Influence of the short implant prosthetic factors implants and the stress distribution from the insertion torques

Author(s)

Bruno Salles Sotto Maior

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2011-04-15

Examining board members

Altair Antoninha Del Bel Cury; Carlos Eduardo Francischone; Fernanda Faot; Dalva Cruz Lagana; Neuza Maria Souza Picorelli Assis

• Advisor: Altair Antoninha Del Bel Cury

Abstract

The short implants are an alternative treatment for edges reabsorbed. However, using short implant at the posterior atrophic mandibular has showed higher biomechanical risk due to higher crown following to the increase of inter-maxillary space. Aiming to offset the unfavorable biomechanics is advisable to use less rigid restorative materials, retention system for the prosthesis to facilitate the stress distribution and use of implants with larger diameters. However, the influences of these prosthetic factors and insertion torque on stress concentration are not clearly understood. Thus, the objectives were to evaluate by tridimensional finite element method the influence of: I) crown-to-implant (C/I) ratio, retention system, restorative material and occlusal loading on stress concentrations within a single posterior crown supported by a short implant; II) different insertion torques on the stress and strain distribution in cortical and cancellous bones. For the first objective, thirty-two finite element models of an atrophic posterior edentulous mandible were created. Each model received a metal-ceramic crown, cemented or screwed, over a single external hexagon implant with 7 mm length and 5 mm diameter at the first molar region. The C/I ratio ranged from 1:1, 1.5:1, 2:1 to 2.5:1. The models were loaded by simulating a normal and traumatic occlusion. After the convergence analysis of 5% to mesh refinement, the numerical analysis was performed on Ansys Workbench 10.0® software. The maximum principal stress for cortical and cancellous bone and von Mises stress (?vM) for the implant and abutment screw were computed and analyzed using analysis of variance. For the second objective, six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm. The ?max and the maximum principal strain (max) were obtained for cortical and cancellous bone. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue. The results showed that traumatic occlusion and increasing C/I ratio significantly increased the stress concentration in cortical bone, cancellous bone, implant and prosthetic screw. The prosthetic retention system significantly influenced the stress concentration, but at a lower level than the C/I ratio or occlusal loading. The screw-retained prosthesis displayed higher stress levels than the cement-retained prosthesis in all components. The stress concentration was not affected by the restorative material. For the second objective, the increase in the insertion torque generated an increase in the ?max and ?max values for cortical and cancellous bone. It is concluded that occlusion is main factor that most influences the stress concentration at the implant prosthodontic supported by short and high insertion torques that increase concentrations of stress and strain in the peri-implant bone tissue (AU)

• FAPESP's process: 09/14982-4 - BIOMECHANICAL BEHAVIOR OF DIFFERENT CROWN/IMPLANT RATIOS IN THE INTERFACE IN OSSEOINTEGRATED IMPLANTS - A THREE-DIMENSIONAL FINITE ELEMENT COMPARATIVE STUDY
• Grantee: Bruno Salles Sotto Maior
• Support Opportunities: Scholarships in Brazil - Doctorate