This study aims to observe the effects of keratinized mucosa width on peri-implant tissues by evaluating clinical and biochemical parameters. The main question it aims to answer is: Would increasing the width of the keratinized mucosa with free gingival graft (FGG) in peri-implant mucositis be beneficial in terms of clinical periodontal parameters and peri-implant crevicular fluid levels of inflammatory cytokines compared to non-surgical therapy alone? Our study consists of 4 groups: Peri-implant healthy group with sufficient keratinized mucosa (≥ 2mm) (n=16), peri-implant mucositis group with sufficient keratinized mucosa (n=16), peri-implant mucositis group with insufficient keratinized mucosa (\< 2mm) receiving only non-surgical treatment (n=16), peri-implant mucositis group with insufficient keratinized mucosa receiving FGG in addition to non-surgical treatment (n=16). Clinical and biochemical measurements will be recorded at the baseline, 1st month, 4th month and 7th month of the study. Peri-implant crevicular fluid samples will be collected at baseline, 1st month, 4th month and 7th month. IL-1β, RANKL, OPG levels, and RANKL/OPG ratio will be analyzed from collected samples. Researchers will evaluate the possible benefits of FGG application in addition to non-surgical therapy by comparing the biochemical and clinical changes in areas with and without FGG application in the treatment of peri-implant mucositis.