Long-Term Follow-up of Turned Single Implants Placed in Periodontally Healthy Patients After 16 to 22 Years: Microbiological Outcome

Background: Survival rates in implant dentistry today are high, although late failures do occur due to multifactorial reasons, including peri-implant infections. The primary objective of this study was to investigate microbiota around single turned implants after up to 22 years. Secondary objectives were to compare teeth and implants and to correlate microbiological, radiographic and clinical parameters. Methods: 46 patients with single implants were invited for a clinical examination. Clinical data were collected from implants and contralateral natural teeth. Radiographic bone level was measured around implants. Microbiological samples were taken from implants, contralaterals and the deepest pocket per quadrant. Samples were analysed with DNA-DNA hybridization including 40 species. Statistical analysis was performed using Wilcoxon Signed ranks tests, McNemar tests and Spearman correlation coefficients with 0.05 significance level. Results: Mean follow-up was 18.5 years (range16-22). Tannerella forsythia (1.5x10(5)) and Veillonella parvula (1.02x10(5)) showed the highest concentrations around implants and teeth, respectively. Porphyromonas gingivalis, Prevotella intermedia and T.forsythia were significantly more present around implants than teeth. Mean counts were significantly higher around implants than teeth for Parvimonas micra, P.gingivalis, P.intermedia, T.forsythia and Treponema denticola. Total DNA count was correlated to interproximal bleeding index (r=0.409) and interproximal probing depth (r=0.307). No correlations were present with plaque index, nor radiographic bone level. Conclusions: In the present study, bacterial counts around single implants in periodontally healthy patients are rather low. Although pathogenic bacteria are present, some in higher numbers around implants than teeth (5/40), the majority of implants presents with healthy peri-implant tissues without progressive bone loss.