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Identifiers: LCCN 2016035134 (print) | LCCN 2016035775 (ebook) | ISBN 9780867156683 (hardcover) | ISBN 9780867157482 | ISBN 9780867156683 (softcover)

Classification: LCC RK652.5 (print) | LCC RK652.5 (ebook) | NLM WU 190 | DDC 617.6/95--dc23

All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher.

The Light-Curing Unit: Evaluation and Usage (Courtesy of Richard Price, BDS, DDS, MS, PhD)

• Reline and Repair of Voids or Discrepancies in Acrylic Provisional Crowns Before Cementation

Maintaining Gingival Position After Connective Tissue Grafting Using the Tunneling Technique with Composite Buttons

Extra video content is available online. A thumbnail of the QR code is shown next to any case that has video content. Scan the QR code here to access this supplementary information. The full list of videos may also be found at www.quintpub.com/Flowables.

“The important thing is not to stop questioning. Curiosity has its own reason for existing… Never lose a holy curiosity.”

With these words, Albert Einstein encourages us to use our imagination and intuition to push the boundaries of the commonly accepted and create real progress.

For as long as I have known Douglas Terry, he has always followed that mantra, never satisfied with the status quo and continuously elevating dental care to new heights of clinical excellence.

This book presents such innovative concepts in a most comprehensive and invigorating manner. The incredible breadth of clinical applications of modern flowable composites, especially in combination with a novel injection technique, is demonstrated in such a compelling manner that it calls into question the validity of many “traditional” treatment concepts and materials.

While the existing evidence from a material science standpoint is convincing and supportive of the increased use of flowable composite materials in everyday clinical practice, the clinical simplicity, versatility, and longevity of the techniques described make them a true alternative to conventional protocols and restorative materials.

In addition to exceptional clinical documentation, one of the reasons Douglas’s books stand out in the dental literature and are so popular among clinicians and researchers alike is his unique ability to tell a compelling story. You will be drawn into the journey, starting with the fundamentals of adhesive dentistry and flowable composites and finishing with a variety of clinical applications and techniques you probably never even thought about. The level of detail Douglas provides from both scientific and clinical standpoints is astonishing, but it is never overwhelming due to his fluid and captivating writing style that keeps you reading and learning. In this book he has teamed up with the most renowned researchers and clinicians to distill the critical scientific and clinical information into a comprehensible and visually fascinating message. Whether you are a dental student or a most seasoned clinician or scientist, this book will open a new world to you and spur your curiosity in an unprecedented manner. “Never lose a holy curiosity!”

Professor and Chair, Department of Preventive and Restorative Sciences, Penn Dental Medicine

In the past two decades, dentistry has witnessed a paradigm shift in philosophy that has been guided by a greater understanding of science. Advancements in restorative material formulations and adhesive technology have expanded the treatment possibilities for the patient, clinician, and technician. These advances have increased the myriad of opportunities available to discriminating patients and provided solutions to many of the restorative and esthetic challenges faced by the restorative team. This changing technology has also allowed the clinician to treat many esthetic and restorative challenges through more simple, conservative, and economical methods. This evolution in philosophy and science has resulted in a change in the trend for dental treatment.

Natural esthetics can be perplexing; observation of nature confirms this. The infinite forms and colors and all of their combinations are unlimited. The observation of sunrise with its many different colors reminds us that there is a lack of language to describe the beauty and essence that nature creates. In dentistry, natural esthetics should not be defined by but related to beauty, health, and harmony. Developing natural esthetics requires emotion, experience, judgment, observation, and imagination. Many times our interpretation is clouded by our own definitions and limited experiences. We must go back to our inherent senses to create only a shadow of the true essence of natural esthetics. Formulas and principles are necessary for the development of restorations, but they cannot become the only guiding light. It also requires an anatomical morphologic thinking of the individual characteristics of teeth through continued observation of intraoral and extracted teeth. In addition, the personalities of our patients and the importance of their individuality determine natural esthetics. Each patient, like each sunrise, is always unique and exciting.

I hope that every clinician and technician who reads these pages finds the excitement and fulfillment I have experienced from the pursuit of excellence in dentistry. Although there are different mediums to restore the natural dentition, this book focuses on the use of flowable resin composites to develop natural esthetic restorations. From my travels and hands-on courses around the world, I have realized that this restorative medium has a universal significance. It is not a solution to all restorative considerations, but it can offer an avenue for understanding natural esthetics while providing solutions to many restorative and esthetic challenges. Many clinicians think of restorative materials as a replacement of tooth structure, and composite restorations allow the clinician to understand the importance of the color of the substrate, the optical properties of light, the different restorative materials and their thickness and how this influences color, and even the difference in refractive indices of the materials to tooth structure and how they interrelate. It is by having an understanding of the dimensions of color and developing our senses through observation of nature that we can begin to create more lifelike restorations. We can begin to appreciate and understand the important role of technicians and the information that they need to create natural esthetic restorations on stone models without faces.

During my career in dentistry, I have researched in the laboratory and chairside, investigated resin composites, and worked with scientists, clinicians, and technicians around the world to develop techniques and materials with different hybrid composites to create natural esthetics. Many years ago, with the influence of Dr Vincenzo Musella and his inverse layering technique, I began a journey with flowable resin composites. Although the initial formulations were disappointing, at that same time, Dr John Burgess and Dr John Powers began studies with a new generation of universal flowables that showed promise. The clinical results in this book are a compilation of my endeavors. At the 3-year point, I was calling the restorations developed with the injectable technique transitional restorations. However, after discussions with Burgess and Powers regarding their clinical and laboratory findings with highly filled flowable resin composites, I learned that these restorations should be considered part of the armamentarium that the clinician can use in everyday practice.

The purpose of this text is to provide the clinician and technician with information to develop and stimulate their powers of observation, imagination, evaluation, decision-making, and application of flowable resin composites. It provides a detailed presentation of the inverse injection layering technique, which can be used for provisional restorations, pediatric crowns, posterior restorations, provisional restoration repair, resurfacing existing resin restorations, and prototyping during interdisciplinary treatment such as crown lengthening, ovate pontic development, and development of the peri-implant region during implant therapy. The follow-up results shown in this book provide not only the technique and materials to develop natural-looking restorations but also sound evidence that these highly filled flowable materials have significance in improving the practice of dentistry.

The text provides a detailed and scientific description of the evolution of flowable resin composites and the adhesive design concept and illustrates the same order of development that I use in my restorative procedures with the inverse injection layering technique. A detailed presentation of the various adhesive preparation designs, applications and restorative techniques, adhesive protocols, and finishing procedures is also provided. The scientific data and microscopic illustrations are intertwined to provide clarity and evidence for these procedures. In addition, chapter 2 provides a detailed description of the light-curing unit (by Richard Price) and the significance of understanding its mechanism for proper selection and use, which play an integral role in the adhesive design concept for optimal bonding. The majority of the book demonstrates the information presented in the early chapters through illustrated case presentation. My desire is that these clinical and laboratory procedures may provide another vantage point for the clinician and technician in their pursuit of excellence in restorative dentistry.

My inspiration for writing this book and sharing photographs of these procedures can be attributed to my dear colleagues and students around the world who have expressed interest during presentations and hands-on courses. Compilation of this information would not have been possible without the dedication, persistence, and relentless hard work and long hours of my dear friend and personal assistant, Melissa Nix, who instilled confidence and offered continual support in writing and organizing this information. My mother’s great ability to persuade patients to return for follow-up photographs along with her support and dinners for the team have allowed us to complete this project. Furthermore, this project would not have seen the light of day without the dedication, relentless organization, persistence, and imagination of the Quintessence team. Also, I would like to express my gratitude to my team—Dr John Powers, Dr Jean-François Roulet, Dr Markus B. Blatz, Dr Alejandro James, Dr Wesam Salha, and technicians Victor Castro, Alex Schuerger, Jungo Endo, August Bruguera, and Olivier Tric—for their patience, commitment, and midnight hours to complete this endeavor. More importantly, I would like to thank my patients without whom this project would not have been possible.

Of special significance in my life is my teacher, Maestro Willi Geller, whose friendship and early-morning conversations in the cellar have expanded my understanding and vision of esthetic dentistry and, more importantly, of life. And of course I must thank my colleagues in Oral Design for their friendship and brotherhood. Finally, I give special thanks to my Creator who makes me realize that teeth are simple in His hands but so complex in mine.

The year 1996 was an exciting one all over the world. The Dow Jones Industrial Average reached a record high of 6,000; the Nobel Prize in Chemistry was awarded to Robert F. Curl Jr, Harold W. Kroto, and Richard E. Smalley for their discovery of fullerene, a molecule composed entirely of carbon; General Motors launched the first electric car of the modern era; divers discovered the ancient port of Alexandria; eBay opened its doors for business; DVDs hit the market in Japan; Will Smith made his electrifying performance in the film Independence Day; David Bowie was inducted into the Rock and Roll Hall of Fame; and flowable resin composites were developed and introduced to the world as a revolutionary restorative biomaterial.¹ The average individual would probably rank this discovery as the least significant of these events, but this milestone dramatically affected the practice of adhesive dentistry.

The evolution of adhesive dentistry, with filled adhesives and sealants, led to the development and discovery of flowable resin composites. However, it was not until 1996 that these biomaterials had their own identity and became known as flowables. These first-generation flowable formulations were designed to simplify the placement technique and to expand the range of clinical applications for resin composites¹^,² They were configured by using filler particle sizes identical to those of conventional hybrid composites while reducing the filler load and/or increasing the diluent monomers.³^,⁴ Thus, a multitude of variations in viscosity, consistency, and handling characteristics were available to the discriminating clinician for addressing many of the restorative and esthetic challenges presented to them each day.

These biomaterials were marketed by manufacturers for a wide range of applications, which included all classifications of anterior and posterior composite restorations, amalgam margin repair, block-out materials, composite repair, core buildup, crown margin repair, cavity liners, pit and fissure sealants, porcelain repair, anterior incisal edge repair, preventive resin restorations, provisional repair, porcelain veneer cementation, composite veneer fabrication, tunnel preparation restorations, adhesive cementation, restoring enamel defects, air abrasion cavity preparations, and void repairs in conventional resin composite restorations.¹^,⁵ Unfortunately, these early flowable formulations demonstrated poor clinical performance, with inferior mechanical properties such as flexural strength and wear resistance compared with the conventional hybrid composites.¹^,² In fact, the mechanical and physical properties of composite materials improve in proportion to the volume of filler added,⁶ and the filler content of these early flowable formulations was reported to be 20% to 25% by weight less than that of the universal composite materials.¹ Numerous mechanical properties depend on this filler phase, including compression strength and/or hardness, flexural strength, elastic modulus, coefficient of thermal expansion, water absorption, and wear resistance.⁶ Thus, a reduction in the filler content of these first-generation flowables substantiates the reports by Bayne et al,¹ which state that the mechanical properties of these low-viscosity materials were approximately 60% to 80% of those of conventional hybrid composites. One scientific study⁷ reported that a comparison of flowable light-cured resin composites and conventional resin composites of the same brand name had very different characteristics and mechanical properties. Early attempts to use these flowable formulations in a wide variety of applications resulted in shortcomings that led to confusion and uncertainty for clinical predictability and performance when using these biomaterials. These shortcomings resulted in limitations on the expanded applications previously suggested by the manufacturer. Clinicians realized that these first-generation flowable composites were neither the same nor adequate substitutes for the highly filled conventional composites.

Since the inception of these initial formulations, a multitude of flowables have undergone continuous evaluation and improvement through scientific research and development. These “next-generation” flowable composites are being re-engineered as alternatives to conventional hybrid composites. The development of new technology continues to improve the ability of the scientist, manufacturer, and clinician to measure more effectively and therefore create a more ideal composite. However, the search continues for an ideal restorative material that is similar to tooth structure, is resistant to masticatory forces, has similar physical and mechanical properties to that of the natural tooth, and possesses an appearance akin to natural dentin and enamel. As the mechanical properties of a restorative material approximate those of enamel and dentin, the restoration’s longevity increases.⁸ An ideal restorative material should fulfill the three basic requirements of function, esthetics, and biocompatability.⁹ At present, no restorative material fulfills all of these requirements. However, nanotechnology used in dental applications may provide some of these solutions.

When selecting the proper material for a particular clinical situation, clinicians must consider two significant factors for the material’s anticipated use: the mechanical requirements and the esthetic requirements. In addition, other compounding variables that have the potential to influence the clinical behavior and material performance should be considered before restorative treatment. These variables include the placement technique, cavity configuration, anticipated margin placement, curing light intensity, tooth anatomy and position, occlusion, patients’ oral habits, and ability to isolate the operative field.¹⁰^–¹⁵ In view of these considerations, it is understandable that clinicians have uncertainties about the selection of biomaterials and the techniques needed to optimize the materials’ properties and achieve predictable, long-term results. A review of the mechanical and esthetic requirements for choosing a resin composite system for a specific clinical situation may provide insight into future selection and application.

In resin composite technology, the amount and size of particles represent crucial information for determining how best to use the composite materials. Alteration of the filler component remains the most significant development in the evolution of resin composites,¹⁶ because the filler particle size, distribution, and quantity incorporated dramatically affect the mechanical properties and potential clinical success of resin composites.¹⁷ In general, mechanical and physical properties of composites improve in relation to the amount of filler added. Many of the mechanical properties depend on this filler phase, including compressive strength and/or hardness, flexural strength, elastic modulus, coefficient of thermal expansion, water absorption, and wear resistance.⁶

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Fig 1-1 These scanning electron micrographs provide a comparison of the size, shape, orientation, and concentration of filler components for specific conventional hybrid and flowable resin composite systems: (a) G-aenial Universal Flo (GC America); (b) G-aenial Flo (GC America); (c) G-aenial Sculpt (GC America); (d) Clearfil Majesty ES Flow Low (Kuraray); (e) Filtek Supreme Ultra Low (3M ESPE).

The esthetic appearance of the surface of a resin composite restoration is also a direct reflection of the particle size. Esthetic restorations require biomaterials to have optical properties similar to those of tooth structure. Because resin composite does not have hydroxyapatite crystals, enamel rods, and dentinal tubules, the composite restoration must create an illusion based on the way light is reflected, refracted, transmitted, and absorbed by dentin and enamel microstructures. Recreating a natural anatomical surface requires a similar orientation of enamel and dentin. Newer formulations of resin composites possess optical properties that render the tooth polychromatic. In addition, the filler particle sizes and distribution can influence the color and esthetics of a restoration through a phenomenon called the double-layer effect, also known as the chameleon effect or blending effect.¹⁸^–²⁰ This mechanism applies to the relationship between natural tooth structure and esthetic materials. It occurs when a composite material is placed as a restoration and diffused light enters from the surrounding hard dental tissues; when emitted from the restoration, the shade is altered by absorbing color from the tooth and the adjacent teeth. This color alteration depends on the scattering and absorption coefficients of the surrounding hard dental tissues and restorative material, which can produce an undetectable color match by blending with tooth color.²¹ Furthermore, the surface quality of the composite restoration is influenced by the composition and the filler characteristics of the composite.²²^,²³ Newer formulations of nanocomposites have altered filler components with finer filler size, shape, orientation, and concentration, improving not only their physical and mechanical properties but also their optical characteristics (Fig 1-1). These universal resin composite systems allow the composite to be polished to a higher degree, which can influence color integration between the material and the tooth structure.

Nanotechnology, or nanoscience,²⁴ refers to the research and development of an applied science at the atomic, molecular, or macromolecular level, also known as molecular engineering/manufacturing. The prefix nano- is defined as a unit of measurement in which the characteristic dimension is one-billionth of a unit.²⁵ Although the nanoscale is small in size, its potential is vast. There has been significant advancement in the world of small. Small has become a common research theme for building nanomotors, nanorobots, nanocircuits, and nanoparticles. Recent advances by scientists and engineers in manipulating matter at this small magnitude indicate potential applications of this nanoscience in every arena of our economy, including telecommunications, aerospace, computers, textiles, homeland security, microelectronics, biomedicine, and dentistry.²⁵

In dentistry, nanotechnology²⁴ may provide resin composites with filler particles that are dramatically smaller in size and that can be formulated in higher concentrations and polymerized into the resin system with molecules designed to be compatible with polymers and provide unique characteristics (physical, mechanical, and optical). In addition, optimizing the adhesion of restorative biomaterials to the mineralized hard tissues of the tooth is a decisive factor for enhancing the mechanical strength, marginal adaptation, and seal of the adhesive restoration, as well as improving its reliability and longevity. Currently, the particle sizes of many of the conventional composites are so dissimilar to the structural sizes of the hydroxyapatite crystal, dentinal tubule, and enamel rod that a potential exists for compromises in adhesion between the macroscopic (40 nm to 0.7 μm) restorative material and the nanoscopic (1 nm to 10 nm) tooth structure.²⁶ However, nanotechnology has the potential to improve this continuity between the tooth structure and the nanosized filler particle and to provide a more stable and natural interface between the mineralized hard tissues of the tooth and these advanced restorative biomaterials.

Flowable composite materials have been evaluated in numerous studies¹^–⁵^,⁷^,²⁷^–⁴⁵ since their inception. Some of the more recent studies³⁹,⁴²,⁴³ indicate that the clinical performance of specifically tested flowable resin composites is similar to or better than that of specifically tested universal resin composites. Attar et al²⁸ showed that different flowable composites possessed a wide range of mechanical and physical properties. Earlier studies by Gallo et al²⁹ on specific flowable resin composites suggested that these materials should be limited to small- and moderate-sized restorations with isthmus widths of one-fourth or less of the intercuspal distance.³⁶ However, Torres et al⁴³ reported that, after 2 years of clinical service, no significant differences were found between Class II restorations restored with GrandioSO (VOCO) conventional nanocomposites and those restored with GrandioSO Heavy Flow (VOCO) flowable hybrid nanocomposites. A study by Karaman et al³⁹ showed similar clinical performances over 24 months in restorations of noncarious cervical lesions restored with conventional nanocomposites (Grandio, VOCO) and those restored with flowable material (Grandio Flow, VOCO). A more recent study by Sumino et al⁴² indicated that the flowable materials G-aenial Universal Flo, G-aenial Flo, and Clearfil Majesty Flow (Kuraray) had significantly greater flexural strength and a higher elastic modulus than the corresponding conventional nanocomposite materials, Kalore (GC America) and Clearfil Majesty Esthetic (Kuraray). The wear and mechanical properties of these specific flowable materials suggested an improved clinical performance compared with that of the universal composites. Several in vitro studies conducted at GC Research and Development comparing specific flowable material properties of several conventional composites found results similar to those of Sumino et al. Of the next-generation flowable systems studied, G-aenial Universal Flo and Clearfil Majesty ES Flow (Kuraray) showed superior gloss retention and similar wear resistance to the conventional nanocomposites tested, which included Filtek Supreme Ultra (3M ESPE), Herculite Ultra (Kerr), Clearfil Majesty ES-2, and G-aenial Sculpt (Table 1-1).

According to these studies, the recently developed specific nanohybrid flowable resin (or universal injectable) composite systems (ie, Clearfil Majesty ES Flow and G-aenial Universal Flo) may possess properties that meet the aforementioned mechanical, physical, and optical requisites. These properties and the clinical behavior of the biomaterial formulations are contingent on their structure. New resin filler technology allows higher filler loading because of the surface treatment of the particles and the increase in the distribution of particle sizes. The unique resin filler matrix allows the particles to be situated very closely to each other, and this reduced interparticle spacing and homogenous dispersion of the particles in the resin matrix increases the reinforcement and protects the matrix.⁴⁶^–⁴⁸ In addition, the proprietary chemical treatment of the filler particles allows proper wettability of the filler surface by the monomer and thus an improved dispersion and a stable and stronger bond between the filler and resin. Research studies⁴⁸^–⁵² clearly indicate the importance that filler content and coupling agents represent in determining characteristics such as strength and wear resistance. Recent studies⁴^,³⁶^,⁵³ report that flowable composites have comparable shrinkage stress to conventional composites. According to the manufacturers, these next-generation flowable composite formulations are purported to offer mechanical, physical, and esthetic properties similar to or better than those of many universal composites.⁵⁴ The clinical attributes of universal flowable composites include easier insertion and manipulation, improved adaptation to the internal cavity wall⁵⁵ (Fig 1-2), increased wear resistance, greater elasticity, color stability, enhanced polishability and retention of polish, and radiopacity similar to enamel. Furthermore, the clinical indications for these next-generation flowable resin composites are increasing as the properties of the materials and the bond strength of adhesives to dental tissues improve. With improved mechanical properties reported,⁴² these highly filled formulations are indicated for use in anterior and posterior restorative applications.⁵⁶ The clinical applications of these specific next-generation composites include sealants and preventive resin restorations; emergency repair of fractured teeth and restorations; fabrication, modification, and repair of composite prototypes and provisional restorations⁵⁷; anterior and posterior composite restorations; composite tooth splinting⁵⁸; and intraoral repair of fractured ceramic and composite restorations.⁵⁸ In addition, these composites can be used to repair denture teeth,⁵⁸ establish vertical dimension, alter occlusal schemes before definitive restoration,⁵⁶ manage spatial parameters during orthodontic treatment, eliminate cervical sensitivity,⁵⁸ resurface occlusal wear on posterior composite restorations,⁵⁸ establish incisal edge length before esthetic crown lengthening,⁵⁶ develop composite prototypes for copy milling,⁵⁶ and place pediatric composite crowns.⁵⁹

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Fig 1-2 (a) Hybrid resin composite (Estelite Sigma Quick, Tokuyama) placed without a flowable resin composite liner. Note the gap at the interface between the resin composite (RC) and the all-in-one bonding agent (B). (b) Same hybrid resin composite placed with a flowable resin (FR) composite liner. There is no gap between the flowable resin composite and the bonding agent. D, dentin. (Confocal laser scanning microscope images courtesy of Alireza Sadr, DDS, PhD.)

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Fig 1-3 (a)(b)(c and d)