Mechanical Testing Machine Research Articles

Investigation of shape stability of semi-finished samples in the form of a ring made of plastic ceramic material based on SiC, obtained by injection molding

The concept of form stability is considered. A semifinished product in the form of a ring from a thermoplastic mass based on SiC powder has been made on the installation for injection molding developed at the Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine in accordance with the established technological parameters optimized by the results of computer modeling. Schemes of loading and dividing the ring into samples in the form of prismatic segments are presented. A technique for the preparation of experimental samples is proposed. The study of the compressive strength of the samples from the injected semi-finished product has been carried out on the FP-5 mechanical test machine and a corresponding здще of its change has been constructed. The formation of a barrel shape during compression tests of samples, both along the radial and tangential directions, has been established. The values of the minimum and maximum loads at which the samples are destroyed have been determined. An increase in the compaction of the thermoplastic mass around the injection point has been experimentally proved. The scheme and the actual image of crack distribution as a result of destruction of samples have been presented. It is shown that the failure occurs in the area of the presence of the calculated parting lines, which have become stress concentrators.

Comparison Method of Biomechanical Analysis of Trans-Tibial Amputee Gait with a Mechanical Test Machine Simulation

Energy-storing-and-returning prosthetic feet are frequently recommended for lower limb amputees. Functional performance and stiffness characteristics are evaluated by state-of-the-art biomechanical testing, while it is common practice for design engineers and researchers to use test machines to measure stiffness. The correlation between user-specific biomechanical measures and machine evaluation has not been thoroughly investigated, and mechanical testing for ramps is limited. In this paper, we propose a novel test method to assess prosthetic foot stiffness properties in the sagittal plane. First, biomechanical data were collected on five trans-tibial users using a variable stiffness prosthetic foot on a split-belt treadmill. Gait trials were performed on level ground and on an incline and a decline of 7.5°. The same prosthetic foot was tested on a roll-over test machine for the three terrains. The sagittal ankle moment and angle were compared for the two test methods. The dorsiflexion moment and angle were similar, while more variability was observed in the plantarflexion results. A good correlation was found for level-ground walking, while decline walking showed the largest differences in the results of the maximum angles. The roll-over test machine is a useful tool to speed up design iterations with a set design goal prior to user testing.

Biomechanical study on different high-strength sutures and suture site for repairing posterior root tear of the medial meniscus

To compare biomechanical characteristic of different high-strength sutures and suture sites for repairing posterior root tear of the medial meniscus with modified Mason-Allen technique. Forty-eight specimen of medial meniscus of knee joint from fresh porcine (female, aged from 5 to 9 months with an average of 7 months) were chosen and established experimental model. The samples were divided into red zone fixation group and red-white zone fixation group according to suture sites, 24 in each group; and then were randomly divided into 3 subgroups which 8 in each group, and fixed with Ethibond suture, Ultrabraid suture and FiberWire suture, respectively. Biomechanical tests were performedon universal electromagnetic and mechanical testing machine. Each specimen was underwent 1 000 cyclic tests on the first time, then pull out test until failure. The maximum failure load, yield load, stiffness and displacement were analyzed. All specimen were successfully completed biomechanical tests. The failure mode of Ethibond group was caused by suture fracture; 6 cases of Ultrabraid suture group was caused by suture fracture which belong to red zone fixation group, 10 cases were caused by suture pull out, which 2 cases belong to red zone fixation group, 8 cases belong to red-white zone fixation group;8 cases of FiberWire group was caused by suture pull-out. Biomechanical test showed that:(1)In terms of suture strength, comparison of the maximum failure load, yield load and stiffness showed that Ethibond suture group <Ultrabraid suture group <FiberWire suture group, and had statistical differences among groups (P<0.05);comparison of cyclic displacement at 100, 500 and 1 000 cycles showed that Ethibond suturegroup>Ultrabraid suture group >FiberWire suture group, and had statistical differences among groups (P<0.05);the results showed the suture strength in Ethibond was the best, Ultrabraid suture took the second place, and FiberWire suture was the worst. (2)As for different suture sites, comparison of the maximum failure load, yield load and stiffness showed that red zone fixation group >red-white region fixation group, and had statistical difference between two groups(P< 0.05);comparison of cyclic displacement at 100, 500 and 1 000 cycles showed that red zone fixation group <red-white zone fixation group, and had statistical difference between two groups (P<0.05);the results showed that suture strength in red zone fixation group was better than that of red white zone fixation group. Mason-Allen suture could effectively fix posterior root tear of the medial meniscus and meet needs of early partial weight bearing after surgery. Suturing with Fiberwire in red zone is stronger and better for the meniscus healing and rehabilitation.

Compressive Fatigue Behavior of Gum and Filled SBR Vulcanizates.

The influence of carbon black on physical mechanical properties, compressive fatigue life, and the temperature changes during compression fatigue process of styrene-butadiene rubber (SBR) vulcanizates were explored. A series of unfilled and filled SBR compounds were prepared, and the compressive fatigue behaviors of the vulcanizates were performed on a mechanical testing and simulation (MTS) machine. The top surfaces of the filled SBR were imaged using scanning electron microscopy (SEM) after 105 cycles of compressive fatigue. The filled SBR shows greater compressive fatigue resistance than the unfilled SBR. The incorporation of carbon black into SBR improves the creep resistance. The best compressive fatigue resistance for the filled SBR was achieved by the addition of 30 phr carbon black. With the increase of carbon black content, the energy dissipation and the heat build-up increase simultaneously. Furthermore, SEM images of the vulcanizates suggest that the crack propagation mechanism of the unfilled and the filled SBR was different. For the unfilled SBR, due to periodical compressive stress, the polymer chains can be destroyed, and the cracks can be easily initiated and propagated, showing serious damage on the top surfaces of the specimen. However, for the filled SBR, the carbon black agglomeration around the cracks can greatly delay the generation of the cracks, decrease the fatigue damage, and ultimately improve the fatigue resistance.

Osteoarthritis-Related Degeneration Alters the Biomechanical Properties of Human Menisci Before the Articular Cartilage.

An exact understanding of the interplay between the articulating tissues of the knee joint in relation to the osteoarthritis (OA)-related degeneration process is of considerable interest. Therefore, the aim of the present study was to characterize the biomechanical properties of mildly and severely degenerated human knee joints, including their menisci and tibial and femoral articular cartilage (AC) surfaces. A spatial biomechanical mapping of the articulating knee joint surfaces of 12 mildly and 12 severely degenerated human cadaveric knee joints was assessed using a multiaxial mechanical testing machine. To do so, indentation stress relaxation tests were combined with thickness and water content measurements at the lateral and medial menisci and the AC of the tibial plateau and femoral condyles to calculate the instantaneous modulus (IM), relaxation modulus, relaxation percentage, maximum applied force during the indentation, and the water content. With progressing joint degeneration, we found an increase in the lateral and the medial meniscal instantaneous moduli (p < 0.02), relaxation moduli (p < 0.01), and maximum applied forces (p < 0.01), while for the underlying tibial AC, the IM (p = 0.01) and maximum applied force (p < 0.01) decreased only at the medial compartment. Degeneration had no influence on the relaxation percentage of the soft tissues. While the water content of the menisci did not change with progressing degeneration, the severely degenerated tibial AC contained more water (p < 0.04) compared to the mildly degenerated tibial cartilage. The results of this study indicate that degeneration-related (bio-)mechanical changes seem likely to be first detectable in the menisci before the articular knee joint cartilage is affected. Should these findings be further reinforced by structural and imaging analyses, the treatment and diagnostic paradigms of OA might be modified, focusing on the early detection of meniscal degeneration and its respective treatment, with the final aim to delay osteoarthritis onset.

Influence of heat treatment on the tensile properties and fatigue properties of Mg-8.8Gd-3.5Y-1.5Zn-0.5Zr alloy

The microstructure, tensile properties and fatigue properties of Mg- 8.8Gd- 3.5Y- 1.5Zn- 0.5Zr alloy under T4 and T6 heat treatment have been studied. The as-cast alloy was homogenized to eliminate the inhomogeneous structure and the strength of the alloy was increased by aging treatment. The microstructure evolution and mechanical properties of the alloy were investigated by optical microscope, scanning electron microscope, energy dispersive spectrometer and universal mechanical testing machine. The as-cast alloy is composed of dendritic α-Mg matrix, metastable lamellar stacking fault, eutectic Mg24(Gd, Y, Zn)5, massive long-period stacking ordered (LPSO) phase Mg12(Gd, Y)Zn and a few rare earth rich phases. In the process of homogenization, the lamellar phase and Mg24(Gd, Y, Zn)5 eutectic phase dissolved in the α-Mg matrix gradually, and the massive LPSO phase disappeared gradually, while the lamellar LPSO phase steadily grew into grains and formed some precipitate particles near the grain boundary. As the tensile temperature increases, the ductility of solid solution alloy increases, but decreases at 250 °C, which is related to the melting reaction of γ phase at high temperature and the cracking caused by grain boundary sliding. Intergranular fracture occurs at 250 °C. When the tensile temperature rises to 150 °C, the ultimate tensile strength of the alloy increases first before 150 °C and decreases after 150 °C, which is related to two strengthening mechanisms, namely, dissolution of Gd and Y elements into α-Mg matrix results in solid solution strengthening and the co-lattice strengthening between petal β′ and α-Mg matrix. Compared with the fatigue properties of the alloy after solution treatment and aging treatment, the fatigue life of the alloy after aging treatment is longer.

The study and comparison of elastic modulus of pineapple fruit in macroscopic and microscopic modes.

According to bibliography, elastic modulus studies of agricultural produce at the macro-scale using a resistance measuring (as Magness-Taylor penetration test or compression test) by an Instron Universal Mechanical Testing Machine is often used to express this characteristic. However, the determination of the elastic properties of agricultural produce at the macro-scale result widely varying values for a particular agricultural produce. So in this study, to decrease the variability which now exists in the elastic modulus results of agricultural produce measured at the macro-scale, measuring and comparison of the elastic modulus of agricultural produce, pineapple fruit as case study, in macroscopic (by Hook's theory on the cylindrical specimen and Hertz theory in the mode of spherical indenter contact on the whole specimen) and microscopic (by atomic force microscopy) modes was investigate. There is concluded that with changing the type of theory, the behavior of the elastic modulus changes significantly at a 1% level. In microscopic mode studies, the lowest elastic modulus (0.135 MPa) was obtained by using Hertz theory in the mode of spherical indenter contact on the whole specimen while the highest elastic modulus value (0.779 MPa) was seen by using Hook's theory on the cylindrical specimen. In microscopic mode studies, the Sneddon model had the lowest elastic modulus while Hertzian model showed the highest elastic modulus value. Consequently, due to some reasons such as complex shape of most agricultural produce, assumptions required for three elastic theories of contacting bodies in macroscopic mode, complex structure and viscoelastic behavior of agricultural produce, it is found that the variability of the information can be reduced at micro-scale, or, to a lesser extent.

Evaluation of effect of calcium hydroxide as a root canal dressing material on dentin micro tensile fracture strength in primary teeth: An in-vitro study

Background: Root canal treatment in primary teeth is indicated when the radicular pulp exhibits clinical signs of irreversible pulpitis or pulp necrosis while the roots show minimal or no resorption. The present study was conducted to evaluate the effect of calcium hydroxide as a root canal dressing material on dentin microtensile fracture strength in primary teeth. Materials and methods: 60 human maxillary primary incisor were divided into two experimental groups. The teeth were immersed in saline at room temperature for 7 (group I), 30 (group II) and 90 days (group III). The saline was changed with a fresh sterile solution once a week. In group IV, 15 teeth with root canals filled with sterile saline and the orifices sealed with IRM. Microtensile fracture strength was measured in Mechanical tester Lloyd testing machine. Results: The mean microtensile fracture strength in group I was 30.5 MPa, in group II was 25.7 MPA, in group III was 92 MPA and in group IV was 34.9 MPa. The difference was significant (P< 0.05). Conclusion: Calcium hydroxide placed in root canals for an extended time had a significantly negative effect on root strength.

Effect of Annealing Temperature on the Microstructure of 2195 Al-Li Alloy Sheet

The annealing temperature is a key parameter for the mechanical properties and microstructure control of the 2195 Al-Li alloy sheet in the annealing process. In the present study, the effect of annealing temperature on the microstructure of 2195 Al-Li alloy sheet was investigated using a general mechanical testing machine, scanning electron microscope (SEM), transmission electron microscope (TEM), and backscattered electron microscope (EBSD). It was found that the optimized annealing temperature for 2195Al-Li alloy sheet of H112 state is 400°C, the alloy sheet shows the satisfactory mechanical properties. In addition, with the increase of annealing temperature, the δ' phase, the θ' phase and the T1 phase are formed in the alloy sheet, which leads to the strength of the alloy increase. Furthermore, the annealing temperature obviously affect the texture component and intensity during annealing treatment process.

Annular Defects Impair the Mechanical Stability of the Intervertebral Disc.

A biomechanical study. The purpose of this study was to investigate the effects of cruciform and square incisions of annulus fibrosus (AF) on the mechanical stability of bovine intervertebral disc (IVD) in multiple degrees of freedom. Eight bovine caudal IVD motion segments (bone-disc-bone) were obtained from the local abattoir. Cruciform and square incisions were made at the right side of the specimen's annulus using a surgical scalpel. Biomechanical testing of three-dimensional 6 degrees of freedom was then performed on the bovine caudal motion segments using the mechanical testing and simulation (MTS) machine. Force, displacement, torque and angle were recorded synchronously by the MTS system. P value <.05 was considered statistically significant. Cruciform and square incisions of the AF reduced both axial compressive and torsional stiffness of the IVD and were significantly lower than those of the intact specimens (P < .01). Left-side axial torsional stiffness of the cruciform incision was significantly higher than a square incision (P < .01). Neither incision methods impacted flexional-extensional stiffness or lateral-bending stiffness. The cruciform and square incisions of the AF obviously reduced axial compression and axial rotation, but they did not change the flexion-extension and lateral-bending stiffness of the bovine caudal IVD. This mechanical study will be meaningful for the development of new approaches to AF repair and the rehabilitation of the patients after receiving discectomy.

Determination of texture properties of banana fruit cells with an atomic force microscope: A case study on elastic modulus and stiffness

Characterization of biological materials with their elasto-mechanical properties is considered essential for understanding their nature. In addition, elasto-mechanical studies at the macroscale are frequently used to determine these characteristics by a resistance measurement such as the Magness-Taylor penetration test or compression test using an Instron Universal Mechanical Testing Machine. In this regard, the atomic force microscopy (AFM) was presented as a new method for identifying the alterations of elasto-mechanical properties at a nanoscale. Therefore, the present study estimated the elastic modulus and stiffness of the cell walls which were isolated from the banana mesocarp with AFM-based nanoindentation. Then, the elastic modulus of a cell and stiffness were determined by analyzing the force-separation curves using the theory of Hertz and the mechanics of Sneddon. Using two tips of the distinct radius of the curvature (10 and 10,000 nm), it was revealed that the tip geometry significantly affected the measured elasto-mechanical properties. Further, the elastic modulus was around 95 ± 45 and 18.5 ± 12.5 kPa for the sharper tip (R = 10 nm) and a bead (R = 10,000 nm) tips, respectively. Furthermore, a large variability was considered regarding the elasto-mechanical property (>100%) among the cells which were sampled from the same region in the fruit. Therefore, the AFM can be highly suitable for evaluating the structure-related properties of biological materials at the cellular and subcellular scales by combining nano elasto-mechanical properties with topography imaging.

The Influences of Third Alloying Element on the Internal Friction Behavior and the Mechanical Properties in the Water Quenched Ti-12Mo Alloys

The influences of third alloying element on the internal friction behavior and the mechanical properties in the water quenched Ti-12Mo alloys were investigated using multifunctional internal friction apparatus and mechanical testing machine, respectively. The two relaxational internal friction peaks that are named as P1 and P2 peaks were found in the water quenched Ti-12Mo alloys. Third alloying element has influences on the P1 and P2 peaks. In addition, the young modulus and yield strength are also influenced by the addition of Third alloying element.

Effect of Stringer Design on the Stability of Stiffened Composite Panel Under In-plane Shear: An Experimental Study

The safe exploitation of the buckling and post-bulking region of stiffened composite panels is of prime interest in aerospace engineering. Experiments were carried out to investigate the effects of stringer design on the buckling and post-buckling behavior of stiffened composite panels subjected to in-plane shear loading in this study. Three configurations of I-shape stringers were designed with the same skin in the stiffened composite panels. The shear loading was applied through a customized picture-frame rig which is loaded by a mechanical test machine. Ten specimens in total were manufactured and tested to obtain the buckling loads and the final failure loads, respectively. The experimental results show that the stringer design has much more influence on the buckling load than the final failure load of the stiffened composite panel.

Nonwoven Scaffolds Under Tension: In Situ High‐Resolution Ultrasound Observation of Microstructure Evolution in the Volume

Fibrous scaffolds represent the basic material for tissue engineering, where creation of matrices with predictable properties is an important issue. Typically, the assessment of scaffold characteristics, including the mechanical behavior, is conducted in the air environment that is far from the natural physiological conditions in a living organism, despite possible differences in the properties obtained in dry and water‐filled specimens. The studies of the mechanical behavior of scaffolds in the wet environment are limited by the properties of visualization methods. The optimal method for studying fibrous objects in the wet environment is ultrasonic techniques, for which water immersion is a prerequisite for the experiment. Herein, a high‐frequency (200 MHz) acoustic microscopy is combined with a horizontal mechanical testing machine for in situ visualization of microstructural transformation in the volume of elastic and rigid electrospun scaffolds under tension. For the first time, the results show that in situ ultrasound monitoring provides high‐resolution imaging of the internal microstructure in water‐filled specimens. This work provides the foundation for future experimental setups for characterization of tissue‐engineered constructs in the conditions close to those in a living organism.

Ladybug Inspired Double‐Layered Adhesive with Enhanced Robustness of Surface Roughness

AbstractSurface flexibility and structure stability are two design considerations and opposing sides for biologically‐inspired dry adhesives in real world. Here a ladybug inspired adhesive with double‐layered structure is presented to solve this problem. The bottom layer is made of magnetorheological elastomers (MREs) and the top layer is made of polydimethylsiloxane (PDMS) with controllable Young's modulus and thickness. To investigate the adaptability of the double‐layered adhesives to surface roughness, silicon wafers are polished to achieve various surface roughness. The adhesion performance of composite structure is characterized by using a mechanical testing machine with the target Si surfaces. The experiment results indicate double‐layered adhesive shows good surface adaptation and robustness to different surface roughness with approximately 3 N/cm2 adhesion stress. This work shows the adhesion performance of double‐layered dry adhesive considering the real world surface and illustrates that the mechanical properties of the biomimetic adhesives have a significant impact on their adhesion performance.

Biomechanical Evaluation of Opponensplasty for Low Median Palsy: A Cadaver Study

PurposeImpaired thumb opposition associated with advanced carpal tunnel syndrome may be treated by opponensplasty at the time of open carpal tunnel release. However, it is unclear which opponensplasty technique achieves the greatest functional improvement. This study aimed to compare the biomechanics of thumb opposition after Camitz, modified Camitz, and Burkhalter opponensplasties.MethodsWe used 6 fresh-frozen cadaveric arms. Each procedure was reproduced on each arm: Camitz opponensplasty, modified Camitz opponensplasty involving palmaris longus transfer routed around the flexor carpi ulnaris pulley, and Burkhalter opponensplasty. Arms were fixed with the wrist in 0° flexion and the forearm in neutral pronosupination, and sensors were placed on the thumbnail, radial styloid, and dorsal aspect of the second metacarpal head. The donor tendon was pulled using a mechanical testing machine with a maximum force of 25 N, and the locations of the sensors in thumb opposition were recorded. The first web space and thumb pronation angles were measured for each procedure and compared.ResultsThe mean first web space and pronation angles produced using 25 N were 55° and 20°, 57° and 26°, and 53° and 29° for the Camitz, modified Camitz, and Burkhalter opponensplasties, respectively. The first web space angle was significantly larger after modified Camitz opponensplasty compared with Burkhalter opponensplasty with 25 N loading. Camitz opponensplasty resulted in a significantly smaller pronation angle compared with modified Camitz and Burkhalter opponensplasties with 25 N loading.ConclusionsThe modified Camitz opponensplasty produces a relatively balanced biomechanical outcome in terms of the first web space and pronation angles. Conversely, Burkhalter opponensplasty has been shown to be a favorable technique for improving pronation.Clinical relevanceModified Camitz opponensplasty with a pulley offers effective restoration of thumb opposition, including pronation. On the other hand, Burkhalter opponensplasty represents a suitable option not only for patients with high median palsy and injury to the palmar aponeurosis but also for those who require improved pronation.

Fracture Resistance of Teeth with Truss Endodontic Access: An In Vitro Study and Literature Review

Abstract Objective This article evaluates the fracture resistance of teeth with different endodontic access cavities and conducts literature review on the effects of truss endodontic cavity. Material and Methods Eighty human mandibular first molars were assigned randomly to four groups (n = 20); group 1: truss access cavity (TrussAC); group 2: conservative access cavity (ConsAC); group 3: traditional access cavity (TradAC); and group 4: served as control (no access). Accesses were prepared in groups 1 to 3, respectively. Endodontic treatment was performed on all accessed teeth and composite restoration placed. Teeth in all groups were loaded until fracture using a mechanical testing machine. The maximum load at fracture and patterns of fracture were recorded. Additionally, a literature search was performed on studies related to TrussAC and its importance. Statistical Analysis Fracture strengths were compared using one-way analysis of variance complemented by Bonferroni test. Fracture patterns were analyzed using chi-square test. Results TradAC showed significantly lower mean load at fracture than TrussAC, ConsAC, and intact teeth. Fracture resistance of teeth with TrussAC and ConsAC was not significantly different. All three test groups showed significantly more frequent unrestorable fractures. The literature review revealed that TrussAC did not improve the fracture strength significantly; however, pulp chamber debridement was significantly impaired. Conclusion TrussAC improved the fracture strength of endodontically treated teeth, but not significantly as compared to ConsAC. Restorable fractures were more in intact teeth compared with all prepared ones.

Biomechanical Comparison of Krackow and Uchiyama Suture Techniques for Acute Tendon Repair in an Ex Vivo Porcine Model

This study compared the maximum load to failure of Krackow and Uchiyama suture techniques in an acute tendon repair in an ex vivo porcine model. Achilles tendon rupture is a common injury in athletes and active individuals. In 2007, Uchiyama et al. published a case series of a modified operation for Achilles tendon ruptures. This technique is reported to allow strong and stable repair with subsequent early weight bearing and range of motion exercises. However, no biomechanical studies have been performed to compare this novel suturing technique to a standard like Krackow. Twenty freshly harvested porcine digital flexor tendons were transected transversely at the mid-substance. Ten were repaired with double-strand Krackow suture technique using non-absorbable polyester braided suture Ethibond®2. The other 10 tendons were further divided into bundles approximately 5 mm wide—2 proximal and 2 distal. The Uchiyama repair was completed by gathering each bundle by Bunell-like sutures using Ethibond®2-0. Biomechanical testing was conducted on the samples using a mechanical universal testing machine (Shimadzu® AGS-X Series). Longitudinal traction at an advancement rate of 0.85 mm/second was performed and maximum load to failure and mode of failure were statistically compared. The average maximum load to failure was not significantly different between the Krackow repair (119.18 N ± 37.4) and Uchiyama (112.98 ± 32.06) ( p = 0.34). All modes of failure were due to suture breakage. There is no significant difference between the maximum load to failure of Uchiyama and Krackow suture technique. Uchiyama suture technique may be an alternative to open repair of acute tendon of Achilles rupture. This warrants further studies to investigate other properties like failure to cyclic loading, tendon gapping, etc. In vivo studies may be geared toward effect of greater surface contact and smaller caliber sutures in tendon healing. Gonzales MRC, Italia KR, Canlas JRC, et al. Biomechanical Comparison of Krackow and Uchiyama Suture Techniques for Acute Tendon Repair in an Ex Vivo Porcine Model. J Foot Ankle Surg (Asia Pacific) 2021;8(1):8–11.

Study on Performance of Flame Retardant and Smokeless Reed/Magnesite Cement Inorganic Particleboard

Abstract Flame-retardant reed inorganic particleboard was prepared by hot-pressing with reed particles as a reinforcing material and using magnesite cement as an inorganic adhesive. The effects of inorganic sizing amount, density, and hot-pressing temperature and time on the properties of reed inorganic particleboard were investigated by orthogonal testing. Particleboard properties were tested and characterized by means of a universal mechanical testing machine, scanning electronic microscopy (SEM), X-ray diffraction (XRD), and cone calorimetry. The results showed that the mechanical properties of particleboard prepared under conditions of 60 percent sizing capacity, 100°C hot-pressing temperature, 15 minutes hot-pressing time, and 1.2 g/cm3 density were the best, reaching the national standard for cement particleboard. At 60 percent sizing, the characteristic peak value of inorganic adhesive hydrate crystal phase was the largest, the crystallization area dense and orderly, and the coating effect on shavings good; these attributes confirmed the trend of mechanical properties of reed shavings board increasing with sizing amount. Thus, the sizing amount had a significant influence on flame retardancy and smoke suppression performance of this particleboard. With an increased application amount, the heat release and total heat release rates of the particleboard and total smoke generation rate showed decreasing trends. Additionally, when the ignition time was delayed, the flame retardancy and smoke suppression performance of the particleboard was enhanced.

Comparative Analysis of Fracture Strength of Remaining Tooth Structure after Endodontic Treatment with Various Access Cavity Preparation Techniques

Background:A perfect balance needs to be maintained between various types of endodontic access cavity preparation designs like - Traditional and conservative designed preparation to have access to the root canal system for proper cleaning and shaping of root canals without compromising the fracture resistance of the tooth structure.Aims and Objectives:We aimed to assess as well as draw comparisons of resistance against fracture of remaining tooth structure post the endodontic treatment after preparing access cavity through a variety of techniques so that we can estimate which type of cavity design technique will help endodontically treated teeth to withstand excessive load without fracture.Methods:Forty-two intact teeth (mandibular molars) were randomly selected and then were assigned to 07 different groups, inclusive of control and test groups. Various designs of access cavity preparation were done on sample teeth. The groups were divided based on different access cavity preparation designs as well as residual walls. The samples were then mounted on a composite cylinder, which was loaded under a mechanical testing machine at 0.5mm/min speed till the tooth structure fractured. This measurement of force was denoted in newton. The later analysis was carried out with the help of two-way Analysis of Variance (ANOVA) as well as Tukey’s post-hoc statistical tests.Results:There was negligible statistically relevant variance in strength towards fracture between traditional and conservative designs in teeth having three remaining walls. However, teeth with only two remaining walls fractured easily.Conclusion:Fracture resistance of teeth with remaining 03 residual walls did not show any significant difference among Traditional (TEC) and Conservative Cavity (CEC) design groups, but increased fracture strength was reported in CEC with 02 residual walls.