In one patient with three implants and long intake of corticosteroids against rheumatoid arthritis (7.5 mg prednisolone per day for at least 2 years), no complication was detected in our study. Long-term use of corticosteroids can also lead to implant failures, according to Wood and Vermilyea [34] by modifying the patient’s response to bacterial infection [35], but at the present time, there is no important consideration for avoiding implant placement in those patients [36].

One implant removal was also performed on a patient with Marfan syndrome. While there are no reports in the literature regarding implant placement in patients with Marfan syndrome [37], analytical studies of bone mineral density reported adult patients demonstrated a high risk for developing osteoporosis [38]. Implant failures in postmenopausal women with osteoporosis [39] can lead to an assumption that this category of patients might be in higher risk for implant loss.

Our study showed no statistically significant difference between groups with local RFs such as periodontitis or implant placement in areas with a previous endodontic treatment and without any RFs. Hultin et al. [40] reported that a local specific inflammatory reaction related to the presence of bacteria occurs around the implants leading to marginal bone loss and infection (peri-implantitis) and that its incidence is four times higher in patients with history of chronic periodontitis than in patients who have never manifested periodontal disease. Moreover, patients without history of periodontitis present an average of 96.5% of implant survival in comparison to 90.5% of survival in individuals with history of periodontitis [40, 41]. Similar findings [42] were observed by the development of a retrograde peri-implantitis and how it affects the implant either from an adjacent tooth or from remaining infected periapical tissue in the prior position of the tooth [13]. The incidence of retrograde peri-implantitis was 7.8% in a study of 128 implants placed in areas adjacent to the teeth that had received endodontic treatment [43]. The mechanism of this procedure is considered multifaceted [15].