Maximum Von Mises Stress Values Research Articles

Numerical Study of Mechanical Development of Patient-Specific Mandibular Reconstruction Implant

Patient-specific mandibular reconstruction implants are a new technique to deal with ameloblastoma tumors. Although they could solve the integration problem which is attributed to the graft reconstruction approach, they may increase the risk of infection due to poor blood supply around it. Using bone grafts besides customized plates with smaller geometries would be considered as an alternative. However, they would also have possible complications like poor graft integration and plate fracture. Considering weight reduction patterns on implants would efficiently help to solve the mentioned problems. In this study, two design concepts of mandibular reconstruction implants which were different in weight reduction pattern’s location were presented. Also, a finite element assessment was performed to evaluate the mechanical performance and functionality of the implants under chewing load. Results revealed that designing patterns all over the implant geometry would lead to minimum jaw deviation and maximum Von Mises stress values around 120 MPa which is much less than Ti6Al4V yield stress. Compared to the solid design, the patterns would enhance the implant function by decreasing the deviation which would result in a function similar to the intact side. Although results showed the proper functionality of the implant clinical trials with multiyear follow-ups are still needed to investigate the detailed clinical results of this concept.

Comparison of biomechanical behaviors of different designs and configurations of titanium and zirconium dental implants with finite elements analysis.

Finite element analysis helps to understand the biomechanical behavior of implants with different designs and material characteristics. This study aimed to compare the biomechanical behaviors of different designs and configurations of titanium (tapered or cylindric) and zirconia dental implants in the edentulous anterior maxilla through this analysis. Three-dimensional models of the edentulous maxilla, dental implants, and prosthetic structures were modeled, and different loading conditions were applied to simulate realistic conditions. A total of 6 different models were evaluated: the model (M1) in which tapered implants were located in bilaterally central-canine; the model (M2) in which tapered implants were located in bilaterally lateral-canine; the model (M3) in which cylindric implants were located in bilaterally central-canine; the model (M4) in which cylindric implants were located in bilaterally lateral-canine; the model (M5) in which zirconia implants were located in bilaterally central-canine and the model (M6) in which zirconia implants were located in bilaterally lateral-canine. Maximum tensile and compressive stress values were recorded at M4 under vertical loading and at M6 under oblique loading, while minimum stress values were recorded at M1 under all loading conditions. Maximum von Mises stress values under vertical and oblique loading conditions were observed at M3 and M4, while the minimum stress was observed at M1 and M2. In conclusion, zirconia implants may present a biomechanically convenient and aesthetical alternative treatment option in edentulous anterior maxilla rehabilitation compared to tapered and cylindric implants.

The stress distribution of a primary molar tooth restored with stainless steel crown using different luting cements

BackgroundThe aim of this study is to evaluate the stress distributions of a primary molar tooth restored with a stainless steel crown (SSC) using resin and glass ionomer luting cements by Finite Element Analysis (FEA).MethodsOriginal DICOM data of a primary molar was used to create a 3D model. One model was prepared as a tooth model with SSC. A 30 μm cement layer was used in model. Two different luting cements were tested in the study: self-cure adhesive resin cement, and glass ionomer cement. Vertical and oblique loads of 330 N were applied to simulate maximum bite force and lateral forces in the occlusal contact areas of the models. Maximum von Mises stress values in the models were evaluated as MPa.ResultsThe maximum von Mises stress value was observed in the force application and general occlusal contact areas for all models. The maximum von Mises stress values were higher in the tooth model with SSC using self-cure adhesive resin cement (478.09 MPa and 214.62 MPa) than in the tooth model with SSC using glass ionomer cement (220.06 MPa and 198.72 MPa) in both vertical and oblique loading, respectively.ConclusionsDepending on the magnitude of the bite force on the SSC, fracture of the luting cement materials could occur if the stress exceeds the endurance limit of the luting cement. Cementation with glass ionomer cement may help to reduce stress levels in SSC restorations of primary molars in children.

Stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional finite element analysis.

Success/failure of dental implants depends on stress transfer and distribution at the bone-implant interface. This study aimed to assess the stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional (3D) finite element analysis (FEA). In this FEA, a geometric model of an edentulous maxilla, Zimmer screw-vent tantalum and solid titanium implants were modelled. Four models with the all-on-four concept were designed. The fifth model had 6 vertical implants (all-on-six). Two different implant types (porous tantalum and solid titanium) were modelled to yield a total of 10 models, and subjected to 200 N bilateral vertical load. Pattern of stress distribution and maximum von Mises stress values in cancellous and cortical bones around implants were analysed. In tantalum models, the effect of increasing the distal tilting of posterior implants was comparable to the effect of increasing the number of implants to 6 on von Mises stress values in cortical bone. However, in cancellous bone, the effect of increasing the tilting of posterior implants on stress was slightly greater than the effect of increasing the number of implants to 6. In solid titanium models, the effect of both of the abovementioned parameters was comparable on stress in cancellous bone; but in cortical bone, the effect of increasing the implant number was slightly greater on stress reduction. Despite similar pattern of stress distribution in bone around implants, higher maximum von Mises stress values around tantalum implants indicate higher stress transfer capacity of this type of implant to the adjacent bone, compared with solid titanium implants.

Finite element evaluation of dentin stress changes following different endodontic surgical approaches.

The aim was to compare the effect of different endodontic surgical treatments on the stress distributions in dentin of a simulated first mandibular molar tooth using the finite element analysis method. Three surgical endodontic procedures (apical resection, root amputation, and hemisection) were simulated in a first mandibular molar. Biodentine or mineral-trioxide-aggregate was used to repair the surgery site in apical resection and root amputation models; the remaining root canal spaces were filled with gutta-percha. Access cavities were restored using resin composite. In hemisection model, root canal was filled with gutta-percha, and coronal restoration was finished with a monolithic zirconia crown. A sound tooth model was created as a control model. An oblique force of 300N angled at 45° to the occlusal plane was simulated. Maximum von Mises stresses were evaluated in dentin near the surgery regions and the entire tooth. Apical resection/Biodentine and apical resection/mineral-trioxide-aggregate models generated maximum von Mises stresses of 39.001MPa and 39.106MPa, respectively. The recorded maximum von Mises stresses in root amputation models were 66.491MPa for root amputation/Biodentine and 73.063MPa for root amputation/mineral-trioxide-aggregate models. The highest maximum von Mises stress value among all models was observed in the hemisection model, measuring 138.87MPa. Hemisection induced the highest von Mises stresses in dentin, followed by root amputation and apical resection. In apical resection, Biodentine and mineral-trioxide-aggregate did not show a significant difference in stress distribution. Biodentine in root amputation may lead to lower stresses compared to mineral-trioxide-aggregate.

Biomechanical comparative finite element analysis between a conventional proximal interphalangeal joint flexible hinge implant and a novel implant design using a rolling contact joint mechanism

BackgroundThe rolling contact joint (RCJ) mechanism is a system of constraint that allows two circular bodies connected with flexible straps to roll relative to one another without slipping. This study aims to compare the biomechanical characteristics between the conventional proximal interphalangeal joint (PIPJ) flexible hinge (FH) implant and the novel PIPJ implant adopting a RCJ mechanism during PIPJ range of motion using finite element (FE) analysis.MethodsThe three-dimensional (3D) surface shape of a conventional PIPJ FH implant was obtained using a 3D laser surface scanning system. The configuration and parameters of the novel PIPJ implant were adapted from a previous study. The two implants were assumed to have the same material characteristics and each implant was composed of a hyperelastic material, silicone elastomers. The configuration data for both implants were imported to a computer-aided design program to generate 3D geometrical surface and hyperelastic models of both implants. The hyperelastic models of both implants were imported into a structural engineering software to produce the FE mesh and to perform FE analysis. The FE analysis modeled the changes of mechanics during flexion–extension motion between 0° and 90° of two PIPJ implants. The mean and maximum values of von-Mises stress and strain as well as the total moment reaction based on the range of motion of the PIPJs were calculated. The mean values within the PIPJ’s functional range of motion of the mean and maxinum von-Mises stress and strain and the total moment reaction were also determined.ResultsThe maximum values for the von-Mises stress, and strain, as well as the total moment reactions of the conventional PIPJ FH and novel PIPJ implants were all at 90° of PIPJ flexion. The maximum value of each biomechanical property for the novel PIPJ implant was considerably lower compared with that of the conventional PIPJ FH implant. The mean values within the PIPJ’s functional range of motion of the maximum von-Mises stress and strain for the novel PIPJ implant was approximately 6.43- and 6.46-fold lower compared with that of the conventional PIPJ FH implant, respectively. The mean value within a PIPJ’s functional range of motion of the total moment reaction of the novel PIPJ implant was approximately 49.6-fold lower compared with that of the conventional PIPJ FH implant.ConclusionsThe novel PIPJ implant with an RCJ mechanism may offer improved biomechanical performance compared with conventional PIPJ FH implant.

Single implant retained overdentures: Evaluation of effect of implant length and diameter on stress distribution by finite element analysis.

Single implant retained mandibular overdenture treatment has been shown to be a minimally invasive, satisfactory, and cost-effective option for edentulous individuals. However, the impact of implant diameter and length on stress distribution at the implant, bone, and other components in this treatment approach remains unclear. The purpose of this 3D finite element analysis was to evaluate the effect of implant length and diameter on equivalent von Mises stress and strain distribution in single implant retained overdentures at bone, implant, and prosthetic components. Nine models were constructed according to implant lengths (L) (8, 10, 12mm) and diameters (D) (3.3, 4.1, 4.8mm). The implants were positioned axially, in the midline of the mandible. A 3D model of the edentulous mandible was created from a computed tomography image. A single implant, abutment with insert PEEK and a housing, acrylic denture, and Co-Cr framework were modeled separately. In the ANSYS software program, occlusal loads were applied as 150 N, bilaterally vertical direction, or unilaterally oblique direction to the first molar. Minimum principal stress values were evaluated for bone and equivalent von Mises stress and strain values were evaluated for implant and prosthetic components. Von Mises stress values for vertical load increased at implant, housing, and insert PEEK for all groups when the length of the implant increased. When oblique load was applied, 3.3mm diameter implant groups showed maximum von Mises stress values for implants, cortical bone, cancellous bone, and housing among all groups. A minimum stress level for implant was found in D4.1/L8 group. Regarding the insert PEEK, strain values were found to be higher as the diameter of the implant increased both for vertical and oblique loads. Cortical bone showed higher minimum principal stress values as compared to cancellous bone under both loading conditions. The 3.3mm diameter implant groups exhibited the highest von Mises stress and strain values for both loading conditions at the implant. The diameter of the implant had a greater impact on stress and strain levels at the implant site compared to length. For vertical loading, stress value increased at implant, housing, and PEEK when the length of the implant increased.

Analysis of Torsen Differential Using Autodesk Inventor Nastran

Abstract: In this work the 3D model of the Torsen differential assembly was designed using Autodesk Inventor 2023 and finite element analysis is performed using Nastran software by applying restrictions, contact conditions and loads conditions. The materials taken for static analysis are chosen in concordance with the literature data. Maximum Von Mises stress values were obtained at the base of the gear tooth. After running the fatigue analysis, the tendency to reduce the life of the gear was observed, by breaking the teeth due to fatigue, which occurs due to repeated bending of the tooth, which results in fatigue cracks and finally tooth breakage

Using the fatigue crack initiation parameter for prediction of the crack location on a curved track by 3D-FE analysis

Dynamic modeling of wheel-rail interaction is significant in accurate fatigue analysis of railways. Both location and magnitude of the contact stresses in the contact area must be evaluated accurately and efficiently via computational tools. In curved railway tracks, the distribution of the force exerted on the wheel is complex as it is multiaxial rather than uniaxial; thus, a more comprehensive computational model is required. In this work, a numerical procedure is developed to investigate the fatigue crack initiation on the curved tracks. The Universal Mechanism software is used to specify the spectrum of axial wheel force as input to a three-dimensional explicit finite element model to obtain the resulting stresses at the wheel-rail contact region. A critical element with the maximum von Mises stress value is treated as the element where the fatigue crack is most probably to be initiated. In this element, the critical plane method is used to determine the orientation of the crack initiation. The effect of the radius and slip ratio on the exact site of fatigue crack initiation is established in this approach, and the contact point influence on the fatigue crack initiation parameter is investigated. The proposed model successfully predicts a practical wheel-rail dynamic response to cyclic loading, applying the geometry of the curved track.

Multi-Objective Parametric Shape Optimisation of Body-Centred Cubic Lattice Structures for Additive Manufacturing

There has been significant interest in additively manufactured lattice structures in recent years due to their enhanced mechanical and multi-physics properties, making them suitable candidates for various applications. This study presents a multi-parameter implicit equation model for designing body-centred cubic (BCC) lattice structures. The model is used in conjunction with a multi-objective genetic algorithm (MOGA) approach to maximise the stiffness of the BCC lattice structure while minimising von-Mises stress within the structure under a specific loading condition. The selected design from the MOGA at a specific lattice density is compared with the classical BCC lattice structure and the designs generated by a single-objective genetic algorithm, which focuses on maximising stiffness or minimising von-Mises stress alone. By conducting a finite element analysis on the optimised samples and performing mechanical testing on the corresponding 3D-printed specimens, it was observed that the optimised lattice structures exhibited a substantial improvement in mechanical performance compared to the classical BCC model. The suitability of multi-objective and single-objective optimisation approaches for designing lattice structures was further investigated by comparing the corresponding designs in terms of their stiffness and maximum von-Mises stress values. The results from the numerical analysis and experimental testing demonstrate the significance of the application of an appropriate optimisation strategy for designing lattice structures for additive manufacturing.

Study on the Restoration of Class II Carious Cavities by Virtual Methods: Simulation of Mechanical Behavior.

The restoration of class II cavities is predominantly carried out with composite materials. Due to the high failure rate in restoring this type of cavity, composite materials with much-improved properties and new application techniques have been promoted. The study aimed to analyze the mechanical behavior of several topical composite materials (nanocomposites, nanohybrids and ormocer) using different application techniques. In a lower second molar, a class II occlusal cavity was prepared. As filling materials, we used the following combinations: Admira Fusion and Admira Fusion Flow, Grandio and Grandio Flow, Filtek Supreme XT and Filtek Supreme Flow. These were applied using a snow plow, injection molded and Bichacho techniques. Three-dimensional scanning of the molar with the prepared cavity was performed, and then scanning of each layer of added composite material was performed, obtaining three-dimensional models. The virtual molar models were analyzed with software specific to the finite element analysis method, where their physical-mechanical properties were entered and assigned to the components of the virtual molar. Simulations at high forces specific to bruxism were then carried out and analyzed, and compared. The values of displacements and strain, for all six analyzed situations, are relatively small (range from 5.25 × 10-6-3.21 × 10-5 for displacement, 6.22 × 10-3-4.34 × 10-3 for strain), which validates all three methods and the materials used. As far as the stress values are concerned, they are similar for all methods (250-300 MPa), except for the snow plow and injection-molded techniques using Grandio and Grandio Flow composites, where the maximum von Mises stress value was more than double (approximately 700 MPa). When using the combination of Grandio and Grandio Flow materials, the 1 mm thickness of the fluid composite layer was found to have a major influence on occlusal forces damping as opposed to 0.5 mm. Therefore, the Bichacho technique is indicated at the expense of the snow plow and injection-molded techniques. The composite materials used by us in this study are state-of-the-art, with clear indications for restoring cavities resulting from the treatment of carious lesions. However, their association and application technique in the case of Class II cavities is of clinical importance for resistance to masticatory forces.

Fore Poppet Design and Optimization to Apply on Norway type Trawler Fishing Ships

In the classical sea landing methods of ships, aquaplaning and slipway support systems are used. In Norwegian Type Trawler Fishing vessels, the outer shell surface geometry is very delicate. Therefore; the incoming forces are extreme and the use of wooden poppets by these forces in normal sea landings is insufficient. This work; It includes two different steel fore poppet designs and analyzes for the Norwegian type trawler fishing vessel, which cannot be launched with conventional slipway support systems after landing calculations. Within the scope of this study, two different steel fore poppets were designed. After the analyzes and examinations, it was decided that the Norwegian type trawler fishing vessel, which is the subject of the article, with which steel fore poppet design will be launched without any problems. Studies carried out in this context; Two different steel fore poppet designs were made using the Rhinoceros analysis program, which is a 3D design program.Rhinoceros Scan & Solve analysis was performed and simulation was run by applying forces to the designed steel fore poppets. A force of 3e+06N, including gravity, was applied to both designed structures. As a result of this; In the first steel fore poppet structure, a maximum displacement of 1.18611mm occurred. In structures designed under a force of 3e+06N; In the first structure, the maximum Von Mises Stress value was found to be 505.761MPa. In the second structure, the maximum Von Mises Stress value was found to be 163.142MPa.

Optimal hinge level in opening wedge high tibial osteotomy: Biomechanical analysis using finite element method

BackgroundWhile the concept of a safe zone, which can minimize the hinge fracture when performing opening wedge high tibial osteotomy, has been introduced, there is a lack of understanding of the biomechanical environment at the lateral tibial cortex. This study aimed to evaluate the effect of the hinge level on the biomechanical environment at the lateral cortex of the tibia with heterogeneous finite element models. MethodsFinite element models of biplanar opening wedge high tibial osteotomy based on computed tomography images of a control subject and three patients with medial compartment knee osteoarthritis were created. In each model, three different hinge levels (proximal, middle, and distal) were set. The process of opening the gap during the operation was simulated, and the maximum von Mises stress values at the lateral tibial cortex were calculated for each hinge level and correction angle. FindingsThe maximum von Mises stress value at the lateral tibial cortex was the lowest when the hinge was at the middle, while the value was the highest when the hinge was at the distal level. Furthermore, it was demonstrated that a higher correction angle yielded a higher probability of lateral tibial cortex fracture. InterpretationThe findings of this study demonstrate that the hinge at the point where the upper end of the articular cartilage of the proximal tibiofibular joint is located provides the least possibility of lateral tibial cortex fracture, as this is an anatomically independent position from the fibula.

Low and high viscosity bulk-fill composite resins stress distribution in primary molar tooth inlay cavity

The aim of this study is to evaluate the stress distributions of low and high viscosity bulk-fill composite resins at class II MOD inlay cavity in primary molar tooth using Finite Element Analysis (FEA). Original DICOM data of a primary molar tooth from a research archive was used to create a 3D model. Two models were prepared as Model 1: the tooth model without restoration (control group) and Model 2: the tooth model with class II MOD inlay restoration. Two different bulk-fill composite resins were tested in study: Model 2 A (class II MOD inlay cavity model restored with low viscosity bulk-fill composite resin) and Model 2B (class II MOD inlay cavity model restored with high viscosity bulk-fill composite resin). Occlusal vertical loading of 232 N was applied to the teeth in occlusal contact areas. Maximum Von Mises stress values in the models for enamel, dentin, and restorative material were evaluated as MPa. More intense stress accumulation is observed in enamel than in dentin. In addition, more stress values were determined in Model 2B (206.15 MPa, 32.76 MPa, 128.95 MPa) than in Model 2 A (203.39 MPa, 29.77 MPa, 120.61 MPa) for enamel, dentin and restorative material, respectively.

Finite element analysis of biplanar customized reconstruction plates for lateral and central segmental defects of mandible

The purpose of this study is to compare biplanar custom mandibular reconstruction plates with locking reconstruction plates in bridging central and lateral mandibular segmental defects by using the finite element method. Central and two different types of lateral segmental defects were created on mandibular model that was generated from computed tomography of a male patient. Segmental defects were fixed with conventional locking reconstruction plates and two different custom designed plates with caudobuccal and dorsobuccal cover. Stress formation on hardware and screws, strain on bone under masticatory simulation were evaluated with a finite element model. The stress values on plate and screws were higher in conventional reconstruction plate than custom plates. Simulations of central segmental defect revealed maximum von Mises stresses of 643.62 MPa and 101.83 MPa in conventional reconstruction plate and biplanar plate, respectively. Biplanar plates revealed slightly higher von Mises stresses than extended surfaced biplanar plates. The screws close to resection area were exposed to higher stress than farther screws for whole groups. In conventional reconstruction plate, the maximum von Mises stress values of fixation screws were 268.66 MPa and 95 MPa for central segmental defect and lateral segmental defect, respectively. The study reveals that the biplanar custom reconstruction plates had a favourable effect on stress distribution and can enhance function and aesthetics as supporting mandible and flaps from two different planes.

Analisis Variasi Desain Rangka Sepeda Motor Listrik Terhadap Kekuatan Rangka dengan Ansys Workbench

Designing a fuel-based electric motorcycle frame needs to be modified to be able to place electrical components. Design and simulation of frame design variations are needed to obtain optimal frame strength by having the lowest stress, lowest deformation, and highest safety factor. The research objective is to obtain a frame design with optimal frame strength. The research method uses a comparative method in the form of three frame design variations simulated by Ansys Workbench. The frame simulation uses two types of loads, namely normal loads (146.2 kg) and heavy loads (316.2 kg). The simulation material uses AISI 4130 material. The selected and optimal frame design is the frame with the lowest maximum von Mises stress value and not more than the yield stress, the lowest maximum total deformation, and the highest minimum safety factor and > 2.5. From the research results, it was found that design 2 was the design with the best strength compared to design 1 and design 3. Simulation with normal load (146.2 kg) obtained a maximum von Mises stress of 50.38 MPa, maximum total deformation of 0.036 mm, minimum safety factor of 8.237. While the heavy load simulation (316.2 kg) obtained a maximum von Mises stress of 144.64 MPa, a maximum total deformation of 0.863 mm, a minimum safety factor of 2.869.

Numerical analysis of the influence iron type on Von Mises Stress and safety parameters for compost processing machine frame construction

The installation of other engine parts, such as the engine, transmission, shaft, blade, and cover, includes the engine frame. The engine frame must be developed and constructed with the strength to support other components. The building of the waste processing machine frame with variants of square tube type and angle bar type will be analyzed in this study, with a focus on the analysis of von Mises’s stress and safety aspects. Using Solidworks software, finite element analysis is the research methodology used. The examination of the waste processing machine’s frame modelling using square tubes and angular bars yielded maximum von Mises stress values of 3.77e+7 N/m2 and 3.162e+4 N/m2, respectively. The maximum deformation values for the square tube iron and angular bar used in the modelling analysis of the waste processing machine frame are 2,499e+1mm and 9,725e+1mm, respectively . and 8.5 and 1 is the required minimum safety factor value for modelling the frame of a waste processing machine made of square tube iron. The safety factor value of 2-3 is the primary criterion for a suitable design. It is safe and advised to utilize the waste processing machine frame made of square tube iron for this purpose.

Effect of implant placement depth on bone remodeling on implant-supported single zirconia abutment crown: A 3D finite element study.

This study aimed to evaluate the influence of subcrestal implant placement depth on bone remodeling using time-dependent finite element analysis (FEA) with a bone-remodeling algorithm over 12 months. Seven models of different subcrestal implant placement depths (0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm) were analyzed using FEA to evaluate the biomechanical responses in the bone and implant, including von Mises equivalent stress, strain energy density (SED), and overloading elements. SED was used as a mechanical stimulus to simulate cortical and cancellous bone remodeling over the first 12 months after final prosthesis delivery. The highest increase in cortical bone density was observed at Depth 1.5, whereas the lowest increase was observed at Depth 3.0. In contrast, the highest increase in bone density was observed at Depth 3.0 in the cancellous bone, whereas the lowest increase was observed at Depth 0. The highest peak von Mises stress in the cortical bone occurred at Depth 2.5 (107.24 MPa), while that in the cancellous bone was at Depth 2.5 (34.55 MPa). Notably, the maximum von Mises stress values in the cancellous bone exceeded the natural limit of the bony material, as indicated by the overloading elements observed at the depths of 2.0, 2.5, and 3.0 mm. Greater bone density apposition is observed with deeper implant placement. An implant depth of more than 1.5 mm exhibited a higher maximum von Mises stress and greater overloading elements.

The stress distribution of different types of restorative materials in primary molar

AbstractThe aim of this finite element analysis study is to evaluate the stress distributions of different types of restorative materials at Class I cavity in the primary molar. The non-cracked caries-free primary mandibular second molar that is extracted for orthodontic reasons is used to create a three-dimensional model. Two models were prepared as Model 1: the tooth model without restoration (control group) and Model 2: the tooth model with Class I restoration. Five different types of restorative materials were tested in Model 2 (resin modified glass ionomer [Fuji II LC], compomer [Dyract AP], giomer [Beautiful II], glass carbomer [GPC Glass Fill] and ionic resin material with bioactive properties [Activa Kids Bioactive]). A force of 197 N was applied in the vertical and oblique directions in the ANSYS program (Ansys Workbench 19.0, Canonsburg, PA). The maximum Von Mises stress values were compared in the models. The vertical or oblique loading created different stresses in enamel, dentin and restorative materials. The stresses in the enamel tissue were higher than that in the dentin tissue. The stresses in vertical loading were higher than in the oblique loading for restorative materials. The different restorative materials exhibited similar stress distribution patterns, except Activa Kids Bioactive (vertical and oblique loading 446.16 and 8.57, respectively).

Impact of different axial wall designs on the fracture strength and stress distribution of ceramic restorations in mandibular first molar

BackgroundThe purpose of this study was to investigate the fracture strength and stress distribution of four ceramic restorations.MethodsForty human mandibular first molars were collected and randomized into four groups after establishing the distal defect: full crown group with 4 mm axial wall height (AWH) (FC4); short AWH crown group with 2 mm AWH (SC2); occlusal veneer group with 0 mm AWH (OV0); occlusal distal veneer group with only the distal surface prepared, and 4 mm AWH (OD4). The teeth were prepared according to the groups and the ceramic restorations were completed using celtra duo ceramic blocks. The ceramic thickness of the occlusal surface is about 1.5 mm and the edge is about 1 mm. The failure load values and fracture modes of each group were detected by mechanical test in vitro. According to the groups to establish three-dimensional finite element analysis (FEA) models, a 600 N loading force was applied vertically using a hemispherical indenter with a diameter of 6 mm. and compare the stress distribution under the condition of different restorations.ResultsIn vitro mechanical tests showed that the failure load values were SC2 (3232.80 ± 708.12 N) > OD4 (2886.90 ± 338.72 N) > VO0 (2133.20 ± 376.15 N) > FC4(1635.40 ± 413.05 N). The failure load values of the short AWH crown and occlusal distal veneer were significantly higher than that of occlusal veneer and full crown (P<0.05). The fracture modes of the full crown and occlusal veneer groups were mainly ceramic fractures and some were restorable tooth fractures. The short AWH crown and occlusal distal veneer groups presented with three fracture modes, the proportion of non-restorable tooth fracture was higher. The results of FEA show that under the spherical loading condition, the stress of ceramic was concentrated in the contact area of the loading head, the maximum von Mises stress values were FC4 (356.2 MPa) > VO0 (214.3 MPa) > OD4 (197.9 MPa) > SC2 (163.1 MPa). The stress of enamel was concentrated in the area where the remaining enamel was thinner, the maximum von Mises stress values was OD4 (246.2 MPa) ≈ FC4 (212.4 MPa) > VO0 (61.8 MPa) ≈ SC2 (45.81 MPa). The stress of dentin is concentrated in the root furcation and the upper third region of the root. However, stress concentration was observed at the tooth cervix in the full crown.ConclusionUnder certain conditions, the occlusal distal veneer shows better performance than the full crown.