The International Journal of Prosthodontics 88 REVIEWS The Implant Supracrestal Complex and Its Signifcance for Long-Term Successful Clinical Outcomes Nikos Mattheos, DDS, MASc, PhD Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand; Department of Dental Medicine, Karolinska Institute, Sweden. Ioannis Vergoullis, DDS, MS Department of Periodontics, Louisiana State University, Baton Rouge, Louisiana, USA. Martin Janda, DDS, MSc, PhD Department of Prosthodontics, Malmö University, Malmö, Sweden. Alberto Miseli, DDS Department of Prosthodontics, Universidad Central de Venezuela, Caracas, Venezuela. Emerging evidence implies signifcant interrelations between the condition of the peri-implant tissues and the implant-abutment-prosthesis complex. A new paradigm for studying the peri-implant tissues in close interrelation with the implant-abutment-prosthesis complex in the presence of the oral bioflm is essential. The aims of this paper are to introduce the concept of the “implant supracrestal complex” (ISC) and to describe the critical elements that defne it as a unique anatomical and functional system of human tissues, mechanical components, and oral bacteria/bioflm. This paper reviews recent evidence to identify the impact of design features on short-term clinical outcomes and long-term health of the peri-implant bone and soft tissues. Prosthetic-driven implant placement is a prerequisite for proper ISC design, which in turn can indirectly infuence the structure and dimensions of the peri-implant soft tissues. Design features of the implant- prosthesis-abutment complex, such as the emergence profle, emergence angle, and cervical margin, as well as the design of the implant-abutment and abutment-prosthesis junctions and their locations in relation to the tissues of the ISC, can have a signifcant impact on the maintenance of stable and healthy peri-implant tissues in the long term. Int J Prosthodont 2021;34:88–100. doi: 10.11607/ijp.7201 Correspondence to: Dr Nikos Mattheos Department of Oral and Maxillofacial Surgery Faculty of Dentistry Chulalongkorn University, Bangkok, Thailand 34 Henri Dunant Road, Wangmai, Patumwan Bangkok, Thailand 10330 Fax.: +66-2218-8581 Email: nikos@mattheos.net Submitted June 15, 2020; accepted August 23, 2020. ©2021 by Quintessence Publishing Co Inc. A multitude of terms have been used to describe the peri-implant tissue coronal to the marginal bone. Initial terms were a direct extrapolation of periodontal terms, from the concept of the “biologic width” 1 to the recently introduced “supracrestal tissue attachment.” 2 However, the signifcant anatomical and structural differences between periodontal and peri-implant tissues (with the latter displaying “attachment” only at the level of the junctional epithelium [JE]) do not allow for a direct extrapolation of terms from the periodontium. Consequently, the terms “peri- implant soft tissue barrier,” 3 “peri-implant mucosa,” 4 “implant mucosal tunnel,” 5 and, most recently, the specifc “peri-implant phenotype,” 6 have been suggested to describe peri-implant tissues. Although such defnitions appear adequate for describing the peri-implant soft tis- sues, there is an increasing body of evidence pointing toward signifcant interrelations between the condition of the peri-implant tissue and the implant-abutment-prosthesis (IAP) complex, all in the constant presence of oral bacteria. Emerging evidence suggests that factors such as the type of implant-abutment junction (IAJ) and prosthesis design and retention can have a signifcant infuence on the short-term clinical outcomes and long-term health of the peri-implant bone and soft tissues. 7,8 Consequently, a new paradigm is essential by which peri-implant tissues will be studied in close interrelation with the IAP complex under the presence of oral bio- flm as one multi-element anatomical and functional unit. In such a system of close © 2021 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART M AY BE REPRODUCED OR TRANSM ITTED IN ANY FORM WITHOUT WRITTEN PERM ISSION FROM THE PUBLISHER.