Bacterial Leakage Along the Implant-Abutment Interface

Titanium implants have been successfully and increasingly used for the substitution of dental elements in the treatment of total or partial edentulism, exhibiting success rates frequently above 90%, since the earliest reports on this technique in the 1960 decade (Lang et al., 2004; Pjetursson et al., 2007; Jung et al., 2008). When treatment failures are calculated based on patients who lost implants and not on implant lost by the population in general, success rates may be considerably lower (Lambrecht et al., 2003; Stavropoulos et al., 2007; Esposito et al., 2010). Excessive premature loading, occlusal trauma and poor bone support are considered the main factors associated with early implant loss (Esposito et al., 2000; Piattelli et al., 2003). Recent reports demonstrated that microorganisms in the oral cavity, especially the ones involved in periodontal diseases, together with unfavorable occlusal factors are considered as the main causes of unsuccessful treatment with implants (Mombelli & Lang, 1998; Covani et al., 2006). A direct correlation between presence of microorganisms and disease of the peri-implant tissues has been demonstrated. Gram-negative, anaerobic species like Fusobacterium spp, Prevotella spp and spirochetes are frequently found in large quantities in affected sites. In contrast, healthy sites are predominantly colonized by Gram-positives (Mombelli & Lang, 1998; Quirynen et al., 2006). Periodontitis in proximity to implants and presence of periodontal pathogenic bacteria in the peri-implant sulci are considered risk factors to the success of dental implants (Mombelli et al., 1995; Mombelli & Décaillet, 2011). Surface characteristics, physical properties, as well as biological factors involved in this type of treatment may facilitate bacterial colonization and growth of potentially pathogenic microorganisms at the implant sites (Mombelli et al., 1995; Jansen et al., 1997; Covani et al., 2005). Another risk factor to the peri-implant tissues is the presence of marginal discrepancies between prosthetic crowns and implants abutments, although it is a controversial issue. The assessment of these discrepancies varies largely depending on the material employed for crown fabrication, type of cement, measuring methods, etc. Studies using human extracted teeth have reported marginal discrepancies ranging from 5 to 430 μm (Abbate et al., 1989; Felton et al., 1991; Valderrama et al., 1995; Kosyfaki et al., 2010). The highest values, varying from 110 to 160 μm, are frequently associated to feather–edge cast gold crowns (Marxkors,