Purpose: Proximal carious lesions comprise a constant clinical problem. The aim of this investigation was to test the safety and clinical effect of a new treatment for proximal caries. Materials and Methods: In 50 patients with two proximal initial lesions (D1-3 without cavitation, bitewing radiograph), orthodontic rubber rings were applied to gain access to the interproximal space. One of the lesions was sealed with a thin polyurethane-dimethacrylate foil using a bonding agent; the other lesion received oral home care with dental floss and fluoridated toothpaste, and was left as control. Results: In clinical follow-ups after 6 and 12 months and radiographic evaluation after two years, clinical retention of proximal tape and the underlying sealant, marginal adaptation, discoloration, tooth vitality, proximal plaque, and gingivitis were checked. In addition, carious lesions were assessed clinically and radiographically. The sealants showed good retention, marginal adaptation, and color. After two years, vitality of all teeth was still positive and no relevant differences in plaque accumulation or gingival status were found between sealed and control teeth. Nine sealed lesions showed caries regression and 2 progression. In contrast, only 4 control lesions regressed and also 2 showed progression. The loss of tape had no significant influence on the lesion progression, indicating the effect of the underlying bond. All other sealants and control lesions were stable, indicating an arrest of the lesion. Conclusion: Sealing initial proximal lesions showed no clinical problems and mostly arrest of initial carious lesions on bitewing radiographs. Keywords: proximal surfaces, sealant, clinical, radiographic