Biomechanical analysis of maxillary full-arch fixed prosthetic frameworks manufactured according to all-on-four or all-on-six concept

Author(s)

Cláudia Lopes Brilhante Bhering

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2016-04-15

Examining board members

Valentim Adelino Ricardo Barão; José Maurício dos Santos Nunes Reis; Pedro Yoshito Noritomi; Rafael Leonardo Xediek Consani; Marina Xavier Pisani

• Advisor: Valentim Adelino Ricardo Barão; Marcelo Ferraz Mesquita

Abstract

This study used a three-dimensional (3D) finite element analysis (FEA) to evaluate two treatments concept alternatives to bone grafting procedure for the rehabilitation of edentulous maxilla with dental implants (all-on-four and all-on-six), and the effect of the prosthetic framework material on the stress distribution on implant-supported system. A geometric 3D model was built simulating an entirely edentulous maxilla with moderate maxillary sinus pneumatization, in posterior region and was rehabilitated with full-arch fixed dental prosthesis. The models were confectioned with four implants according to all-on-four (F) treatment concept or six implants according to all-on-six (S) ones. The prosthetic framework was modeled from scanning of a waxed prosthetic framework for full-arch fixed dental prosthesis with ceramic veneering. Three materials were evaluated as prosthetic framework material: cobalt-chrome (CoCr), commercially pure titanium (Ti) and zirconia (Zr). All structures were modeled in Rhinoceros 5.0 SR8 software. Six models were obtained according to groups: F-CoCr, F-Ti, F-Zr, S-CoCr, S-Ti, S-Zr. The assembly was transported to HyperMesh 13.0 in which were generated the mesh with tetrahedral elements. All structures were considered homogeneous, isotropic and linearly elastic. After obtaining the mesh and boundary and loading conditions, the models were transported to the mechanical simulation software (Optistruct 13.0). A preload of 10 N.cm (138.9N) was applied over prosthetic screws. Then, unilateral oblique force (30 degrees inclination) of 150 N was applied to the occlusal surface of the posterior teeth of the prosthetic framework. The results were evaluated using von Mises stress (?VM), maximum (?max) and minimum (?min) principal stress and displacement. The stress distribution observed between the materials tested was similar. Regarding to the treatment concepts, the all-on-six group showed a stress distribution in a larger area. All-on-six treatment concept showed smaller ?min, ?VM and ?max values on the cortical bone, implants and trabecular bone, respectively. Greater displacement of the implant-supported system was noted in all-on-four group. Ti framework resulted in higher stress values on the cortical bone, implants, abutments, prosthetic screws, and set displacement. Similar stress values were noted for CoCr and Zr frameworks. Higher stress values in prosthetic framework were seen when more rigid materials were employed (CoCr and Zr). It can be conclude that all-on-six approach allows the elimination of the cantilever and showed the most favorable biomechanical behavior. The prosthetic framework material influences the stress levels in implant-support system. Stiffer materials decreased the stress levels for bone, implants, screws, abutments and reduced displacements level of the implant-supported system (AU)

• FAPESP's process: 13/22232-0 - Biomechanical analyses of the fixed maxillary full-arch frameworks made according to the all-on-four or all-on-six concepts
• Grantee: Cláudia Lopes Brilhante Bhering
• Support Opportunities: Scholarships in Brazil - Doctorate