Diagnosis and Management of Fractured Teeth; Review Article

Traumatic damage to the teeth and oral tissues are the most common causes of tooth fracture. Because of their location in the oral cavity, front teeth in the upper jaw are the most commonly fractured. Sports, car accidents, and physical violence are the most prevalent causes. Cracked teeth are often diagnosed by visually inspecting the tooth (preferably utilizing microscopes). The size and form of the fracture plane are not always determined by looking at the crack line. One factor that contributes to the difficulty of effectively making an endodontic diagnosis is the inability to visualize the depth of the fracture through a clinical exam alone. Transillumination, microscopes and dyes are a useful tool for finding and diagnosis of the crack, treatment of the crack depends on the type, extend of the crack as well as the condition of the patient. In this review we’ll be looking at the diagnosis, etiology and management of fractured teeth.

Crack Repairing of Aluminum Alloy 6061 by Reinforcement of Al2O3 and B4C Particles Using Friction Stir Processing

Crack repairing of aluminum alloys is done using conventional welding techniques or mechanical methods, which results in the redundancy of mechanical properties due to defects formation. Friction Stir Welding/Processing (FSW/FSP) is a solid-state joining technique which is used to join various different similar and dissimilar metals, along with the fabrication of surface composites to cater the mentioned problem. The objective of this study is to repair the crack produced in 6061 aluminum alloy by the reinforcement of ceramic particles, Al2O3 and B4C, to further increase the efficiency of the joint along the crack line. Weld parameters, equipment used and the processing conditions are emphasized. The mechanical testing and the characterization of the weld as well as base metal was done and compared using tensile testing, micro hardness test and microstructural analysis. X-Ray Diffraction (XRD) was performed for crystallinity and intermetallic study. The dispersion of the particles was investigated using Field Emission Scanning Electron Microscope (FESEM). The crack in the Al-6061 was effectively repaired using FSP. The reinforced samples showed improved mechanical properties as compared to non-reinforced ones.

Numerical Solution of Integro-Differential Equations Modelling the Dynamic Behavior of a Nano-Cracked Viscoelastic Half-Plane

The scattering of time-harmonic waves by a finite, blunt nano-crack in a graded, viscoelastic bulk material with a free surface is considered in this work. Non-classical boundary conditions and a localized constitutive equation at the interface between crack and matrix, following the Gurtin-Murdoch surface elasticity theory are introduced. An efficient numerical technique is developed using integro-differential equations along the nano-crack line that is based on an analytically derived Green‘s function for the quadratically inhomogeneous half-plane. The dependence of the diffracted and scattered waves and of the local stress concentration fields on key problem parameters such as viscosity, inhomogeneity, surface elasticity, and interaction between the nano-crack and the free surface are all examined through an extensive parametric study.

Two equal collinear cracks in magneto-electro-elastic materials: A study of electric and magnetic poling influences

In this paper, the problem of two equal collinear cracks is analytically studied for two-dimensional (2D) arbitrarily polarized magneto-electro-elastic materials. The electric and magnetic poling directions make arbitrary angles with the crack line. The Stroh's formalism and complex variable methodology is utilized to reduce the problem into non-homogeneous Riemann Hilbert problem. This numerical problem is then comprehended with the Riemann Hilbert way to obtain the intensity factors for stress, electric displacement and magnetic induction. A numerical contextual analysis is displayed for the BaTiO3 – CoFe2O4 composite. The numerical examination demonstrates that the change in electric/magnetic poling directions influences the intensity factors.

Near Crack Line Elastic-Plastic Field for Mode I Cracks under Plane Stress Condition in Rectangular Coordinates

By using the crack line analysis method, this paper carries out an elastic-plastic analysis for mode I cracks under plane stress condition in an elastic perfectly plastic solid and obtains the general form of matching equations of the elastic stress field and the plastic stress field near the crack line in rectangular coordinate form. The analysis in rectangular coordinates in this paper avoids the conversion from rectangular coordinates into polar coordinates in the existing analysis and greatly simplifies the power series forms of the elastic stress field and plastic stress field near the crack line during the solving process. Furthermore, by focusing on a new problem, i.e., the center-cracked plate with finite width under unidirectional uniform tension, this paper obtains the elastic stress field, plastic stress field, and the length of the elastic-plastic boundary near the crack line by using the general form of the solution. When the dimensions of the plate tend to be infinite, the results of this paper are consistent with those obtained for an infinite plate with a mode I crack. Furthermore, the variation curves of the length of the elastic-plastic boundary are also delineated in different sized center-cracked plates, and the results are compared with those obtained under the small-scale yielding conditions. The solving process and the results in this paper abandon the small-scale yielding conditions completely. The method used in this paper not only makes the solving process simpler during the elastic-plastic analysis near the crack line but also enriches the crack line analysis method.

Mathematical modeling of elastic state in a three-component plate containing a crack due to the action of unidirectional tension

Purpose. A two-dimensional mathematical model for the problem of elasticity theory in a three-component plate containing rectilinear crack due to the action of mechanical efforts is examined. As a consequence, the intensity of stresses in the vicinity of tops of the crack increases, which significantly affects strength of the body. This may lead to the growth of a crack and to the local destruction of a structure. Such a model represents to some extent a mechanism of destruction of the elements of engineering structures with cracks, we determined stress intensity factors (SIFs) at the tops of the crack, which are subsequently used to determine critical values of the tension. Therefore, the aim of present work is to determine the two-dimensional elastic state in plate containing an elastic two-component circular inclusion and crack under conditions of power load in the case of unidirectional tension of the plate perpendicular for the crack line. This makes it possible to determine the critical values of unidirectional tension in order to prevent crack growth, which will not allow the local destruction of the body. Methodology. The methods of studying two-dimensional elastic state body with crack as stress concentrators based on the function of complex variable method by which the problem of elasticity theory is reduced to singular integral equations (SIE) of the first and second kind, the numerical solution by the method of mechanical quadratures was obtained. Findings. In this paper two-dimensional mathematical model in the form of the system of two singular integral equations on closed contour (boundary of inclusion) and unclosed contour (crack) are obtained; numerical solutions of these integral equations were received by the method of mechanical quadratures; stress intensity factors at the tops of a crack are identify and explored to detect the effects of mechanical character. Graphical dependencies of SIFs, which characterize distribution of the intensity of stresses at the tops of a crack as function of elastic properties of inclusion and also as function of the distance between crack and inclusion are obtained. This makes it possible to analyze the intensity of stresses in the vicinity of a crack's tops depending on the geometrical and mechanical factors, as well as to determine the limit of permissible values of unidirectional tension of the plate perpendicular to the crack line at which the crack begins to grow and the body being locally destroyed. It is shown that the proper selection of elastic characteristics of the components of three-component plate can help achieve an improvement in the strength of the body in terms of the mechanics of destruction by reducing SIFs at the crack's tops. Originality. Scientific novelty lies in the fact that the solutions of the new two-dimensional problems of elasticity for a specified region (plate containing an elastic two- component circular inclusion and a rectilinear crack) under the action of unidirectional tension of the plate perpendicular to the crack line are obtained. Practical value. Practical value of the present work lies in the possibility of a more complete accounting of actual stressed-strained state in the piecewise-homogeneous elements of a structure with cracks that work under conditions of different mechanical loads. The results of specific studies that are given in the form of graphs could be used when designing rational operational modes of structural elements. In this case, the possibility for preventing the growth of a crack through the appropriate selection of composite's components with the corresponding mechanical characteristics is obtained.

Mitigación de daños ocasionados por grietas en el suelo

The design of a trench of granular material is shown. This design can be used to mitigate the damages caused by cracks that have appeared in the soil in certain zones of Mexico City. The most destructive cracks are associated with differential settlements due to the regional subsidence of Mexico City and can show escarpments of considerable height. The proposal solution consists of constructing a trench of sand on the crack line, called “Dissipative box of unit deformations”. The trench behavior is assessed by means of numerical simulations with discontinuous media approach using the discrete element method. It is drawn that the unit deformations (differential settlements/horizontal distances) on the surface decrease when the depth of trench increases. The simulations allow to obtain an optimal design of the dissipative box distributing the vertical displacements in a sufficient horizontal length so that the escarpment disappears and is replaced by a surface with moderate inclination. In this way, a road affected by a crack can continue open to traffic. Analyzes with continuous media approach are presented, their results are compared with the discrete approach ones. Some conclusions and practical recommendations for the mitigation of damage caused by cracks are given.

Bending by concentrated force of thin plate located on elastic foundation and weakened by contact crack

The paper considers the two-dimensional formulation of the problem of the contact interaction of the crack edges in a plate bent by the concentrated force on the elastic Winkler foundation. The crack closure is described using the model of contact along a line in one of the plate surfaces. Within the framework of this model, the boundary value problem is formulated for the equations of the classical theories of plate bending on the elastic foundation and a plane stress state with interrelated tension and bending conditions on the crack line. The obtained boundary value problem has been solved using singular integral equations method. Based on numerical solutions of the integral equation the dependences of forces and moments intensity factors in the vicinity of the defect tips and distribution of contact forces along the crack line on the parameters of elastic foundation stiffness and the coordinate of the application point of the load have been investigated. The effect of crack closure and influence of the elastic foundation stiffness on the limit equilibrium of the plate, depending on the coordinate of the point of application of the concentrated force, has been evaluated. The area of the correctness of the problem statement when the crack closure occurs throughout its length has been established. It was found that the crack closure leads to the appearance of nonzero forces intensity factor, reduction of the moments intensity factor and increase of the limit load. The dependences of the forces and moments intensity factors and the limit load on the dimensionless coordinate of the point of application of the concentrated force are nonmonotonic. Numerical analysis showed that increasing the elastic foundation stiffness, as well as the displacement of the point of application of the force from the center of the cut, increase the limit load and weaken the contact reaction.