Abstract
The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. 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 on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6%) drove the mesh refinement. Maximum principal stress (δmax) and maximum principal strain (εmax) were obtained for cortical and cancellous bones around to implant. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5%. The increase in the insertion torque generated an increase in the δmax and εmax values for cortical and cancellous bone. The δmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The εmax was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.
Highlights
Over the last 30 years, clinical studies with osseointegrated implants have shown excellent longterm results, with over 90% success rate (1,2)
An adequate stability of the dental implant in the surrounding bone plays an important role in the bone healing processes, avoiding micromovement and damage to the bone healing process (17,19)
Clinical assessment of primary stability can be performed by the implant insertion torque at the moment of placement (19)
Summary
Over the last 30 years, clinical studies with osseointegrated implants have shown excellent longterm results, with over 90% success rate (1,2). Early failures may occur during the healing process affecting osseointegration (3). These failures may have biological causes, such as periimplantitis and systemic diseases. Biochemical factors can negatively influence implant success; for instance, bone over heating during the surgical procedure, occlusal overload, besides the effects of tensile strength, shear and compressive stresses in the peri-implant bone tissue (4). Excessive tension may cause irreversible damage to the periimplant bone tissue (6). Recent computerized simulations have suggested that compressive stresses and hydrostatic tensions of the interstitial liquid may modulate tissue differentiation and bone remodeling (4,7,8). Byrne et al (7), using mathematical models about cellular differentiation in bone repair, verified that the stress increase changes the bone repair process, reducing the amount of newly formed bone tissue by 23% and increasing the amount of cartilage by 21%. Checa and Prendergast (8) verified less newly formed bone and greater connective
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