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Research has shown that short implants are not only a viable option but oftentimes a superior one that carries fewer risks for the patient and dentist, especially in resorbed jaw sites. As clinical trials continue to underscore the safety and efficacy of short implants, more dentists are considering their use with real interest, and this book provides the information clinicians need to incorporate short implants into their own practice. The book reviews the clinical effectiveness of short implants and then describes treatment protocols for the various types of short implants and their placement in different areas of the mouth. Case presentations demonstrate the recommended techniques and showcase the results.

Short and Ultra-Short Implants

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To my sister, Patti Jane, who died as a child 56 years ago and is always in my thoughts.

Library of Congress Cataloging-in-Publication Data

Names: Deporter, Douglas, editor.

Title: Short and ultra-short implants / [edited by] Douglas Deporter.

Description: Hanover Park, IL : Quintessence Publishing Co Inc, [2018] | Includes bibliographical references and index.

Identifiers: LCCN 2018013422 (print) | LCCN 2018014232 (ebook) | ISBN 9780867157864 (ebook) | ISBN 9780867157857 (softcover)

Subjects: | MESH: Dental Implantation--methods | Dental Implants | Dental Prosthesis Design

Classification: LCC RK667.I45 (ebook) | LCC RK667.I45 (print) | NLM WU 640 | DDC 617.6/93--dc23

LC record available at https://lccn.loc.gov/2018013422

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©2018 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: Marieke Zaffron

Design: Sue Zubek

Cover Design and Production: Angelina Schmelter

Printed in China

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Foreword

Preface

Acknowledgments

Contributors

1Why Avoid Using Short Implants?

2The Performance of Short and Ultra-Short Implants

3A Single Practitioner’s 20-Year Experience with Short Implants

4Using Short Implants for Overdenture Support

5Threaded Implants in the Posterior Maxilla

6Threaded Implants in the Atrophic Posterior Mandible

7Press-Fit Sintered Porous-Surfaced Implants

8Plateau Root Form Implants

9Ultra-Wide Threaded Implants for Molar Replacement

10The Way Forward

Index

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In many clinical situations, placing what have been considered standard-length dental implants can be difficult or impossible due to anatomical limitations such as proximity of the mandibular canal, pneumatization of the maxillary sinus, and alveolar ridge deficiencies. The health, age, and willingness of the patient to undertake invasive treatments can all be additional barriers. Of course, there are a number of surgical procedures available to facilitate future implant placement in patients with advanced alveolar ridge resorption. More complex approaches include the use of autogenous inlay or onlay bone grafts harvested intra- or extraorally, distraction osteogenesis, zygomatic arch implants, transposition of the inferior alveolar nerve, guided bone regeneration, and various maxillary sinus cavity manipulations. However, these approaches are case sensitive, technically demanding, time consuming, and stressful, not to mention that they increase postoperative morbidity as well as the total cost and duration of the therapy.

The use of short and ultra-short implants is currently able to offer the best and least costly option in many situations, but some clinicians still refuse to accept their suitability. This book is the most comprehensive presentation to date on the use of short and ultra-short implants, and it will give dentists a better understanding of their appropriate application in solving clinical situations from restoring a single tooth to fully edentulous cases. An evidence-based approach in the early chapters of the book sheds light on the long-term performance of various short and ultra-short implant designs, attempting to address concerns of more conservative clinicians who—from personal experience or the opinions of others—feel that such implants are more likely to fail than implants of standard lengths. I foresee that going forward, this book will offer the scientific community a further chance to debate and finally embrace this modern implant treatment approach, and I would like to thank the authors and congratulate them. I feel confident that this text will make a significant contribution to improving our patients’ health and quality of life—goals that all clinicians aim to achieve.

Tiziano Testori, MD, DDS

Founder and Scientific Director

Lake Como Institute

Como, Italy

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My first encounter with Prof P-I Brånemark was during a site visit that my colleagues and I made to Göteborg in the fall of 1979. The purpose of this visit was to determine whether it would be appropriate for our faculty at the University of Toronto to replicate a prospective clinical investigation of the Brånemark-type machine-turned threaded implant prior to its formal introduction to North America. The team leader was Prof George Zarb, our head of prosthodontics at the time. And while I ultimately did not participate in this study, I left Göteborg with a definite interest in the field that was soon to flourish—implant dentistry.

Following the onset of the so-called Toronto Study,1 the concept of osseointegration was introduced to select academic oral surgeons and prosthodontists at a meeting in Toronto in 1982, after which began the quest to more fully understand bone-to-implant fixation and how best to achieve it.2 Thousands—if not tens of thousands—of basic animal and human clinical studies have since been published, and yet there continues to be much more to learn in the field. As it happened, around the time of the Toronto meeting, our faculty was serendipitously joined by none other than Prof Bob Pilliar, the biomaterials scientist and engineer who had invented the cementless hip implant a decade before.3 The cementless hip implant consisted of a solid metal implant core onto which a porous surface multilayer of spherical metal beads of defined size range was secured using a high-temperature, carefully controlled sintering process. This surface topography promoted bone ingrowth into the porous regions, leading to a three-dimensional micromechanical interlocking (or interdigitation) of bone with the porous implant surface. Up until that time, most contemporary hip implants had been secured at placement using bone cement, an acrylic grout material (polymethyl methacrylate) introduced from the dentistry field. The problem, however, was that with time in function the cement was prone to breaking down. This was due primarily to relative micromovements at the cement-to-implant or cement-to-bone interface, resulting in release of fine wear debris that resulted in endosteolysis, bone loss at the interface, and implant loosening. This was inevitably followed by the need for replacement implant surgery. (Interestingly, when orthopedic surgeons were presented with a cemented hip implant that had become loose, they referred to it as being in need of “revision”— thereby avoiding the unpleasant term failure. If only we as dentists could also have this advantage of never having failures!)

Prof Pilliar and I attended the Toronto meeting in 1982 with others in our faculty and afterward started to think about alternative designs for endosseous dental implants. Specifically, we began wondering if the sintered porous-surfaced concept could be translated from orthopedics to dentistry and whether this would offer any advantages over a machine-turned threaded implant. We set out immediately to write grant proposals, and in 1983, we were fortunate to gain generous funding from a Canadian federal research agency (Medical Research Council of Canada) to pursue this idea. We undertook studies first in animals and later (starting in 1989) in human clinical trial investigations. What we soon came to realize was that the sintered surface feature of the dental implant that we had conceived provided a much stronger bone-to-implant interface than a threaded implant with a machine-turned surface (ie, resistant to shear, tensile, and compressive interface forces).4

From that point began our premise that sintered porous-surfaced dental implants (SPSIs) could function well in short lengths (as short as 5-mm designed intrabony length).5 By the early 1990s, the United States Food and Drug Administration had reviewed and given approval for SPSIs to be tested in the United States by a small group of dentists who were already highly experienced in implant dentistry. However, the catch was that based on their previous experiences with other dental implant designs, these clinicians felt that longer implant lengths would be needed to improve the likelihood of success in their own patients. So the company licensed by the University of Toronto to produce the SPSI created a 12-mm-long version—that being the longest one possible given that the design included a 5-degree taper angle. However, ongoing human clinical trials have confirmed that the original shorter lengths worked as well, if not better, than that 12-mm length.6

It is now well over 25 years since my colleagues and I began reporting that short dental implants (≤ 8 mm) predictably perform well in both edentulous and partially edentulous patients. Finally, the floodgates have opened and many well-respected clinical investigators have begun to report good outcomes with short moderately rough threaded implants both with and without calcium phosphate nanocoatings. Even ultra-short implants (< 6 mm) are coming into use, and as they do, we will continue to unravel the tale of two lengths (standard versus short and ultra-short).7

The authors who I selected to participate in this book all have considerable experience with short and ultra-short implants and continue to challenge the false tenet that they are used with greater risk than much longer ones. However, it is unwise for beginners in the use of short and ultra-short endosseous implants to assume that they are in any way less difficult than those of more traditional lengths because they most certainly are not. Nevertheless, it is my hope that we have presented the topic effectively and in sufficient detail for clinicians to consider short implants as a viable treatment option for their patients and have an increased probability of success when they choose this approach.

References

1.Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated dental implants: The Toronto study. Part I: Surgical results. J Prosthet Dent 1990;63:451–457.

2.Zarb GA. Proceedings of the Toronto Conference on Osseointegration in Clinical Dentistry. St Louis: Mosby, 1983.

3.Pilliar RM. Porous-surfaced metallic implants for orthopedic applications. J Biomed Mater Res 1987;21(A1 suppl):1–33.

4.Deporter D, Watson PA, Pilliar RM, Chipman ML, Valiquette N. A histological comparison in the dog of porous-coated vs. threaded dental implants. J Dent Res 1990;69:1138–1145.

5.Renouard F, Nisand D. Impact of implant length and diameter on survival rates. Clin Oral Implants Res 2006;17(suppl 2):35–51.

6.Deporter D, Todescan R, Riley N. Porous-surfaced dental implants in the partially edentulous maxilla: Assessment for subclinical mobility. Int J Periodontics Restorative Dent 2002;22:184–192.

7.Neugebauer J, Nickenig HJ, Zöller JE; Department of Cranio-maxillofacial and Plastic Surgery and Interdisciplinary Department for Oral Surgery and Implantology; Centre for Dentistry and Oral and Maxillofacial Surgery, University of Cologne. Update on short, angulated and diameter-reduced implants. Presented at the 11th European Consensus Conference, Cologne, 6 Feb 2016.

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First, I of course wish to thank the contributors to this book who were equally excited as I to share their experiences and knowledge on the previously controversial topic of short and ultra-short dental implants. Their generosity and enthusiasm helped to keep me focused on the project whenever I found it to be daunting. I would also like to thank my colleague Howard Tenenbaum who, as former Head of Periodontics in our faculty, encouraged me to continue my work at a time when others nearby were so heavily critical. I need to acknowledge Dr Daniel Cullum who invited me several years ago to coedit a book with him on minimally invasive dental implant surgery. Working on and helping to complete that earlier book gave me the incentive and courage to undertake the present endeavor as sole editor. Many thanks are due to Jeff Comber, the senior photographer in the Faculty of Dentistry at the University of Toronto, for his tireless efforts to provide and scrutinize many of the images presented in the book. I also wish to thank the welcoming and helpful staff at Quintessence for their assistance in making the project as stress-free as possible.

When I first undertook patient trials of a short dental implant with my coinvestigator Philip Watson in 1989, I had no previous clinical experience in implant dentistry and no idea what to expect. The consensus among “experts” at the time was that implants less than 10 to 13 mm in length were at very high risk of failure, and I was reminded of this for many years by widespread skepticism whenever I presented the results of our work. Robert Summers’s innovation of transcrestal sinus elevation in the mid 1990s boosted my enthusiasm. Using his approach to sinus grafting, I soon learned that short and ultra-short implants could be as successful in the resorbed posterior maxilla as in the resorbed posterior mandible. It is of great satisfaction to me that, after almost 30 years of trying to convince the dental community that implants need not be long to be successful, the time has come for short and ultra-short implants to take their place in routine clinical practice. The contributors to this book have made and will continue to make this achievement a reality. And, by the way, they were all a pleasure to work with.

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Murray Arlin, DDS

Private Practice Limited to Periodontics and Implantology

Toronto, Ontario

Pierluigi Balice, DDS, MDSC

Resident

Department of Periodontology

School of Dental Medicine

University of Connecticut

Farmington, Connecticut

Carlo Barausse, DDS

Doctoral Student

Department of Biomedical Science and Neuromotor Sciences

University of Bologna

Bologna, Italy

Hugo De Bruyn, DDS, MSC, PhD

Professor

Department of Periodontology, Oral Implantology, Removable and Implant Prosthetics

Faculty of Medicine and Health Sciences

Ghent University

Ghent, Belgium

Douglas Deporter, DDS, PhD

Professor

Faculty of Dentistry

University of Toronto

Toronto, Ontario

Pietro Felice, MD, DDS, PhD

Researcher

Department of Biomedical Science and Neuromotor Sciences

University of Bologna

Bologna, Italy

André Hattingh, BChD, MChD

Private Practice Limited to Periodontics and Implantology

Sevenoaks, Kent

United Kingdom

PhD Student

Department of Periodontology, Oral Implantology, Removable and Implant Prosthetics

Faculty of Medicine and Health Sciences

Ghent University

Ghent, Belgium

Henny J. A. Meijer, DDS, PhD

Professor

Department of Dentistry, Oral Surgery, and Medicine

Faculty of Medical Sciences

University of Groningen

Groningen, The Netherlands

Vittoria Perrotti, DDS, PhD

Research Fellow

Department of Medical, Oral and Biotechnological Sciences

School of Medicine and Health Sciences

University of Chieti-Pescara

Chieti, Italy

Adriano Piattelli, MD, DDS

Professor of Oral Pathology and Medicine

Department of Medical, Oral and Biotechnological Sciences

School of Medicine and Health Sciences

University of Chieti-Pescara

Chieti, Italy

Professor and Chair of Biomaterials Engineering

Catholic University San Antonio de Murcia

Murcia, Spain

Roberto Pistilli, MD

Resident

Department of Oral and Maxillofacial Surgery

San Camillo Hospital

Rome, Italy

Gerry M. Raghoebar, DDS, MD, PhD

Professor

Department of Oral Disorders, Oral Surgery, and Special Dentistry

Faculty of Medical Sciences

University of Groningen

Groningen, The Netherlands

Franck Renouard, DDS

Private Practice Limited to Oral and Implant Surgery

Paris, France

Antonio Scarano, DDS, MD

Associate Professor of Oral Surgery

Department of Medical, Oral and Biotechnological Sciences

School of Medicine and Health Sciences

University of Chieti-Pescara

Chieti, Italy

Kees Stellingsma, DDS, PhD

Assistant Professor

Department of Oral Disorders, Oral Surgery, and Special Dentistry

Faculty of Medical Sciences

University of Groningen

Groningen, The Netherlands

Rainier A. Urdaneta, DMD

Private Practice Limited to Prosthodontics

Worcester, Massachusetts

Stefan Vandeweghe, DDS, PhD

Associate Professor

Department of Periodontology, Oral Implantology, Removable and Implant Prosthetics

Faculty of Medicine and Health Sciences

Ghent University

Ghent, Belgium

AUTHOR’S NOTE

There has been discussion over the years on exactly what constitutes a short or ultra-short implant. The classification used in this book is based not on total implant length but on the designed intrabony length (DIL). This is the part of the implant responsible for osseointegration and does not include collars or transgingival segments that are not meant to fixate to bone. A standard-length implant is defined as one with a DIL greater than 8 mm. Implants with a DIL between 6 and 8 mm are considered short, while those with a DIL less than 6 mm are considered ultra-short. Please also note that all implant dimensions in this book are given as length × width.

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It has been more than 50 years since the first successfully osseointegrated implant procedure was performed by Dr Per-Ingvar Brånemark, and yet controversy remains regarding the optimal shape and size of solid endosseous root-form dental implants. There are few medical fields with this degree of uncertainty despite the wealth of relevant scientific data. The recommended lengths of dental implants are a striking example. A quick search on PubMed in December 2016 identified 5,400 articles mentioning short implants, but the majority of articles focused on more complex solutions, relegating short implants to the rank of emergency fallback solutions only. Consequently, the mindset persists that the longer the implant, the more successful it will be both in the short and long term. Advanced, costly, and technique-sensitive collateral procedures often need to be performed to be able to use standard-length implants, such as autogenous (and other) bone block grafting, vertical alveolar ridge augmentation, mandibular nerve repositioning, and open sinus grafting. Interestingly, however, the first implants developed and tested successfully by Brånemark in the 1960s were all under 8 mm in length, and some were even shorter than 5 mm.

The reluctance of clinicians to use short implants derives largely from their reading of statistical assessments of implant failure while neglecting other considerations like the patient’s sex, the size of the patient’s mouth, the risk of complications with more complex procedures, and the feasibility of such procedures being undertaken by nonspecialists in a private practice setting. If the intention is to provide the simplest, least invasive, least complicated, and least stressful procedure, it is worth asking: why should we avoid using short implants? Arguments commonly put forward include the following:

Their success rate may be lower compared with standard-length implants.

Stress distribution with loading of short implants may result in increased biomechanical risk due to the poor crown-to-implant (C/I) ratio.

There may be a greater risk of failure if crestal bone loss occurs due to mechanical overload or inflammation and infection (eg, mucositis or peri-implantitis).

It is difficult to move away from more familiar ways of doing things.

This chapter addresses these concerns.

Success Rates

Are the success rates for short implants worse than those of procedures that use standard-length implants? The poor reputation of short implants is—for the most part—based on early implant literature using the original Brånemark-type implant: A commercially pure titanium threaded screw with a machine-turned (ie, minimally rough) surface finish.14 In each of these reports, the authors stated in their abstracts and/or conclusions that failure of short (ie, ≤ 10 mm) implants was higher than that of longer ones. This was enough to establish a dogma that was not easily challenged. However, a closer reading of these articles reveals that although the failure rates with short implants were higher, the difference compared with longer implants was less significant than the authors implied. For example, in the report by Friberg et al2 examining 4,641 implants, the failure rate of short maxillary implants covering everything from single crowns to full-arch reconstructions in fully edentulous patients was only 7%. Looking only at the results for partially edentulous patients in this study, the failure rate of short implants plummeted to 1.3%. Moreover, the authors stated that most of the failures were early—once short implants had been fully integrated in bone, they behaved just like longer implants. In 1991, these clinicians were not only using cylindric, machined-surface implants; they were also following a standard and identical drilling protocol for both short and longer implants and regardless of the bone density encountered.

Likewise, a closer look at the report by Lekholm et al4 shows the failure rate for short implants as not significantly different from that of procedures using longer implants. In the study by van Steenberghe et al,1 short implants were separated into those with lengths of 7 mm and 10 mm, and the 7-mm implants had a higher success rate than those with lengths of 10 mm. The adaptation of these findings to comply with the general consensus at the time (ie, that implants shorter than 10 mm fail more often despite contrary objective data) is termed confirmation bias. This type of bias is a very common cognitive behavior: Once a decision has been made or a “fact” learned, the human brain will always look for data that corroborate the preconceived notion in question and dismiss data challenging these notions. It is an unfortunate but frequent occurrence in many scientific fields.5

As implant research continued, the influences of length and diameter on implant survival and success have been studied using a more objective approach to scientific publications: reviewing the facts prior to drawing conclusions. For instance, Renouard and Nisand6 published a systematic review of articles published between 1990 and 2005. Using Medline resources, papers were initially selected if implants were placed in healed sites in human subjects and if the studies provided (1) relevant data on implant lengths and diameters, (2) implant survival rates that were either clearly stated or calculable, and (3) clearly defined criteria for implant failure. A total of 34 studies fulfilled these inclusion criteria, and of these, 13 were devoted to short implants. The investigators in these 13 studies were able to report outcomes for a total of 3,173 implants in 2,072 patients. Implants from a number of manufacturers were included, and the mean implant length was 7.9 mm. Observation periods ranged from 0 to 168 months with a median period of 47.1 months. A total of 9.5% of the study patients were reported as having dropped out, leading to a mean implant survival rate of 95.9%, which is more or less the same as for longer implants of the time. However, some authors reported noticeably lower success rates than this mean, and readers need to understand why.

In 2005, Hermann et al7 analyzed a large number of failed implant procedures and reported that short implants had usually been used in sites with low bone volume and density, whereas longer implants were nearly always placed in denser bone. This observation challenges implant length as the cause of failure. For example, did an implant in the posterior maxilla fail because of its length, or was the result caused by low bone density and the clinician’s failure to appropriately modify osteotomy preparation?

If a short implant is to be eliminated as a treatment choice, the clinician and patient need to be aware of the likely risks, complications, and possibility of implant failure if longer implants are to be used in conjunction with maxillary sinus grafting or a vertical ridge augmentation procedure. Recent research addressed some of these issues using randomized controlled clinical trials in humans comparing short implants alone with longer implants placed in previously grafted bone. Unlike a lot of the early work with short implants, the investigators employed moderately rough (eg, particle-blasted or acid-treated) rather than machine-surfaced implants.8 In resorbed posterior mandibles, Esposito et al9 provided a 3-year report on the use of 6.3-mm-long implants versus 9.3-mm-long implants placed in sites where earlier vertical ridge augmentation had been done using interpositional block xenografts. Each patient received two or three implants that were allowed submerged healing and ultimately restored with splinted fixed prostheses. Two short implants failed and three standard-length implants failed, all in different patients. However, there were significantly more complications in the augmented patients with standard-length implants (22 complications in 20 augmented patients) than those with short implants (5 complications in 5 patients). In a similar vein, Pieri et al10 compared 6- to 8-mm implants with 11-mm implants placed in conjunction with a lateral window sinus grafting procedure. After a mean functional time greater than 3 years, the implant survival rates were similar, but again there were significantly more surgical complications with the sinus group (10 complications in 9 patients with standard-length implants compared with 1 complication in the short implant group).

Choosing not to use short implants because of their supposed inferior performance then appears not to be a wise decision. Indeed, it seems clear that short implants should be the treatment of first choice in sites with low bone volume unless there are other considerations (eg, esthetics) that would contraindicate short implant use.

Implant Stress Distribution and C/I Ratio

In the 1990s, articles began to appear on the impact and patterns of mechanical stress distribution with functioning dental implants. Using finite element analyses, as early as 1992 Meijer et al11 predicted that when dental implants are subjected to lateral (ie, off-axis) loading, stress will be chiefly concentrated in crestal bone surrounding the neck regions of implants. It was concluded that changing implant length had no significant impact on stresses being received by peri-implant crestal bone. Similar conclusions were later drawn by Pierrisnard et al.12 In line with basic mechanical principles, the greater the angle at which a force is received, the greater the stress concentration at the implant neck, with this stress diminishing toward the implant apex.

The ratio of crown length to tooth root length (C/R) has long been considered a key factor in designing traditional, tooth-supported prostheses. Having a C/R ratio greater than 1 was considered a risk factor for failure, and this precept was initially thought to apply to dental implant performance as well. With the anticipated implant C/I ratio significantly greater than 1, many clinicians preferred to use collateral surgical techniques to allow for the placement of longer implants. In the posterior mandible, for example, some clinicians have gone as far as to recommend lateralization of the mandibular nerve to enable longer implants to be placed—even though no prospective trials have been reported comparing this risky procedure with short implants. However, numerous authors have now shown that C/I ratio is not an issue for the most part, meaning that once again short implants may be the treatment of first choice.1315 This is not to say that there are no upper limits for C/I ratio because there certainly may be; however, whether an implant is 5 mm long or 15 mm long, it will ultimately experience the same stress patterns and minimize the importance of C/I ratio on biologic complications. Nevertheless, a long implant-abutment complex will increase the length of the lever arm (measured to the implant neck) and therefore increase the risk of prosthesis overload. This means that selection of the number of short implants used and the use of splinting are important considerations.

Risk of Bone Loss and Peri-implantitis

The long-standing Albrektsson criteria16 for dental implant success continue to be used in clinical practice, including the recommendation that bone loss should not be greater than 1.2 mm during the first year of implant function and not greater than 0.2 mm annually thereafter. The majority of successful implants, however, do not show progressive bone loss with time in function, but rather reach a steady state after which no detectable bone loss will occur. Therefore, the Albrektsson criteria have helped create the misconception that in the space of a few years, there could be sufficient bone loss around a short implant for it to lose integration. A number of investigators have demonstrated that the pattern of bone loss with time with short implants appears similar to that experienced by longer ones.17 In contrast, Naert et al18 and Rokni et al15 determined that bone loss was greater with standard-length implants than with short ones. This is assuming of course that the short implants were placed using appropriate surgical protocols and with attention to the fact that final buccal bone needs to be of sufficient thickness (ie, greater than 2 mm) to minimize its postoperative resorption with exposure of rough implant surfaces.19 Should such exposure occur, there is always the risk of bacteria-induced inflammatory bone loss (ie, peri-implantitis). This condition is an inflammatory process that generally leads to further and often progressive bone loss around the implant. This latter bone loss can be stabilized by remedial procedures in some cases, but a short implant in this condition would certainly be at greater risk of loss of integration than a longer one.

Implant Length and Human Factors

Placing an implant is a stressful procedure for most practitioners, especially if it is done infrequently. The more complex the surgical procedure the practitioner has to undertake, the more stress-inducing both before and during the procedure. Studies in the field of general surgery have demonstrated that more complex procedures result in a greater likelihood of complications arising from human error.20 Complex procedures magnify the impact of human factors. As far as is possible, it is wise to use the simplest and least invasive procedures possible to reduce the likelihood of human error, also called nontechnical errors. Performing a lateral window sinus floor elevation or grafting procedure to be able to place a long implant can create a stress level significant enough to impair the clinician’s ability to concentrate on what matters most for implant placement: that the implant is correctly positioned.

Studies from the field of aviation offer indisputable evidence that human mental resources are finite regardless of the action being performed. The greater the stress, the harder it is to stay focused for any length of time on what really matters.21,22 Physiologic changes linked to stress prevent the surgeon from holding to a line of thinking or respecting a protocol that he or she would adopt or implement without question in less stressful scenarios. Opting for simpler courses of action will make it easier to remain focused on the key task at hand. Susceptibility to stress varies between individuals, but electing to use short implants could help reduce stress and assist the clinician in making intraoperative decisions.

Conclusions

Short implants are not necessarily inferior to long implants, but nor are they necessarily more infallible than long implants. The objective is not to always choose short implants but to always include them for consideration when making a decision about which approach to take. Short implants should be seen as a reliable alternative with a low risk of complications. They are suitable in many circumstances and offer a workable, reliable solution.

References

1.van Steenberghe D, Lekholm U, Bolender C, et al. Applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: A prospective multicenter study on 558 fixtures. Int J Oral Maxillofac Implants 1990;5:272–281.

2.Friberg B, Jemt T, Lekholm U. Early failures in 4,641 consecutively placed Brånemark dental implants: A study from stage 1 surgery to the connection of completed prostheses. Int J Oral Maxillofac Implants 1991;6:142–146.

3.Jemt T, Lekholm U. Implant treatment in edentulous maxillae: A 5-year follow-up report on patients with different degrees of jaw resorption. Int J Oral Maxillofac Implants 1995;10:303–311.

4.Lekholm U, Gunne J, Henry P, et al. Survival of the Brånemark implant in partially edentulous jaws: A 10-year prospective multicenter study. Int J Oral Maxillofac Implants 1999;14:639–645.

5.Kapur N, Parand A, Soukup T, Reader T, Sevdalis N. Aviation and healthcare: A comparative review with implications for patient safety. JRSM Open 2015;7:2054270415616548.

6.Renouard F, Nisand D. Impact of implant length and diameter on survival rates. Clin Oral Implants Res 2006;17(suppl 2):35–51.

7.Herrmann I, Lekholm U, Holm S, Kultje C. Evaluation of patient and implant characteristics as potential prognostic factors for oral implant failures. Int J Oral Maxillofac Implants 2005;20:220–230.

8.Albrektsson T, Wennerberg A. Oral implant surfaces: Part 1—Review focusing on topographic and chemical properties of different surfaces and in vivo responses to them. Int J Prosthodont 2004;17:536–543.

9.Esposito M, Cannizarro G, Soardi E, Pellegrino G, Pistilli R, Felice P. A 3-year post-loading report of a randomised controlled trial on the rehabilitation of posterior atrophic mandibles: Short implants or longer implants in vertically augmented bone? Eur J Oral Implantol 2011;4:301–311.

10.Pieri F, Caselli E, Forlivesi C, Corinaldesi G. Rehabilitation of the atrophic posterior maxilla using splinted short implants or sinus augmentation with standard-length implants: A retrospective cohort study. Int J Oral Maxillofac Implants 2016;31:1179–1188.

11.Meijer HJ, Kuiper JH, Starmans FJ, Bosman F. Stress distribution around dental implants: Influence of superstructure, length of implants, and height of mandible. J Prosthet Dent 1992;68:96–102.

12.Pierrisnard L, Renouard F, Renault P, Barquins M. Influence of implant length and bicortical anchorage on implant stress distribution. Clin Implant Dent Relat Res 2003;5:254–262.

13.Blanes RJ, Bernard JP, Blanes ZM, Belser UC. A 10-year prospective study of ITI dental implants placed in the posterior region. II: Influence of the crown-to-implant ratio and different prosthetic treatment modalities on crestal bone loss. Clin Oral Implants Res 2007;18:707–714.

14.Tawil G, Aboujaoude N, Younan R. Influence of prosthetic parameters on the survival and complication rates of short implants. Int J Oral Maxillofac Implants 2006;21:275–282.

15.Rokni S, Todescan R, Watson P, Pharoah M, Adegbembo AO, Deporter D. An assessment of crown-to-root ratios with short sintered porous-surfaced implants supporting prostheses in partially edentulous patients. Int J Oral Maxillofac Implants 2005;20:69–76.

16.Albrektsson T, Dahl E, Enbom L, et al. Osseointegrated oral implants. A Swedish multicenter study of 8139 consecutively inserted Nobelpharma implants. J Periodontol 1988;59:287–296.

17.Renouard F, Nisand D. Short implants in the severely resorbed maxilla: A 2-year retrospective clinical study. Clin Implant Dent Relat Res 2005;7(suppl 1):S104–S110.

18.Naert I, Duyck J, Hosny M, Jacobs R, Quirynen M, van Steenberghe D. Evaluation of factors influencing the marginal bone stability around implants in the treatment of partial edentulism. Clin Implant Dent Relat Res 2001;3:30–38.

19.Spray JR, Black CG, Morris HF, Ochi S. The influence of bone thickness on facial marginal bone response: Stage 1 placement through stage 2 uncovering. Ann Periodontol 2000;5:119–128.

20.Barach P, Johnson JK, Ahmad A, et al. A prospective observational study of human factors, adverse events, and patient outcomes in surgery for pediatric cardiac disease. J Thorac Cardiovasc Surg 2008;136:1422–1428.

21.Wetzel CM, Kneebone RL, Woloshynowych M, et al. The effects of stress on surgical performance. Am J Surg 2006;191:5–10.

22.Weigl M, Stefan P, Abhari K, et al. Intra-operative disruptions, surgeon’s mental workload, and technical performance in a full-scale simulated procedure. Surg Endosc 2016;30:559–566.

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In 1981, osseointegrated dental implants were first introduced to a worldwide audience by Dr Brånemark and his Swedish colleagues.1 The original Brånemark-type implant had a machine-turned or minimally rough surface finish, and many early users maintained from the outset that the short implant had a high failure rate (eg, 25% with 7-mm lengths), especially in the posterior maxilla.25 Despite decades of progress in implant design and technique and the revelation that shortening implant lengths has no significant impact on their stability, many clinicians still believe that short implants are more likely to fail.6,7 The Periotest device (Medizintechnik Gulden) and resonance frequency testing have shown that failure is not increased with shorter implants, and resonance frequency testing has even demonstrated that increasing implant length may actually reduce implant primary stability.8,9 However, since more successful research has been carried out and minimally invasive implant procedures have become the preferred treatment, short implants have become trendier.1012 Most implant manufacturers now market them—although not all with adequate premarket clinical testing.

The current definition of short implant is one with a designed intrabony length (DIL) of 6 to 8 mm, while an ultra-short implant has a DIL of less than 6 mm.13,14 (Note that the DIL refers to the length meant to be responsible for implant fixation to bone, not the total implant length.) The most common location for short implant use is the resorbed posterior mandible (Fig 2-1), but they can also be appropriate in the resorbed anterior mandible1518 (Figs 2-2 and 2-3). In a posterior maxilla with resorption or a pneumatized sinus (Figs 2-4 and 2-5), some short implant designs have proven to be a legitimate substitute for longer implants used in conjunction with a dedicated open sinus floor elevation and grafting procedure.10,1921 Using short or ultra-short implants in this last situation greatly reduces the associated risks, patient morbidity and anxiety, and cost. One recent investigator22 actually concluded that there is little justification for open lateral window sinus grafting where 5 mm of subantral bone remains preoperatively because a short implant with or without minimal indirect sinus floor elevation (eg, using hand osteotomes) will often work equally well.19,23 Using short or ultra-short implants can also simplify treatment in sites with alveolar ridge undercuts that would otherwise lead to apical bone fenestrations with longer implants (Fig 2-6).

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FIG 2-1 | This prosthesis is supported by two 8-mm-long Straumann Tissue Level moderately rough threaded implants (MRTIs). The implant diameters are 4.1 mm (mesial implant) and 4.8 mm (distal implant). Crestal bone remodeling primarily affects the machined collar segments with some signs of increased crestal bone density on the mesial of the more anterior implant. (Restoration courtesy of Dr Simon Yeh, Toronto, Ontario.)

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FIG 2-2 | A radiograph of three 7 × 3.75–mm MRTIs that were used to support a fixed mandibular prosthesis. This radiograph was taken after 5 years in function. The opposing dentition was a fixed, implant-supported prosthesis. (Courtesy of Dr Pietro Felice, University of Bologna, Italy.)

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FIG 2-3 | (a) This patient participated in a clinical trial in 1990 and received three freestanding, short, and sintered porous-surfaced implants (SPSIs) to retain a complete mandibular overdenture.18 The photographs were taken after 20 years in function. (b) The overall length of the implants was 8 mm, but the DIL was only 6 mm because there was a 2-mm machined transgingival collar segment.13 Note that the implants are encircled by healthy keratinized gingival tissue. (c) A radiograph corresponding to the short SPSIs.

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FIG 2-4 | (a) A preoperative radiograph shows a hopeless maxillary left first molar. The tooth was extracted with socket preservation using a xenograft and a dense polytetrafluoroethylene barrier material (Regentex, Osteogenics Biomedical). (b) This SPSI was placed in the first molar site in 2001 using transcrestal sinus floor elevation (ie, bone-added osteotome sinus floor elevation) of 2 mm.19 The original sinus floor can no longer be seen in this radiograph taken in 2017 after the implant had functioned with its original restoration for over 16 years. The implant was 7 × 5 mm with a 2-mm machined collar, making the DIL only 5 mm. (Restoration courtesy of Dr Reynaldo Todescan, Toronto, Ontario.)

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FIG 2-5 | This splinted maxillary prosthesis is supported by three 5 × 5–mm MRTIs. The radiograph was obtained after the restoration had been in function for 3 years. (Courtesy of Dr Pietro Felice, University of Bologna, Italy.)

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FIG 2-6 | (a) This patient received two 5-mm-long SPSIs (DIL: 4 mm) and a 7-mm-long SPSI (DIL: 6 mm).13 All implants had diameters of 4.1 mm and were used to support a hybrid fixed maxillary anterior prosthesis. Such short implants were chosen to avoid creating labial dehiscences given that the ridge had a marked labial undercut. The implants opposed natural mandibular teeth. (b) The 7 × 4.1–mm SPSI was placed in the canine site where there was no ridge undercut. (c) A clinical photograph of the hybrid prosthesis with lips retracted. (Courtesy of Dr Ester Canton, Toronto, Ontario.) (d) The hybrid prosthesis with normal lip posture.

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