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To evaluate the stress behavior of ceramic fragment restoration, varying the thickness of the cement layer and intraoral temperature variation. A solid model of a upper lateral incisor was obtained and a defect at enamel distal/incisal edge was restored with a ceramic fragment. Based on this initial model, 4 different models (M) were built: M1 - absence of cement layer (CL) (0 μm of thickness); M2 - CL with an uniform thickness of 50 μm; M3 - CL with 50 μm at the margin of ceramics and 100 μm in the inner area far from margins; M4 - CL with 50 μm at the margin of ceramics and 200 μm in the inner area far from margins. The environment temperature changed from 5 °C to 50 °C in 4 increments. The finite element analysis was performed. Increase the cement layer thickness generated higher stress levels on ceramic surface in all temperatures, as well as on cement interface. In general hot temperature was the worst scenario for ceramic fragments integrity, since tensile and compressive stress were more intense. The maximum principal stress on ceramic fragment was found 90 MPa for M4 at 50 °C, followed for M3 (87 Mpa). For CL, the peak of stress was found for M3 at 5 °C (47 MPa). Is it possible to conclude that thick resin cement layer contribute to higher stress concentration on ceramic fragment, and extremely hot temperatures increase the risk of structural failure, since both ceramic and \cl are exposed to higher compressive and tensile stresses.

The aim of this study was to evaluate stress distribution on the peri-implant bone, simulating the influence of Nobel Select implants with straight or angulated abutments on regular and switching platform in the anterior maxilla, by means of 3-dimensional finite element analysis. Four mathematical models of a central incisor supported by external hexagon implant (13 mm × 5 mm) were created varying the platform (R, regular or S, switching) and the abutments (S, straight or A, angulated 15°). The models were created by using Mimics 13 and Solid Works 2010 software programs. The numerical analysis was performed using ANSYS Workbench 10.0. Oblique forces (100 N) were applied to the palatine surface of the central incisor. The bone/implant interface was considered perfectly integrated. Maximum (σmax) and minimum (σmin) principal stress values were obtained. For the cortical bone the highest stress values (σmax) were observed in the RA (regular platform and angulated abutment, 51 MPa), followed by SA (platform switching and angulated abutment, 44.8 MPa), RS (regular platform and straight abutment, 38.6 MPa) and SS (platform switching and straight abutment, 36.5 MPa). For the trabecular bone, the highest stress values (σmax) were observed in the RA (6.55 MPa), followed by RS (5.88 MPa), SA (5.60 MPa), and SS (4.82 MPa). The regular platform generated higher stress in the cervical periimplant region on the cortical and trabecular bone than the platform switching, irrespective of the abutment used (straight or angulated).

Purpose: The aim of this study was to evaluate stress distribution on peri-implant bone simulating the influence of implants with different lengths on regular and switching platforms in the anterior maxilla by means of three-dimensional finite element analysis., Materials and Methods: Four mathematical models of a central incisor supported by an external hexagon implant (diameter, 5.0 mm) were created, varying the length (15.0 mm for long implants [L] and 7.0 mm for short implants [S]) and the diameter of the abutment platform (5.0 mm for regular models [R] and 4.1 mm for switching models [S]). The models were created using the Mimics 11.11 (Materialise) and SolidWorks 2010 (Inovart) software. Numerical analysis was performed using ANSYS Workbench 10.0 (Swanson Analysis System). Oblique forces (100 N) were applied to the palatine surface of the central incisor. The bone/implant interface was considered perfectly integrated. Maximum (σ(max)) and minimum (σ(min)) principal stress values were obtained., Results: For the cortical bone, the highest stress values (σ(max)) were observed in the SR (73.7 MPa) followed by LR (65.1 MPa), SS (63.6 MPa), and LS (54.2 MPa). For the trabecular bone, the highest stress values (σ(max)) were observed in the SS (8.87 MPa) followed by the SR (8.32 MPa), LR (7.49 MPa), and LS (7.08 MPa)., Conclusions: The influence of switching platform was more evident for the cortical bone in comparison with the trabecular bone for the short and long implants. The long implants showed lower stress values in comparison to the short implants, mainly when the switching platform was used.

Purpose: The aim of this study was to evaluate the influence of different Young moduli of the ceramic crown on the distribution of tensions in the region of the abutment-crown interface by making use of 2D finite element analysis., Materials: Two representative models of a sagittally sectioned maxilla were built through AutoCad program showing an implant in the region of the upper central incisor and were restored by means of IPS e.max Press or Procera AllCeram on zircon abutment. Numerical analysis (Ansys 10.0) was performed under 2 loading conditions (50 N): on the lingual face, at 45 degrees with the implant's long axis (L1) and perpendicular to the incisal edge (L2). The von Mises equivalent stress (σvM) and maximum principal stress (σmax) were obtained., Results: It was noticed that, independent of the restoring system, the maximum σvM values were in the incisal region of the cementation interface for both loading conditions. The IPS e.max Press system showed higher σvM on the adhesive interface with higher L1 influence. The same behavior was also observed as regards the σmax variation., Conclusions: It was concluded that a restoring system with a lower Young modulus shows higher stress concentration on the abutment-crown interface when cemented on an abutment with a high Young modulus. Thus, IPS e.max Press system provides higher stress concentration in the resin cement layer than Procera AllCeram system, suggesting that the resin cement layer shows lower failure risk when the Procera crown is used.

Purpose: The purpose of this study was to evaluate the influence of different types of bone on the stress distribution in the mandibular bone supporting a prefabricated bar-type implant prosthesis using three-dimensional finite element analysis., Materials and Methods: Four finite element models (M) of a completely edentulous mandibular arch were built. The bone types varied from type 1 to type 4 (M1, M2, M3, M4). The arch was restored using a prefabricated bar system supported by four interforaminal implants for the protocol prosthesis. Computer software was used to determine the stress fields. Three unilateral posterior loads (L) of 150 N were exerted on the prosthesis: L1, perpendicular to the prefabricated bar; L2, oblique (30 degrees) in the buccolingual direction; and L3, oblique (30 degrees) in the linguobuccal direction. The maximum principal stress (Omax) and the maximum principal strain (Emax) were obtained for cortical and trabecular bone., Results: Types 3 and 4 bone showed the highest smax (MPa) in the cortical bone (19.9 and 18.2 for L1, 34.6 and 31.3 for L2, and 3.88 and 24.4 for L3, respectively). The maximum principal strain (Emax) was observed in type 4 cortical bone for all loads (1.80 for L1, 2.4 for L2, and 2.36 for L3)., Conclusions: The cortical bone in M3 and M4 showed the highest stress concentration in the axial and buccolingual loading conditions. Bone types 1 and 2 showed the lowest stress concentrations. For the linguobuccal loading condition, the cortical bone in M4 showed the highest stress concentration, followed by bone types 3, 2, and 1. Cortical bone in M4 showed the highest strain for all loading conditions. The bone type might not be the only decisive factor to influence the stress distribution the bone supporting an implant prosthesis anchored by a prefabricated bar.

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.