Biomechanical effect of inclined implants in fixed prosthesis: strain and stress analysis

Abstract

Introduction Implant inclinations can be corrected using mini abutments at different angulations. Objective To analyze the influence of external hexagon implants in different inclinations (3 levels) on the microstrain distribution generated around three implants. Method A geometric bone model was created through Rhinoceros CAD software (version 5.0 SR8, Mcneel North America, Seattle, WA, USA). Three implants (4.1 × 13 mm) were modeled and inserted inside the substrate at three different inclinations: 0º, 17º and 30º. Next, all groups received mini conical abutments, fixation screws and a simplified prosthesis. The final geometry was exported in STEP format to analysis software and all materials were considered homogeneous, isotropic and linearly elastic. An axial load (300N) was applied on the center of the prosthesis. An in vitro study was conducted with same conditions and groups for validating the tridimentional model. Result Stress was concentrated on the external area of the implants, in contact with the cortical bone and external hexagon. For the bone simulator, the strain increased in the peri-implant region according to the increase in the implant’s inclination. The difference between groups was significant (p = 0.000). The 30º group presented higher stress and strain concentration. Conclusion The microstrain and stress increase around implants directly proportional to the increase of the installation angle.

Stress distribution of complete-arch implant-supported prostheses reinforced with silica-nylon mesh

“…with a length of 0.2 mm were glued 1mm below the implants, two of them were glued distally to the most distal implants, and the other two in the most anterior implant (vestibular and lingual) in superior view (Fig. 1) (10). The admeasurement of each strain gauge, 120 Ω, was performed using a multimeter (Minida ET 2055: Minida).…”

“…The copper surface of the end plates and the two wires from each strain gauge were welded (Solderingunit: Mark VII Strain Gage Lineaccessories, Measurements Group Inc.; Solder connection: 44 rosin core solder) and were connected to an electrical signal conditioner (Model 5100 Scanner – System 5000 - Instruments Division Measurements Group, Inc.). The electrical variations are converted into units of microstrain (με) in the signal conditioner (10). After the strain gauge bonding, the prostheses were installed with 10 N.Cm in each prosthetic screw and submitted to 30 kgf loading (10) for 10 s in the left molar or premolar.…”

“…The electrical variations are converted into units of microstrain (με) in the signal conditioner (10). After the strain gauge bonding, the prostheses were installed with 10 N.Cm in each prosthetic screw and submitted to 30 kgf loading (10) for 10 s in the left molar or premolar. These procedures were repeated two more times, totaling 3 loads per application point.…”

“…The 4 three-dimensional model files were exported to the analysis program (ANSYS 17.0) for the static structural mechanical analysis (10,11). After the mesh generation (following a mesh convergence test), all materials were considered homogeneous, isotropic and linear ( Table 1) (12).…”

“…The elastic modulus of polyurethane and silica-nylon mesh were calculated by the excitatory pulse method. The contacts were considered perfectly bonded in all structures (10,11). The same load application (30 kgf) with vertical displacement restrictions of the base was performed according to the in vitro assay.…”