Moy / Pozzi / Beumer Fundamentals of Implant Dentistry, Volume II

Surgical Principles
2. Auflage 2019
ISBN: 978-0-86715-876-2
Verlag: Quintessence Publishing Co, Inc
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, Band 2, 448 Seiten

Reihe: Volume

Since the concept of osseointegration was introduced to the dental community more than 35 years ago by Professor P-I Brånemark, significant improvements have been achieved in patient evaluation, methods used to enhance the bone and soft tissues of potential implant sites, and surgical techniques to prepare the osteotomy sites and place the implants. In particular, CBCT scans and associated software planning programs now enable the implant team to analyze the bone sites in three dimensions in relation to the proposed contours of the implant-retained prostheses; select implants of suitable diameter, length, and configuration; position them virtually in ideal locations; and fabricate surgical templates that enable surgeons to prepare the osteotomy sites and place the implants with great precision. These topics are thoroughly discussed from the perspective that an interdisciplinary approach will yield the most predictable outcomes for treatment of the dental implant patient. The authors address the sometimes controversial topic of immediate loading and provide useful insights regarding when this approach can achieve predictable outcomes and when it is to be avoided. The use of CAD/CAM technologies is emphasized throughout the text, and the latest developments and their use in this rapidly expanding arena are fully described.

Peter K. Moy, DMD is a clinical professor of oral and maxillofacial surgery in the Division of Diagnostic & Surgical Sciences at the UCLA School of Dentistry. He is the first person to hold the Nobel Biocare Endowed Chair in Surgical Implant Dentistry. He also serves as the director of the UCLA Dental Implant Center and the Straumann Surgical Dental Clinic. Dr. Moy treat patients in the UCLA Straumann Surgical Dental Clinic as well as in his private practice located in Brentwood, California. John Beumer III, DDS, MS, received his DDS from the University of California, San Francisco in 1967. He subsequently completed his postgraduate training in oral medicine there in 1970 before continuing with postgraduate training in prosthodontics at UCLA. He is a Distinguished Professor Emeritus in the Division of Advanced Prosthodontics at the UCLA School of Dentistry and was formerly chair of that division. Dr Beumer has published extensively in the scientific literature, including Maxillofacial Rehabilitation (Quintessence, 2011) and Fundamentals of Implant Dentistry Quintessence, 2015-2016). Alessandro Pozzi: After completing his initial education in dentistry at the University of Rome in 1997, Professor Pozzi continued developing his knowledge and skills in oral surgery-implant dentistry, orthodontics, gnathology and prosthodontics. Having worked as a Research Scientist and a Professor in Oral Rehabilitation at the University of Rome since 2009, he has been selected to receive the 2013 Judson C. Hickey Scientific Writing Award in the Clinical Report Category. Currently He holds the interim Chair of oral surgery-implantology at the Polytechnic University of Marche, Italy and Guest Lecturer at the Continuing Education and Implant Center of UCLA University, Los Angeles, California. He has been researching and lecturing extensively on guided surgery, novel implant design and concepts, and minimal invasive implant esthetics. Prof. Pozzi also leads several theoretical and practical training courses on minimally invasive implant surgery, CAD/CAM prosthetics and esthetics in his office based in Rome.

Autoren/Hrsg.

Moy, Peter K

Pozzi, Alessandro

Beumer, John III

Leseproben

The Evolution of Modern Dental Implant Surfaces Takahiro Ogawa
Basil Al-Amleh
Ichiro Nishimura
John Beumer III 2 Since titanium implants were introduced more than 30 years ago, a sustained effort has been made to make their surfaces more osteoconductive. Following placement of a dental implant made of titanium, a blood clot forms between the surface of the implant and the walls of the osteotomy site.1 Plasma proteins are attracted to the area, platelets are activated, and cytokines and growth factors are released.2–4 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.5 This process takes anywhere from 2 weeks to 4 months, depending on the osteoconductivity of the implant surface. The process of machining the implants to create their screw-shaped macrostructure was responsible for the implant surface texture of the original Brånemark implant introduced in the 1980s. A wavy surface irregularity was created, depending on the methods employed during machining (Fig 2-1). The machined implant surfaces were osteo-inert (the passive process by which osteogenesis initiates exogenously and approaches the implant surface) as opposed to osteoconductive (the recruitment of osteogenic cells and their migration to the surface of the implant); in the early years, osseointegrated implants were used with great success in edentulous patients when the implant sites were composed of relatively dense cortical bone. However, initial attempts to restore partially edentulous patients, particularly those with poor-quality type IV bone were met with frustration and an unacceptable rate of failure.6 Unfortunately, these frustrations and failures were underreported in the literature. Significant difficulty was encountered when restoring posterior quadrants in the maxilla with implants in partially edentulous patients, especially when cortical layers of bone were thin and the trabecular bone exhibited poor density. Successful results with machined-surface implants in these sites were achieved primarily when the implants were stabilized by so-called bicorticalization (ie, positively engaging the cortical layers of bone associated with the floor of the maxillary sinus and the alveolar process). This procedure was technically demanding, particularly prior to the introduction of computed tomography scans, which allow accurate assessment of the bone sites in three dimensions. As a result, there began a sustained effort to develop implant shapes that could achieve improved initial mechanical stabilization and whose surfaces were more osteoconductive. Fig 2-1 Machined-surface implant. Note the surface morphology. It has been shown that this surface is less bioreactive and osteoconductive than the modern implant surfaces with more favorable surface topography. Several different types of implants were introduced during the 1980s, with surface topography modified by titanium plasma spray (TPS) or airborne-particle abrasion and titanium implants purportedly coated with hydroxyapatite (HA). All had dramatically different surface topographies compared with implants with machined surfaces. However, none of these surfaces provided a significant improvement in clinical outcomes. The surfaces of implants prepared with TPS were quite rough and irregular; the surface irregularities ranged from 10 to 200 microns in size (Fig 2-2). The surface roughness did increase the surface area of the implant, resulting in improved implant anchorage compared with machined-surface implants.7,8 However, when the roughened implant surfaces became exposed to the oral cavity, they retained plaque and calculus tenaciously, leading to inflammation of the peri-implant tissues and loss of bone (peri-implantitis).9,10 Also, during placement, small particles of titanium were often sheared off the surface of the implant, attracting macrophages and giant cells into the area intent upon phagocytizing these particles (Fig 2-3). This process was accompanied by an inflammatory response in the local tissues (so-called particle disease). Fig 2-2 TPS surface. Note the surface irregularities, which range from 10 to 200 microns in size. Fig 2-3 Note the particles of titanium within the tissues. In some instances, this will lead to so-called particle disease. The surface roughness of implants treated with airborne-particle abrasion, like the TPS surfaces, varied considerably depending on the size of the abrasive particles and air pressure. However, these implants presented clinicians with an additional problem: Given the technologies available during the 1980s, it was difficult to completely remove the surface contaminants associated with the process of airborne-particle abrasion, leaving the surface of the implant contaminated and negatively affecting the process of osseointegration. Plasma spray HA–coated titanium implants were initially thought to be advantageous because of their chemical similarity to bone. The so-called HA–calcium phosphate (HA-CaP) surface was more osteoconductive than the titanium surfaces then available. The enhanced osteoconductivity led to rapid deposition of bone onto the entire surface of the implant following placement. Within 6 weeks, almost the whole implant surface was covered with bone11 (Fig 2-4a). During healing, calcium and phosphate ions were released from the HA-CaP coating in the peri-implant region. This led to the precipitation of a biologic apatite on the surface of the implant, which served as a substrate for osteoblasts producing bone. The biologic apatite substrate also facilitated adhesion of migrating mesenchymal stem cells and accelerated the differentiation of these cells into bone-producing cells. Fig 2-4 (a) An HA-coated implant 6 weeks after implantation. The new bone is easily seen with the tetracycline label (yellow). (b) HA-coated implants 3 years after insertion. The HA coating has become exposed, leading to irritation of the peri-implant tissues. Note the bone loss associated with the implants. However, the surfaces of the original plasma spray HA–surface implants were mostly composed of tricalcium phosphate (TCP) rather than HA.12 This occurred because the techniques used to apply the HA to the surface transformed its crystalline structure to TCP, which is rapidly resorbed. Also, when the so-called plasma spray HA–CaPO4 surface became exposed to the oral cavity, it was colonized by oral microorganisms, which in turn provoked an aggressive inflammatory response of the peri-implant tissues. The bacterial colonization, bone loss (Fig 2-4b), and occasional delamination of the so-called HA layer from the titanium surfaces (the adhesion of the HA to the titanium implant surface was purely mechanical) led to high failure rates compared with titanium implants.13 By the end of the 1980s, it became apparent that these surface treatments had not significantly improved clinical outcomes, particularly in patients with poor-quality bone sites. Machined surfaces remained the standard. However, several new technologies were evolving that allowed researchers to gain insight into the initial molecular events associated with the process of osseointegration and that eventually would lead to the development of implant surfaces that were osteoconductive as opposed to osteo-inert machined-surface implants. Microrough Surfaces Research efforts in the last 20 years have attempted to improve the bioreactivity of the implant surface in order to decrease healing time, improve the quality of the bone anchorage, and enable more predictable use in marginal or poor-quality bone sites. In the early 1990s, several new methods were introduced to roughen the surfaces of titanium implants (eg, acid etching, combined airborne-particle abrasion and acid etching, titanium grit blasting, anodic oxidation). The implant surfaces created by these methods were considerably less rough than those created by the TPS method or by airborne-particle abrasion and were more consistent; the surface irregularities ranged from 0.5 to 2.0 microns in size (Fig 2-5). Fig 2-5 The surface topography resulting from double acid etching. This three-dimensional image was taken by atomic force microscopy. At first, the main advantage appeared to be improved mechanical anchorage. The initial studies concentrated on the bone-to-implant contact (BIC) area. The early publications showed that the BIC for implants with microrough surfaces was greater than that seen with machined-surface implants.11,14–18 This was initially thought to be secondary to the improved retention of the fibrin clot, which immediately forms between the implant and the osteotomy sites upon placement of the implant.19 As a result, the initial events (adsorption of plasma proteins, platelet activation, clot formation, angiogenesis, mesenchymal stem cell migration and attachment, cell differentiation) associated with osseointegration were facilitated. Subsequent reports indicated that in addition to improved BIC, the process of osseointegration was accelerated.20–22 However, it soon became evident that the substantial improvement in anchorage seen in...