Adaptation of overdenture-bars casted in different metals and their influence on the stress distribution—A laboratory and 3D FEA

An implant-supported overdenture for a mandibular defect after tumor resection guided by 3-dimensional finite element analysis: A clinical report

This clinical report describes the rehabilitation of a mandibular defect after tumor resection with an implant-supported overdenture and the attachment selection as guided by 3-dimensional finite element analysis. Autologous bone grafting was declined by the patient who demanded the restoration of lateral appearance and mastication function. Three implants were placed based on the condition of the bone, and a satisfactory definitive prosthesis was provided that corresponded with the results of the finite element analysis.

The effects of bar holder material, cantilever and vertical misfit on stresses in implant supported overdentures: Three dimensional finite element analysis

Background/Aim: The aim of this study is to examine with finite element analysis the distal bar extension, the bar substructure material type and the amount of bar substructure-abutment mismatch, and the stress caused by the implant at the surrounding bone tissue in bar-retained prostheses. Material and Methods: A bar-retained prosthesis model has been designed on three implants placed in the fully toothless lower jaw at the places of both canines and the midline. Bar holder according to distal cantilever lengths was modeled to be 0 mm, 8 mm and 14 mm. The vertical incompatibility of the bar holder substructure with the abutment was modeled to be 0 µm, 100 µm and 200 µm. A total of twenty-seven (3x3x3) different models were obtained with three different bar infrastructure materials (titanium, gold and chromium-cobalt). 150 N occlusal force was applied to the central fossa of the left 1st molar tooth with a rigid food stuff. Results: In the cortical bone, the highest maximum principle stress value (2.78 MPa) was analyzed around the anterior implant socket in the model 13 (gold, cantilever 0mm, misfit 100 µm). The highest von Mises stress value (343.43 MPa, which occurred at the selected joints in bar holders) was observed in model 27 (chrome-cobalt, cantilever 14mm, misfit 200 µm). Conclusions: When the length of the cantilever is 14 mm, it causes a significant increase in stress around the implant, especially near the cantilever. It has been observed that bar infrastructures with high elastic modulus create higher stress values.

How many implants are needed for mandibular full-arch rehabilitation?

Aim: To analyze the stress distribution at the peri-implant bone tissue of mandible in full-arch implant-supported rehabilitation using a different number of implants as support. Methods: Three-dimensional finite element models of full-arch prosthesis with 3, 4 and 5 implants and those respective mandibular bone, screws and structure were built. ANSYS Workbench software was used to analyze the maximum and minimum principal stresses (quantitative analysis) and modified von Mises stress (qualitative analysis) in peri-implant bone tissue after vertical and oblique forces (100N) applied to the structure at the cantilever site (region of the first molars). Results: The peak of tensile stress values were at the bone tissue around to the distal implant in all models. The model with 3 implants presented the maximum principal stress, in the surrounding bone tissue, higher (~14%) than the other models. The difference of maximum principal stress for model with 4 and 5 implants was not relevant (~1%). The first medial implant of the model with 5 implants presented the lower (17%) stress values in bone than model with 3 implants. It was also not different from model with 4 implants. Conclusion: Three regular implants might present a slight higher chance of failure than rehabilitations with four or five implants. The use of four implants showed to be an adequate alternative to the use of classical five implants.

Implant Inclination and Horizontal Misfit in Metallic Bar Framework of Overdentures: Analysis By 3D-FEA Method

Abstract The aim of this study was to evaluate by three-dimensional finite element analysis (3D-FEA) the biomechanics involved in bar-framework system for overdentures. The studied factors were latero-lateral angulation in the right implant (-10, -5, 0, 5 and 10 degrees), and different bar cross-sections (circular, Hader and oval) presenting horizontal misfits (50 or 150 µm) on the opposite implant. Positive angulation (5 and 10 degrees) for implant inclination to mesial position, negative angulation (-5 and -10 degrees) for distal position, and zero degree for parallel implants. The von Mises stresses evaluated the bar, screw and the implant; maximum principal, minimum principal and shear stress analyses evaluated the peri-implant bone tissue. Parallel implants provide lower stress in alveolar bone tissue; mesial inclined bars showed the most negative effect on prosthetic structures and implants. In conclusion, bar cross-section showed no influence on stress distribution for peri-implant bone tissue, and circular bar provided better behavior to the prosthetic system. Higher stress concentration is provided to all system as the misfit increases.