The effects of restorative material and connector cross-section area on the stress distribution of fixed partial...

This study aimed to evaluate the effects of restorative materials and connector cross-section areas (CSAs) on the stress distribution of monolithic fixed partial dentures (FPDs).

FPDs, abutment teeth, periodontal ligament (PDL), and alveolar bone were modeled by computer-aided design. Four materials with varied elastic modulus (3 mol% yttria-stabilized tetragonal zirconia polycrystals [Zr], lithium disilicate [LD], polymer-infiltrated ceramic network [PICN], and resin composite [RC]) and five CSA of connectors (4, 6, 8, 10, and 12 mm²) were set as FPD variables for finite element analysis (FEA). The stress distribution on FPDs, abutment teeth, PDL, and alveolar bone was analyzed under two different loading modes (three-point loading and pontic loading). The results of FEA were further verified by photoelastic test.

Both FPD material and CSA influenced the stress distribution of the FPD-tooth-bone complex. At a constant CSA of 8 mm², Zr, with the highest elastic modulus, exhibited the lowest stress on abutment teeth (2.4177 MPa). As the materials' elastic modulus decreased, the stress increased by 2.37%, 7.67%, and 13.16% for LD, PICN, and RC, respectively. Increasing the CSA from 4 mm² to 12 mm² reduced stress on abutments by 1.65% and 1.54% in the Zr and PICN groups, respectively. However, in the RC group, the stress increased significantly by 115.63%.

Materials with a higher elastic modulus tend to confine stress within the FPDs, reducing the downward transmission of stress. As the CSA increases, stress might be more evenly distributed from FPD to the periodontium, potentially reducing stress concentration.