Analysis of implant‐supported cantilever fixed partial denture: An in vitro comparative study on vertical misfit, stress distribution, and cantilever fracture strength

Abstract

AbstractPurposeTo evaluate the vertical misfit, stress distribution around dental implants, and cantilever fracture strength of 3‐unit implant‐supported cantilever fixed partial dentures (FPDs) using frameworks made from different materials and manufacturing techniques.Materials and MethodsForty FPDs were fabricated and divided into 5 groups (n = 8) based on the framework material used: LAS Co‐Cr (Conventional casting—laser welding); TIG Co‐Cr (Conventional casting –TIG welding); OP Co‐Cr (Conventional casting—one‐piece); CAD Co‐Cr (CAD‐CAM); and CAD Zr (CAD‐CAM ZrO2). The vertical misfit was evaluated before porcelain application (T1) and before (T2), and after thermomechanical cycling (T3) by stereomicroscopy. Cantilever fracture strength was tested with a 50 kN (5000 kgf) load cell at a crosshead speed of 0.5 mm/min. Qualitative and quantitative photoelastic analysis was performed to evaluate stress distribution at seven specific points in five FPDs (n = 1/group) subjected to occlusal loading.ResultsOnly the molar showed interaction among the three factors (G × S × T; F(20.932) = 1.630; p = 0.044). Thermomechanical cycling (T2 vs. T3) had a significant effect on intra‐group vertical misfit in molar, especially in LAS Co‐Cr (Δ = 5.87; p = 0.018) and OP Co‐Cr (Δ = 5.39; p = 0.007), with no significant effect in premolar (p > 0.05). Ceramic application combined with thermomechanical cycling (T1 vs. T3) caused a significant intra‐group increase in vertical misfit in all groups, both in the molar and premolar (p < 0.05). OP Co‐Cr was associated with greater vertical misfit and stress concentration. Frameworks manufactured by the CAD‐CAM system exhibited lower vertical misfit and better stress distribution. FPDs with metal frameworks (>410.83 ± 72.26 N) showed significantly higher fracture strength (p < 0.05) than zirconia (277.47 ± 39.10 N), and the first signs of ceramic veneering fracture were observed around 900 N.ConclusionsFPDs with frameworks manufactured using a CAD‐CAM system appear to be associated with lower vertical misfit and better stress distribution, although the section of the frameworks followed by welding may be a viable alternative. In addition, metal frameworks exhibit high fracture strength.