Objective: the purpose of the present study was to evaluate the microbiological effect of different designs of direct retainers of removable partial dentures (attachments, and clasp retainers “metal and PEEK") in mandibular distal extensions partial dentures.
Materials and methods: 30 patients having Kennedy class I or class II mandibular partially edentulous ridges with fully dentate maxillary arch were divided into three equal groups. Group A received a lower partial denture retained with attachments (OT attachment), Group B received a partial retained with an RPI metal clasp, and Group C received a lower partial denture retained with a thermoplastic material (PEEK). The adhesion of bacteria of the three groups was measured by using (a brain heart infusion agar plate): at the time of denture insertion, after two weeks, after four weeks, six weeks, and 8 weeks of denture insertion. The collected data were tabulated and statistically analyzed.
Results: within the group that received partial denture retained with attachments, the bacterial growth has increased as the follow-up period measured, more than that group received partial denture retained with PEEK retainer and more than that retained with cast clasp direct retainer. During the follow-up period, there was a statistically significant difference between the three groups.
Conclusion: Attachments retained removable partial denture-induced higher bacterial count than retained with PEEK (Polyetheretherketone ) retainer and metal clasp retainer.