biology Review Peri-Implantitis Regenerative Therapy: A Review Lorenzo Mordini 1, * , Ningyuan Sun 1 , Naiwen Chang 1 , John-Paul De Guzman 1 , Luigi Generali 2 and Ugo Consolo 2   Citation: Mordini, L.; Sun, N.; Chang, N.; De Guzman, J.-P.; Generali, L.; Consolo, U. Peri-Implantitis Regenerative Therapy: A Review. Biology 2021, 10, 773. https:// doi.org/10.3390/biology10080773 Academic Editor: José R. Pineda Received: 30 May 2021 Accepted: 5 August 2021 Published: 13 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Periodontology, Tufts University School of Dental Medicine, Boston, MA 02111, USA; ningyuan.sun@tufts.edu (N.S.); nai-wen.chang@tufts.edu (N.C.); johnpaul.deguzman@tufts.edu (J.-P.D.G.) 2 Department of Surgery, Medicine, Dentistry andMorphological Sciences with Transplant Surgery, Oncology and Regenerative Medicine Relevance (CHIMOMO), University of Modena and Reggio Emilia, 41124 Modena, Italy; luigi.generali@unimore.it (L.G.); ugo.consolo@unimore.it (U.C.) * Correspondence: Lorenzo.Mordini@tufts.edu Simple Summary: Regenerative therapies are one of the options to treat peri-implantitis diseases that cause peri-implant bone loss. This review reports classic and current literature to describe the available knowledge on regenerative peri-implant techniques. Abstract: The surgical techniques available to clinicians to treat peri-implant diseases can be divided into resective and regenerative. Peri-implant diseases are inflammatory conditions affecting the soft and hard tissues around dental implants. Despite the large number of investigations aimed at identifying the best approach to treat these conditions, there is still no universally recognized protocol to solve these complications successfully and predictably. This review will focus on the regenerative treatment of peri-implant osseous defects in order to provide some evidence that can aid clinicians in the approach to peri-implant disease treatment. Keywords: peri-implant disease; peri-implant mucositis; peri-implantitis; re-osseointegration; regen- erative therapy 1. Introduction Due to the increasing number of dental implants placed every day in clinical practice, the biological complications related to these treatments are increasing. These complications range from inflammation and bleeding upon probing (BOP) to severe peri-implant bone resorption and implant failure [1]. Despite many investigations aimed at identifying the best approach to treat these conditions, there is still no universally recognized protocol to solve these complications successfully and predictably. The techniques available for the clinicians can be divided into non-surgical and surgical. Among the surgical options, the two main approaches are resective and regenerative treatments. Several methods have been explored to determine the most predictable and successful treatment protocol for arresting or reversing the loss of peri-implant bone. These methods included non-surgical, resective, and regenerative treatments along with various methods of adjunctive surface decontamination [2]. Generally speaking, if the peri-implant defect does not have bone walls or has a supra-bony component, the resective approach is usually preferred. The focus of this review will be the regenerative treatment of peri-implant osseous defects. The goals of this article will be to answer questions to assist clinicians pursuing peri-implant disease treatment: is any product superior to the other? Should a membrane be added to the graft? Is any method of decontamination superior? The authors reviewed recent studies on peri-implant regeneration and their outcomes, with background studies that led to the current knowledge of materials and techniques. Although this paper does not represent a systematic review, an effort was made to include as many scientific references on peri-implantitis surgical regenerative treatments. An electronic search in the database PubMed (National Library of Medicine) was performed. English Biology 2021, 10, 773. https://doi.org/10.3390/biology10080773 https://www.mdpi.com/journal/biology