Fundamentals of Implant Dentistry: Prosthodontic Principles
Volume 1
Fundamentals of Implant Dentistry
Prosthodontic Principles
Edited by
John Beumer III, DDS, MS
Distinguished Professor Emeritus
Division of Advanced Prosthodontics
School of Dentistry
University of California, Los Angeles
Los Angeles, California
Robert F. Faulkner, DDS, MS
Lecturer
Division of Advanced Prosthodontics
School of Dentistry
University of California, Los Angeles
Los Angeles, California
Private Practice
Cincinnati, Ohio
Kumar C. Shah, BDS, MS
Clinical Associate Professor
Director, Residency in Advanced Prosthodontics
Division of Advanced Prosthodontics
School of Dentistry
University of California, Los Angeles
Los Angeles, California
Peter K. Moy, DMD
Nobel Biocare Clinical Professor of Surgical Implant Dentistry
Director, Straumann Implant Surgery Clinic
School of Dentistry
University of California, Los Angeles
Private Practice
Los Angeles, California
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Dedication
To Jan, for her continuing love and support.
— John Beumer III
To my wife, Terry, whose continued love, support, and belief in me has made my life’s journey truly amazing.
— Robert F. Faulkner
To my entire family for their love and encouragement: to my father (Chimanlal) and mother (Kusum) for always believing in me; to my siblings, Jigar and Hetal, for their unconditional support; to my son, Kiaan, who has inspired me to keep trying no matter what; and last but definitely not least, to my wife, Shreya, for everything she does and her love and support.
— Kumar C. Shah
To my parents and grandparents who, as immigrants, imbued in me a strong work ethic. This has carried me through my professional training and career, instilling the drive to be the best that I can be. For this, I am forever grateful.
— Peter K. Moy
Library of Congress Cataloging-in-Publication Data
Fundamentals of implant dentistry / edited by John Beumer III, Robert F. Faulkner, Kumar C. Shah, and Peter K. Moy.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-0-86715-585-3 (v. 2)
I. Beumer, John, III, 1941- , editor. II. Faulkner, Robert F., editor. III. Shah, Kumar C., editor. IV. Moy, Peter K., editor.
[DNLM: 1. Dental Implants. 2. Dental Implantation--methods. 3. Tooth Diseases--surgery. WU 640]
RK667.I45
617.6’93--dc23
2014028016
© 2015 Quintessence Publishing Co, Inc
Quintessence Publishing Co, Inc
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Editor: Leah Huffman
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Contents
Foreword
by George Zarb
Preface
Contributors
Section I Introduction and Biologic Basis
1 History and Biologic Foundations
John Beumer III, Robert F. Faulkner, Kumar C. Shah, and Peter K. Moy
2 Osseointegration and Its Maintenance
Ichiro Nishimura
Section II Restoration of Edentulous Patients
3 Edentulous Patients: Patterns of Bone Resorption and Clinical Outcomes with Implants
Neal Garrett, Ichiro Nishimura, and John Beumer III
4 Restoration of Edentulous Mandibles with Overdentures
John Beumer III, Robert F. Faulkner, Karl Lyons, Sunyoung Ma, Suzanne M. Hanlin, and Hiroaki Okabe
5 Restoration of Edentulous Mandibles with Fixed Prostheses
John Beumer III, Robert F. Faulkner, Kumar C. Shah, Hiroaki Okabe, Michael Moscovitch, Haim Keren, Julia Keren, and Sil Park
6 Restoration of Edentulous Maxillae with Overdentures
John Beumer III, Robert F. Faulkner, Karl Lyons, and Hiroaki Okabe
7 Restoration of Edentulous Maxillae with Fixed Prostheses
Aria Davodi, John Beumer III, Robert F. Faulkner, Ole T. Jensen, Mark W. Adams, Steven G. Lewis, and Hiroaki Okabe
Section III Restoration of Partially Edentulous Patients
8 Restoration of the Posterior Quadrants of Partially Edentulous Patients: Patient Selection and Treatment Planning
Kumar C. Shah, John Beumer III, Robert F. Faulkner, Robert Love, and Ting-Ling Chang
9 Restoration of the Posterior Quadrants of Partially Edentulous Patients: Examination and Prosthodontic Procedures
Robert F. Faulkner, John Beumer III, Kumar C. Shah, Donald R. Schwass, and Chandur Wadhwani
10 Restoration of Multiple-Tooth Defects in the Esthetic Zone
Robert F. Faulkner, John Beumer III, Kumar C. Shah, and Chandur Wadhwani
11 Restoration of Single-Tooth Defects in the Esthetic Zone
Pravej Serichetaphongse, Robert F. Faulkner, John Beumer III, Kumar C. Shah, and Chandur Wadhwani
Section IV Special Topics
12 Implants and Removable Partial Dentures
Ting-Ling Chang and John Beumer III
13 Implants for the Growing Child
Arun B. Sharma, John Beumer III, and Robert F. Faulkner
14 Implants in Irradiated Tissues
John Beumer III, Eric C. Sung, and Karl Lyons
15 Implants and Orthodontics: A Symbiotic Partnership
Nabil J. Barakat, Roy Sabri, Nadim AbouJaoude, and Robert F. Faulkner
Glossary
Index
Foreword
The recruitment of osseointegrated dental implants in the management of edentulous patients made its North American debut at the 1982 Toronto conference. I was privileged to have organized that event and to subsequently join Per-Ingvar Brånemark and his protégé Tomas Albrektsson in co-authoring the first text on tissue-integrated prostheses, published by Quintessence in 1985. Both seminal events helped usher in osseointegration as a novel development, leading to an exciting era of service, education, and research for the dental profession; and the clinical technique remains an extraordinary example of the merits of scrupulously tested biologic convictions and clinical observations. The Brånemark breakthrough was a far cry from the currently praised, if infrequently achieved, standard of randomized controlled clinical trials. However, it succeeded in changing traditional convictions about the feasibility and desirability of dental implants. Its subsequent worldwide trajectory catalyzed a prosthodontic management revolution in oral rehabilitative dentistry.
The ensuing three decades have seen numerous clinical scientists coloring in novel additional details to the technique, resulting in expansion of its versatility and application. These initiatives have also led to a quasi-panacea treatment status for partially and completely edentulous patients accompanied by a prevailing entrepreneurial spirit and aggressive marketing culture. A virtual implantomania has resulted from the rapidly emerging clinical confidence in osseointegration, which makes this text an opportune and welcome reminder of the importance of prudent and informed clinical judgment in the application of prosthodontic principles for all forms of dental implant therapy.
I am also privileged to have known the lead editor since the inception of the academically driven osseointegration transformation within our discipline. He has excelled at sharing knowledge and innovation in the field as well as surrounding himself with outstanding clinical scholars who contributed immeasurably to developments in implant dentistry. This book—with its stellar cast of contributors and lucid, comprehensive coverage of all that is needed to provide dentists with a synthesis of the best available evidence—is a gift to the dental profession. It is a gratifying reminder of how far the discipline has come since the Brånemark star lit up the sky of our traditional clinical interventions. It has also burnished John Beumer’s well-deserved reputation and guarantees him even more recognition for his outstanding clinical scholarship and professional leadership.
George Zarb
Emeritus Professor, University of Toronto
Editor-in-Chief, International Journal of Prosthodontics
Preface
Some maintain that the concept of restoring missing dentition with osseointegrated implants has had a greater impact on the practice of dentistry than any new technology introduced during the last half century, and we are inclined to agree. These implant systems enable teams of restorative dentists and surgeons to restore functional and esthetic deficits with a degree of success only dreamed of prior to their introduction. However, in order to achieve this high level of predictability, the implant team must be aware of factors that predispose to their failure as well as a successful outcome. In this text, we have attempted to make the reader aware of the limits of this technology and provide a prescription for the clinician, or a formula if you will, that will ensure the highest degree of success.
In recent years, it has been acknowledged that implant dentistry is driven by the prosthodontic needs of the patient, and so this volume of our two-volume series is dedicated to implant prosthodontics. Although this textbook is devoted to designing and fabricating implant-retained prostheses, we have also attempted to indicate when conventional approaches (tooth-supported fixed partial dentures, removable partial dentures, and the restoration of diseased teeth with endodontic therapy and conventional restorative procedures) should be considered. We have also attempted to provide prosthodontic perspectives of the most commonly employed surgical procedures used to facilitate the bone and soft tissues of the potential implant sites that have evolved during the last 30 years. Even though this text is focused primarily on implant prosthodontics, we hope our colleagues in surgery will find the contents of this book interesting and pertinent to the issues they face in their daily practice. We are well aware that many are asked to provide advice and counsel to their restorative colleagues.
In the early years, osseointegrated implants were used primarily to restore function of edentulous patients experiencing difficulty manipulating mandibular complete dentures. Initial attempts to restore partially edentulous patients were met with frustration and an unacceptable rate of failure. Unfortunately, these frustrations and failures were underreported in the literature. However, with the development of more osteoconductive implant surfaces, and the clinical experience gained from our earlier failures, these implant systems can now be used quite successfully when restoring the partially edentulous patient. Yet restoring partially edentulous patients is considerably more complex and challenging. Issues such as occlusal plane discrepancies, malposed teeth, unfavorable jaw relations, implant biomechanics, and the occlusal scheme to be used, among others, must be carefully addressed when developing plans of treatment.
We strongly believe that the best results are achieved when an interdisciplinary approach is employed, particularly when restoring partially edentulous patients. Some patients present with relatively simple problems and can be handled by a solo practitioner. However, as noted above, many partially edentulous patients present with significant prosthodontic complexities, periodontal compromise of existing dentition, and significant bone and soft tissue defects. Delivery of definitive care for such patients requires the prosthodontist/restorative dentist to have close interaction with oral and maxillofacial surgeons, periodontists, orthodontists, and endodontists as well as dental technicians and staff associated with biomedical modeling centers.
Prosthodontists and restorative dentists placing osseointegrated implants are obligated to understand the basic biologic mechanisms associated with this phenomenon and in particular the factors important to maintaining the long-term health of the peri-implant soft tissues and the anchoring bone. Therefore, the first section of this book is devoted to the biologic processes associated with osseointegration. In order to put these new implant systems in proper perspective, a brief description of implant systems used prior to the introduction of osseointegration is presented, as well as reasons why these systems were unpredictable.
Section two is devoted to the use of these implants in edentulous patients. The basic concepts for restoring these patients have not changed significantly since osseointegrated implants were introduced to the global community over 30 years ago. However, there has been a steady evolution in methods of evaluation, surgical procedures employed, and the methods and materials used to fabricate prostheses for these patients. The rapid development of CAD/CAM technologies has had a particularly significant impact, and we have attempted to put these new technologies in proper perspective. It is also our hope that the reader will realize that conventional complete dentures still remain an effective treatment for most edentulous patients with regard to most outcome measures.
Section three is devoted to restoration of partially edentulous patients with particular emphasis on the esthetic zone. This application has evolved significantly over the years, particularly with the introduction of new means of surgically enhancing the soft tissues and bone of the potential implant sites. The first two chapters of this section place special emphasis on implant biomechanics, particularly when restoring posterior quadrants with linear implant configurations. The last two chapters of the section are largely devoted to restoration of the esthetic zone.
The fourth section of the book addresses special and sometimes controversial topics in implant dentistry, including the use of implants in growing children and in irradiated patients. In addition, chapters are included that discuss the use of implants to facilitate the stability, retention, and support of removable partial dentures and the symbiotic relationship between orthodontics and osseointegration.
Lastly, we have included an illustrated glossary. A new language has evolved with the development of this field, and we recognize the need to provide those just embarking on their careers in this arena with a resource defining the terminology that has evolved.
Acknowledgments
Creating these volumes is a tremendous task, and we would like to thank our many contributors for their tireless and timely efforts. We have made a conscious effort to include as many of our international colleagues as possible in this project.
John Beumer would like to take this opportunity to personally thank his mentors—Dr Sol Silverman, Jr, Distinguished Professor of Oral Medicine, University of California, San Francisco (UCSF); Dr Thomas A. Curtis, Professor of Prosthodontics, UCSF; and Dr F. J. Kratochvil, Professor of Prosthodontics, UCLA. These individuals are rightly considered giants in their respective disciplines. Their commitment to excellence and enthusiasm for their work have been inspiring to me and countless others in our profession. I would also like to thank Dr Henry Cherrick, Professor and Dean Emeritus, UCLA School of Dentistry. His leadership, vision, and support as dean permitted our team at UCLA to build a strong implant program in research, clinical training, and education. Also, his encouragement and support were essential to the development of the Jane and Jerry Weintraub Center for Reconstructive Biotechnology, which could not have been conceived and built without his efforts.
First and foremost, Robert Faulkner dedicates this book to his parents, Bob and Betty Faulkner. My mom’s love and encouragement through the years of her life will remain with me and serve as a constant reminder to set goals and to reach for them with all of my being; and my Dad has served as an incredible role model and is truly the man I have always admired and aspired to emulate the most. He has continued to believe in my abilities, even when I doubted myself. To my children, Lauren and Rob, whom God blessed me with, for their love and understanding; I am so proud of the adults they are becoming, and I am honored to be their father. I would also like to acknowledge my co-editors. They have been tireless in their commitment to this book and are a reflection of the level of excellence that we have strived to achieve in our profession of prosthodontics. There are several other individuals who have helped shape my life’s journey, and they, too, have given much to develop my path toward the culmination of this book. I would like to express my sincere gratitude to these mentors—Dr Wayne Payne, Professor Emeritus, Ball State University, Department of Health Science and Physiology, whose encouragement allowed the completion of my master’s thesis; Dr Julian Woelfel, Professor Emeritus in Prosthodontics, and Dr Wayne Campagni, Professor Emeritus, The Ohio State University, College of Dentistry, both of whom guided my early development in prosthodontics. These two individuals have helped shape many prosthodontists’ careers, and it has been my honor to be influenced by their mentorship. Dr Theodore Berg, Jr, Professor Emeritus, UCLA School of Dentistry, remains one of my most cherished mentors in prosthodontics. His careful ways of teaching and encouraging students to excel is unparalleled, and he has remained an inspiration to me through my years in private practice and continues to be a constant reminder as to the true meaning of being a teacher. Finally, I would like to thank the countless friends and colleagues that have worked with me and have been supportive of my efforts throughout these many years. Without their support, this book would have only been a dream.
Kumar Shah would like to thank his co-editors for the opportunity to engage with them on this enormous task. Their friendship and support have been invaluable. In this process, I have learned a great deal, especially from Dr John Beumer, on what it takes to put something like this together; it is truly a work of passion. Two other individuals have had a big impact on my professional life—Dr Wayne Campagni and Dr Ernest D. Svensson, Professor Emeritus, The Ohio State University. Their dedication to prosthodontic education and their passion had a great influence on my early career. Their exemplary talents and patience have been a motivation for my career in education.
Peter Moy would like to thank two surgical mentors, Dr Bruce Sanders and Dr Jay Weiner, who were instrumental in teaching me the value of preprosthetic surgery to assist our restorative colleagues in managing our edentulous patients. After all, dental implant surgery is an extension of surgical procedures used formerly to prepare our edentulous patients for prosthodontic rehabilitation. To my prosthodontic mentors, I am indebted to Dr John Beumer for first seeing the potential abilities in me as a surgeon and for selecting me as the surgeon to represent the implant team from UCLA to be trained by Professor Brånemark. He has truly been an inspirational leader and an advocate of the team approach to implant dentistry but, most importantly, a trusted friend.
Contributors
Nadim AbouJaoude, DDS, CES, DU, FICD
Lecturer, Lebanese University
Clinical Associate, American University
Private Practice
Beirut, Lebanon
• Chapter 15: Secondary author
Mark W. Adams, DDS
Private Practice
Denver, Colorado
• Chapter 7: Secondary section author, “All-on-four concept”
Nabil J. Barakat, BDS, MS
Professor Emeritus and Chair
Department of Oral and Maxillofacial Surgery
School of Dentistry
Lebanese University
Private Practice
Beirut, Lebanon
• Chapter 15: Primary author
John Beumer III, DDS, MS
Distinguished Professor Emeritus
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 1: Primary author
• Chapter 3: Secondary author
• Chapter 4: Primary author
• Chapter 5: Primary author
• Chapter 6: Primary author
• Chapter 7: Secondary author
• Chapter 8: Secondary author
• Chapter 9: Secondary author
• Chapter 10: Secondary author
• Chapter 11: Secondary author
• Chapter 12: Secondary author
• Chapter 13: Secondary author
• Chapter 14: Primary author
Ting-Ling Chang, DDS
Clinical Professor
Chair, Section of Removable Prosthodontics
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 8: Secondary author
• Chapter 12: Primary author
Aria Davodi, DDS
Lecturer
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
Private Practice
Beverly Hills, California
• Chapter 7: Primary author
Robert F. Faulkner, DDS, MS
Lecturer
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
Private Practice
Cincinnati, Ohio
• Chapter 1: Secondary author
• Chapter 4: Secondary author
• Chapter 5: Secondary author
• Chapter 6: Secondary author
• Chapter 7: Secondary author
• Chapter 8: Secondary author
• Chapter 9: Primary author
• Chapter 10: Primary author
• Chapter 11: Secondary author
• Chapter 13: Secondary author
• Chapter 15: Secondary author
Neal Garrett, PhD
Professor
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 3: Primary author
Suzanne M. Hanlin, MDS, FRACDS, MRACDS (Pros), FADI, FICD
Senior Lecturer
Department of Oral Rehabilitation
Faculty of Dentistry
University of Otago
Dunedin, New Zealand
• Chapter 4: Secondary author
Ole T. Jensen, DDS, MS
Visiting Professor
Department of Maxillofacial Surgery
Hebrew University
Jerusalem, Israel
Private Practice
Greenwood Village, Colorado
• Chapter 7: Primary section author, “All-on-four concept”
Haim Keren, MDT, CDT, FNGS
Keren Laboratory
Montreal, Canada
• Chapter 5: Secondary section author, “Monolithic Zirconia Fixed Prostheses”
Julia Keren, IT
Keren Laboratory
Montreal, Canada
• Chapter 5: Secondary section author, “Monolithic Zirconia Fixed Prostheses”
Steven G. Lewis, DMD
Former Associate Professor
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
Private Practice
Fort Mill, South Carolina
• Chapter 7: Secondary section author, “All-on-four concept”
Robert Love, BDS, MDS, PhD, FRACDS
Professor
Department of Oral Diagnosis and Surgical Sciences
Faculty of Dentistry
University of Otago
Dunedin, New Zealand
• Chapter 8: Primary section author,
“Endodontically restored teeth versus implants”
Karl Lyons, MDS, PhD
Professor
Department of Oral Rehabilitation
Faculty of Dentistry
University of Otago
Dunedin, New Zealand
• Chapter 4: Secondary author
• Chapter 6: Secondary author
• Chapter 14: Secondary author
Sunyoung Ma, BDS, DClinDent
Senior Lecturer
Department of Oral Rehabilitation
Faculty of Dentistry
University of Otago
Dunedin, New Zealand
• Chapter 4: Secondary author
Michael Moscovitch, DDS, CAGS (Prosth)
Assistant Clinical Professor
Department of Restorative Dental Sciences/Biomaterials
Boston University
Boston, Massachusetts
Lecturer
McGill University Faculty of Dentistry
Jewish General Hospital, Dental Residency Program
Private Practice
Montreal, Canada
• Chapter 5: Primary section author, “Monolithic Zirconia Fixed Prostheses”
Peter K. Moy, DMD
Nobel Biocare Clinical Professor of Surgical Implant Dentistry
Director, Straumann Implant Surgery Clinic
UCLA School of Dentistry
Private Practice
Los Angeles, California
• Chapter 1: Secondary author
Ichiro Nishimura, DDS, PhD
Professor
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 2: Primary author
• Chapter 3: Secondary author
Hiroaki Okabe, CDT
Director
Training Program for Laboratory Technicians: Implant Prosthodontics
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 4: Secondary author
• Chapter 5: Secondary author
• Chapter 6: Secondary author
• Chapter 7: Secondary author
Sil Park, DMD
Assistant Clinical Professor
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 5: Primary section author, “CAD/CAM metal frameworks”
Roy Sabri, DDS, MS
Private Practice
Beirut, Lebanon
• Chapter 15: Secondary author
Donald R. Schwass, BDS, DClinDent(Pros)
Senior Lecturer
Department of Oral Rehabilitation
Faculty of Dentistry
University of Otago
Dunedin, New Zealand
• Chapter 9: Primary section author, “Implant screw mechanics”
Pravej Serichetaphongse, DDS
Deputy Dean for Hospital Affairs and Quality Assurance Head, Maxillofacial Prosthetics Unit
Faculty of Dentistry
Chulalongkorn University
Bangkok, Thailand
• Chapter 11: Primary author
Kumar C. Shah, BDS, MS
Clinical Associate Professor
Director, Residency in Advanced Prosthodontics
Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 1: Secondary author
• Chapter 5: Secondary author
• Chapter 8: Primary author
• Chapter 9: Secondary author
• Chapter 10: Secondary author
• Chapter 11: Secondary author
Arun B. Sharma, DDS
Clinical Professor
Director, Maxillofacial Prosthetics
Division of Preventive and Restorative Dental Sciences
School of Dentistry
University of California, San Francisco
San Francisco, California
• Chapter 13: Primary author
Eric C. Sung, DDS
Professor of Clinical Dentistry
Director, Hospital Dentistry Residency Program
Vice Chair, Division of Advanced Prosthodontics
UCLA School of Dentistry
Los Angeles, California
• Chapter 14: Secondary author
Chandur Wadhwani, BDS, MSD
Affiliate Faculty
Department of Restorative Dentistry
School of Dentistry
University of Washington
Seattle, Washington
Private Practice
Bellview, Washington
• Chapter 9: Primary section author, “Cement-retained restorations”
• Chapter 10: Primary section author, “Cement-retained restorations”
• Chapter 11: Primary section author, “Cementation-retained restorations” and “Crowns with supragingival, esthetic adhesive margins”
1
History and Biologic Foundations
John Beumer III
Robert F. Faulkner
Kumar C. Shah
Peter K. Moy
Introduction and Historical Perspectives
It can be argued that osseointegration has had a greater impact on the practice of dentistry than any technology introduced during the last 50 years. Since the introduction of osseointegrated dental implants more than 30 years ago, significant advances have been achieved in implant surface bioreactivity; methods used in diagnosis and treatment planning, particularly three-dimensional (3D) imaging and computeraided design/computer-assisted manufacture (CAD/CAM) techniques; enhancement of bone and soft tissues of potential implant sites; and prosthodontic approaches and techniques. A degree of predictability with implants has been achieved that was unthinkable a generation ago when the authors of these volumes received their initial dental and surgical training.
When the concept of osseointegration was introduced to the international dental community in the early 1980s, it represented a radically new concept in implant dentistry.1,2 These implants were made of titanium, and when an implant was placed, bone was deposited on its surface, firmly anchoring the implant in the surrounding bone (Fig 1-1). The phenomenon of osseointegration was discovered by Professor Per-Ingvar Brånemark while he was conducting a series of in vivo animal experiments assessing wound healing in bone. In these experiments, he placed in a rabbit tibia an optical chamber made of titanium that was connected to a microscope (Fig 1-2). When he attempted to remove the chamber from its bone site, he noticed that the bone adhered to the titanium chamber with great tenacity. He recognized the importance of this discovery, and during the next several years he experimented with various sizes and shapes of dental implants, including designs with features of both subperiosteal and endosteal implants. Over 50 designs were tested. He and his colleagues finally settled on a simple screw shape with a hex at the top.
Fig 1-1 Bone is deposited on the surface of the implant, firmly anchoring the implant in bone. (Courtesy of Dr M. Weinlander, Vienna, Austria.)
Fig 1-2 A radiograph of the titanium chamber embedded in bone. (Courtesy of Dr P-I. Brånemark, Gothenburg, Sweden.)
Most of the previous implant systems were made of chrome-cobalt alloys, which were subject to corrosion. Corrosion, with release of metallic ions into the surrounding tissue, precipitated both acute and chronic inflammatory responses, resulting in encapsulation of the implant with fibrous connective tissue. Subsequently, epithelial migration along the interface between the implant and the fibrous capsule led to development of extended peri-implant pockets, and the chronic infections resulting from these pockets led to exposure of the implant framework and its eventual loss (Fig 1-3).
Fig 1-3 (a) Subperiosteal implants of chrome-cobalt are enveloped by fibrous connective tissue. (Courtesy of Dr R. James, Loma Linda, California.) (b) Epithelial migration led to the formation of extended peri-implant pockets, which in turn developed into chronic infection. The infection led to exposure of the implant struts and eventual loss of the implant.
In general, these implant systems survived for 5 to 7 years before the infections prompted their removal (Table 1-1). The infections were particularly destructive of bone and soft tissue in the maxilla (Fig 1-4).
Table 1-1 Implant survival rates reported in the 1978 Harvard-NIH Implant Consensus Conference3
| Survival rate | |||
| Implant type | 5 years | 10 years | Notes |
| Subperiosteal | 90% | 65% | 200 patients (5 investigators) |
| 46% | 39% | 94 patients (1 investigator) | |
| Staple | 95% | NA | Unreliable due to self-reported data |
| Transosteal | Undetermined | Small sample size | |
| Vitreous carbon | 50%-60% | NA | 3-year data (2 investigators) |
| Blade | 90% | NA | 200 implants (1 investigator) |
| 65% | NA | 70 implants (2 investigators) | |
| 75% | NA | 89 patients; full-arch blade implants (self-reported data from 1 investigator) | |
Fig 1-4 Substantial portions of the hard palate were lost secondary to infections caused by a subperiosteal implant.
Most metals are not suitable as implantable biomaterials because of the aforementioned corrosion and continuous release of metal ions into adjacent tissues. The presence of these ions precipitates acute and chronic inflammatory responses, which eventually result in fibrous encapsulation of the offending material. Epithelial migration then follows if the material extends through the skin or mucosa. Titanium, however, is resistant to corrosion and spontaneously forms a coating of titanium dioxide, which is stable and biologically inert and promotes the deposition of a mineralized bone matrix on its surface. In addition, it is strong and easily machined into useful shapes.
Following placement of the implant, a blood clot forms between the surface of the implant and the walls of the osteotomy site.4 Plasma proteins are attracted to the area, accompanied by platelet activation and the release of cytokines and growth factors.5–7 Angiogenesis begins, and mesenchymal stem cells migrate via the fibrin scaffold of the clot to the osteotomy site and the surface of the implant. These cells differentiate into osteoblasts and begin to deposit bone on the surface of the implant and the walls of the osteotomy site, eventually leading to anchorage of the implant in bone (the result of contact and distance osteogenesis)8 (Fig 1-5). The initial events of this process take anywhere from 8 weeks to 4 months, depending on the osteoconductivity (the recruitment of osteogenic cells and their migration to the surface of the implant) of the implant surface.
Fig 1-5 The gap between the wall of the osteotomy and the surface of the implant is filled in with bone by means of contact and distance osteogenesis.
The original dental implants developed by Professor Brånemark and his colleagues were prepared with a machined surface (Fig 1-6). These machined-surface implants were predictable in bone sites of favorable quantity and quality, such as the mandibular symphysis region, but were problematic when restoring posterior quadrants in partially edentulous patients. Since then, special surface treatments (eg, sandblasting, acid etching, titanium grit blasting, electrolytic processes) designed to change the microtopography of the implant surface have evolved that have significantly improved the osteoconductivity of titanium implants, making these implants highly predictable in less favorable sites, such as when restoring the posterior quadrant of the maxilla in partially edentulous patients (see chapter 8).
Fig 1-6 (a) The original Brånemark machined-surface implant. (b) Machined-surface topography.
Prerequisites for Achieving Osseointegration
Uncontaminated implant surfaces
The osteoconductivity of implant surfaces is impaired if they become contaminated with organic molecules. The surface charge is changed from positive to negative, the surface becomes less wettable, and, upon implant placement, adsorption of plasma proteins is inhibited. Recent studies indicate that implant surfaces can be decontaminated by exposure to ultraviolet light.9,10 Decontaminating implant surfaces with ultraviolet light enhances adsorption of plasma proteins initially after implant placement and promotes more rapid differentiation of mesenchymal stem cells into osteoblasts once they reach the surface of the implant.
Creation of congruent, nontraumatized implant sites
Careful preparation of the implant site is critical to obtaining osseointegration of a titanium implant in bone on a consistent basis (Fig 1-7). In an ideal situation, the gaps between the wall of the osteotomy and the implant are small, the amount of damaged bone created during surgical preparation of the bone site is minimal, and the implant remains immobilized during the period of bone repair. Under these circumstances, the implant becomes osseointegrated a very high percentage of the time (95% or greater with the modern microrough implant surfaces). The smaller the gap between the osteotomy site and the implant surface, the better the chance for osseointegration. In addition, during surgical preparation of the site, excessive bone temperatures should be avoided (above 47ºC), because they result in the creation of a zone of necrotic bone in the wall of the osteotomy site and lead to impaired healing and an increased likelihood of a connective tissue interface forming between the implant and the bone (Fig 1-8).
Fig 1-7 (a) Surgical drill guide. Note the bushings incorporated with the drill guide. (b and c) Osteotomy sites being created. Note the completed osteotomy sites.
Fig 1-8 The osteotomy site is considerably larger than the implant itself, particularly around the coronal two-thirds of the implant. As a result, this implant will be at increased risk of failure.
Primary implant stability
Osseointegration is obtained more consistently when initial primary stability of the implant is achieved in the surrounding bone. This is particularly important when one-stage surgical procedures are employed and is absolutely necessary if the implant is to be immediately placed into function (ie, restored). In attempting to establish initial primary stability, surgeons often underprepare the implant site when the bone is porous or soft. If the implant is not stable in its prepared osteotomy site, many clinicians prefer to replace it with an implant of a slightly larger diameter. This was particularly necessary when machined-surface implants were routinely employed. Today, implant surfaces are considerably more bioreactive, and unstable implants have a reasonable chance of achieving osseointegration as long as the clot remains undisturbed during the initial period of healing (see volume 2, chapter 5).
No relative movement of the implant during the healing phase
Micromovement of the implant is thought to disturb the tissue and vascular structures necessary for initial bone healing.11 Excessive micromovement of the implant during healing prevents the fibrin clot from adhering to the implant surface. Eventually, the healing processes are reprogrammed, leading to a connective tissue–implant interface as opposed to a bone-implant interface. These phenomena have clinical significance. For example, immediate loading of dental implants provides a unique challenge. Implants placed into function immediately must be sufficiently stable so as to reduce micromovement to physiologic levels during healing. Otherwise, the implant may fail to osseointegrate. This issue is discussed in detail in the subsequent chapters.
Advances in Implant Surface Osteoconductivity
Implants prepared with a microrough surface topography are considerably more osteoconductive compared with the original machined-surface implants12,13 (Fig 1-9). There are several reasons why these surfaces are such an improvement over the original machined surfaces. First, the modern implant surfaces with microrough surface topographies retain the fibrin blood clot more effectively than implants with machined surfaces.14 As a result, the initial critical events (ie, plasma protein adsorption, clot formation, angiogenesis, mesenchymal stem cell migration and attachment, cell differentiation) associated with osseointegration are facilitated.
Fig 1-9 (a and b) Microrough surface topography. Implant surfaces with similar microsurface topography are more osteoconductive than the original machined-surface implants.
In addition, mesenchymal stem cells differentiate more rapidly into functioning osteoblasts following attachment to the microrough surfaces as compared with machined surfaces. These surfaces also upregulate and accelerate the expression of genes of the differentiating osteoblasts associated with the osseointegration process.15 This leads to a different combination of collagenous and noncollagenous proteins making up the bone deposited on the microrough surfaces as compared with the bone deposited on machined-surface topographies. As a result, bone deposited on implant surfaces with micro-rough surface topography is harder and stiffer than bone deposited on machined surfaces.16,17
An active and efficient remodeling apparatus is key to maintaining osseointegration during functional loading of the implants.18 Osseointegration of the implant with bone continues to occur up to 1 year following delivery of either a provisional or definitive prosthesis.19 Following initial healing and functional loading within physiologic limits, progressive osteogenesis continues to where the bone-implant contact area approaches almost 90% in favorable sites (Fig 1-10).
Fig 1-10 (a) Following initial healing and when loading forces are favorable, the bone contact area on the surface of the implant continues to increase. (b) Note the bone density of the peri-implant bone 7 years following delivery.
The Implant–Soft Tissue Interface
The peri-implant mucosa is similar to the mucosa circumscribing natural teeth. It is composed of nonkeratinizing epithelium in the sulcus, junctional epithelium, and a supracrestal zone of connective tissue. The connective tissue layer contains a dense zone of circumferential collagen fibers intermingled with fibers extending outward from the alveolar crest. These fibers run parallel to the long axis of the implant. The zone of connective tissue adjacent to the implant is relatively avascular and acelluar and similar to scar tissue histologically. The soft tissue barrier (interface) assumes a minimal dimension during the healing process. If this dimension is less than 2 to 3 mm, bone resorption occurs in order to establish an appropriate biologic dimension of the peri-implant soft tissue barrier.20
The titanium–soft tissue interface appears to be similar to but not exactly the same as that seen between gingiva and natural dentition. The epithelial-implant interface is based on the hemidesmosome basal lamina system, similar to that seen between gingiva and teeth. When implants emerge through attached keratinized mucosa, collagen fibers circumferentially configured around the neck of the implant interwoven with collagen fibers running from the crest of the alveolus and the periosteum to the free gingiva hold the epithelium in close proximity to the surface of the implant. The epithelial cells in the sulcus epithelium secrete a sticky substance (a protein network composed of glycoproteins) onto the surface of the implants, enabling the epithelial cells to adhere to the implant surface via hemidesmosomes. The epithelial cuffs that form as a result of the basal lamina hemidesmosomal system and the zone of connective tissue just apical to it effectively seal the bone from oral bacteria (Fig 1-11). However, what differentiates the soft tissues around implants from the gingival tissues around natural teeth is the absence of gingival fibers inserting into a cementumlike tissue. Hence, the soft tissues around implants are much more easily detached from the surfaces of the implant than are the soft tissues surrounding natural teeth. This difference is clinically significant for a number of reasons, especially when cement systems are used for retention of implant prostheses because of the risk of embedding cement subgingivally during cementation of the prosthesis,21 thereby precipitating peri-implantitis22 (Fig 1-12).
Fig 1-11 Implant–soft tissue interface.
Fig 1-12 (a) Patient referred with an infection associated with the soft tissues surrounding the implant crown on the maxillary left central incisor. (b) Note the cement retained around the abutment and extending onto the surface of the implant. (c) Flap reflected. Note the cement on the distal surface of the implant. (Courtesy of Dr C. Tang, Nanjing, China.)
The phenomenon of biologic width applies not only to the natural dentition but also to the soft tissues around implants. Biologic width is defined as the combined length of the supracrestal connective tissue and the zone of junctional epithelium associated with the epithelial attachment. This dimension averages approximately 3 mm around implants20 and is slightly greater than that associated with the natural dentition. In general, the width of the epithelial component is greater and demonstrates more variability than the width of the connective tissue zone. This phenomenon has particular impact in the esthetic zone, because, as with the natural dentition, the level and contours of the underlying bone primarily determine the contours and level of the overlying soft tissues (Fig 1-13).
Fig 1-13 (a and b) A provisional implant crown. It was delivered at the same time the implant was uncovered, and the soft tissues were adapted to its contours. As a result, the soft tissue contours are idealized. (c) A customized impression coping was used to make the final impression. (d) The definitive restoration.
The dimension of the biologic width in relation to the nature and topography of the implant surface has been the subject of much debate in recent years. However, there is no clear consensus on whether differences in biologic width exist with respect to the varieties of surface topographies and surface treatments currently in use.23 Also, the evidence appears to indicate that there are no significant differences in biologic width between one-piece and two-piece implant systems or between one-stage and two-stage surgical procedures.
However, it appears that the nature of the microgap between the abutment and the implant and its position in relation to the bone crest increases the biologic width (see chapter 10). The deeper the implant-abutment connection in relation to the gingival crest, the greater the biologic width will be, particularly the epithelial component. Multiple abutment manipulations appear to induce an apical migration of the connective tissue–epithelial attachment zone, resulting in marginal bone loss.24 The lack of stability of the abutment-implant connection may also precipitate an apical migration of the connective tissue–epithelial attachment zone accompanied by marginal bone loss around the neck of the implant, presumably as a result of increased levels of bacterial colonization. The long-term clinical consequences of these findings with respect to implant survival have yet to be determined.
In the esthetic zone, techniques have evolved that idealize the soft tissue contours around the implant prostheses. Provisional restorations are designed to support the soft tissues and develop ideal contours, and these contours can be recorded using customized impression techniques (see Fig 1-13). In addition, surgical procedures have been developed that can be used to enhance bone and soft tissue contours.
Impact of 3D Imaging and CAD/CAM on Diagnosis, Treatment Planning, and Prosthesis Fabrication
Computer-based imaging has had an enormous impact on diagnosis and treatment planning. With these tools, clinicians are able to identify vital structures such as the inferior alveolar nerve, determine the 3D nature of the potential implant bone sites, predetermine implant position and angulation with great precision, and fabricate surgical drill guides that allow placement of implants into their intended positions via guided surgery (Fig 1-14; see also Fig 1-7). In addition, CAD software programs allow for the design and manufacture of customized implant connecting bars, custom abutments, provisional restorations, and definitive restorations with great precision (Figs 1-15 to 1-17). It will soon become necessary for all those who practice implant dentistry to become intimately familiar with these emerging technologies. The two volumes of this series describe these new methods and attempt to place them in proper context regarding diagnosis, treatment planning, guided surgery, and fabrication of implant prostheses.
Fig 1-14 (a to c) Using scans and CAD/CAM techniques, vital structures can be visualized; bone volumes can be assessed in three dimensions; and implant size, position, and angulation can be determined prior to surgical placement.
Fig 1-15 An implant-supported connecting bar milled to a 2-degree taper with Hader bar–type attachments can be designed with CAD/CAM techniques.
Fig 1-16 (a and b) CAD/CAM programs can be used to design and manufacture custom abutments.
Fig 1-17 (a) Two implants have been placed to restore this posterior mandibular defect. (b and c) CAD software can be used to design the provisional and/or the definitive prosthesis (d and e). (Courtesy of Dr M. Moscovitch, Montreal, Canada.)
Summary
Osseointegrated implants are highly predictable when used appropriately, and in many situations implant treatment is as predictable or even more predictable than any of the conventional restorative procedures used to restore missing dentition. The key to predictable outcomes when implants are employed is accurate diagnosis and appropriate treatment planning, taking into account significant patient history findings such as parafunction as well as implant biomechanics and the occlusal schemes to minimize undesirable occlusal forces. Successful outcomes are best accomplished in a multidisciplinary setting. The purpose of these volumes is to share with clinicians the approach to patient evaluation and treatment that has enabled the authors to provide these services with a very high degree of success. Indeed, when implant therapy is planned and executed properly, taking into account the basic principles of prosthodontics, it is the authors’ expectation that once the implants are osseointegrated, while the prostheses that are retained by the implants may need replacement due to wear or breakage, the implants should last the lifetime of the patient.
References
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