etch approach to ensure optimal bonding to the most important substrate of all: enamel. With very few exceptions, even new generation self-etch adhesives simply will not bond as well to enamel by themselves, especially uncut enamel, as will more traditional etch-and-rinse systems that remain the “gold standards.”
Unfortunately, many clinicians and more importantly, those in the dental industry, have lost sight of the most significant determinant of success with resin-bonded restorations: the bond to enamel. Regardless of the adhesive type or generation employed, ultimately clinical success with resin-bonded restorations is determined primarily by the quality of the bond to enamel, not to dentin.26-29 Bonds to enamel are essential; bonds to dentin are secondary in importance. The problem is that self-etch adhesives by their very nature are better suited for bonding to dentin than enamel. In my opinion, the primary reason that self-etch adhesives sell so well and are so popular is the fact that they are simple to use and do not typically open the dentinal tubules when applied to dentin, so low sensitivity is easier to achieve for most general dentists. I get it. But this attribute comes at a very significant clinical cost if these materials are used solely as self-etching adhesives: the absence of optimal bonding to enamel.
New improved formulations of self-etch adhesives do demonstrate significant improvements over past generations. Most are less subject to hydrolysis, are simpler to use, and possess greater versatility in bonding applications. However, virtually all (except perhaps OptiBond™ XTR from Kerr, which has demonstrated impressive bonds to enamel in early studies30) still rely upon supplemental acid etching with phosphoric acid to ensure optimal bonds to enamel. Only time and well conducted clinical trials will reveal the extent to which these new generation adhesives truly represent “all-in-one” adhesives.
DR. SUH: Yes, the new “universal” category of adhesives (not to be confused with previous hydrophilic seventh-generation all-in-one adhesives) can be used for everything, including:
• as a single-layer adhesive (hydrophobic enough).
• any etching technique: total-etch, self- etch, or selective-etch modes.
• both direct and indirect clinical procedures using light-cure, dual-cure, or self-cure materials (without the need for a separate self-cure activator).
• bonding to indirect substrates (low film thickness < 10 µm).
However, not all new “universal” adhesives are created equal. Some are more hydrophobic (optimized water content), or require a second hydrophobic resin layer. Also, some require a separate self-cure activator in order to be used with dual-cure/self-cure restorative materials. In addition, some contain silane, claiming to be effective as a coupling agent, but research has shown that silane is not effective because bis-GMA and other resins in the formula inhibit the condensation reaction. The condensation reaction occurs between the silanol (-Si-OH-) and ceramic substrate’s –OH group, slowly liberating water molecules to form stable siloxane (-Si-O-Si-) bonds. The liberation of water molecules is essential for the condensation reaction to continue, which can be inhibited by the presence of extra resin, which slows or prevents water evaporation (Le Chatelier’s principle).
Peter Burtscher, PhD
“Light-cured composites saw a lot of improvements over the past 30 years. The survival rate in the patient mouth increased significantly. Physical and the esthetic properties reached a very high acceptance level. One of the biggest drawbacks of light-cured composites is the limited increment thickness. The introduction of bulk-fill materials, with a recommended increment thickness of 4 to 5 mm, is a real step forward.
Dr. Burtscher is director of R&D/organic chemistry for Ivoclar Vivadent.
Marion Wanner, PhD
Dr. Wanner is senior research associate for Ivoclar Vivadent.
Brad Craig, PhD
“The incorporation of nanotechnology into dental composites over the past decade has allowed for esthetics coupled with strength and wear characteristics that were previously mutually exclusive. Well-designed composite materials today, if placed properly with a good adhesive and clinical technique and fully cured, are capable of lasting 20+ years. Part of the challenge in defining the “ideal” composite material is that each practitioner has his
or her own preferences.
Dr. Craig is lead product development specialist at 3M ESPE.
Bernard Koltisko, PhD
“If we could take today’s esthetic composites and eliminate the need for adhesive bonding, improve moisture tolerance during placement, and eliminate polymerization stress and the need for light curing, we would certainly have materials that could be more durable and consistent in the hands of all clinicians and restorative challenges. Any one of these desires poses significant challenges in product development, so
it is clear that there is still a lot of work ahead to create the “ideal” composite.
Dr. Koltisko is director of research and development at DENTSPLY Caulk.
ID: What is the future for bioactive composites?
DR. BURTSCHER: Natural teeth are mineralized with apatite, a mineral containing calcium, phosphate, hydroxyl, and fluoride ions. Calcium phosphate–based fillers are capable to leach calcium and phosphate ions and thus may support remineralization and formation of secondary dentine. The idea to incorporate such fillers into composites to add remineralizing and a “bioactive” feature is not a new one. For example, there was Degufil Mineral from Degussa containing calcium phosphate fillers, but acceptance by the market was quite low. For the time being, most of the state-of-the-art composites do not contain calcium phosphate–based fillers.
Typically composites contain silica-based fillers with a refractive index of 1.45 to 1.55 and a corresponding polymer matrix with an adjusted refractive index to ensure good optical properties, especially translucency. Calcium phosphate and apatite have a refractive index of 1.65 and 1.63, respectively. By adding these fillers to a regular composite, it will become very opaque with poor esthetics. The way around to maintain sufficient esthetics would be to utilize such filler in nano scale. Nano-fillers keep their optical properties only if they are perfectly deagglomerated, however, which is a big technical challenge. Additionally, leaching of calcium and phosphate ions supporting the formation of secondary tooth substrate typically weakens the structure of the composite and lowers its physical properties.
Therefore, the overall benefit of calcium phosphate–based fillers in regular composites for the purpose of remineralizing effects is doubtful. The benefits of calcium phosphate might be more attractive in liners or temporary materials, where the optical properties and the strength of the material are of less importance.
DR. CRAIG: If you follow the literature, there has been a significant increase in the number of companies and research institutions looking at various materials, ranging from bioglass or calcium phosphate type materials that potentially remineralize on one end of the spectrum to stem cell research and complete regrowth of tissue on the other end. There are a number of products on the market today in the preventive areas that are already incorporating the “remineralizing” types of compounds. The real challenge for most of these “bioactive” materials going forward is regulatory in nature, as anything that interacts with the body needs a tremendous amount of data (and associated testing and cost) to commercialize, as it can be considered a drug by many regulatory bodies around the world as soon as you start talking about physiologic interactions. I think that government regulation of the field will probably be the limiting factor on what materials are introduced, and at what rate this technology and implementation advances, and how the materials ultimately end up being utilized.
DR. KOLTISKO: We have seen an increasing trend in the number of research papers and patents related to the use of bioactive materials in restorative application. While important, this work is at a very early stage. As an industry, we have spent significant efforts making materials which are strong and durable, and preferably unaffected by the oral environment. We are now asking composite materials to interact with the oral environment to promote rebuilding or better integration with tooth structure. Incorporation of these materials into hydrophobic resin systems lends significant challenges to long-term release of ionic species required for the bioactivity. Conversely, this interaction could lead to reduction in overall properties of the composite material over time. Glass ionomer and related restoratives would be more amenable to these mechanisms, but these materials do not have the overall mechanical performance required for long-term durability. As a result, a significant level of development of both the composite matrix and bioactive components is required to make bioactive composites a reality.
ID: What long-term clinical data are available regarding the use of bulk-fill composites?
DR. CRAIG: Bulk-fill materials have been around in one form or another for a fairly extended period of time (10-15 years). Many of the early generation of materials introduced over that time focused on polymerization shrinkage, whereas many of them entering the market today focus more on stress, or force on the tooth, which is probably a good paradigm shift. There is a bit of a misunderstanding in the larger dental community on what is really important (shrinkage or stress), and it is the stress, or force on the tooth, not the shrinkage, which is important. Two materials with the same shrinkage, for instance, can have vastly different stress profiles. Some of the early bulk fills were fairly low-shrinkage but high-stress materials. The amount of clinical data on these materials that I’ve personally seen has been somewhat limited, as the adoption of the early “bulk-fill” materials was not high, for a number of reasons (eg, “real” cure depth limitations, handling, stresses on the tooth). Thus there’s not a huge volume of clinical data to draw from. The newer “low-stress” materials on the market have only been available for a very few years, so the clinical data on those are obviously even more limited. Some of the newer bulk fill materials being used today are similar in physical properties to some older RMGI materials, which also could be used in a “sandwich technique,” with a universal composite as a capping layer, and that might be a good place to draw a clinical corollary.
DR. KOLTISKO: There have been several “bulk-fill” materials introduced into the dental market over the last few years. Our recent literature review uncovered only two 3 year clinical studies for these materials. The two studies were focused on DENTSPLY Caulk’s SureFil® SDR® composite. A 95% success rate was achieved for 170 restorations placed over 3 years. The clinical performance was comparable to conventional incrementally placed composites available in the market.
DR. WANNER: Even with bulk filling of medium-sized cavities (up to 5 mm) with a composite (Prodigy condensable) with a volumetric shrinkage of about 2%, the clinical results that could be achieved after 3 years were comparable to those where incremental technique was applied.31
In a clinical study where QuiXfil™ (DENTSPLY International) was compared with Tetric® Ceram (Ivoclar Vivadent; predecessor of Tetric EvoCeram®), after 4 years the researchers observed complete failures in 4 of 46 (9%) restorations for Quixfil and 1 of 50 (2%) for Tetric Ceram. The failures for Quixfil were fractures of the tooth (2) and the composite (1) as well as postoperative sensitivities.32
From the previous studies available, it can be summarized that concerning the clinical criteria such as marginal staining and marginal integrity as well as secondary caries and necessity of replacement, those restorations which were filled with bigger increments or bulk had a slightly worse performance compared with those being filled in small increments. However, the differences were not dramatic. But is has to be mentioned that the database is still small and often it is not really clear whether the filling of the cavity was a real bulk fill even if the cavity depth was only 4 to 5 mm.
In an internal study with Tetric EvoCeram Bulk Fill, 35 posterior restorations (11 Class I and 24 Class II) with an average cavity depth of 4 mm were placed by 3 dentists. At baseline there were no postoperative complaints. Anatomical form, esthetic appearance, surface discoloration, material fracture, tooth integrity, and patient satisfaction were classified as excellent or good in all cases at baseline. Subsequent recalls are planned in 12-month intervals.
COMPOSITE & ADHESION CE RESOURCES
Resin-Based Composite as a Direct Esthetic Restorative Material: dentalaegis.com/go/id838
Self-Etch and Etch-and-Rinse Adhesive Systems in Clinical Dentistry: dentalaegis.com/go/id839
Flowable Composite Resins: Do They Decrease Microleakage and Shrinkage Stress?: dentalaegis.com/go/id840
Posterior Composites: Material Selection: dentalaegis.com/go/id841
Direct Resins: Evolution, Applications, and Techniques: dentalaegis.com/go/id842
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