Stress distribution in fixed mandibular prostheses fabricated by CAD/CAM and conventional techniques: Photoelastic and strain gauge analyses

Abstract

BackgroundThe aim of this study was to evaluate the distribution of stress in complete fixed mandibular prostheses with infrastructures (IE) fabricated with different materials and techniques, under compressive force.Material and MethodsA model of an edentulous mandible, which received five 4x11 mm external hexagon implants between the mental foramens, was fabricated. The groups were divided into: Group I - IE in nickel-chromium with an acrylic resin occlusal coating; Group II – IE in nickel-chromium with a ceramic occlusal coating; Group III – IE milled in zirconia with a ceramic coating. For the photoelastic methodology, 70 N axial loads were applied in three regions. Photographic images were taken and analyzed according to the number of high-intensity fringes. For the strain gauge methodology, the measurement of stresses was performed in two distinct regions. The same compression tests described earlier were then performed. The registered stress values were grouped in tables and submitted to two-factor variance analysis (ANOVA) and the Tukey test with 5% significance.ResultsThe results of the two methodologies demonstrated smaller stress values for Group I, when compared to the other groups.ConclusionsIt was possible to conclude that the complete fixed prostheses, with infrastructures cast in metal and acrylic occlusal coating, demonstrated better biomechanical results. Key words:Dental implants, mandibular prosthesis implantation, biomechanics.

Evaluation of Stresses on Implant, Bone, and Restorative Materials Caused by Different Opposing Arch Materials in Hybrid Prosthetic Restorations Using the All-on-4 Technique

“…In addition to that, all the maxillary prosthesis showed lower stresses in the bone surrounding the implant when opposed by a mandibular implant-supported acrylic prosthesis. These results correlate to the result obtained by other authors [ 18 , 28 , 29 ]. Another study showed that the use of acrylic resins resulted in a lower stress distribution when compared to ceramics [ 17 ].…”

“…When planning an implant-retained prosthesis, the clinical implication could change drastically depending on the surrounding conditions as intra-oral conditions are not always perfect. While some materials have been found to increase the amount of stress transmitted to the opposing prosthesis, other materials have been shown to transfer lower stresses [ 3 , 7 , 16 , 17 , 18 ]. As a result, it has been believed that the type of opposing structure influences the level of crestal bone change and the amount of stresses that are being transferred [ 19 ].…”

Stress distribution on different bar materials in implant-retained palatal obturator

“…According to Bhering et al [ 50 ], rigid frameworks transmit lower load to the implant and prosthetic components, when compared to the less rigid ones. Nonetheless, variations of framework material rigidity did not demonstrate a significant effect on the stress values in the marginal bone around the implants [ 51 ] and Medeiros et al [ 26 ] observed that the occlusal coating had a greater influence on the load dissipations than the framework. In consonance with Erkmen et al [ 52 ] the current study demonstrated that by using less rigid material for milled bar in implant-retained prostheses the stresses within both, the framework and the veneering parts, decreased due to the flexible nature of the material that absorbs stresses.…”

“…The assessment of biomechanical behavior can be performed through simulations to obtain pre-clinical data with bioengineering tools such as strain gauge, digital image correlation, photoelasticity and finite element analysis (FEA). The latter allows us to understand how the distribution of strain in bone tissue and stress in implants can be influenced by the restorative material [23], prosthesis and framework design [24,25], manufacturing technique [26], number and distribution of implants [27][28][29] and attachment systems [30,31]. Computer-assisted implant planning has become an important diagnostic and therapeutic tool in modern dentistry.…”