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SEPEMBER 2016 • V3 • N51 eBook CE Continuing Dental Education

A Review of Direct Restorations, Their Applications, and Possibilities

Todd C. Snyder, DDS

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of Direct CDEWorld eBooks and A Review of Direct Restorations, Their Applications, and Possibilities are published by Den- tal Learning Systems, LLC. Copyright ©2016 by Dental Learning Systems, LLC. All Restorations, rights reserved under United States, International and Pan-American Copyright Conventions. No part of this pub- Their Applications, and Possibilities lication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without prior written permission from the publisher. PHOTOCOPY PERMISSIONS POLICY: This publication­ is registered with Copyright Clearance Center (CCC), Inc., About the Author 222 Rosewood Drive, Danvers, MA 01923. Permission is granted for photo­copying of specified articles provided the Todd C. Snyder, DDS base fee is paid directly to CCC. Dr. Snyder has been on the faculty at University of The views and opinions expressed in the articles appear- California Los Angeles in the Center for Esthetic ing in this publication are those of the author(s) and do not necessarily reflect the views or opinions of the editors, the Dentistry and is currently on the faculty at Esthetic editorial board, or the publisher. As a matter of policy, the Professionals, Tarzana, California. editors, the editorial board, the publisher, and the university affiliate do not endorse any products, medical techniques, or diagnoses, and publication of any material in this journal DISCLOSURE: The author had no disclosures to report. should not be construed as such an endorsement. WARNING: Reading an article in CDE- World and A Review of Direct Restorations, Their Applications, and Possibilities does not nec- essarily qualify you to integrate new techniques or procedures into your practice. Dental Learning Systems, LLC expects its readers to rely on their judgment regarding their clinical expertise and rec- ommends further education when necessary before trying to implement any new procedure. Printed in the U.S.A.

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A Review of Direct Restorations, Their Applications, and Possibilities Todd C. Snyder, DDS

ABSTRACT t has been said that, “you can never experience progress; you Growing esthetic demands from can only record it.” In relation to the dental profession and the patients and disproportional fear Imaterials that clinicians use on an almost-daily basis, it is quite over in fillings interesting to reflect on how tooth-colored direct restoratives have over the past 70 years has led to changed since the initial silicate cements were first introduced a significant increase in the use of in the United States in 1908. Since the introduction of adhesive composite resin for both anterior bonding in the late 1950s and the emergence of modern composites and posterior restorations. One of and visible light-curing around 1978, substantial progress has oc- the best attributes of composite curred in dentists’ ability to place tooth-colored direct restorative materials and improve upon adhesion, durability, polymerization resins that practitioners could 1 truly embrace was that they shrinkage, color, and microleakage. required little to no preparation, allowing for minimally invasive In 1947, tooth-colored direct restorations comprised of methyl procedures that would preserve methacrylate resins were introduced in the United States. Composite tooth structure and offer natural- resins, developed by Bowen in 1962, marked a dramatic decrease in looking results to their patients. the use of silicate cements and acrylic resins. In fact, approximately 2 years after composite resins were introduced, the use of silicate This article will review the class 2 of direct composite materials, cements and acrylic resins essentially came to an end. including indications for their clinical application. In the 1970s, the first acrylic resin replacement was introduced to the dental profession: composites.3 The mixing problems that had LEARNING OBJECTIVES plagued practices near and far seemed to become all but a memory as polymerization via electromagnetic radiation was brought into • Review the history and virtually every operatory. Unfortunately, this new material had evolution of tooth-colored direct its own issues: The particles were far too large, the resins were restorative materials. rather difficult to polish, and even though it presented patients with • Identify the characteristics a much-desired tooth-colored restoration, only four shades were of microfilled resins, hybrid available. The acid-etch techniques also took their toll on remaining composites, and nanofilled tooth structure, necessitating eventual endodontic therapy. composites. However, composite filling materials did provide new and excit- • Describe the appropriate ing esthetic results the likes of which dentistry had never seen, clinical applications for each of but with the new materials came new challenges; less understood the materials discussed. were incremental layering and material shrinkage.3 • Discuss the future development possibilities for direct MICROFILLED RESINS restoratives. Microfilled resins came into use in the late 1970s and early 1980s.

VOLUME 3 • NUMBER 51 CDEWORLD.COM 3 Filled with 35% to 50% pre-polymerized, 0.02-µm 1- μm.2 These composites demonstrate good to 0.04-µm silicone-dioxide particles, microfilled handling characteristics and initial high polish- composites demonstrated high polishability, stain ability; however, they cannot maintain gloss due resistance, and enamel-like translucency.2 These to the large particle conglomerates being plucked restorations provided some of the lowest wear of out of the resin matrix.2 Therefore, manufac- any composite resin material to date. Indicated turers developed microhybrid composite resins for restoring anterior teeth and cervical abfrac- with particle sizes reduced to 0.04 µm to 1 µm, tions, microfilled composites still can rival any making handling and polishing simpler.2 The composite currently used for anterior esthetics. strength of hybrid composites allows for their They are not, however, used in heavy stress- use in both the posterior and anterior regions as bearing restorations because they are prone to a universal composite.2 bulk fracture and marginal chipping.2 Microfills do demonstrate high compressive strength and NANOHYBRID COMPOSITES excellent wear characteristics. However, their Today’s nanohybrid composite resins produce higher thermal expansion coefficients, greater highly esthetic, long-lasting restorations for water sorption, polymerization shrinkage, and many different indications.2 Microleakage and lower modules of elasticity, tensile strength, and fracture rate concerns have decreased signifi- fracture toughness made them less than ideal.2 cantly as the industry has gained greater under- standing of advanced layering techniques, bulk- COMPOMER COMPOSITES fill materials, low-stress materials, and modern Compomer composites were introduced in the early self-curing chemistries.5 In many cases, fewer 1990s as a hybrid combination of resin composite shades of composites are necessary, with sig- and glass-ionomer chemistry. Compomer contains nificantly improved chameleon effects offering poly-acid–modified monomers and fluoride-releas- exceptional esthetic outcomes, while enhanced ing silicate glasses. An acid-base reaction occurs particles promote excellent polishing, fin- as the compomer absorbs water after contact with ishing, and longevity.5 saliva, which facilitates cross-linking structure and fluoride release. Just like a composite, compomers Increasingly used for anterior and posterior required a bonding agent and could release fluoride restorations, composite resins have evolved con- like a glass ionomer but could not recharge their siderably.6 Modern nanohybrid composite resins fluoride ion content due to the resin component. demonstrate greater durability, better handling Furthermore, the amount of fluoride they were characteristics, less shrinkage, improved polish- able to release was only one-tenth of the amount ing, enhanced bond strengths, and highly esthet- released by glass ionomers. Compomers lacked ic outcomes.6,7 However, composite placement the same strength and durability of composites or remains technique-sensitive, and polymerization fluoride-releasing glass ionomers; hence, they were shrinkage and stress are still issues.6,7 not used for long.4 NANOFILLED COMPOSITES HYBRID COMPOSITES Nanofilled composites, consisting of nanomers Hybrid composites have a heterogeneous ag- (5-nm to 75-nm particles) and nanocluster ag- gregate of filler particles that are typically filled glomerate fillers (0.6 µm to 1.4 µm), are made up with 70% to 80% by weight with 0.04-μm and of zirconia/silica nanoparticles ranging from 5 1-μm to 5-μm filler particles. Hybrid compos- nm to 20 nm in size.2,3 A major positive esthetic ites typically have an average particle size of > feature of these materials is their outstanding

4 CDEWORLD.COM SEPTEMBER 2016 polishability and gloss retention.2,3 Their makeup Because shrinkage stress and the resulting enables them to withstand a higher load, which leakage and sensitivity that can develop remain allows the materials to be used in both the pos- major concerns, many manufacturers con- terior and anterior. Because of the smaller par- tinue to develop dental composites comprised ticles’ inability to reflect light, typically larger of nanoparticles and larger agglomerates that particles are added, improving the overall esthet- demonstrate lower polymerization shrinkage.8 ics of the material. Some additional products that manufacturers have been testing and are attempting to incor- RESEARCH AND DEVELOPMENT EFFORTS porate are spiroorthocarbonate, epoxy polyol, In more recent years, any modifications to compos- and siloxane-oxirane monomers.3 ite resins have been to improve their physical and mechanical properties.1 With a variety of shades, This new research led to such products as translucencies, effects, opacities, and innovative SureFil® SDR® flow (Dentsply Sirona, www. placement techniques, today’s composites allow dentsply.com), which was introduced in 2009. simple reproduction of the polychromatic and opti- This innovative material used a “polymeriza- cal properties of the natural dentition.2 tion modulator” in the resin that reduced stress build-up upon polymerization without a reduc- After more than 30 years of development, tion in the polymerization rate or conversion.9 during which most manufacturers were concen- The polymerization modulator in the resin cre- trating on filler particle sizes and filler content ates a more relaxed network and significantly by weight and volume, the research and devel- lowers the polymerization stress compared to opment departments of some companies began conventional resins. Furthermore, the unique looking at the chemistry of a tooth-colored resin chemistry allows for self-leveling and low direct restoration differently. In one example, stress for a dentin replacement flowable.9 GC America teamed up with DuPont to create a different chemistry for its resin composite A massive influx of bulk-fill flowable backbone, offering a unique carbon chain that composites gave rise to concerns over depth provided characteristics previously unseen. of polymerization, shrinkage rates, and com- The production of G-aenial™ Universal Flow pressive strengths along with microbubbles (GC America, www.gcamerica.com) marked and microleakage. Sonicfill™ (Kerr, www. the introduction of another new chemistry in kerrdental.com), because of its proprietary dentistry. delivery device, became the first light-cured composite that integrated rheologic filler par- Most manufacturers still ticles and ultrasonic technology. The rheologic concentrate on building their current traditional filler particles allow the highly filled com- systems, addressing polymerization shrinkage posite material to have its viscosity reduced by adding a bis-GMA/TEGDMA or bis-GMA/ by ultrasonic agitation, which is not possible UEDMA/TEGDMA monomer combination to with conventional particles. This allows the the organic matrix.3 For dentin replacement, material to be better able to adapt in deeper, bulk-fill, low-shrinkage flowable composites narrower preparation designs and require less were introduced as a result of heightened con- adaptation compared to traditional composite cerns over C-factor stress, which could induce chemistries. Many manufacturers followed microgaps and microleakage along the margins suit, looking to create light-cured bulk-fill of the restoration–tooth complex. direct resins. Decreasing stress is one of the

VOLUME 3 • NUMBER 51 CDEWORLD.COM 5 main drawbacks of placing large quantities of Thus, the conventional glass ionomers that resin as direct restorations; the other drawback have existed since 1968 and have undergone some is technique sensitivity with bonding to tooth chemistry modifications to allow them to be used structure. Having less stress on the bonding as standalone, bulk-fill direct restorative materi- agent could allow for higher levels of suc- als with indications to fill restorations Classes cessful long-term adhesion to tooth structure I through V are another viable option to offer provided the bond to tooth is durable and patients. The chief benefits of glass ionomers are long-lasting. that they are hydrophilic, they do not require a bonding agent, and they actually hypermineralize Long-term failure often occurs along the the dentin with which they come in contact.15 tooth margin and composite interface, typi- cally in the deepest areas and proximal box, Self-cure, bulk-fill glass ionomers allow for due to light-curing shrinkage stress and volu- decreased C-factor cusp deformation stress, po- metric shrinkage. This problem has prompted lymerization shrinkage, and sensitivity while at a resurgence of traditional bulk-fill, self-cure the same time removing the need for a bonding materials. Thus, without visible light-curing agent.16,17 There are many different brands of of the direct composite resins, manufacturers conventional glass ionomers on the market, and can substantially decrease composite shrink- continued research and development is helping age and stress. Bulk EZ™ (Danville Materials, improve their physical properties. For example, www.danvillematerials.com) and Fill Up!™ continued development over the past 15 years has (Coltene, www.coltene.com) are two examples brought about many changes with the chemistry of the many new similar resin technologies us- of the GC Fuji IX line of products (GC America). ing dual-cure materials. Both of these products The most recent restorative to be introduced is have the ability to be light-cured in addition to the EQUIA® Forte (GC America), which can be self-curing, although light-curing should not used as a conventional bulk-fill glass ionomer be performed until after the material has had with indications for use in Class I through V adequate time to self-cure. lesions as well as core buildups. Riva SC HV (SDI, www.sdi.com) is an example of a conven- Self-curing chemistries offer significant reduc- tional glass ionomer that provides the benefits tion in C-factor stress but they still have polymer- of chemically fusing to the tooth without the ization shrinkage, which can create microtears or need for a bonding agent, along with remineral- gaps if the technique and adhesion of the dentin izing tooth structure and working well in a moist bonding agent to the tooth is not strong enough environment. Many other companies also have to withstand the polymerization shrinkage. The conventional and resin-modified glass-ionomer development of dentin bonding agents has been technologies. The main drawback has previously another significant advancement. Many genera- been in the areas of strength and esthetics.18,19 tions of such agents have existed since their in- troduction in the late 1950s.10 Although markedly These glass ionomers have many valuable improved since their inception, bonding agents characteristics; not requiring a bonding agent may not be the best material to interact with the and providing potentially less microleakage than tooth structure in the long term, due either to a technique-sensitive resin chemistry in deep matrix metalloproteinases attacking the hybrid preparation designs is highly advantageous when zone or their hydrophilic nature offering limited restoring teeth.20-23 More development in this area durability and declining mechanical properties.11-14 of technology and/or fusing this technology with

6 CDEWORLD.COM SEPTEMBER 2016 other materials could prove beneficial because of composite offers the benefits of glass iono- the glass ionomers’ true adhesion to tooth struc- mers in a strong, durable, resin matrix. Like ture, their ability to bond to moist dentin and pro- glass ionomers, it chemically bonds to teeth, vide fluoride release, and having a coefficient of seals against bacterial microleakage, releases thermal expansion similar to dentin. Additionally, fluoride, is bioactive, and is more durable and they offer decreased gap formation and cusp defor- fracture-resistant than most conventional com- mation along with less technique sensitivity when posites. It releases and recharges with calcium, compared with resin technologies. phosphate, and fluoride ions.25-33

Knowing how effective glass ionomers can Manufacturers have developed increasingly be in helping to seal and restore a damaged innovative products by combining many of the tooth, many companies have incorporated some best characteristics in currently used materials. of the technology and characteristics into new Dental composites are most often made up of types of products. Shofu (www.shofu.com), for an inorganic matrix, an organic matrix, and a example, has integrated glass-ionomer technol- coupling agent, as discussed earlier. Some com- ogy into its Beautifil® product line, in which a panies have gone so far as to incorporate glass- proprietary surface pre-reacted glass (S-PRG) ionomer technology into their resins for added filler particle is used within the resin matrix. benefits that traditional composites cannot offer. This unique technology, which the manufacturer refers to as Giomer technology, releases six ions Another unique new concept for restoring (fluoride, sodium, strontium, aluminum, silicate, teeth has emerged. VOCO’s (www.voco.com) and borate) into the tooth. This S-PRG filler Ormocer® (Organically Modified CERamics) particle has been shown to inhibit plaque forma- technology, which was developed by the tion and possess significant acid-neutralization Fraunhofer Institute for Silicate Research and capabilities.24 first used in 1999, has seen the incorporation of nanohybrid technology along with continued Another product merges the physical proper- development of the Ormocer material, which has ties of a self-cured resin—strength, durability, resulted in a new universal nanohybrid for di- esthetics, and polishability—with glass-ion- rect restorations, Admira Fusion. Whereas most omer technology to eliminate the need for a composites use a resin chemistry, this product bonding agent while also offering the ability to uses silicon oxide as the main element making remineralize a tooth. ACTIVA™ BioACTIVE- up the chemistry. Nanofillers, glass ceramics, RESTORATIVE™ (Pulpdent, www.pulpdent. and the resin matrix are all comprised of sili- com) is a fusion of two different chemistries cate technology and free of any traditional resin in one bioactive product that helps strengthen monomers (ie, bis-GMA, TEGDMA, HEMA). a tooth and fight off and micro- Currently, conventional resin composites have leakage while still maintaining occlusion and initial shrinkage rates of approximately 2% to withstanding occlusal forces. ACTIVA is the 3%, but historically they have been as high as first bioactive composite with an ionic resin 5%. The Ormocer technology substantially re- matrix, a shock-absorbing resin component, duces the amount of shrinkage by up to 50% and bioactive fillers that mimic the physical and with only 1.25% by volume. Additionally, the chemical properties of natural teeth without the shrinkage stress is very low at only 3.87 MPa, addition of any bisphenol A (BPA), bis-GMA, which allows Admira Fusion to have very low and BPA derivatives. This highly esthetic shrinkage stress, minimizing the risk of C-factor

VOLUME 3 • NUMBER 51 CDEWORLD.COM 7 stresses. It also offers a high level of marginal 7. Puckett AD, Fitchie JG, Kirk PC, Gamblin J. Direct integrity.34 composite restorative materials. Dent Clin North Am. 2007;51(3):659-675. THE POTENTIAL FUTURE 8. Duarte S Jr, Botta AC, Phark JH, Sadan A. Selected me- OF THESE MATERIALS chanical and physical properties and clinical application of a New tooth-colored direct restorative materi- new low-shrinkage composite restoration. Quintessence Int. als continue to improve upon traditional resin 2009;40(8):631-638. technology as glass-ionomer components are incorporated and even new types of materials 9. Goodchild JH. Why use bulk-fill flowable composites? altogether are created. Conventional glass iono- Inside Dentistry. 2013;9(8):92-95. mers will undoubtedly continue to evolve and 10. Bowen RL, Marjenhoff WA. Development of an adhesive perhaps incorporate other technologies to pro- bonding system. Oper Dent. 1992;suppl 5:75-80. vide even better strength characteristics. Further 11. De Munck J, Van Landuyt K, Peumans M, et al. A critical levels of glass-ionomer technology may continue review of the durability of adhesion to tooth tissue: methods to be developed within current resin materials. and results. J Dent Res. 2005;84(2):118-132. Resin-free organically modified ceramic tech- 12. Tay FR, Pashley DH. Have dentin adhesives become too nology is an interesting category that is unique hydrophilic? J Can Dent Assoc. 2003;69(11):726-731. in the industry. 13. Hebling J, Pashley DH, Tjäderhane L, Tay FR. The path for future direct restorations is un- Chlorhexidine arrests subclinical degradation of dentin hybrid certain, but the profession can be sure that work layers in vivo. J Dent Res. 2005;84(8):741-746. will continue on the next big developments in 14. Pashley DH, Tay FR, Yiu C, et al. Collagen degrada- tooth-colored direct materials. tion by host-derived enzymes during aging. J Dent Res. 2004;83(3):216-221. REFERENCES 15. Khoroushi M, Keshani F. A review of glass-ionomers: 1. Minguez N, Ellacuria J, Soler JI, et al. Advances in the From conventional glass-ionomer to bioactive glass-ionomer. history of composite resins. J Hist Dent. 2003;51(3):103-105. Dent Res J. 2013:10(4);411-420. 2. Sensi LG, Strassler HE, Webley W. Direct composite resins. 16. Wilson AD. Glass-ionomer cement—origins, develop- Inside Dentistry. 2007;3(7):76-79. ment and future. Clin Mater. 1991;7(4):275-282. 3. Hervás-Garcia A, Martínez-Lozano MA, Cabanes- 17. Wilson AD. A hard decade’s work: steps in the invention of Vila J, et al. Composite resins. A review of the materials the glass-ionomer cement. J Dent Res. 1996;75(10):1723-1727. and clinical indications. Med Oral Patol Oral Cir Bucal. 18. Piwowarczyk A, Ottl P, Lauer HC, Büchler A. Laboratory 2006;11(2):E215-E220. strength of , compomers, and resin com- 4. Trachtenberg F, Maserejian NN, Soncini JA, et al. Does posites. J Prosthodont. 2002;11(2):86-91. fluoride in compomers prevent future caries in children? J 19. Gladys S, Van Meerbeek B, Lambrechts P, Vanherle G. Dent Res. 2009;88(3):276-279. Evaluation of esthetic parameters of resin-modified glass- 5. Fortin D, Vargas MA. The spectrum of composites: ionomer materials and a polyacid-modified resin composite new techniques and materials. J Am Dent Assoc. 2000;131 in Class V cervical lesions. Quintessence Int. 1999;30(9):607- suppl:26S-30S. 614. Erratum in: Quintessence Int. 1999;30(12):845. 6. Ritter AV. Direct resin-based composites: current recom- 20. Perry R, Kugel G, Duong T, Tran LT. Microleakage testing mendations for optimal clinical results. Compend Contin Educ in vitro using three different bases under composites [abstract]. Dent. 2005;26(7):481-490. J Dent Res. 2007;86(spec iss A): Abstract 366.

8 CDEWORLD.COM SEPTEMBER 2016 21. Basso M, Brambilla E, Benites MG, et al. Glassionomer 28. Garcia-Godoy F, Morrow B. Wear resistance of new cement for permanent dental restorations: a 48-months, multi- ACTIVA compared to other restorative materials [abstract]. centre, prospective clinical trial. Stoma Edu J. 2015;2(1):25-35. J Dent Res. 2015;94(spec iss A): Abstract 3522. 22. Peumans M, De Munck J, Mine A, Van Meerbeek B. 29. Garcia-Godoy F, Morrow B, Pameijer CH. Flexural Clinical effectiveness of contemporary adhesives for the res- strength and fatigue of new Activa RMGICs [abstract]. J Dent toration of non-carious cervical lesions. A systematic review. Res. 2014;93(spec iss A): Abstract 254. Dent Mater. 2014;30(10):1089-1103. 30. Chao W, Girn V, Harsono M, et al. Comparison of deflec- 23. Giray FE, Peker S, Durmus B, Kargül B. Microleakage of tion at break of four dental restorative materials [abstract]. J new glass ionomer restorative materials in permanent teeth. Dent Res. 2015;94(spec iss A): Abstract 2375. Eur J Paediatr Dent. 2014;15(2):122-126. 31. Cannavo M, Harsono M, Finkelman M, Kugel G. 24. Saku S, Kotake H, Scougall-Vilchis RJ, et al. Antibacterial Microleakage of dental bulk fill, conventional, and self- activity of composite resin with glass-ionomer filler particles. adhesive composites [abstract]. J Dent Res. 2014;93(spec iss Dent Mater J. 2010;29(2):193-198. A): Abstract 847. 25. Slowikowski L, John S, Finkelman M, et al. Fluoride ion 32. Girn V, Chao W, Harsono M, et al. Comparison of me- release and recharge over time in three restoratives [abstract]. chanical properties of dental restorative material [abstract]. J J Dent Res. 2014;93(spec iss A): Abstract 268. Dent Res. 2014;93(spec iss A): Abstract 1163. 26. Zmener O, Pameijer CH, Hernandez S. Resistance against 33. Bansal R. Wear of a calcium, phosphate and fluoride re- bacterial leakage of four luting agents used for cementation of leasing restorative material [abstract]. J Dent Res. 2015;94(spec complete cast crowns. Am J Dent. 2014;27(1):51-55. iss A): Abstract 3797. 27. Murali S, Epstein N, Perry R, Kugel G. Fluoride release of 34. Torres CRG. Clinical evaluation of class II pure bioactive restoratives with bonding agents [abstract]. J Dent ORMOCER and methacrylate composite restorations. Res. 2016;95(spec iss A): Abstract 368. University of São José dos Campos, Brasil. Report for VOCO. 2015.

VOLUME 3 • NUMBER 51 CDEWORLD.COM 9 Quiz TO TAKE THE QUIZ, VISIT CDE 2 CDE Credits CDEWORLD.COM/EBOOKS/CE/51 A Review of Direct Restorations, Their Applications, and Possibilities Todd C. Snyder, DDS

1.  Microfilled resins came into use in the late 1970s and 6. The “polymerization modulator” in resin creates early 1980s; microfilled composites demonstrated: a more relaxed network and significantly does what A. high polishability. B. stain resistance. compared to conventional resins? C. enamel-like translucency. D. All of the above A. Increases polishability B. Decreases polishability 2. Compomer composites were introduced in the early 1990s C. Lowers the polymerization stress as a hybrid combination of: D. Raises the polymerization stress A. resin composite and glass-ionomer chemistry. B. microfilled resins and silicate cement. 7. Rheologic filler particles allow highly filled C. acrylic resins and silicate cement. composite material to: D. acid etching with fluoride release. A. darken one shade on polymerization. 3. Hybrid composites cannot maintain gloss due to: B. lighten one shade on polymerization. A. residual trapped acid from the etching process leaching to C. chemically break down to smaller particles during the composite surface. light-curing. B. the large particle conglomerates being plucked out of the D. have its viscosity reduced by ultrasonic agitation. resin matrix. 8. Self-curing chemistries offer significant reduction in C. creation of an extra thick oxygen-inhibited layer after curing. C-factor stress but: D. formation of a very thin oxygen-inhibited layer after curing. A. they are very expensive. B. they still have polymerization shrinkage. 4. Nanofilled composites consist of: C. there is a dramatic increase in postoperative sensitivity. A. nanomers (5-nm to 75-nm particles) only. D. they require the temperature to remain constant while B. silicone dioxide particles. curing. C. nanomers (5-nm to 75-nm particles) and nanocluster agglomerate fillers (0.6 µm to 1.4 µm). 9. Self-cure, bulk-fill glass ionomers allow for decreased D. a heterogeneous aggregate of filler particles. C-factor cusp deformation stress, polymerization 5. Most dental composite manufacturers address shrinkage, and sensitivity while at the same time: polymerization shrinkage by adding a bis-GMA/TEGDMA A. removing the need for a bonding agent. or bis-GMA/UEDMA/TEGDMA monomer combination B. releasing sodium fluoride. to the: C. releasing calcium fluoride. A. inorganic matrix B. organic matrix. D. releasing strontium fluoride. C. resin filler. D. luting agent. 10. Glass ionomers have a coefficient of thermal expansion: A. similar to dentin. B. similar to enamel. C. much greater than enamel. D. much less than dentin.

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