Purpose: The aim of this study was to evaluate the clinical performance of glass fiber-reinforced composite-based resin-bonded fixed partial dentures (GFRC-RBFPDs) as periodontal splints for periodontal support-reduced anterior partially edentulous dentition and for replacing lost teeth. Materials and Methods: A total of 39 subjects were enrolled who required fixed restorations for lost mandibular anterior teeth where the adjacent teeth offered severely reduced periodontal support. GFRC-RBFPDs were cemented to replace the lost teeth and to stabilize the adjacent teeth. The survival rates were recorded, and the periodontal condition (bone height, bleeding index, and probing depth) was evaluated at 1, 2, 3, and 4 years after the restorations. The results were statistically analyzed with single-factor variance analysis and chi-square tests (α = .05). Results: The complete survival rate was 89.7%, and the functional survival rate was 92.3% at the fourth year. The main reason for failure was fracture of the connector of the GFRC-RBFPDs. In 21.7% of adjacent teeth, the bone height decreased; in the other 78.3%, it increased from 1 year after the restoration to the end of the observation period and the heights were statistically different from the initial values. The periodontal condition of the adjacent teeth was improved after the restoration. Conclusions: This 4-year clinical evaluation indicated that GFRC-RBFPDs may be useful as fixed prostheses to replace one to three lost anterior teeth with damaged periodontal support in adjacent teeth.