Fundamentals of Implant Dentistry: Surgical Principles

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) | eISBN: 9780867158762
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

© 2016 Quintessence Publishing Co, Inc

Quintessence Publishing Co, Inc
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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.

Editor: Leah Huffman
Production: Sue Robinson

Dedication

To my loving and devoted wife and life partner, Irene, who has graciously given me the needed time and space to complete this book, and my wonderful children, Janine and Geoffrey, for their understanding and for accepting the many missed tennis tournaments, jumping competitions, ball games, and wrestling matches. Thank you for your support and unconditional love.

– Peter K. Moy

To my mother, Anna, for guidance and discipline. And to my brother, Giuseppe—his passion for minimally invasive surgery encouraged me to pursue my dreams.

– Alessandro Pozzi

To Jan, for her continuing love and support.

– John Beumer III

Contents

In Memoriam

Preface

Contributors

  1.  History and Introduction to Implant Surgery

Peter K. Moy, John Beumer III, and Tomas Janson

  2.  The Evolution of Modern Dental Implant Surfaces

Takahiro Ogawa, Basil Al-Amleh, Ichiro Nishimura, and John Beumer III

  3.  Medical History and Physical Examination

Nora Kahenasa, Peter K. Moy, John Beumer III, and Alessandro Pozzi

  4.  Workup and Diagnostic Procedures

Peter K. Moy, John Beumer III, Robert F. Faulkner, and Alessandro Pozzi

  5.  Implant Surgery Basics

Peter K. Moy, Patrick Palacci, Alessandro Pozzi, and John Beumer III

  6.  Computer-Guided Planning and Surgery

Alessandro Pozzi, Peter K. Moy, Robert F. Faulkner, and John Beumer III

  7.  Tilted and Zygomatic Implants

Joan Pi-Urgell, Jay Jayanetti, Peter K. Moy, and John Beumer III

  8.  Hard and Soft Tissue Augmentation

Peter K. Moy, Alessandro Pozzi, Patrick Palacci, Ravi Chandran, Daniel Spagnoli, Giovanni Cricchio, Stefan Lundgren, Tara Aghaloo, Joan Pi-Anfruns, Oz Simel, and Anil Danda

  9.  Reconstruction of Major Maxillary and Mandibular Defects with Implants

Beomjune B. Kim, Waleed Zaid, Daniel Spagnoli, Peter K. Moy, and W. Howard Davis

10.  Surgical Considerations for the Esthetic Zone

Alessandro Pozzi, Peter K. Moy, Robert F. Faulkner, and John Beumer III

11.  Immediate Loading, Immediate Provisionalization, and Delayed Loading

Alessandro Pozzi, John Beumer III, Peter K. Moy, and Robert F. Faulkner

12.  Maintenance and Follow-Up

David B. Krill and Robert F. Faulkner

13.  Surgical Complications of Implant Placement

Peter K. Moy, Alessandro Pozzi, and John Beumer III

Glossary

In Memoriam

Per-Ingvar Brånemark, MD, PhD

May 3, 1929–December 20, 2014

In today’s world we instantly recognize great entrepreneurs, innovators, and people who have made a profound difference in our world and transformed our daily lives. Today more than 8 million people have benefited from Brånemark’s landmark discovery of osseointegration and surgical techniques since he treated his first implant patient in 1965. Professor Brånemark has played the quintessential role in transforming the world of dentistry with his discovery.

Preface

Although it is accepted that implant dentistry is restoratively driven, the surgical aspects are none the less critical to producing successful outcomes. In volume 1 we stressed that sound prosthodontic principles and an interdisciplinary approach are key to managing dental implant patients. This volume demonstrates how the surgeon plays a leading role in the decision-making process during treatment planning and surgical management. When restorative dentists and nonsurgical specialists place dental implants, the accountability is the same as it is for a trained surgical specialist. Therefore, we strongly encourage restorative specialists to seek further surgical training before taking on this responsibility. We continue to believe that an interdisciplinary approach is best and will provide better outcomes, especially in more complex implant cases.

It is virtually impossible for one individual to stay abreast of the many significant and rapid advancements in implant dentistry. These include technologic advancements in computer-aided design/computer-assisted manufacturing (CAD/CAM), new implant designs and surfaces, compatibility and effectiveness of new biomaterials, and evolving surgical approaches enabling more accurate and ideal positioning of dental implants. Thus, the team approach as initially taught by Professor P-I Brånemark, whereby the surgical and restorative specialists work together, still holds true. This volume promotes this concept throughout.

The first four chapters illustrate the basic approach that should be taken in implant dentistry, emphasizing the importance of the patient’s medical history and the need for an interdisciplinary diagnostic workup. The middle chapters present both the routine surgical procedures used in implant dentistry and more novel techniques such as tilting the implant to gain additional length and better biomechanical distribution. Advanced surgical techniques such as hard and soft tissue grafting, managing the esthetic zone, and various loading protocols are then described, and the concluding chapters discuss maintenance and complications. Because success rates for dental implants are high, novice surgeons sometimes forget that the hard and soft tissue support around implants can be disrupted and will be lost with time if the patient does not maintain adequate home care. Dental implants are not impervious to poor surgical and prosthetic techniques, lack of maintenance and home care, or overloading forces. The clinician providing implant treatment must maintain a watchful eye from start to finish.

Finally, as in volume 1, we have included an illustrated glossary to bring the implant surgeon up to date on the ever-changing terminology associated with the new concepts, techniques, and materials introduced to the field of implant dentistry.

Acknowledgments

The editors would like to acknowledge and thank our friends and colleagues from around the world in this wonderful profession who have been mentors, instructors, and advisors, setting shining examples of how to be the consummate professional in dentistry. We also want to thank all of the authors and coauthors who have given their time and tremendous effort to complete this second volume and shared their vast knowledge and expertise. Last but not least, we would like to thank Professor P-I Brånemark for imparting to all of us his infinite wisdom, enthusiasm, determination to find answers and solutions to problems, and compassion for the patient. We truly hope he is reading this book with a smile on his face, a gleam in his eyes, and a nod of approval.

Contributors

Tara Aghaloo, DDS, PhD

Professor

Section of Oral and Maxillofacial Surgery

UCLA School of Dentistry

Los Angeles, California

• Chapter 8: Primary section author, “Growth Factors in Implant Dentistry”

Basil Al-Amleh, BDS, DClinDent (Otago), MRACDS(Pros)

Senior Lecturer

Department of Oral Rehabilitation

Faculty of Dentistry

University of Otago

Dunedin, New Zealand

• Chapter 2: Primary section author, “Ceramic Dental Implants”

John Beumer III, DDS, MS

Distinguished Professor

Emeritus Division of Advanced Prosthodontics

UCLA School of Dentistry

Los Angeles, California

• Chapter 1: Secondary author

• Chapter 2: Secondary author

• Chapter 3: Primary section author, “Impact of cancerocidal doses of radiation to potential implant sites,” “Impact of chemotherapy and concomitant chemoradiation,” and “Impact of bisphosphonates and related medications”

• Chapter 4: Secondary author

• Chapter 5: Secondary author

• Chapter 6: Secondary author

• Chapter 7: Secondary author

• Chapter 10: Secondary author

• Chapter 11: Secondary author

• Chapter 13: Secondary author

Ravi Chandran, DMD, PhD

Assistant Professor

Oral and Maxillofacial Surgery

University of Mississippi Medical Center

Jackson, Mississippi

• Chapter 8: Secondary section author, “The Need for Hard Tissue Augmentation”

Giovanni Cricchio, DDS, PhD

Department of Oral and Maxillofacial Surgery

Umeå University

Umeå, Sweden

Private Practice

Palermo, Italy

• Chapter 8: Primary section author, “Sinus Augmentation Techniques”

Anil Danda, BDS

Advanced Clinical Training Program, Surgical Implant Dentistry

Division of Diagnostic and Surgical Sciences

UCLA School of Dentistry

Los Angeles, California

• Chapter 8: Secondary section author, “Growth Factors in Implant Dentistry”

W. Howard Davis, DDS

Retired Oral and Maxillofacial Surgeon

Long Beach, California

• Chapter 9: Secondary author

Robert F. Faulkner, DDS, MS

Lecturer

Division of Advanced Prosthodontics

UCLA School of Dentistry

Los Angeles, California

Private Practice

Cincinnati, Ohio

• Chapter 4: Secondary author

• Chapter 6: Secondary author

• Chapter 10: Secondary author

• Chapter 11: Secondary author

• Chapter 12: Secondary author

• Chapter 13: Secondary author

Tomas Janson, DDS

Retired Prosthodontist

San Diego, California

• Chapter 1: Secondary author

Jay Jayanetti, DDS

Assistant Clinical Professor

Division of Advanced Prosthodontics

UCLA School of Dentistry

Los Angeles, California

• Chapter 7: Primary section author, “Zygomatic Implants”

Nora Kahenasa, DMD

Lecturer

Section of Oral and Maxillofacial Surgery

UCLA School of Dentistry

Private Practice

Los Angeles, California

• Chapter 3: Primary author

Beomjune B. Kim, DMD, MD

Assistant Professor

Department of Oral and Maxillofacial Surgery

School of Dentistry

Louisiana State University

New Orleans, Louisiana

• Chapter 9: Primary author

David B. Krill, DMD

Private Practice

Cincinnati, Ohio

• Chapter 12: Primary author

Stefan Lundgren, DDS, PhD

Professor and Chairman

Department of Oral and Maxillofacial Surgery

Umeå University

Umeå, Sweden

• Chapter 8: Secondary section author, “Sinus Augmentation Techniques”

Peter K. Moy, DMD

Nobel Biocare Chair of Surgical Implant Dentistry

Director, Straumann Implant Surgery Clinic

Clinical Professor, Section of Oral and Maxillofacial Surgery

UCLA School of Dentistry

Private Practice

Los Angeles, California

• Chapter 1: Primary author

• Chapter 3: Secondary author

• Chapter 4: Primary author

• Chapter 5: Primary author

• Chapter 6: Secondary author

• Chapter 7: Secondary author

• Chapter 8: Primary author

• Chapter 9: Secondary author

• Chapter 10: Secondary author

• Chapter 11: Secondary author

• Chapter 13: Primary author

Ichiro Nishimura, DDS, PhD

Professor

Division of Advanced Prosthodontics

UCLA School of Dentistry

Los Angeles, California

• Chapter 2: Secondary author

Takahiro Ogawa, DDS, PhD

Professor

Division of Advanced Prosthodontics

UCLA School of Dentistry

Los Angeles, California

• Chapter 2: Primary author

Patrick Palacci, DDS

Private Practice

Marseilles, France

• Chapter 5: Secondary author

• Chapter 8: Primary section author, “Soft Tissue Augmentation Techniques”

Joan Pi-Anfruns, DDS

Assistant Clinical Professor

Division of Diagnostic and Surgical Sciences and Restorative Dentistry

UCLA School of Dentistry

Los Angeles, California

• Chapter 8: Secondary section author, “Growth Factors in Implant Dentistry”

Joan Pi-Urgell, MD, DDS

Private Practice

Barcelona, Spain

• Chapter 7: Primary author

Alessandro Pozzi, DDS, PhD

Interim Chair

Oral Surgery and Implant Dentistry

Marche Polytechnic University

Ancona, Italy

Private Practice

Rome, Italy

• Chapter 3: Secondary author

• Chapter 4: Secondary author

• Chapter 5: Secondary author

• Chapter 6: Primary author

• Chapter 8: Secondary author

• Chapter 10: Primary author

• Chapter 11: Primary author

• Chapter 13: Secondary author

Oz Simel, DDS

Resident, Section of Oral and Maxillofacial Surgery

Division of Diagnostic and Surgical Sciences

UCLA School of Dentistry

Los Angeles, California

• Chapter 8: Secondary section author, “Growth Factors in Implant Dentistry”

Daniel Spagnoli, DDS, MS, PhD

Private Practice

Southport, North Carolina

• Chapter 8: Secondary section author, “The Need for Hard Tissue Augmentation”

• Chapter 9: Secondary author

Waleed Zaid, DDS, MSc

Assistant Clinical Professor

Department of Oral and Maxillofacial Surgery

School of Dentistry

Louisiana State University

New Orleans, Louisiana

• Chapter 9: Secondary author

The phenomenon of osseointegration has had a greater impact on the practice of dentistry than any technology introduced during the last 35 years. Since its introduction, significant advances have been achieved in implant surface bio reactivity; methods used in diagnosis and treatment planning, particularly three-dimensional (3D) imaging and computer-aided design/computer-assisted manufacturing (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 before the introduction of the concept of osseointegration.

What is meant by the term osseointegration? The first definition, and the definition used by most clinicians and researchers today, was coined in the 1960s by the discoverer of the concept, the late Per-Ingvar Brånemark, Professor of Anatomy at the University of Gothenburg in Sweden. He defined osseointegration as the “direct structural and functional contact between ordered, living bone and the surface of a load-carrying implant” (Fig 1-1). This definition has been refined and expanded as researchers have gained additional insight into the process of osseointegration by electron microscopy and other sophisticated research tools.

Fig 1-1 Bone is deposited on the surface of the implant, firmly anchoring the implant in bone. (Courtesy of Dr M. Weinländer, Vienna, Austria.)

Management of a Dental Implant Patient

Since the introduction of osseointegration, the evolution of implant dentistry has achieved a high level of sophistication, resulting in highly predictable and successful clinical outcomes. The management of a dental implant patient is similar to that of a dental patient with complex dental needs. The treatment for an implant patient requires the same meticulous workup and diagnostic evaluations/measurements, regardless of whether a single tooth, multiple teeth, or the fully edentulous arches are to be restored. Patients requiring complex dental treatment often require the expertise of numerous dental specialists and close coordination and cooperation between all dental care providers. The patient will often need treatment provided by an orthodontist for realignment of the dentition and correction of occlusal discrepancies, a surgeon for correction of skeletal discrepancies and to enhance hard and soft tissue volume or improve gingival health and quality, an endodontist to manage adjacent teeth with periapical pathology, and a restorative specialist to manage the sequence of treatment and to design and fabricate the definitive dental prostheses. Interdisciplinary collaboration and management is especially important for the dental implant patient because the esthetic and functional outcomes of the dental implant–retained prosthesis is dependent on the health of the adjacent natural dentition and supporting structures.

Due to the significant advancements in implant dentistry, including improved bioreactivity of modern implant surfaces, advances in the configuration of the implant body design and thread pattern, new methods and use of growth factors to enhance bone and soft tissue, use of allogeneic stem cells to provide new means for augmenting peri-implant mucosa, computer-based planning and guided surgical placement of implants, computer-designed and -manufactured abutments, prosthetic frameworks and prostheses, and improvement of implant-abutment connections, the implant team members providing implant treatment must learn and master several new technologies if ideal outcomes and long-term success are to be achieved. The implant team must also be aware and make known to the patient that appropriate esthetic and functional outcomes can be achieved with conventional treatment approaches and that these options are often in the best interest of the patient.

If the implant treatment option is selected, the implant team must be well aware of clinical conditions that affect treatment outcomes. The implant patient may require significant augmentation of bone and soft tissues. The clinician is dealing with missing teeth in a variety of intraoral sites (functional versus esthetic zones), and often these teeth have been lost over extended periods, thus seriously impacting hard and soft tissue volumes. The impact of these tissue changes is time-dependent and may be exacerbated by the use of a poorly designed and ill-fitting removable prosthesis.

The ability of the clinician to achieve acceptable functional and esthetic outcomes with implant treatment will be dependent on the clinician’s knowledge of surgical and prosthetic principles and his or her application of these principles to correct the clinical deficiencies. When an augmentation procedure is required, regardless of the need to embellish hard and/or soft tissues, special consideration must be given to the donor graft materials selected. With advancements in stem cell research and the identification of growth factors, there are many new viable options and solutions. The clinician performing these augmentation procedures must understand basic biologic principles and use sound surgical techniques to achieve optimal outcomes for their patients.

Prior to the actual implant placement, the clinician must determine the best implant design to meet the specific requirements of the prosthetic plan and the expectations of the patient. Due to the improved understanding of the osseointegration process and improvements in the osteoconductivity of modern implant surfaces, most implants commercially available today achieve successful clinical outcomes. The choices made by the implant team are often dependent on the prosthetic components available and the particular needs of the dental prosthesis (eg, is the esthetic zone or the posterior quadrants to be restored?). The selection of the appropriate implant design is dependent on the restorative plan, the type of prosthesis anticipated (eg, will it be fixed or removable?), whether it will be screwed-retained or cement-retained, whether the patient demands that the prosthesis be placed into immediate function, and perhaps other factors.

Once the implants have been placed, the implant team members must make critical decisions regarding the appropriate length of healing times, loading protocols, and postsurgical prosthetic management. The implant team should be well versed in managing potential adverse side effects of the surgical procedures that are performed. Not all planned treatments proceed as expected, so the implant team must be prepared to manage unexpected setbacks or delays in treatment. When the implant team prepares and plans well, unexpected delays or complications may be managed appropriately to minimize poor outcomes.

Close collaboration between the implant surgeon and the restorative dentist is mandatory if satisfactory outcomes are to be achieved. The implant surgeon and the restorative dentist obtain diagnostic information, the data is collated and shared, the basic issues are discussed, and a tentative diagnosis and plan of treatment are agreed upon. Once the tentative treatment plan is determined, additional diagnostic studies are performed, a definitive diagnosis is formulated, and a definitive plan of treatment is then developed. In the past, logistics made collaboration between team members difficult, but today, with the continued refinement of CAD/CAM programs, these collaborations are facilitated because needed information can be exchanged digitally and treatment-planning conferences conducted live over the Internet. The pros and cons of the variety of options available can be considered and debated with the central idea being that the implant therapy should be prosthodontically driven. Successful collaborations are based on mutual trust and an open and frank exchange of views regarding the merits of treatment options available.

Disconcerting Trends in Implant Dentistry

Implant treatment is elective, so the old maxim “Do no harm” is especially relevant when considering implant treatment. This maxim is particularly important to consider when restoring the esthetic zone, because form and function can be restored for most patients with conventional treatment methods (eg, fixed dental prostheses, bonded partial dentures, removable partial dentures, complete dentures). Although the outcomes of implant treatment achieve very high levels of predictability when executed by experienced implant teams, when treatment is delivered by ill-prepared or poorly trained teams or individuals, outcomes may be suboptimal.

Regrettably, the authors of this textbook, because of our association with academic institutions, have seen far too many failures of implants and implant prostheses. Moreover, negative outcomes are underreported in the literature. They can be secondary to poor treatment planning, inattention to detail, poor knowledge and appreciation of implant biomechanics, poor surgical execution, poor prosthetic designs, and inadequate knowledge and appreciation of the basic principles of occlusion as they relate to implant prostheses. Unfortunately, it has become far too common for restorative dentists to expect the surgeon to place and uncover the implants, make an impression, and send the impression to the dental laboratory for design and fabrication of the prosthesis, so that the only function executed by the restorative dentist is to deliver the prosthesis. Conversely, all too frequently a surgeon will place implants without consulting with the restorative dentist. Under these circumstances, implants may not be positioned or aligned consistent with fabricating a prosthesis that is esthetic and/or functional. Both of these practices often lead to negative outcomes, and frequently the implants and/or prostheses do not meet the expectations of the patient or the standard of care.

Osseointegrated implants enable implant teams to restore functional and esthetic deficits with a degree of success only dreamed of prior to their introduction. However, in order to achieve a high level of predictability, the implant team must be aware of factors that predispose to failure as well as successful outcomes. Furthermore, most implant treatment is complex, and it is incumbent upon the implant team to possess detailed knowledge of the basic principles of surgery and prosthodontics before entering into the exciting and yet challenging milieu of implant dentistry. All too many of our colleagues do not understand the complexities of implant dentistry, including the basic biomechanical limitations of these systems regarding numbers, the lengths and diameters of implants needed to withstand occlusal forces, the impact of misaligned implants, the risks associated with immediate loading, and the special requirements for restoration of the esthetic zone.

Historical Overview

Previous implant systems: Their biology and why they failed

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 (Table 1-1). 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, triggered both acute and chronic inflammatory responses, resulting in encapsulation of the implant with fibrous connective tissue (Fig 1-2). Subsequently, epithelial migration along the interface between the implant and the fibrous connective tissue led to development of extended peri-implant pockets, and the chronic infections originating in these pockets led to exposure of the implant framework and its eventual loss (see Fig 1-2). In general, these implant systems survived for 5 to 7 years before the infections prompted their removal (see Table 1-1).

Table 1-1 Implant survival rates reported in the 1978 Harvard-NIH Implant Consensus Conference³

NA, not available.

Fig 1-2 (a) A customized subperiosteal implant designed and fabricated from an impression and cast made of the exposed edentulous mandibular alveolar ridge. During this era, most were made of chrome-cobalt and rested on top of the alveolar bone. (b) The implant framework is surgically positioned. It was secured to the bone with fixation screws. (c) With this design, the implant posts were then connected to the framework. The overlying soft tissues are well healed. (d) Eventually, subperiosteal implants of chrome-cobalt are enveloped by fibrous connective tissue. (Courtesy of Dr R. James, Loma Linda, California.) (e) When the implant was placed into function, the framework would settle into the bone as seen in this panoramic radiograph, resulting in loss of bone (arrows). (f) Over time, the epithelial migration led to development of extensive peri-implant pockets, acute and chronic infections, exposure of the implant, and eventually its removal.

When subperiosteal implants failed in the mandible, alveolar bone was often lost, but the patient retained most of the basal bone. The principle damage was caused to the overlying mucosa. Most of the keratinized, attached tissues were lost, and that which remained was heavily scarred. The chronic infections associated with failing implant frameworks in the maxilla were much more damaging because of extensive loss to bone and soft tissue, exposing vital anatomical structures such as the floor of the nose/nasal cavity and sinus cavity (Fig 1-3). Frequently, large volumes of alveolar and basal bone were lost, and on occasion, large oral defects developed with extension into the paranasal sinuses (see Fig 1-3d).

Fig 1-3 (a) A subperiosteal implant fabricated for an edentulous maxilla. (b) The implant framework is secured to the alveolar bone. This particular chrome-cobalt implant framework was coated with hydroxyapatite. (Courtesy of Dr R. James, Loma Linda, California.) (c) A subperiosteal implant that had been in position for 3 years has become infected and mobile. (d) Following removal of the implant framework in another patient, the patient lost significant portions of the anterior maxilla.

Most metals are not suitable as implant biomaterials because of the aforementioned corrosion and continuous release of metal ions into adjacent tissues. The presence of these metal ions triggers acute and chronic inflammatory responses, which eventually result in fibrous encapsulation of the implant. If the implant extends through the skin or mucosa, the epithelium slowly migrates (1 to 2 mm per year if the patient has been compliant with oral hygiene) along the interface between the implant and the fibrous connective tissue capsule. The result is peri-implant pockets of significant depths, often exceeding 15 to 20 mm. These pockets are subject to local infections. Titanium, however, is resistant to corrosion and spontaneously forms a coating of titanium dioxide, which is stable, 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.

The groundbreaking work of P-I Brånemark

Professor Per-Ingvar Brånemark discovered the phenomenon of osseointegration while he was conducting a series of in vivo animal experiments studying revascularization and wound healing in traumatically induced bone defects. In these experiments, he used an optical chamber made of titanium placed into a rabbit tibia that was connected to a specially prepared microscope (Fig 1-4). A thin layer of newly formed tissue was transilluminated, and tissue repair and maturation processes were visualized in vivo. When Brånemark attempted to remove the chamber from its bone site, he noticed that the bone adhered tenaciously to the surfaces of the titanium chamber. He immediately 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 (Fig 1-5). Over 50 designs were tested.

Fig 1-4 A radiograph of the titanium optical chamber embedded in bone. When Brånemark attempted to remove the device from the bone, he noticed that the bone had grown against the surface of the titanium. (Courtesy of Professor P-I Brånemark, Gothenburg, Sweden.)

Fig 1-5 One of the early implant designs tested in dogs. Note that the bone has become closely adapted to the surface of the implant threads. (Courtesy of Professor P-I Brånemark, Gothenburg, Sweden.)

Research was then conducted aimed at developing clinical procedures that pemitted the osseointegration of implants on a consistent basis (ie, gentle surgical preparation, absence of contamination of the implant surface, and immobilization of the implant during healing). Investigations conducted in dogs using radiographic and histologic analysis indicated that the implants remained osseointegrated with little loss of bone for as long as 10 years in function in spite of the fact that the fixed prostheses supported by the implants were only cleaned twice per year (Fig 1-6).

Fig 1-6 (a) Fixed implant-supported prostheses in a dog. (b) Radiograph of a fixed implant-supported prosthesis in a dog after 4 years in function. (Courtesy of Professor P-I Brånemark, Gothenburg, Sweden.)

Clinical studies

Following an extensive period of animal testing, human studies were begun (Fig 1-7). Initial human studies were conducted in edentulous patients, and the first patient was restored in 1965. Clinical outcome studies were designed and conducted by his team, but Brånemark did not attempt to commercialize his invention until long-term clinical follow-up data (10 years) was available.^1,2 This data confirmed the clinical efficacy of titanium implants, so he began the long and difficult process of disseminating this information to the professional community. Brånemark and his team finally settled on a screw-shaped design with a hex on the top (Fig 1-8). Since then, several additional designs have been introduced, particularly aimed at improving initial implant stability.

Fig 1-7 One of the early designs tested in humans. It was removed with a trephine. The implant has been sectioned longitudinally. Note that bone is firmly adherent to the implant surface. (Courtesy of Professor P-I Brånemark, Gothenburg, Sweden.)

Fig 1-8 The final design: a screw with a hex on top.

Biologic Basis of Osseointegration

Biologic processes

Titanium is a unique metal and has been used for many years to reconstruct a variety of types of bony defects by oral and maxillofacial surgeons, orthopedic surgeons, and neurosurgeons. It is resistant to corrosion and spontaneously forms a coating of titanium dioxide on its surface. Following creation of the osteotomy sites and placement of the implant, a blood clot forms between the surface of the implant and the walls of the osteotomy site,⁴ and plasma proteins are attracted to the area and adsorbed onto the surface of the implant. The vascular injury associated with the surgical procedure immediately activates platelets. These platelets adhere to each other, and the injured tissue releases a variety of enzymes and growth factors that are essential for the cascade of events leading to coagulation and the development of the fibrin clot. The activated platelets also regulate the subsequent inflammatory response and the processes associated with wound healing.^5–7

As a fibrin clot fills the interface between the surface of the implant and the osteotomy site, angiogenesis begins almost instantaneously. The structure of the fibrin network is determined by multiple factors such as pH, clotting rate, coagulation factor concentrations, and polymerization of fibrin molecules and generally occurs within the first 24 hours following placement of the implant. The organized fibrin network is further modified by the incorporation of fibronectin molecules, which effects bone formation in the fibrin scaffold. Fibronectin is a large glycoprotein with active binding sites not only to fibrin but also to other extracellular matrix molecules and integrin-expressing cells. A subset of macrophages originating in the bone marrow (referred to as myeloid suppressor cells) regulates inflammatory responses by suppressing T-cell activities. In addition, these cells induce angiogenesis and secrete a set of growth factors that support rapid wound healing.⁸ The presence of these macrophages appears to be essential for creating a tissue repair environment for wound healing and bone formation.

Mesenchymal stem cells are attracted by chemotaxis to the surface of the implant and the osteotomy site and migrate via the fibrin scaffold associated with the clot. 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 as the result of contact and distance osteogenesis⁹ (Fig 1-9). Distance osteogenesis associated with the bony walls of the osteotomy site is initiated first, and the osteotomy site undergoes an ordinary sequence of bone wound healing similar to that seen in the tooth extraction socket. Initially, woven bone is deposited in this area. This bone is characterized by high cellularity, a haphazard arrangement of collagen fibrils, and poor mineralization. At this stage, its biomechanical resistance to functional loads is poor. However, this bone will eventually remodel into dense lamellar bone. This process may take as long as 18 months.

Fig 1-9 The bone that is deposited onto a microrough implant surface (arrows) becomes harder and stiffer than trabecular bone as it matures. (Courtesy of Dr P. Schüpbach, Zurich, Switzerland.)

Once the fibrin network adjacent to and in contact with the implant surface is remodeled and modified by the incorporation of fibronectin, osteogenesis begins within this network. There is a small but distinct time lag between distance osteogenesis and contact osteogenesis, but recent modifications of the implant surfaces appear to significantly accelerate contact osteogenesis (see chapter 2). The small gaps between regenerating bone and the implant surface may be filled as early as 7 days, depending on the osteoconductivity (the recruitment of osteogenic cells and their migration to the surface of the implant) of the implant surface, provided the surface is free of contaminants. In clinical settings, this process plus the maturation of the bone deposited on the surface of the implant requires anywhere from 8 weeks to 4 months to complete, depending on the osteoconductivity of the implant surface.

The unique nature of peri-implant bone

The nature and characteristics of the bone formed in close proximity to the implant surface play an essential role in the sustained support of the implant after it is placed into function (for details, see volume 1, chapter 2). Bone is a composite tissue composed of collagen-based fibers and crystalline hydroxyapatite (HA). The bone-mineral content is regulated by the composition of the organic collagen matrix, which is largely composed of type I collagen. The quality of the bone that ultimately anchors the implant and sustains it during function appears to be affected by the nature of this organic collagen matrix. The bone deposited within the fibrin scaffold adjacent to the implant surface is formed in response to the implant itself and is likely different than the bone created in the osteotomy site; it is probably influenced by the implant surface topography, chemistry, and charged energy. Indeed, it has been demonstrated that the presence of the implant and its specific physiognomies affect the unique characteristics of the bone deposited onto the surface of the implant.^10–12

It has been shown that the hardness and stiffness of peri-implant bone in direct contact with the implant surface may be associated with specific implant fixture surface modifications.¹¹ The hardness of peri-implant bone adjacent to the original machined titanium implant introduced in the 1980s by Brånemark progressively increases from 2 weeks to 4 weeks after surgical implant placement and eventually reaches the equivalent hardness of trabecular bone. The bone hardness associated with moderately rough (double acid-etched) implants likewise undergoes a progressive increase; however, this bone was found to be much harder and reached the equivalent hardness of cortical bone.¹¹ Recently, a similar experiment using a rabbit model revealed that the hardness of peri-implant bone almost doubled when a moderately rough (airborne-particle abraded/acid-etched) implant surface was further modified with nano-HA coating.¹² The increased presence of collagen cross-linking enzymes associated with bone adjacent to the surface of implants with microrough surface topography is thought to contribute to the formation of stronger peri-implant bone.¹⁰

Direct bone attachment to the implant surface has been considered the foundation of osseointegration, and as a result, histologic assessment of osseointegration commonly used the percent area of bone-to-implant contact (BIC). Recently, increasing numbers of studies have reported that BIC does not correlate with mechanical load as shown by pull-out tests and microcomputed tomography (microCT) analysis. Using the implant push-in test and microCT-based 3D BIC in the rat model, the moderately rough implant with double acid etching showed three times higher shear strength than the relatively smooth surface machined implant.¹³ This increase could not be accounted for by the differences in BIC between these surfaces. The discrepancy between the BIC measurement and the mechanical withstanding load assay suggests that while bone formation around the implant must be a prerequisite, the development of osseointegration may rely on the actual bonding between the bone and the implant surface.

For many years, the existence of a thin layer of tissue between the bone and the surface of the implant has been reported. This tissue layer has been described as an electron-dense zone of 20 to 50 nm^14,15 and a zone of 100 to 200 nm without typical collagen fibers¹⁶ followed by the collagen-rich bone tissue. The precise molecular composition of the interface tissue has not been elucidated. The molecules composing this interface tissue between the bone and the implant surface (proteoglycans, osteopontin, type X collagen) no doubt hold the key to understanding the mechanical withstanding force of osseointegrated implants (for details, see volume 1, chapter 2).

The rapid formation of bone marrow trabecular bone, with woven bone characteristics, immediately following implant placement may occur within 1 to 2 weeks and may potentially contribute to the immediate implant stability. Whether this early woven bone can support the occlusal load has not been established. During the transition stage from resorption of a large volume of new woven bone to the maturation of well-organized trabecular bone, there may be a vulnerable period during which the degree of implant anchorage may temporarily drop. This phenomenon has been observed in an animal model and may have clinical significance.¹⁷ The initial stability created by mechanically engaging the bone site may therefore be suboptimal, and if the implants were loaded immediately, they may be vulnerable to mobilization during this period (see chapter 11).

The woven bone formed in response to ablation wounding is subject to intensive remodeling and is largely resorbed to create fatty bone marrow. Following maturation and remodeling, the bone just adjacent to but not contacting the implant surface is composed of osteones arranged parallel to the long axis of the implant. Uniquely, bone deposited in the vicinity of implant surfaces appears to resist this catabolic bone remodeling and thus maintains the osseointegration for an extended period.¹⁸ Trabecular bone derived from distance osteogenesis around an implant may be relatively unstable and can disappear due to physiologic bone remodeling. On the contrary, peri-implant bone derived from contact osteogenesis appears to avoid bone marrow remodeling and remains around the implant fixture for long periods unless the implant is exposed to excessive loads.

Osteoclasts play a central role in resorption and remodeling. These cells are formed by the fusion of monocytes as a result of being exposed to chemical stimuli, including receptor activator of nuclear factor κB ligand (RANKL). During the developmental stage, RANKL is secreted from osteoblasts and hypertrophic chondrocytes. However, when bone matures, RANKL is primarily secreted from osteocytes embedded in bone as a result of exposure to mechanical stimuli.¹⁹ It follows that before remodeling can be initiated, the occlusal load applied to an implant fixture must be sensed by osteocytes in the implant-supporting bone. It is conceivable that the mechanical properties of peri-implant bone adjacent to implants with microrough surfaces (harder and stiffer) may insulate the embedded osteocytes, which as a result may not secrete RANKL when favorable occlusal forces are generated. Indeed, there may be an increased threshold for mechanical stimulation required for peri-implant bone osteocytes. However, implant overloading beyond this threshold may stimulate the osteocytes to initiate the secretion of RANKL, resulting in osteoclast formation and initiation of the so-called resorptive remodeling response.^20–26 This is most likely the cascade of biologic events associated with implant overload, bone loss, and implant failure.

Prerequisites for Achieving Osseointegration

Uncontaminated implant surfaces

The osteoconductivity of implant surfaces is impaired if they become contaminated with organic molecules (see chapter 2, “Biologic Aging and Photofunctionalization of Implants”). The surface charge is changed from positive to negative, the surface becomes less wettable, and upon implant placement, adsorption of plasma proteins is suppressed. Recent studies indicate that implant surfaces can be decontaminated by exposure to ultraviolet light.^27,28 Decontaminating implant surfaces with ultraviolet light (photofunctionalization) enhances adsorption of plasma proteins and activation of platelets, which leads to more rapid differentiation of mesenchymal stem cells into osteoblasts once they reach the surface of the implant. Implants that have been stored in plastic packaging for extensive time periods become less bioreactive because of contamination secondary to carbon-containing molecules. Therefore, it is advised that implants be used prior to their expiration dates.

Creation of congruent, nontraumatized implant sites

Careful preparation of the implant osteotomy site is essential to obtaining osseointegration of a titanium dental implant in bone on a consistent basis (Fig 1-10). Because the adjacent bone is an important source of cells, regulatory and growth factors, and vasculature that contribute to bone healing, it is essential to minimize trauma when preparing the implant osteotomy sites. In ideal situations, the gap between the wall of the osteotomy and the implant is small, the amount of bone traumatized 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 (at least 95% with modern microrough implant surfaces). The smaller the gap between the osteotomy site and the implant surface, the better. In addition, during surgical preparation of the implant osteotomy site, excessive bone temperatures should be avoided, because this leads to the creation of a zone of necrotic bone in the wall of the osteotomy site, impairing healing and increasing the likelihood of a connective tissue interface forming between the implant fixture and the bone.

Fig 1-10 The implant osteotomy sites must be prepared precisely with minimal trauma (a) before the implant is placed (b).

Primary implant stability

Osseointegration is obtained more consistently when initial primary stability of the implant is achieved with the surrounding bone. This is particularly important when single-stage surgical procedures are employed, and it is an obvious necessity if the implant is to be immediately placed into function. 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 after placement into 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, the modern microrough implant surfaces are osteoconductive, and unstable implants (so-called “spinners”) that are buried and remain immobile during the healing process have an excellent chance of achieving osseointegration as long as the clot remains undisturbed during the initial period of healing.

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.^29–31 Excessive micromotion (greater than 100 to 150 micrometers) of the implant during the initial healing period may detach the fibrin clot from the implant surface. Furthermore, movement of this magnitude impairs differentiation of osteoblasts. The healing processes are then reprogrammed, leading to a fibrous connective tissue–implant interface as opposed to the creation of a bone-implant interface. These phenomena have clinical significance. Implants placed into function immediately must have sufficient initial stability to resist functional forces so as to reduce micromovement to physiologic levels during healing. Otherwise, the implant will fail to osseointegrate (see chapter 11).

The Implant–Soft Tissue Interface

The implant–soft tissue interface is similar to the gingival tissue interface circumscribing natural teeth and serves as a barrier to microbial invasion. 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 specific dimension (biologic width) during the healing process.

Fig 1-11