IntroductionDental implant rehabilitation has become widely used due to its highly predictable functional and aesthetic results compared to conventional crown/bridge and denture work. Furthermore, titanium implant materials offer not only biocompatibility but also osseointegration. Osseointegration refers to the direct connection between living bone and the implant surface during function and loading in the oral cavity. Despite the high success rate of dental implants, there is a small percentage of failures that can partly be attributed to peri-implantitis. It refers to changes in pathological inflammation that occurs in the tissue surrounding a load-bearing dental implant. Another challenge in orofacial implantology is that the surface of the dental implant is subject to microbial colonization and biofilm formation which can eventually lead to infection of the implant-supported tissue [1,2,4,10]. The classification of failure and function of the dental implant can be divided into two phases: early or late. The initial stages of implant failures occur due to incomplete osseointegration before or after functional loading of the implant. Failures include: early loading, surgical contamination, inefficient healing, and unwanted biocompatibility of the implant material. Late failure of dental implants includes disruption of the function of osseointegrated implants, mainly due to chronic infection of the implant tissue [7]. There are risk factors for peri-implantitis such as poor oral hygiene, systemic conditions, alcohol consumption, susceptibility genes, smoking and a previous history of periodontitis. From a clinical point of view, it is quite possible to distinguish between peri-implant mucositis, which...... half of the document ......bone marrow is what distinguishes peri-implantitis [3].ConclusionThe formation of biofilm on the surface of the implant is similar to that of natural teeth which leads to inflammation and consequent damage to the surrounding tissue. The adjacent teeth, periodontal pocket, saliva, and oral soft tissue serve as reservoirs for contamination of the implant surface. There is also a similarity in the microbiological characteristics of peri-implantitis and periodontitis, but there are some exceptions including some specific microbiota such as staphylococci, peptostreptococci, enterobacteria and candida spp. which are found in peri-implantitis. Furthermore, the immune response of the cells is quite similar in peri-implantitis both in terms of events and qualitatively. On the other hand, the destruction of inflammatory tissue in peri-implantitis is more rapid and extensive than in periodontitis..