Purpose: The primary prevention of peri-implantitis onset is a key factor in long-term implant success, and the evaluation of the antibacterial efficacy of different implant surfaces is fundamental in this way. The aim of this study was to assess if implants with collars coated with anatase were less subjected to bacterial colonization than implants with noncoated collars, and to investigate how implant bacterial colonization varies over time. Materials and Methods: Eighteen patients in need of implant-supported rehabilitation were selected to have two adjacent implants placed, one with an anatase-coated collar and one with the collar uncoated. Biofilm samples were collected at four sites around each implant at four different time points. Samples were analyzed through polymerase chain reaction (PCR) to detect and calculate the colonization rate of Aggregactibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Prevotella intermedia. Results: Due to one patient dropout and two nonosseointegrated implants, 32 out of 36 placed implants were followed up for 12 months, and 128 samples for each time point were collected: in total, 512 biofilm samples were analyzed. The type and rate of bacterial colonization were not significantly different between the two groups at all the intervals. However, the anatase-coated collar showed no proliferation of T forsythia. A significant difference in marginal bone level could be observed at the 12-month follow-up only. No significant difference in the other clinical and radiographic indexes was observed. Conclusion: In this study, anatase-coated collar implants did not seem to provide significantly different microbiologic outcomes than uncoated collar implants. However, the absence of colonization of the species T forsythia and the slightly smaller peri-implant bone loss at the 12-month follow-up suggest that further investigations on anatase coating are needed. Nevertheless, data on bacterial colonization and crestal bone levels need further investigations to draw meaningful conclusions, due to the statistical power of this pilot study. Keywords: anatase, coated materials, dental implants, osseointegration, peri-implantitis, polymerase chain reaction