This prospective clinical comparative study will evaluate the surface wear of BioHPP (modified polyetheretherketone) clasps opposing either natural tooth abutments or zirconia full-coverage abutments in mandibular bilateral distal extension removable partial dentures. Ten participants will be randomly assigned to two equal groups. Surface topography changes of the clasp fitting surfaces will be assessed using scanning electron microscopy (SEM) at denture insertion, 6 months, and 12 months. The findings will help determine the influence of abutment material on the wear behavior of BioHPP clasps and provide evidence for selecting appropriate abutment materials in removable partial denture treatment.

Inclusion Criteria:

Adults aged 40-50 years. Mandibular Kennedy Class I partial edentulism. Bilateral distal extension edentulous areas. Presence of healthy canines and first premolars suitable as abutment teeth. Adequate oral hygiene and healthy periodontal condition. Adequate interarch space for removable partial denture fabrication. Ability and willingness to attend all scheduled follow-up visits and provide written informed consent.

Exclusion Criteria:

Systemic diseases or medications that could affect bone or soft tissue healing. Active periodontal disease or poor oral hygiene. Severe parafunctional habits (e.g., bruxism or clenching). Smoking. Pregnancy or lactation. Allergy or hypersensitivity to any study materials. Inability to comply with study procedures or follow-up visits.