Comparative Evaluation of Microbial Counts in GCF of Patients with Onlay- Retained Fixed Partial Denture Fabricated with Monolithic Zirconia and DMLS – An Ex vivo Study

A BSTRACT Background: Onlay-retained resin-bonded fixed partial dentures (RBFPDs) are a conservative option for posterior tooth replacement. However, their impact on periodontal health, especially microbial colonization in the gingival crevicular fluid (GCF), remains underexplored. This study compares the microbial load in GCF around RBFPDs fabricated from Monolithic Zirconia and Direct Metal Laser Sintering (DMLS). Materials and Methods: An ex vivo study was conducted on 80 patients, divided into two equal groups receiving either Zirconia or DMLS-based RBFPDs. GCF samples were collected at baseline, one week, and three months post-cementation. Samples were cultured on Blood and MacConkey agar. Microbial counts were recorded using a digital colony counter and analyzed using SPSS v24 (IBM Corp., Armonk, NY, USA). Independent and paired t-tests were applied; P ≤ 0.05 was considered statistically significant. Results: Microbial counts were consistently higher in the DMLS group at all time points. Statistically significant differences were observed at baseline and 1-week post-cementation in both Blood and MacConkey agar cultures. At three months, microbial differences were not significant but remained higher in the DMLS group. Conclusion: Monolithic Zirconia showed superior periodontal compatibility due to lower microbial accumulation, making it a preferred material for onlay-retained RBFPDs.