Implant therapy: 40 years of experience M ARC Q UIRYNEN ,D AVID H ERRERA ,W IM T EUGHELS &M ARIANO S ANZ Dental implants placed under favorable conditions in healthy patients have success rates of over 95%, even after 15 years of follow up. In spite of this excellent outcome, technical, biologic and esthetic complications do occur (17, 27, 30, 31). Moreover, the outcome can be less desirable if dental implants are placed in patients affected with sys- temic diseases or other compromising conditions (2, 4, 13, 22, 25). Metabolic disorders or immune deficiencies can, for example, give rise to surgical complications and may also interfere with bone apposition and/or remodeling at the implant–bone interface. Similarly, radiation therapy in the surgical area may significantly reduce cellularity and vascu- larity, and hence affect the healing of oral implants. In compromised patients, implant-based treatment may be a questionable choice. Medica- tion, such as biphosphonates and/or anticoagu- lants, may also affect the outcome of implant placement or increase the frequency of postopera- tive complications. The placement of dental implants in such patients must adhere to strict treatment protocols (19, 20). The clinical protocol for the placement of dental implants has changed significantly over the past 40 years (Table 1). From the initial ‘biocompatibility’- oriented protocol, aiming at osseointegration and long-term success, there has been an evolution toward less stringent criteria for implant placement in order to ‘speed the healing process’ and ‘improve the esthetic results’, although it is still questionable whether patients will ultimately bene- fit from these changes. The purpose of this volume of Periodontology 2000 is to evaluate the new developments in implantology, review their scien- tific evidence and analyze their indications, advan- tages and disadvantages. It is organized into 16 chapters dealing with diagnostic and therapeutic concepts, from the use of current three-dimensional radiographic techniques to guided surgical implantation and enhanced surgical protocols. The overall goal is to guide the clinician in decision making around implant therapy and to provide an understanding of the etiology and therapy of peri-implant diseases. Indication/treatment planning Whereas initially only fully edentulous patients with optimal jaw bone dimensions (width and height) were the basic indication for implant therapy, now nearly every edentulous space is considered as suit- able for implant placement. In situations where insufficient bone is available for implant therapy, bone-augmentation techniques are routinely consid- ered. Benic & H€ ammerle (3) concluded that such techniques are highly predictable if the proper indi- cations are respected and appropriate healing time is allowed for bone regeneration. Another approach is the use of the zygoma when the maxillary bone is severely atrophic. As discussed by Aparicio et al. (1), the zygomatic implant technique offers the possibil- ity to treat highly complex situations with low mor- bidity. The bone height in the posterior maxilla is often limited and a sinus lift procedure is recom- mended. Besides the conventional lateral window technique, a less invasive transalveolar approach is described by Pjetursson & Lang (26). As an alterna- tive to surgical bone regeneration, various studies have reported successful outcome with the use of short implants in the mandible as well as in the maxilla. Nisand & Renouard (24) discuss the indica- tions and evidence-based efficacy of the use of short and narrow implants. The esthetic outcome of implant therapy is addressed by Merheb et al. (21) and Thoma et al. (34). Merheb et al. (21) review the optimal implant-placement within the bone 7 Periodontology 2000, Vol. 66, 2014, 7–12 © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Printed in Singapore. All rights reserved PERIODONTOLOGY 2000