Photoelastic analysis of stresses transmitted by universal cast to long abutment on implant-supported single restorations under static occlusal loads

The aim of this study was to compare the stresses resulting from cemented or screw-retained dental prostheses using universal cast to long abutment by the photoelastic method. A photoelastic resin model was fabricated to simulate a segment of the mandibular arch with resin replicas of a first premolar and a second molar, and two 3.75 × 11-mm implants replacing the second premolar and the first molar. Vertical static loads were individually applied on the occlusal surface of the premolar and the molar (5 kgf) and simultaneously on both crowns (10 kgf). Results found variable stress patterns around each implant and concentrated stresses in the individually loaded crowns. Force transfer characteristics of each situation and quantification of the isochromatic fringes were evaluated. Within the limitations of this study and based on the results obtained for implant-supported prosthesis with internal hexagon connection/universal cast to long abutment, it could be concluded that single adjacent screw-retained prosthetic restorations lead to higher stresses around the implants when compared with cement-retained restorations.