The effect of metal- and polymer-based removable partial denture framework on the prognosis of terminal abutment tooth

The biomechanical behaviour of removable partial denture (RPD) frameworks is important for the prognosis of terminal abutment teeth. With increasing use of polyetheretherketone (PEEK) as an alternative to cobalt chromium (CoCr), integration of finite element analysis (FEA) with clinical validation is required. Objectives: To evaluate the biomechanical behaviour of PEEK and CoCr RPD frameworks using FEA and to assess clinical and periodontal outcomes of terminal abutment teeth in Kennedy Class II patients over six months. Methodology: A combined FEA and clinical study were conducted. FEA models were developed from cone beam computed tomography data, comparing lingual bar and lingual plate designs under 120 N bilateral loading. Stress distribution and deformation in the framework, periodontal ligament (PDL), and mucosa were analysed. Clinically, terminal abutment teeth supporting PEEK (n = 16) and CoCr (n = 12) RPD were evaluated for periodontal parameters and patient reported oral health related quality of life was assessed using the Oral Health Impact Profile-14 questionnaire. Results: FEA demonstrated distinct biomechanical behaviours between materials, connector designs, and rest positions. PEEK bar designs showed gentler stress transmission to the PDL and mucosa, with 69–80% lower deformation than PEEK plates, but exhibited 24% higher internal framework stress. PEEK plate designs produced more even load sharing between the PDL and mucosa, supporting their use in patients with compromised periodontal support. CoCr bar designs demonstrated superior performance with 44–57% lower Von Mises Stress in framework, PDL, and mucosa compared with CoCr plates, while CoCr plates are more suitable for patients with strong abutments. Rest position effects were material dependent. In PEEK frameworks, mesial rests reduced internal framework stress by up to 43%, whereas distal rests lowered PDL stress by 49–89%. In CoCr designs, distal rests provided greater abutment protection, reducing PDL stress by 76% in plates and 46% in bars. Clinically, both groups showed comparable periodontal outcomes and significant improvement in quality of life, with no significant intergroup differences. Conclusions: Although FEA identified material and design dependent differences in stress distribution and deformation, these biomechanical variations did not translate into clinically detectable differences in periodontal stability or patient reported outcomes within the six-month observation period.