A Comparative Stress Analysis of Angulated Versus Straight Implants for Tilted Placement

Background Nowadays, tilted implants are increasingly being discussed as an alternative treatment in situations characterized by limited bone height and anatomic limitation. Using angulated orientation for implants allows the use of longer implants, a short cantilever length and larger inter-implant distance. When the regular straight implant is placed in angulation, one side is immersed in the bone. To overcome this inconvenience mostly bone is augmented or one side of the implant stay unsupported. Aim/Hypothesis The newly designed angulated-implant would overcome this bone removal thus cause more support and also increase the surface area. The aim of this FEA study is to compare the stress levels at the bone implant interface of tilted-straight versus angulated-implant designs for the tilted configurations. Material and Methods Three-dimensional models of two different [straight (4.3 × 9 mm) and angulated (4.3 × 11 mm)] implant designs were constructed for the same implant bed in a D2 bone model. The implants are modelled as single unit and the crowns are modeled as lower first molar. The single crown restorations were inserted on these implants via angulated abutments. All materials’ Young modulus and Poisson's ratio were defined. To simulate chewing forces, oblique load of 300 N was applied to the distal occlusal surface (1.5 mm2) of the crown in all three directions (x, y, and z). The stresses in the peri-implant tissues and the implant components were investigated by analyzing max-min principle and von Mises stresses using 3D-FEA software program. Results According to the results, analysis predicted that in peri-implant tissues, the maximum stress was found around the neck region of the implant for all models. The finite element analysis performed with the 30° tilted-straight implant show partial, high stress peaks in the region of the implant shoulder region and its components, whereas angulated-implant show a very uniform and completely uncritical distribution of the von Mises stresses. The stress peaks usually experienced with this loading can be effectively prevented by the angulated-implant system. This in turn protects the surrounding bone in the angularly placed implants in necessary regions. The angulated-implant design showed a lower absolute value of compressive stress compared with the tilted-straight implant, indicating a possible biomechanical advantage in reducing stresses at the bone-implant interface. Conclusions and Clinical Implications Within the limitations of this FEA study, from a biomechanical point of view, favorable peri-implant stress levels could be induced by angled-implants under oblique loading. The new design can demonstrate superior performance in anatomical design and biomechanical advantage with reduced prosthetic and technical complications. Further clinical and biomechanical studies are necessary to confirm this encouraging results.