## 1 Introduction  
Implant failure due to biological complications, such as peri-implantitis, represents a major concern in implant rehabilitation. According to a recent literature review, the prevalence of peri-implantitis is 19.83% on subject-based evaluation, making this an emerging oral health issue [1]. Despite this high frequency, standardized therapy for peri-implantitis has not been established, though several treatments have been proposed to arrest disease progression and obtain re-osseintegration [2]. According to the most widely diffused theory, the accumulation of a biofilm is the primary etiological factor of peri-implantitis [3], while different microbial species, specifically _Porphyromonas_gingivalis_ and _Streptococcus mutans_, contribute to its development and progression. In fact, both microorganisms are responsible for oral diseases and, in particular, _P. gingivalis_ is recognized as most closely linked to the development of peri-implantitis while _S. mutans_ is known to favor the development of a biofilm coating on titanium surfaces [4]. On this matter, [PERSON] and [PERSON] [5] provided at least five lines of evidence to support the bacterial etiology of peri-implantitis, findings also confirmed by the World Workshop for the Classification of Periodontal and Peri-Implant Diseases and Conditions [6]. Due to the eminently bacterial etiology of the disease, surface decontamination is considered a cardinal principle of the therapy and a prerequisite for restoring bone defects around infected implants. Implant decontamination is based on two different but synergic strategies: mechanical debridement of the implant surface followed by chemical disinfection. This combined approach reflects the need to disrupt the adherent biofilm and to dissolve residual organic contaminants, allowing for re-osseointegration of the previously infected surfaces. However, the mechanical treatments cannot achieve complete removal of the biofilm due to implant design, surface roughness, and limited access to the infected surface [7]; therefore, a wide range of antiseptic agents have been proposed as adjuvant treatment for infected implants in order to reach inaccessible areas where mechanical treatments are ineffective. The antimicrobial activity of antiseptics is based on different mechanisms of action and can be influenced by many factors such as formulation and bacterial load [8]. From a biological perspective, the ideal antiseptic agent should have rapid action, broad-spectrum antimicrobial activity and low toxicity on host cells, essential factors when topical antiseptics are used in close contact with the host tissue. Despite the numerous antiseptics proposed for the treatment of infected implants, to date, there is no evidence of the superiority of any specific antiseptic, the choice of which is mainly based on the individual preferences of clinicians. In the clinical practice, a certain degree of toxicity can always be expected when antiseptics are used in the surgical treatment of peri-implantitis, alongside possible alterations of the physicochemical properties of implant surfaces [9]. Indeed, these alterations have been shown to affect osteoblastic differentiation of mesenchymal stem cells, osteoblast maturation, as well as the production of factors that regulate bone formation, influencing, thereby, the process of osseointegration [9; 10]. As a result, it is important to evaluate the effects of antiseptic agents on titanium surface by detecting any change in the elemental composition. Therefore, in order to reduce the significant side effects on the bone, it might be helpful to confine the antiseptic agent to the infected surface and, in this regard, gel formulation might represent a valid approach since it avoids overflows and allows an increased contact time. To the authors' knowledge, no study has investigated the effects of different formulations of the same chemical agent on contaminated implant surfaces.