There is considerable evidence supporting the view that peri-implant diseases are infectious in nature and mainly linked to an uncontrolled accumulation of bacterial plaque biofilms [1]. Basically, diseased implant sites are dominated by gram-negative anaerobic bacteria and therefore feature microbiological characteristics similar to those noted for chronic periodontal infections [2]. Even though the history of periodontitis is a documented risk indicator for peri-implant diseases [3,4], the diversity of microbiota at diseased tooth sites was reported to be higher than that noted at diseased implant sites [5]. Common periodontopathogenic bacteria could be isolated at both healthy and diseased implant sites [6], and the microbiological analysis of 40 species did not markedly differ by the clinical implant status (i.e., healthy, mucositis, peri-implantitis) [7]. However, a most recent analysis of 78 species has pointed to higher counts of 19 bacterial species at peri-implantitis - when compared with healthy implant sites, mainly including Porphyromonas gingivalis (P. gingivalis) and Tannerella forsythia (T. forsythia) [4].

In addition, peri-implantitis was linked with opportunistic pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus (S. aureus), thus pointing to a rather complex and heterogenous ‘polymicrobal infection’. Yeasts are frequently isolated from the oral cavity [8] and were also identified in the submucosal plaque of patients with peri-implantitis [9,10]. These studies, however, mainly focused on the assessment of Candida albicans, and at the time being, a qualitative evaluation of other fungal organisms is lacking. Moreover, the potential role of yeasts and their co-aggregation with either periodontopathogens or other opportunistic bacteria at peri-implantitis sites is unknown.

Therefore, the aim of the present study was to analyze and correlate fungal organisms and bacterial species at peri-implantitis and healthy implant sites as well as teeth with a history of periodontitis using real-time polymerase chain reaction (PCR).