Clinical, microbiological, and immunological aspects of healthy versus peri-implantitis tissue in full arch reconstruction patients: a prospective cross-sectional study

The restoration of missing teeth by means of dental implants has now become a routine treatment in common use [1]. Various longitudinal studies have shown the high survival rates of implants in functional use, which range between 90% and 95% over a follow-up period of up to 20 years [2-4]. Peri-implant disease infection etiology has been described in detail in the literature for both mucositis [5-8] and peri-implantitis [9-12]. Late implant failure is the result of the inability to maintain osseointegration, whose most important cause is peri-implantitis [1].

Using the checkerboard DNA-DNA hybridization method, Socransky et al. [13] identified a consortium of the bacterial species Tannerella forsythia (T. forsythia), Treponema denticola (T. denticola) and Porphyromonas gingivalis (P. gingivalis) as having the highest association with periodontal disease severity. The authors named this microbial consortium “red complex”. Evaluation of the literature has shown the microbiota associated to peri-implantitis to be more complex than that found under healthy peri-implant conditions – the main flora consisting of anaerobic gram-negative bacteria [14]. A high degree of association between this red complex and the appearance of peri-implantitis has been observed [9-12,14]. However, in healthy peri-implant sulci, oral streptococci constitute the predominant bacterial flora [15].

Although different cytokines have been evaluated [16-18], the cytokine concentrations that differentiate between healthy and stable sites and the onset of a pathological periodontal and peri-implant process are not known [19]. In the periodontium, individual differences in inflammatory and immunological responses to bacterial infection may influence the host’s susceptibility to disease [20]. The cascade of inflammatory mediators of the host in response to bacterial infection, which can result in destruction of connective tissue and bone, is determined by genetic factors [21].

The aim of this study was to study the clinical characteristics of peri-implantitis as established by the modified plaque index, modified gingival index and probe depth, examines the microbial and host response Interleukin (IL)-8, IL-1β, IL-6, IL-10 and Tumor Necrosis Factor (TNF)-α characteristics in dental implants with peri-implantitis, and establishes comparisons with healthy dental implants.

Table 1 reports mean patient age (p<0.01), gender, smoking habits (p<0.01), oral hygiene, which arch was rehabilitated (p < 0.05) and prosthetic type (p<0.05) for the two study groups. When prosthetic type was registered, Locator® supporting an overdenture was the most frequent in the patient group with healthy peri-implant sites, while overdentures on bars were the most frequent in implants with peri-implantitis. A total of 61.5% of the patients with peri-implantitis had both arches rehabilitated, compared with 22.7% of patients with healthy peri-implant tissues; there was no implant with peri-implantitis in cases that received mandibular treatment exclusively.

The mean values of clinical parameters for all implants (with or without peri-implantitis) are presented in Table 2. There were no statistically significant differences in the percentage of sites at which plaque was found between the groups. mGI scores were significantly higher around implants with peri-implantitis than around healthy implants (p < 0.001). The recorded mean PPDs in the peri-implantitis group and the healthy group were 5.15 ± 0.68 and 2.72 ± 0.59, respectively, this being a statistically significant difference (p < 0.001) (Figure 2). On examining the PISF volumes, no significant differences were observed between the two groups.

The analysis of putative periodontal pathogens of the red complex (T. forsythia, P. gingivalis, T. denticola) and total bacterial load (TBL) are summarized in Table 3. Subgingival microbiota was composed of a greater number of periodontal pathogens in patients with peri-implantitis, showing significant difference in counts of P. gingivalis (p < 0.01), in P. gingivalis and T. denticola association (p < 0.05), as well as TBL (p < 0.05).

The peri-implantitis group showed a significantly greater level of IL-6 than the healthy group (0.96 ± 0.64 and 0.53 ± 0.63 respectively, p < 0.01); IL-1β (58.5 ± 84.8 and 21.2 ± 24.2 respectively, p < 0.01); IL-10 (0.91 ± 0.90 and 0.45 ± 0.87 respectively, p < 0.05); TNF- α (1.08 ± 1.49 and 0.25 ± 0.56 respectively, p < 0.01) (Figures 3 and 4). Although IL-8 increased in the peri-implantitis group, there was no statistically significant difference in comparison with the healthy implant group. The IL-1β/ IL-10 ratio was found to be 9.9 ± 11.9 for the healthy group and 37.2 ± 44.4 for the peri-implantitis group (p = 0.006).

Due to the world-wide increase in treatments involving implant placement, the incidence of peri-implant disease is increasing. Initial screening of peri-implant tissues will consist of an evaluation of peri-implant pocket probing depth and the degree of bleeding on probing [31]. When increased bacterial plaque and bleeding in response to probing affects over 30% of the dental implants, this situation is related to a high risk of mucositis and peri-implantitis [32]. A study [33] involving 34 patients with 77 dental implants (comprising 23 mucositis and 54 healthy periimplant sites) concluded that bacterial plaque induces an inflammatory response that can lead to the development of peri-implant mucositis. A recent systematic review [34] highlights the lack of uniform treatment and the need to establish additional research to fully provide effective treatments for this common condition, which is the first step to prevention peri-implantitis. These data are consistent with those published by Shibli et al. [11], which found patients with peri-implantitis to have increments in all the evaluated clinical parameters, except the percentage of locations with bacterial plaque. mGI score and PPD are parameters that must be evaluated for the diagnosis of peri-implant disease [27,28,32]. Accordingly, the present study found that both mGI and PPD were significantly higher in the implants with peri-implantitis (p < 0.001).

Most studies regarding risk factors for peri-implant disease have concluded that smoking is clearly involved [35-40]. This is also supported by the present study, in which a significant relationship was found between smoking and the presence of peri-implantitis. However, such data should be viewed with caution, since the group with healthy implants consisted of non-smokers; consequently, smoking could not influence the clinical, microbiological and immunological parameters studied.

Patients with peri-implantitis were significantly younger on average than patients with healthy peri-implant tissues, a finding that differs from other studies in which older patients showed higher rates of peri-implantitis [41]. In this population, when prosthetic type was studied, it was found that overdentures supported by Locator® were more frequent among patients with healthy peri-implant tissues, while overdentures on bars were more frequent on implants with peri-implantitis. In a study by Marrone et al. [41] more cases of peri-implantitis were found in patients wearing overdentures than among patients rehabilitated with fixed prostheses, which agrees with the present results. A total of 61.5% of the patients with peri-implantitis had both arches rehabilitated, compared with only 22.7% of patients with healthy peri-implant tissues, and there were no cases of implants with peri-implantitis who had undergone rehabilitation of the mandible exclusively.

P. gingivalis was detected in the half of gingivitis patients and in more than 80% of the periodontitis patients-derived samples [42]. High counts of T. forsythia, P. gingivalis and T. denticola have been observed in implants with peri-implantitis [9-12]. For the first time, a study demonstrated that the red complex periodontal bacterium Pg produces a concentration of Hydrogen sulfide capable of up-regulating IL-8 expression induced in gingival and oral epithelial cells, revealing a possible mechanism that may promote the inflammation in periodontal disease [43]. In the present study there was a significant relation between peri-implantitis and P. gingivalis, association with P. gingivalis and T. denticola, and total bacterial load. Other studies [14,44-47] found these bacteria in patients with healthy peri-implant tissue, which was similar to the present sample of healthy peri-implant patients, in which red complex was found at 11.1% of healthy peri-implant sites, while red complex was found at 25% of implants with peri-implantitis. In a study by Nowzari et al. [23] it was found that 16.7% of healthy peri-implant tissues showed presence of P. gingivalis, and 25% T. forsythia, results that are similar to this study.

One of the options for diagnosing peri-implant disease is peri-implant sulcus fluid (PISF) analysis, which offers a non-invasive means of studying the host response to peri-implant disease, and may provide an early indication of those patients at risk of developing active disease [16]. In the present study, PISF volume was greater in the healthy implants (91.7 ± 50.3) than in the peri-implantitis group (83.9 ± 43.1), though the difference was not statistically significant.

Many studies have examined the presence of cytokines in patients with periodontitis [48-50]. Due to the similarity between periodontitis and peri-implantitis, many inflammatory markers have been evaluated for monitoring peri-implant health and can indicate the presence of either disease [51-53]. Bacterial products from periodontal pathogens stimulate the production of inflammatory mediators secreted in PISF, which cause the destruction of the peri-implant tissues [17]. Certain cytokines have been proposed as potentially valid diagnostic or prognostic markers of periodontal or peri-implant tissue destruction [16]. An increase in interleukin levels is observed in patients with peri-implant disease, though there is controversy over the effect of interleukins in crevicular fluid and peri-implantitis in relation to implant failure or the development of periimplant disease [54]. The IL-10 is an anti-inflammatory cytokine, produced by T-helper 2 cells (Th2), macrophages and B cells, which inhibits synthesis of pro-inflammatory cytokines such as IL-1, IL-2, IL-6, IL-8, TNF-a and IFN-g (interferon gamma) [55]. On the other hand, IL10 acts as a B cell stimulator, enhancing B cell proliferation and differentiation [56]. These facts suggest that IL10 can play important roles in the regulation of celular and humoral immune responses [57]. As regards IL-10, Liskmann et al. (18) reported a higher concentration of IL-10 in patients with peri-implantitis. In contrast, Duarte et al. [58] observed no differences between healthy subjects and patients with disease. Some studies have previously shown interleukin-1ß (IL-1ß) in PISF to be elevated in cases of peri-implantitis [52,59,60]. TNF-α, a cytokine with some functions similar to those of IL-1β, has been detected at sites affected by periodontitis [61] TNF-α and IL-1β act synergistically to initiate the cascade of inflammatory mediators [62]. IL-6 has pro-inflammatory effects and is responsible for the collagen resorption of gingival tissues [63], while IL-10 is an inhibitor of inflammation [64]. IL-8 acts as a potent chemoattractant for neutrophils in gingival tissues [65]. In this study, it was found that IL-1β (p < 0.01), IL-6 (p < 0.01), IL-10 (p < 0.05) and TNF-α (p < 0.01) were significantly increased at the sites with peri-implantitis, while IL-8 was not.

The main component of soft and hard tissue destruction associated with periodontal disease is believed to be the result of activation of the host immunoinflammatory response to bacterial challenge [66]. IL-1 and IL-6 have both been found to be significantly elevated at diseased periodontal sites compared with healthy or inactive sites [67]. IL-1 has also been positively correlated with increased probe depth and attachment loss [68]. Other clinical data indicate that IL-6 levels are higher in refractory periodontitis, and increased granulocyte chemotactic factor (GCF) levels correlate to gram-negative fimbriae [69]. Based upon the increased expression of IL-1 and IL-6 in inflamed gingiva and high levels of GCF in periodontitis patients, several studies have suggested that an increased production of these cytokines may play an important role in periodontal tissue destruction [48].

An analysis has been made of the clinical, microbiological and host response aspects in implants with peri-implantitis. The results of the present study involving a limited patient sample suggest that the peri-implant microbiota and which dental arch was rehabilitated involved could contribute to bone loss in peri-implantitis. A significant relationship is observed between the concentration of cytokines (interleukins 1β, 6 and 10 and TNF-α) and the inflammatory response in peri-implantitis tissue.