Peri-implantitis is an inflammatory disease, characterized by the progressive loss of the peri-implant support bone tissue (Dos Santos Martins, 2022). It is prevalent in human cases, with an occurrence of 19.53 % in patients and 12.53 % in implants (Diaz, 2022). The condition impacts the tissues surrounding the implant and may manifest clinically as mucosal redness and swelling, increased probing depth, bleeding on probing, and even non-linear bone loss (Berglundh, 2018). If treated improperly or too late, peri-implantitis may lead to implant failure. Current treatment primarily relies on surgical intervention, but the success of these procedures can be tenuous. Peri-implantitis is influenced by a multitude of factors. These include a history of periodontitis, plaque microorganisms, smoking, implant design, and genetic factors. Research has shown that patients who have had implantation failure are at a greater risk of experiencing failure once more. This phenomenon might be associated with genetic polymorphism (Fu & Wang, 2020). As a result, genetic susceptibility constitutes a crucial aspect in the study of the etiology of peri-implant inflammation. Further exploration of new genes and gene loci that may be related to the susceptibility, development and prognosis of peri-implant inflammation is of great significance to fully reveal the genetic basis of the occurrence and development of peri-implant inflammation. In addition, the investigation of the functional impact of the genetic polymorphisms should be highlighted.

MicroRNAs (miRNAs) are small non-coding RNAs, about 21–23 bp in length, that specifically bind to the 3′ untranslated region (3′UTR) of target mRNAs. Their gene expression regulate through post-transcriptional modification or inhibition of translation(Zhang, 2021). In the literature, miRNAs are noted for their role as epigenetic mechanisms that influence cellular processes, significantly affecting inflammatory responses and the development of various diseases (Sonkoly & Pivarcsi, 2009). It has been demonstrated that miRNAs play crucial roles in inflammatory diseases such as periodontitis (Abdulkareem et al., 2021, Daily et al., 2023, Jia et al., 2020), with their aberrant expression potentially leading to various oral conditions. Studies indicate that miR-155 is linked to autoimmunity and inflammation, regulating pro-inflammatory cytokine production by promoting Th1 and Th17 cell growth (Garcia-Diaz et al., 2018, Zhang et al., 2014). The expressions of miR-223, miR-155, and miR-130a are notably upregulated in periodontitis compared to healthy periodontium, contributing to disease progression (M'Baya-Moutoula et al., 2015, Perri et al., 2012, Radovic et al., 2018). Similarly, miR-146a and miR-155, stimulated by toll-like receptors and pro-inflammatory cytokines, show significantly higher expression levels in patients with peri-implantitis than in healthy controls (Hamed & Abdulbaqi, 2024).

Single nucleotide polymorphisms (SNPs) are variations in a single nucleotide that occur at specific DNA locations. These genetic variations notably contribute to individual diversity and influence traits and disease susceptibility (Schork et al., 2000). SNP rs767649, located in the intronic region of miR-155, has been studied extensively. Ji et al. found that the rs767649 T allele enhances miR-155 expression in both hepatocellular carcinoma tissues and adjacent healthy tissues. Their research suggests that miR-155 and rs767649 polymorphisms may increase the risk of hepatocellular carcinoma (Ji, 2016). Additionally, evidence indicates that the miR-155 rs767649 TT genotype is linked to a reduced risk of cervical cancer and an increased risk of systemic lupus erythematosus (Mohammed et al., 2021, Wang et al., 2016). However, the genetic association of miR-155 rs767649 polymorphism with peri-implantitis susceptibility has not been examined. Considering the involvement of miR-155 dysregulation in peri-implantitis patients and the regulatory role of rs767649 polymorphism in miR-155 expression, we speculated that miR-155 rs767649 polymorphism might have a close association with susceptibility to peri-implantitis.

Therefore, a case-control study was designed to investigate whether the miR-155 rs767649 polymorphism was associated with the susceptibility to peri-implantitis in a Chinese Han population.