Objectives: To analyse the microbia composition of 10 healthy dental implants and 10 chronic periodontitis patients. Methods: Subgingival plaque and peri-implant biofilm were sampled at the first molar site before and after implant restoration. The analysis was conducted by 454-prosequencing of bacterial V1 to V3 regions of 16S rDNA. Results: Chronic periodontitis subjects showed greater bacterial diversity compared with implant subjects. The relative abundance of sixteen genera and twelve species differed significantly between implant and chronic periodontitis subjects. The genera Catonella, Desulfovibrio, Mogibacterium, Peptostreptococcus and Propionibacterium were present in higher abundance in chronic periodontitis subjects, while implant subjects had higher proportions of Brevundimonas and Pseudomonas species. Conclusions: Our results demonstrate that implant restoration changes the oral microbiota. The analysis suggests that periodontal bacteria can remain for a prolonged period of time at non-dental sites, from where they can colonise the peri-implant. Keywords: 454 pyrosequencing, implant, microbial diversity, periodontitis