Microbial Colonization of the Peri-Implant Sulcus and Implant Connection of Implants Restored With Cemented Versus Screw-Retained Superstructures: A Cross-Sectional Study

Background: The aim of this study is to investigate peri-implant and intraconnection microflora ofhealthy implants restored with cemented and screwed superstructures.Methods: Patients with two to three implants restored with cemented or screwed restorations and5 years of follow-up were recruited. Samples were taken from peri-implant sulci, adjacent teeth, andthe inner portion of connections. Prevalence of positive sites and bacterial loads for 10 microorganismswere obtained with quantitative real-time polymerase chain reaction. Implant connection permeability tothe studied microorganisms was estimated using a standardized bacterial contamination index. Statisticalanalysis was performed using a generalized estimating equations model, Wald x2 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 atperi-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-implantsulci for the cemented group; at the inner portion of connections, values were significantly higher forP. 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 andscrew-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 butsignificantly lower bacterial loads at the inner portion of the implant connection.