Background and Aim: Keratinized mucosa width (KMW) has an essential role in peri-implant health. This study aimed to evaluate the impact of KMW on marginal bone loss (MBL) around overdenture-supported dental implants.
Materials and Methods: In this cohort study, completely edentulous patients received an overdenture with implants in the maxilla and mandible. Two implants were placed in the maxilla and mandible. Ball attachments were used. KMW was measured, and gingival biotype was determined. MBL was evaluated on digital parallel radiographs taken at 12 and 24 months after loading. KMW was the predictive factor, and MBL was the outcome of the study. Data were analyzed using SPSS 21 via Pearson’s correlation test, independent t-test, and Chi-square test (alpha=0.05). 
Results: Eighty implants in 20 patients were studied. The mean KMW was 2.05±0.88 mm. The mean MBL was 1.32±0.46 mm at 12 months after loading, and 1.71±0.49 mm at 24 months after loading. Analysis of the data demonstrated a correlation between MBL at 12 and 24 months after loading with KMW and dental implant diameter (P<0.001).
Conclusion: It appears that narrow KMW may be associated with an increase in MBL in two-implant-supported overdentures. Gingival biotype may play a role in the detrimental effect of narrow keratinized mucosa on MBL.