Terry Restoring the Intraradicular Space

Esthetic Post Systems
1. Auflage 2021
ISBN: 978-1-64724-111-7
Verlag: Quintessence Publishing Co, Inc
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 268 Seiten

Too often patients with fractured teeth are referred for extraction and implant placement with little consideration given to the conservative option of post and core treatment. But it has been demonstrated that endodontic and implant therapies have equivalent results when the treatments are appropriately chosen and performed at a high level of expertise. After all, advancements in endodontic technology and instrumentation have allowed the clinician to visualize, identify, and treat complexities they could not have fathomed a decade ago, and advancements in restorative material formulations have expanded the treatment possibilities for the patient, clinician, and technician. This changing technology has allowed the clinician to treat many clinical challenges through simpler, more conservative, and more economical methods. As such, this text provides a detailed and scientific description of the evolution of the post and core system and the significance of the adhesive design concept when restoring the intraradicular post space. The author presents the various applications and restorative techniques that he uses on a daily basis for restoring the post space, and the esthetics speak for themselves. Every aspect is covered, from general design criteria and the components of the post and core systems to post materials, adhesive bonding and luting agents, material selection, core buildup, and finally, the extracoronal restoration. The clinical protocols are illustrated meticulously and with stunning quality, and additional scientific content can be accessed via QR code. If you want minimally invasive treatment with maximal esthetics, this book is for you.

Douglas A. Terry, D.D.S. Dr. Terry received his D.D.S. from the University of Texas Health Science Center, Houston Dental Branch in 1978. He is an Assistant Professor in the Department of Restorative Dentistry and Biomaterials at the University of Texas Health Center Dental Branch at Houston, Texas and an adjunct professor in the Department of Restorative Sciences at the University of Alabama. Dr. Terry is an accredited member of the American Academy of Cosmetic Dentistry and the European Academy of Esthetic Dentistry, and an honorary member of the Indian Academy of Restorative Dentistry. He has served as a past research associate for REALITY Research Lab and a clinical associate for REALITY Publishing. He is a member of the International Association for Dental Research. He has received a number of professional awards and has received fellowships in the American and International College of Dentists, Academy of General Dentistry, and the International Academy of Dental Facial Aesthetics. He is a member and the U.S. vice-president of International Oral Design. Dr. Terry is an editorial member of numerous peer-reviewed scientific journals and has published over 230 articles on various topics in aesthetic and restorative dentistry and had authored the textbook 'Natural Aesthetics with Composite Resin.' He has lectured both nationally and internationally on various subjects in restorative and aesthetic dentistry. Dr. Terry is the founder and CEO of design Technique International and the Institute of Esthetic and Restorative Dentistry. He maintains a private practice in Houston, Texas.

Autoren/Hrsg.

Terry, Douglas A.

Leseproben

Photography by Irfan Ahmad, BDS

2

THE ADHESIVE DESIGN CONCEPT

The majority of clinical failures involving fiber-reinforced post systems occur through debonding.1–25 Unfortunately, many clinicians continue to perform outdated procedures with modern restorative materials and then wonder why they continue to have this challenge when restoring the intraradicular post space. The concepts of the “mechanical era” sanctioned the removal of healthy, sound tooth structure in order to retain the restorative material.26 The preparation dimensions were designed to overcome the limited mechanical characteristics (ie, fracture resistance) of the restorative material. At that time, operative dentistry combined the need to eliminate disease (ie, caries) with the requirements to prepare the tooth to accommodate the properties of the restorative materials in use.26 The effect of outdated procedures could be one of the reasons for the relatively short clinical service of these adhesive post systems in general dental practice.27

The second half of the 20th century introduced adhesive surface preparation of the enamel and dentin (ie, acid etching and self-etching) and composite technology, which allowed more conservative preparations without a standard geometric form.28 The adhesive process (bonding restorative materials to enamel and dentin) reestablished unity, integrity, and strength to the restorative-tooth complex. Thus, clinicians began to challenge existing principles, using more conservative preparations in an attempt to preserve the maximum integrity of the natural tooth structure.28,29 Changes in selection of restorative materials, better understanding of tooth morphology (ie, anatomical complexities of root canal systems), modern microsurgical techniques and instrumentation (ie, dental microscope), and improvements in instruments and tissue-cutting concepts all contributed to the evolution of the preparation design (ie, intraradicular, intracoronal, and extracoronal) and revolutionized everyday clinical practice. Advances in materials science and adhesive technology require clinicians to modify their restorative techniques when placing adhesive restorations. This requirement is particularly true when one is considering diagnosis, selection of restorative materials, intraradicular and extracoronal preparation designs, restorative placement techniques, integrating components of the post and core system, light curing, finishing, and maintenance.30

The adhesive design concept requires the selection of adhesive and bioactive restorative materials, simplified modifications of preparation designs, and precise placement procedures and techniques (Fig 2-1). This design concept has been instrumental in the paradigm shift from the principle of extension for prevention to the ultraconservative principle of prevention to eliminate extension. “Prevention from extension” seeks to minimize the biologic cost of the natural tooth as a whole.31,32

Fig 2-1 A successful restorative procedure for adhesive dentistry relies on the interrelationship between three primary elements: adhesion, restorative material selection, and clinical technique.

When developing the intraradicular channel with an adhesive post system, the proper interrelation of these restorative parameters (adhesion, biomaterial selection, and technique) can result in an optimal restorative-tooth interface with improved clinical performance (Fig 2-2a), whereas an improper interrelation of these parameters can lead to gap formation, microleakage, staining, caries, and partial or complete debonding of the restoration that can result in clinical failure33 (Fig 2-2b). Improving the clinical longevity of post systems in the oral cavity requires solutions to these obstacles and the development of an optimal protocol for placing adhesive restorations.34,35 A successful restorative procedure for intraradicular rehabilitation relies on a fundamental adhesive design concept integrating adhesion, biomaterial selection, and clinical application. The fundamental principles of this process require the preservation of sound tooth structure; a sterile, gap-free hybrid layer; and the elimination of microleakage by securing a relatively stress-free restorative-tooth interface.36

Fig 2-2 (a) Scanning electron micrograph (SEM) view illustrating a restorative material improperly bonded to enamel and dentin that can result in clinical failure of the restoration. (b) SEM image showing a restorative material properly bonded to enamel and dentin that provides the potential for long-term functional success of a tooth and restoration. (Courtesy of Jorge Perdigão, DMD, MS, PhD.)

ADHESION

A primary component of the adhesive design concept is adhesion. Adhesion, also known as bonding or hybridization of dental hard tissues by means of polymeric materials, is of paramount importance in contemporary dentistry. A blend of concepts based on bonding procedures and emerging from a biomimetics rationale provide the operator with the ability to restore the biomechanical, structural, and esthetic integrity of teeth. Continuous research and development of bonding materials and their applications has pushed the boundaries of adhesive dentistry and led to considerable improvements in both the medical-biologic aspect (economy of sound tissues and maintenance of tooth vitality) and the socioeconomic context (decreased costs compared with traditional and more invasive prosthetic treatments). However, there are many variables that affect achieving an optimal bond in the post channel, such as the unfavorable conditions in the intraradicular space, post channel preparation, configuration factor (C-factor), depth of light penetration, post channel irrigation, anatomical and morphologic characteristics of the radicular dentin, structural differences in radicular dentin, the incompatibilities of different adhesive systems with resin cements, using dual-cured adhesives, and the competence of the operator.5,12,37–44 Thus, adhesive procedures require high technical sensitivity and a mandatory respect for the small details to achieve predictability and longevity of restorations. In order to optimize esthetic and functional outcomes, a better understanding of the complex biomechanical properties of natural substrates and restorative materials is required.

CHARACTERISTICS OF ENAMEL

The anatomical crown of a tooth is comprised of an acellular calcified material known as enamel, which is the hardest tissue in the body.45 The thickness of the enamel varies according to the shape of the tooth and its location on the crown. The thickest area of enamel is normally located at the crest of the cusp or incisal edges, whereas the thinner regions are usually over the slope, at the cervix, or within the fissures and pits of multicusped teeth45 (Fig 2-3). Human adult enamel is an inert, crystalline structure with high intermolecular forces and has been called a composite bioceramic.46 Enamel has a low-energy surface; however, etching converts enamel into a high-energy surface that improves wetting and spread of an adhesive. Enamel is a highly brittle and rigid structure because it possesses a high modulus of elasticity and low tensile strength.47 Dental enamel is acellular and does not regenerate.45 From a materials science and bioengineering perspective, enamel has been considered a functionally graded biomaterial, and an understanding of its complex biomechanics allows for better design and development of restorative materials.

Fig 2-3 (a and b) These tooth sections depict the varying thicknesses of the enamel according to the shape of the tooth and its location on the crown. (Part a courtesy of Stephan J. Paul, DMD; part b courtesy of Didier Dietschi, DMD, PhD.)

The largest basic structural component is the enamel prism or rod, densely packed and intertwined in a wavy course extending from the dentinoenamel junction (DEJ) up to a few micrometers short of the enamel tooth surface47 (Fig 2-4). The ideal structure of these prisms is a keyhole-like configuration with an average width of about 0.5 µm. The rods appear in a transverse section as a rounded head or body section and as a tail section forming a repetitive series of interlocking prisms. The enamel prism is narrowest at its origin and gradually enlarges as it approaches the surface, with an average diameter of 4.0 µm. Enamel prisms are arranged parallel to each other and run outward from the DEJ in a radial pattern, approximately perpendicular to the external surface of the crown. In the region of the enamel cusps, the rod orientation is perpendicular to the DEJ, while in the cervical region (ie, where the contours of the crown become constricted), prisms exhibit a gingival or apical inclination.47 In the incisal or occlusal third, the prisms form an increasingly acute angle with the surface as the tip of the crown is approached, exhibiting an orientation that is more directly opposed to the forces of mastication.45,48 This basic knowledge is important during cavity preparation in order to avoid undermining enamel rods, which can fracture along cleavage planes paralleling the course of the enamel prisms. It also supports the clinician’s decision to incorporate bevels in adhesive preparation designs to provide union at the ends of the enamel rods instead of at their long axis, which increases surface area and...