Background: The aim of this study is to investigate peri-implant and intraconnection microflora of healthy implants restored with cemented and screwed superstructures.
Methods: Patients with two to three implants restored with cemented or screwed restorations and 5 years of follow-up were recruited. Samples were taken from peri-implant sulci, adjacent teeth, and the inner portion of connections. Prevalence of positive sites and bacterial loads for 10 microorganisms were obtained with quantitative real-time polymerase chain reaction. Implant connection permeability to the studied microorganisms was estimated using a standardized bacterial contamination index. Statistical analysis was performed using a generalized estimating equations model, Wald χ(2) test, and the least significant difference test.
Results: The final sample consisted of 18 patients (55 implants) in the cemented group and 22 patients (46 implants) in the screw-retained group. Regarding prevalence of positive sites, significant differences between groups were only found for Tannerella forsythia, which was 8.7 times more frequent at peri-implant sulci of cemented than screw-retained prostheses. Bacterial loads of Porphyromonas gingivalis, T. forsythia, Parvimonas micra, and total bacterial load were significantly higher at peri-implant sulci for the cemented group; at the inner portion of connections, values were significantly higher for P. micra and Fusobacterium nucleatum for the screw-retained group. Contamination index values demonstrated higher permeability to most microbes in the cemented group.
Conclusions: Internal implant surfaces were microbiologically contaminated for both cemented and screw-retained superstructures. Differences were found between the two methods of prosthetic retention: the cemented group presented significantly higher bacterial loads in the peri-implant sulcus but significantly lower bacterial loads at the inner portion of the implant connection.
Keywords: Dental implant; dental implant abutment design; dental prostheses, implant-supported; microbiology; peri-implantitis; prosthesis.