100-N Load Research Articles

Subregional analysis of joint stiffness facilitates insight into ligamentous laxity after ACL injury.

Purpose: Increased incidence of anterior cruciate ligament injuries has amplified the need for quantitative research in clinical and academic settings. We used a novel digital arthrometer to measure knee laxity in healthy people and patients with anterior cruciate ligament injuries. Changes in stiffness were also assessed to develop new indicators for detecting anterior cruciate ligament injury. The purpose of this study was to use arthrometer to measure the quantitative indicator of knee laxity, bringing clinicians a new perspective on how to identify injury to the ACL. Methods: In this cross-sectional study, anterior tibial displacement under continuous loading was measured using a novel digital arthrometer in 30 patients with unilateral anterior cruciate ligament injury and 30 healthy controls. Load-displacement curves were plotted, using real-time load and displacement changes. Stiffness was defined by the slope of the applied load to tibial displacement. Anterior tibial displacement and instantaneous stiffness values under different loads were compared. The restricting contribution of the anterior cruciate ligament transformed the displacement-stiffness curve from a sharp decrease to a stable increase, resulting in a minimum stiffness value. Using the minimum stiffness as the turning point, the load-displacement curve was divided into regions 1 and 2. The two regions' stiffness changes were compared. Based on the findings, receiver operating characteristic curves were plotted and the area under the curve was calculated to estimate the diagnostic accuracy. Results: Anterior tibial displacement was significantly greater in the anterior cruciate ligament injury group than in the controls under each 10-N increase load (p < 0.05). In the anterior cruciate ligament injury group, instantaneous stiffness was significantly lower on the injured side than on the healthy side (p < 0.05). In the two regions of the load-displacement curve, stiffness was significantly lower in the anterior cruciate ligament injury group than in the control group (all, p < 0.05). Receiver operating characteristic curves were plotted, using changes in stiffness under the two regions in both groups. Stiffness in region 2 had the largest area under the curve (0.94; 95% CI, 0.88-0.99). Using the cut-off value of 9.62N/mm to detect ACL injury, the sensitivity and specificity were 93% and 82%, respectively. Conclusion: Our investigation of ligament stiffness provides novel insights into the properties of knee laxity. Stiffness in the later stages of increased loading <9.62N/mm could be a valid indicator for identifying knee laxity.

Biomechanical Evaluation of the 2 Different Levels of Coracoid Graft Positions in the Latarjet Procedure for Anterior Shoulder Instability.

In the Latarjet procedure, the ideal placement of the coracoid graft in the medial-lateral position is flush with the anterior glenoid rim. However, the ideal position of the graft in the superior-inferior position (sagittal plane) for restoring glenohumeral joint stability is still controversial. To compare coracoid graft clockface positions between the traditional 3 to 5 o'clock and a more inferior (for the right shoulder) 4 to 6 o'clock with regard to glenohumeral joint stability in the Latarjet procedure. Controlled laboratory study. A total of 10 fresh-frozen cadaveric shoulders were tested in a dynamic, custom-built robotic shoulder model. Each shoulder was loaded with a 50-N compressive load while an 80-N force was applied in the anteroinferior axes at 90° of abduction and 60° of shoulder external rotation. Four conditions were tested: (1) intact, (2) 6-mm glenoid bone loss (GBL), (3) Latarjet procedure fixed at 3- to 5-o'clock position, and (4) Latarjet procedure fixed at 4- to 6-o'clock position. The stability ratio (SR) and degree of lateral humeral displacement (LHD) were recorded. A 1-factor random-intercepts linear mixed-effects model and Tukey method were used for statistical analysis. Compared with the intact state (1.77 ± 0.11), the SR was significantly lower after creating a 6-mm GBL (1.14 ± 0.61, P = .009), with no significant difference in SR after Latarjet 3 to 5 o'clock (1.51 ± 0.70, P = .51) or 4 to 6 o'clock (1.55 ± 0.68, P = .52). Compared with the intact state (6.48 ± 2.24 mm), LHD decreased significantly after GBL (3.16 ± 1.56 mm, P < .001) and Latarjet 4 to 6 o'clock (5.48 ± 3.39 mm, P < .001). Displacement decreased significantly after Latarjet 3 to 5 o'clock (4.78 ± 2.50 mm, P = .04) compared with the intact state but not after Latarjet 4 to 6 o'clock (P = .71). The Latarjet procedure in both coracoid graft positions (3-5 and 4-6 o'clock) restored the SR to the values measured in the intact state. A more inferior graft position (fixed at 4-6 o'clock) may improve shoulder biomechanics, but additional work is needed to establish clinical relevance. An inferior coracoid graft fixation, the 4- to 6-o'clock position, may benefit in restoring normal shoulder biomechanics after the Latarjet procedure.

The impact of osteoporosis and diabetes on fracture healing under different loading conditions

BackgroundOsteoporosis and diabetes are two prevalent conditions among the elderly population. Each of these conditions can profoundly influence the fracture healing process by disturbing the associated inflammatory process. However, the combined effects of osteoporosis and diabetes on fracture healing remain unclear. Therefore, the purpose of the present study is to investigate the role of osteoporosis and diabetes in fracture healing and the underlying mechanisms by developing numerical models. MethodThis study introduces a numerical model that consists of a three-dimensional model of a tibia fracture stabilized by a Locking Compression Plate (LCP), coupled with a two-dimensional axisymmetric model which illustrates the transport and reactions of cells and cytokines throughout the inflammatory phase in early fracture healing. First, the model parameters were calibrated using available experimental data. The model was then implemented to predict the healing outcomes of fractures under five varied conditions, consisting of both osteoporotic and non-osteoporotic bones, each subjected to different physiological loads. ResultsThe instability of the fracture callus can significantly escalate in osteoporotic fractures (e.g., when a 150 N physiological load is applied, the unstable region of the osteoporotic fracture callus can reach 26 %, in contrast to 12 % in non-osteoporotic fractures). Additionally, the mesenchymal stem cells (MSCs) proliferation and differentiation can be disrupted in osteoporotic fracture compared to non-osteoporotic fractures (e.g., on the 10th day post-fracture, the decrease in the concentration of MSCs, osteoblasts, and chondrocytes in osteoporotic fractures is nearly double that in non-osteoporotic fractures under a 150 N). Finally, the healing process of fractures can suffer significant impairment when osteoporosis coexists with diabetes (e.g., the concentration of MSCs can be drastically reduced by nearly 37 % in osteoporotic fractures under diabetic conditions when subjected to a load of 200 N) ConclusionsFracture calluses destabilized by osteoporosis can negatively affect the fracture healing process by disrupting the proliferation and differentiation of mesenchymal stem cells (MSCs). Moreover, when osteoporosis coexists with diabetes, the fracture healing process can severely impair the fracture healing outcomes.

Finite element analysis of the angle range in trans-inferior alveolar nerve implantation at the mandibular second molar

BackgroundTrans- inferior alveolar nerve (IAN) implantation technique was wildly used while the potential appropriate angle range in which the residual alveolar bone can bear the stress without absorption are currently unclear. This study aimed to evaluate the stress distribution pattern of the interface between bone and implant by finite element analysis (FEA) to determine the appropriate range of the implant tilt angle.MethodsCone beam computed tomography (CBCT) images of 120 patients with missing mandibular second molars and vertical bone height < 9 mm in the edentulous area were selected. The distances from the mandibular nerve canal to the buccal cortex, the lingual cortex and the alveolar ridge crest were measured by using a combination of software. The angular ranges of the buccal-lingual inclination of simulated trans-IAN implants were measured and three-dimensional finite element models were constructed in the mandibular second molar area according to the differences of the inclination angles. A vertical load (200N) was then applied to analyze the biomechanical conditions of the implant-bone interface during median occlusion.ResultsThe distance at the second molar from the nerve canal to the buccal cortex, lingual cortex and alveolar crest were 6.861 ± 1.194 mm, 2.843 ± 0.933 mm and 7.944 ± 0.77 mm. Trans-IAN implantation was feasible in 73.33% of patients. The minimum angle and maximum angles of the buccal-lingual inclination of the simulated implant were 19.135 ± 6.721° and 39.282 ± 6.581°. When a vertical static load of 200N was applied, the tensile stress in cortical bone gradually increased with the increase of the implant tilt angle. When the inclination angle reached 30°, the tensile stress (105.9 MPa) exceeded the yield strength (104 MPa) of cortical bone. Compared with the conventional implants, the stress peak value of the vertical ultra-short implant in cortical bone was greater than the stress peak value of the conventional implants at 10°(79.81 MPa) and 20°(82.83 MPa) and was smaller than the stress of the implant at 30°(105.9 MPa) and 40°(107.8 MPa). Therefore, when the bone mass allows, conventional-length implants should be selected whenever possible, and an operative range of the trans-IAN implantation in the mandibular second molar could be retained with an inclination angle of < 30°.ConclusionsThe mandibular nerve canal at the mandibular second molar was obviously biased to the lingual side, which ensured sufficient bone mass at the buccal side. In most patients with severe mandibular atrophy, it was possible to maintain a safe distance from the nerve canal with conventional-length implants via the trans-IAN implantation technique.

Modeling dan Simulasi Finite Element Analysis pada Segitiga T Sepeda Motor Menggunakan Sofware Ansys 2023

This study used finite element analysis method to analyze the underbracket T triangle on motorcycles using ANSYS 2023 R1 software. The material used is Structural Steel. The simulation is done by accurately modeling the triangle and meshing using the default algorithm. The boundary conditions are set by providing fixed support at all four-hole points and providing a load of 1000N on the Y-axis. The simulation results show a maximum equivalent stress (Von-Mises stress) of 7.173 MPa, which is still below the strength limit of the material. The underbracket T-triangle undergoes a maximum deformation of 0.00063309 mm at the upper right fork hole. This deformation indicates the extent to which the triangle changes shape due to the load applied. The safety factor obtained is greater than 1, indicating that the triangle has adequate safety to withstand the load. With a better understanding of the structural behavior of the underbracket triangle, the design can be improved to improve the strength and performance of the motorcycle.

FEM: Mono-implant cement retained crown with two different adhesive materials

Background: The finite element method (FEM) is expected to be one of the most effective computational tools for measuring the stress on implant-supported restorations. This study was designed using the 3D-FEM to evaluate the effect of two adhesive luting types of cement on the occlusal stress and deformation of a hybrid crown cemented to a mono-implant. Materials and Method: The mono-screw STL file was imported into the CAD/CAM system library from a database supported by De-Tech Implant Technology. This was to assist in the accurate reproduction of details and design of a simulated implant abutment. Virtually, a digital crown was designed to be cemented on an abutment screw. A minimum occlusal thickness of 1mm and marginal fitting of 1.2mm was intended. An 80µm cement interface thickness for this study’s purposes was applied using U-Cem Premium and 3M RelyXTm adhesives. The FEA software meshed into tetrahedral elements. Two three-dimensional finite element models were simulated under different loads of 200N, 400N, 600N, 800N, 1000N, 1200N, and 1400N. Results: The results showed that the hybrid ceramic crown attached to a mono-implant with each adhesive cement exhibited comparable stress and strain. However, the amount of distortion was less when RelyX cement was used. Conclusion: Overall, it was advisable to use 3M RelyXTm adhesive cement up to 1400N load.

Efficacy comparison of Kirschner-wire tension band and anchor loop plate in treatment of olecranon fracture.

Objective: This study aimed to introduce a new surgical method for the fixation of olecranon fractures, and to compare the biomechanical stability and clinical efficacy of Kirschner wire tension band and anchor loop plate (ALP) in the treatment of olecranon fractures. Methods: A finite element model was established to analyze the mechanical properties of Kirschner wire tension and anchor loop plate fixation for olecranon fracture. The clinical data of 53 patients with olecranon fractures admitted to our hospital from March 2016 to October 2021 were retrospectively analyzed. Among them, 22 cases were fixed with an anchor loop plate (ALP group), and 31 patients were fixed with the Kirschner wire tension band technique. By reviewing the medical records and follow-up results, the final elbow mobility, secondary surgery, postoperative complications and elbow function recovery Mayo score and DASH score were compared between the two groups. Results: The biomechanical analysis of the finite element model showed that under the load of 120N, the maximum displacement of the Kirschner wire group was 1.09 times that of the ALP group, the maximum stress of the Kirschner wire group was 1.33 times that of the ALP group, and the maximum stress of the olecranon proximal bone of the Kirschner wire group was 2.17 times that of the ALP group. Under the load of 200N, the maximum displacement of the Kirschner wire group was 1.19 times that of the ALP group. The overall maximum stress of the Kirschner wire group was 1.59 times that of the ALP group, and the maximum stress of the proximal olecranon bone of the Kirschner wire group was 1.99 times that of the ALP group. The average follow-up time of the Kirschner wire and anchor loop plate groups was similar (p > 0.05). The average age of the two groups was identical (p > 0.05). The final elbow mobility in the anchor loop plate group was significantly greater than in the Kirschner wire group (p < 0.05). The Mayo score of the anchor loop plate group was substantially higher than that of the Kirschner wire group at 3 and 12months after operation (p < 0.05), and the DASH score was significantly lower than that of the Kirschner wire group (p < 0.05). Postoperative complications in the two groups: 1 case (4.5%) in the anchor loop plate group had difficulties with internal fixation stimulation, and no infection occurred; in the Kirschner wire group, 5 cases (16.1%) had complications of internal fixation stimulation, and 1 patient (3.2%) had an infection. Conclusion: The model of olecranon fracture fixed by anchor loop plate and Kirschner wire tension technique was tested under 120 and 200N tension, and no damage was found, indicating that the newly designed anchor loop plate was safe in mechanical structure. The biomechanical stability of the anchor plate technique is more stable, so it is not easy to have postoperative complications such as fracture block cutting and internal fixation failure. And the secondary operation rate and elbow function have better results. This technique is an effective method for the treatment of olecranon fractures.

Marginal fit and fracture resistance of polyetheretherketone, zirconia, and titanium implant-supported prosthesis frameworks for a partially edentulous arch after thermomechanical aging

Although polyetheretherketone (PEEK) and zirconia (Zir) have been used as implant-supported prosthesis (ISP) frameworks, the long-term effects of thermomechanical aging on the marginal fit and fracture resistance of PEEK and Zir ISP frameworks with titanium (Ti) bases for patients with a partially edentulous arch are not clear. The purpose of this in vitro study was to determine the marginal fit and fracture resistance of PEEK and Zir ISP frameworks with Ti bases and Ti ISP frameworks for partially edentulous arches after aging. A total of 30 ISP epoxy resin casts were obtained from a typodont with 1 straight implant (Nobel Biocare) in the mandibular right canine region and 1 implant with a 30-degree distal tilt in the mandibular right first molar region. All frameworks (n=10) were fabricated on their own epoxy resin cast with multiunit abutment replicas by using a computer-aided design and computer-aided manufacturing system (exocad-Yenadent). The PEEK and Zir frameworks were fabricated with Ti-bases. Primer (MKZ) and resin cement (DTK adhesive) were used to cement the frameworks to the Ti-bases under a static load of 10N. After thermomechanical aging (1.2×106 cycles, 120N, 5°C-55°C), marginal gaps between the Ti-bases and cemented frameworks and vertical and passive fits between the Ti-bases and framework and multi-unit abutments were measured by using a stereomicroscope (Euromex) at ×100 magnification. Fracture resistances and types were then determined by using a universal test machine and a stereomicroscope at ×40 magnification. Data were analyzed by using 1-way analysis of variance (ANOVA) and the Tukey HSD and Fisher-Freeman-Halton tests (α=.05). The marginal gaps of the PEEK and Zir frameworks were respectively 83.5 ±27.1 and 81.8 ±17.8µm. PEEK (23.7 ±4.6) and Zir (32.9 ±8.7) had a better vertical fit (µm) than Ti (52.5 ±10.6) (P<.001). Zir (49.3 ±16.2) (P<.001) and PEEK (70.9 ±19.6) (P>.05) frameworks had better passive fit (µm) than Ti (91.3 ±24.2). Ti had the highest mean fracture resistance (N) (14800.2 ±3442.3) followed by Zir (7318.7 ±1385.1) and PEEK (3448.9 ±486.6) (P<.001). Fracture types were different in different groups (P<.001). The PEEK and Zir frameworks with Ti baseshad better vertical and passive fit than the Ti frameworks. All ISP frameworks represented mean marginal fit below 92µm and withstood physiologic occlusal forces after thermomechanical aging.

Mechanical Fracture of Aluminium Alloy (AA 2024-T4), Used in the Manufacture of a Bioproducts Plant

Aluminium alloy (AA2024-T4) is a material commonly used in the aerospace industry, where it forms part of the fuselage of aircraft and spacecraft thanks to its good machinability and strength/weight ratio. These characteristics allowed it to be applied in the construction of the structure of a pilot plant to produce biological extracts and nano-encapsulated bioproducts for the phytosanitary control of diseases associated with microorganisms in crops of Theobroma cacao L. (Cacao). The mechanical design of the bolted support joints for this structure implies knowing the performance under fatigue conditions of the AA2024-T4 material since the use of bolts entails the placement of circular stress concentrators in the AA2024-T4 sheet. The geometric correction constant (Y) is a dimensionless numerical scalar used to correct the stress intensity factor (SIF) at the crack tip during propagation. This factor allows the stress concentration to be modified as a function of the specimen dimensions. In this work, four compact tension specimens were modeled in AA2024-T4, and each one was modified by introducing a second circular stress concentrator varying its size between 15 mm, 20 mm, 25 mm, and 30 mm, respectively. Applying a cyclic load of 1000N, a load ratio R=-1 and a computational model with tetrahedral elements, it was determined that the highest SIF corresponds to the specimen with a 30 mm concentrator with a value close to 460 MPa.mm0.5. Where the crack propagation had a maximum length of 53 mm. Using these simulation data, it was possible to process each one and obtain a mathematical model that calculates the geometric correction constant (Y). The calculated data using the new model was shown to have a direct relationship with the behavior obtained from the simulation.

The Gluteus Medius Experiences Significant Excursion With Hip Flexion

To evaluate the effect of hip flexion and rotation on excursion of the gluteus medius (Gmed) and minimus (Gmin) myotendinous unit. Seven hips from 4 cadaveric specimens (males, 68.5 ± 18.3 years old) were dissected to isolate the Gmed posterior and lateral insertions and the Gmin proximal and distal insertions. Sutures were placed from tendon insertions through origins created in the iliac fossa to simulate the myotendinous unit. A load of 10N was applied. Myotendinous excursion was measured at 10° hip extension and 0°, 45°, and 90° of hip flexion in neutral rotation, and from maximum internal and external rotation in 90° flexion. The amount of abduction and rotation was also measured at each flexion position with 20N applied to each tendon. Repeated-measures analysis of variance with Tukey post hoc was used for statistics. Gmed-lateral excursion ranged from 2.4 ± 0.4 mm in 10° of hip extension to 23.0 ± 1.5 mm in 90° of flexion (P < .001), and Gmed-posterior excursion ranged from 0.92 ± 0.5 mm in 10° of extension to 38.1 ± 1.1 mm in 90° of flexion (P < .001). Gmin excursion shortened with hip flexion from 4.2 ± 0.3 mm in 10° of extension to-0.2 ± 1.5 mm in 90° of flexion (Gmin-prox: P= .525, Gmin-distal: P < .001). At 90° flexion from maximum internal to maximum external rotation, Gmin-distal and proximal demonstrated a 92.6% and 51.3% increase in excursion, respectively (P < .001). Gmed-lateral and Gmed-posterior demonstrated 49.4% and 23.1% increase in excursion with external rotation, respectively (P < .001). The Gmed myotendinous unit undergoes significant excursion with hip flexion, whereas both Gmed and Gmin had significant excursion with femoral external rotation in 90° flexion. It is important to understand whether active or passive hip flexion or rotation in the early postoperative period causes excessive strain to an abductor tendon repair. We found that consideration should be given to limit flexion after Gmed repair and external rotation after Gmed or Gmin repairs.

Mandibular Flexure and Crestal Bone Stress Distribution on an Implant-Supported Fixed Full Arch Mandibular Prosthesis: Finite Element Analysis in Three Dimensions.

Aim This study's objective was to assess and analyze, using 3D Finite Element Analysis, the impact of four mandibular complete arch superstructures on the distribution of stress in the crestal bone during mandibular flexure. Materials and methods Four Finite element models of the mandible with different implant-retained framework designs have been developed. Three of these models had six axial implants placed at intervals of 11.8 mm, 18.8 mm and 25.8 mm from the midline, respectively. One model had two tilted implants and four axial implants splinted with a single piece of framework at intervals of 8.4 mm, 13.4 mm and 18.4 mm from the midline. For analyzing the stress distribution, the finished product was transferred to ANSYS R 18.1 software(Sirsa, Haryana, India) for finite element simulation, the models were constructed, the ends were restrained, and bilateral vertical loads of 50N, 100Nand 150N were applied to the distal part of the framework. Results Bilateral loads were applied to each of the four 3D FEMand after assessment of Von Mises Stress and Total Deformation, a finding was made that the model with six axial implants supported by a single piece of framework underwent the highest total deformation and the model with four axial implants and two implants with distal tilts displayed most significant Von Mises stress. Conclusion Within the constraints of this 3D FEA, it was determined that mandibular flexure and peri-implant bone stress were affected by the way the framework is divided and the nature of mandibular movement. The three types of frames with the least bone stress are demonstrated by the mandibular deformation that results from two-piece frameworks on axial implants. Regardless of the number of implants, the singleframework splinted with six implantsshows aflexure inmandiblewith the highest bone stress around the implant irrespective of the angulation of the implant. Clinical significance When it comes to edentulous jaws, reducing stress in implant-supported restorative systems at varying degrees of the bone and implant interfaces and superstructures of prosthetics is one of the fundamental goals of implant treatment. A framework with proper design and a low modulus of elasticity reduces mechanical risk. Additionally, a larger number of implants helps to prevent cantilevers and spacing between the implants.

The Effect of Ferrule/Crown Ratio and Post Length on the Applied Stress and Strain Distribution to the Endodontically Treated Maxillary Central Teeth: A Finite Element Analysis.

Objectives: One of the most common methods used for the reconstruction of endodontically treated teeth is post and core and crown. Various factors such as the remaining tissue above the cutting margin (ferrule) affect the fracture resistance of teeth restored with post and core and crown. This study aimed to investigate the effect of ferrule/crown ratio (FCR) on the strength of maxillary anterior central teeth using finite element analysis. Materials and Methods: A 3D scan of a central incisor was obtained, and the data were transferred to Mimics software. Then, a 3D model of the tooth was designed. Next, 300N load was applied at a 135° angle to the tooth model. Force was applied to the model both horizontally and vertically. Ferrule height was considered to be 5%, 10%, 15%, 20%, and 25% in the palatal surface and 50% in the buccal surface. The length of post in the model was 11, 13, and 15mm. Results: By increasing the FCR, stress and strain distribution increased in the dental model and decreased in the post itself. As the horizontal angle of load application increased, the level of stress and strain created in the dental model increased as well. The closer the force application site to the incisal area, the higher the stress and strain would be. Conclusion: Maximum stress was inversely correlated with FCR and post length. In ratios of 20% and higher, insignificant changes occurred in stress and strain patterns in the dental model.

THE USE OF EXTENDED LACHMANN TEST TO MEASURE KNEE ROTATION INSTABILITY DURING PCL RECONSTRUCTION

Postoperative knee stability is critical in determining the success after reconstruction; however, only posterior and anterior stability is assessed. Therefore, this study investigates medial and lateral rotational knee laxity changes after partial and complete PCL tear and after PCL allograft reconstruction.The extending Lachman test assessed knee instability in six fresh-frozen human cadaveric knees. Tibia rotation was measured for the native knee, after partial PCLT (pPCLT), after full PCLT (fPCLT), and then after PCLR tensioned at 30° and 90°. In addition, tests were performed for the medial and lateral sides. The tibia was pulled with 130N using a digital force gauge. A compression load of 50N was applied to the joint on the universal testing machine (MTS Systems) to induce contact. Three-dimensional tibial rotation was measured using a motion capture system (Optotrak).On average, the tibia rotation increased by 33%-42% after partial PCL tear, and by 62%-75% after full PCL tear when compared to the intact case. After PCL reconstruction, the medial tibia rotation decreased by 33% and 37% compared to the fPCL tear in the case that the allograft was tensioned at 30° and 90° of flexion, respectively. Similarly, lateral tibial rotation decreased by 15% and 2% for allograft tensioned at 30° and 90° of flexion respectively, compared to the full tear. Rotational decreases were statistically significant (p&lt;0.005) at the lateral pulling after tensioning the allograft at 90°.PCLR with the graft tensioned at 30° and 90° both reduced medial knee laxity after PCLT. These results suggest that while both tensioning angles restored medial knee stability, tensioning the Achilles graft at 30° of knee flexion was more effective in restoring lateral knee stability throughout the range of motion from full extension to 90° flexion, offering a closer biomechanical resemblance to native knee function.

Study of the tribological performance of pre- and post-heat treatment of AISI D2 steel with AlCrN coating under wet conditions

ABSTRACT This study examined the impact of a combination of hardened and tempered surface change technologies and AlCrN coating on the tribological characteristics of AISID2 steel. The duplex surface change, such as the combination of a heat treatment at 600°C for 1 hr and a PVD (sputtering), archives the superior wear resistance and mechanical properties. AlCrN coating has been implemented in AISID2 steel after a hardened and tempered treatment. This process was carried out as part of an appropriate thermal treatment cycle in accordance with ASM Vol.2. Subsequently, the AlCrN coating synthesised by PVD (sputtering) improves the adhesion between the coatings and the AISID2 steel. The wear properties according to ASTMG99 have been tested with a typical load of 10N, 20N and 30N for a sliding distance of 6000 m with a constant velocity of 1.256 ms−1 in wet conditions. Tests revealed that the AlCrN coating deposited on the hardened and tempered steel was more resistant to wear than the AlCrN coating applied to the unhardened steel. Therefore, it should be possible to implement the results of this study for forming operations with low COF and a low amount of resulting wear such as drawing and rolling in dies.

BIOMECHANICAL EVALUATION OF THE EFFECT OF VARYING MEGAPROSTHESIS LENGTHS IN PROXIMAL HUMERAL REPLACEMENT DURING AXIAL LOADING USING FINITE ELEMENT ANALYSIS

To analyse bone stresses in humerus-megaprosthesis construct in response to axial loading under varying implant lengths in proximal humeral replacement following tumour excision.CT scans of 10 cadaveric humeri were processed in 3D Slicer to obtain three-dimensional (3D) models of the cortical and cancellous bone. Megaprostheses of varying body lengths (L) were modelled in FreeCAD to obtain the 3D geometry. Four FE models: group A consisting of intact bone; groups B (L=40mm), C (L=100mm) and D (L=120mm) comprising of humerus-megaprosthesis constructs were created. Isotropic linear elastic behaviour was assigned for all materials. A tensile load of 200N was applied to the elbow joint surface with the glenohumeral joint fixed with fully bonded contact interfaces. Static analysis was performed in Abaqus. The bone was divided at every 5% bone length beginning distally. Statistical analysis was performed on maximum von Mises stresses in cortical and cancellous bone across each slice using one-way ANOVA (0-45% bone length) and paired t-tests (45-70% bone length). To quantify extent of stress shielding, average percentage change in stress from intact bone was also computed.Maximum stress was seen to occur distally and anteriorly above the coronoid fossa. Results indicated statistically significant differences between intact state and shorter megaprostheses relative to longer megaprostheses and proximally between intact and implanted bones. Varying levels of stress shielding were recorded across multiple slices for all megaprosthesis lengths. The degree of stress shielding increased with implant lengthening being 2-4 times in C and D compared to B.Axial loading of the humerus can occur with direct loading on outstretched upper limbs or indirectly through the elbow. Resultant stress shielding effect predicted in longer megaprosthesis models may become clinically relevant in repetitive axial loading during activities of daily living. It is recommended to use shorter megaprosthesis to prevent failure.

COMPARISON OF MECHANICAL PROPERTIES OF THE IMPLANT MATERIALS- TITANIUM, ZIRCONIUM AND PEEK USING THREE DIMENSIONAL FINITE ELEMENT ANALYSIS

Background And Objective:Dental implants have been universally accepted as the best option for prosthetic rehabilitation of missing teeth.A material of choice for manufacturing dental implants was for long time commercially pure titanium due to its excellent bio compatibility and mechanical properties. Zirconia seems to be a suitable alternative dental implant material because of its tooth like color and biocompatibility. The most promising novel alternative to titanium is polyetheretherketone (PEEK) which is a partially crystalline poly aromatic linear thermoplastic substance. The objective of this study is to study and compare the mechanical properties of titanium, zirconium and PEEK implant materials using three dimensional finite element analysis. Methodology: A randomly chosen computerized tomography was used to obtain the digital model in the initial phase of the work. Only the part portion corresponding to tooth number 35 will be extracted from this model. Screwed cylindrical implants of length 12 mm and diameter 4mm will be modeled and simulated to be placed in the section of the bone. The different models used were model A - Titanium, model B – Zirconium, and model C - PEEK implant models. All models were identical, except for the properties of the used materials and all were exported to the Ansys Workbench V10 finite elements simulation software. Vertical and oblique (45 degree) loads in relation to the long axis of the tooth with 100 N in magnitude were applied. Stress analysis performed by comparing the Von Mises stress components. Fatigue strength and mode of failure were also assessed for the three implant materials. Results: Maximum stress in the peri-implant bone when titanium implant was placed in 35 region was 281.40 Mpa under axial load of 100N. Maximum stress when zirconia implant was placed is 277.99 MPa and when peek implant was placed which amounts for 286.78Mpa. Titanium sustains more life cycle (832840.00) compared to Zirconium (743070.00) and PEEK has much less life cycle (302460.00). Factor of safety is rated on a scale of 0 -15 and results were Titanium (12.42) and Zirconium (11.16) had almost similar values. Peek (6.15) had low safety factor compared to Titanium and Zirconia. Conclusion:Titanium was superior to other two groups in all the properties considered. These results prove why Titanium is still considered to be the gold standard material of choice for dental implant fabrication.

Durability and Stability of Coaxial Wire and 3D-Printed Lingual Bonded Retainer: A Finite Element Study

Objective: To evaluate the durability and stability of Coaxial &amp; 3D (Three-dimensional) -printed bonded lingual mandibular retainer wire (3-3) at the middle third position with the application of forces. The objective is to evaluate the displacement of teeth, stiffness, and stresses on the wire. Methods: A comparison of coaxial wire (six-stranded stainless-steel wire) with 3D-Printed retainer wire (chrome cobalt alloy) was done by conducting a FEM (Finite Element Method) study for which mesh models were prepared onto which forces were applied. A load of 10N was applied to simulate biting forces and protrusive jaw movements during mastication. Results: There was a uniform displacement of teeth in the 3D-printed retainer wire whereas, in the case of coaxial retainer wire more force was noted onto the central incisor due to its low stiffness and thus inability to transfer force to an adjacent unit. High stiffness, von mises, and shear stresses were found to be present in the case of a 3D-printed retainer for which the high modulus of elasticity is responsible. The factor of safety for both materials was high but when compared to each other it was higher in the case of the 3D-printed retainer. Conclusion: 3D-Printed retainer wire showed higher durability and stability when compared to coaxial wire retainer, but requires clinical studies for better appraisal.

Endocrown restorations in premolars: influence of remaining axial walls of tooth structure and restorative materials on fatigue resistance.

To evaluate the effect of the remaining tooth structure and different CAD/CAM materials on the fatigue performance and failure mode of endodontically treated premolars restored with endocrowns. Ninety maxillary premolars were endodontically treated and assignedinto 6 groups (n = 15) according to the number of remaining axial walls (four, three, and two) and restorative materials (ultra-translucent zirconia 5Y-PSZ [KATANA UTML] and lithium disilicate [IPS e.max-CAD]). The specimens were subjected tocyclic fatigue loading test(initial load 200 N; 20Hz). An incremental step load of 100N per 10,000 cycles was applied until failure. The fatigue failure load (FFL) and number of failure cycles (CFFs) datawere statistically analyzed with two-way ANOVA and Kaplan-Meier test (α = 0.05). Failedspecimens were examined under a stereomicroscope 25 × and failure modes were determined. FFL and CFF were significantly influenced by restorative material (p < 0.05). 5Y-PSZ endocrowns showed significantly higher FFL when compared with lithium disilicate. The number of remaining walls did not affect the fatigue behavior or failure mode of the specimens. Of the lithium disilicate restorations, 51% had repairable failures, while 95% 5Y-PSZ restorations had non-repairable failures. Zirconia endocrowns showed better FFL than lithium disilicate endocrowns, regardless of the number of remaining axis walls. Lithium disilicate and 5Y-PSZ endocrowns showed FFL higher than the normal masticatory loads. Restoring endodontically treated premolars with endocrown could be a promising treatment, regardless of the remaining axial walls. However, precaution should be taken in material selection since it affects the fatigue resistance and failure mode.

A grey-fuzzy based multi-response optimisation study on the friction and wear characteristics of titanium diboride reinforced aluminium matrix composite

Aluminium matrix composites are nowadays used globally as a substitute for other cast alloys because of their augmented properties. The present experiment deals with the fabrication and characterisation of tribological behaviour of titanium diboride reinforced aluminium matrix composite on a pin-on-disc tribotester under dry sliding condition. In this work, an attempt has been made to minimise the friction and wear characteristics of Al2024-TiB2 composite, by optimising the tribological parameters viz. applied load, sliding speed and sliding distance using grey-fuzzy approach. The tests are carried out based on Taguchi’s L25 orthogonal array. Grey-fuzzy analysis is used for converting the multi-objective optimisation problem into a single-objective optimisation. Based on the grey-fuzzy analysis, the optimal combination of tribological parameters is L1S4D2 (10N load, 2.0 m/s sliding speed and 1000 m sliding distance). The optimal combination of parameters has also been validated with a confirmatory experiment. Analysis of variance (ANOVA) for grey fuzzy grade shows that sliding distance is the most significant parameter affecting tribological performance. SEM analysis of the worn surfaces revealed that, increase in sliding distance results in wear transition from mild to severe. The proposed grey-fuzzy method is found to be successful in solving multi-response tribological problems.

Biomechanics of anterior endocrowns with different designs and depths: Study of finite elements.

To date, there is no clear consensus in the literature on which endocrown design and depth is the most effective treatment option for restoring endodontically treated maxillary central incisors. Aim: To determine the stress distribution of the anterior endocrowns by means of finite element analysis. Nine 3D finite element models (groups A - I) were made, each one representing a restoration system of endodontically treated upper central incisors. The models were endocrowns with and without ferrules at 0, 1, 3, and 5 mm depth and a post-core stump control group. A static load of 100N of force was applied to the palatal face at 45º from the long axis of the tooth. The Von Mise values and the maximum stress in the crown, dentin and resin cementum were evaluated separately. The maximum stress distribution was C < B < A < D < H < F < E < G < I and the Von Mises stresses were in the upper 1/3 of the retainer of endocrowns A, B, C and D. ; in the vestibular neck in endocrowns E and F; in the final 1/3 of the retainer in the endocrown G; in the middle 1/3 of the retainer in the H endocrown; and at the level of the vestibular neck of the crown in model I. The smallest distribution of maximum and Von Mises stresses was observed in model C. Key words:Finite element analysis, Biomechanics, upper central incisor, endodontically treated teeth, dental restoration.