The aim of the present study was to compare the cleansing properties of mechanical supportive care for dental implants with the use of an etching gel. Sixteen patients underwent a 5-month clinical trial with monthly recalls. These patients, wearing maxillary complete dentures and mandibular overdentures supported by a bar device on 4 implants, were treated in a split-mouth study design. Test and control therapy were randomly assigned to left and right sides of the mandible. At the test side, 35% phosphoric etching gel (pH 1) was applied in the peri-implant sulcus. After 1 minute, the sulcus was thoroughly rinsed with a water spray for approximately 15 seconds per implants. Control therapy consisted of supra- and subgingival debridement using carbon fiber curettes and a rubber cup. Plaque, calculus, probing pocket depth, and modified Gingival Index were determined before each treatment. Microbiologic evaluation was performed at baseline, 1 month later, and 5 months later, just before and immediately after each treatment. Per treatment and per assessment, the mean scores of all clinical parameters were calculated for each patient. The number of colony-forming units was used as the primary efficacy variable in the analysis of microbiologic data. At baseline, no differences between test and control sites were observed for any of the clinical parameters. The mean Gingival Index and the mean probing pocket depth were reduced over the 5-month period. The mean reduction in Gingival Index at the test sites proved to be significantly larger at the control sites (P = .03). Both treatment modalities resulted in an instant reduction of the number of colony-forming units, where the reduction by chemical cleaning was larger (P .05). This short-term study employing a high recall frequency indicates that local application of 35% phosphoric acid gel can be as effective as conventional mechanical supportive therapy. Schlagwörter: acid gel, implant, maintenance