Effect of Aligned Implants on the Stress Promoted by Loads in Fixed Partial Prosthesis: A Photoelastic Study

This in vitro study verified the effect of aligned implants on the stress in partial fixed prosthesis when the teeth were submitted to axial or oblique loads. A photoelastic model (n=1) was made for each implant type (EH - External hexagon, IH - Internal hexagon, and MT- Morse taper) in which were placed three aligned implants, and a Ni-Cr framework with three units. The prostheses were subjected to axial (AL) or oblique (OL) loads of 100 N applied on the occlusal of the teeth. A polariscope analyzed the photoelastic behavior of the models with Fringes software in Matlab platform. Qualitative analysis: EH/AL - Lower stress at second premolar and greater stress concentration at implant apexes of the first and second molars; IH/AL - Less stress concentration at second premolar and first molar, and larger stress at implant apex of the second molar; MT/AL - Different stress concentrations in the implant regions with more intensity at implant apex of the second premolar; EH/OL - Greater stress concentration at apex regions of the first and second molars; IH/OL - Greater stress concentration at apex regions of the first and second molars; and MT/OL – Greater and similar stress concentration at apex regions of the second premolar, and first and second molars. Quantitative analyses: EH/AL (T=18.24 and Nf=1.82); IH/AL (T=18.14 and Nf=1.81); MT/AL (T=18.27 and Nf=1.81); EH/OL (T=20.13 and Nf=2.01); IH/OL (T=19.84 and Nf=1.89); and MT/OL (T=20.22 and Nf=2.02). In conclusion, linearly aligned implants in partial fixed prosthesis promoted similar stress concentrations when the teeth were submitted to axial or oblique loads.