Understanding Mechanical Properties of Dental Materials
Dental material selection and usage require a thorough understanding of mechanical properties. Stress, types of stress (tensile, compressive, shear, and flexural), and their respective behaviors are crucial for predicting material performance. Knowledge of these properties aids in optimizing design and techniques for maximum efficacy and longevity in dental applications.
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Dental material Lecture 4 MSc Sadiq Almayali
Mechanical properties of dental material Introduction To select and use a dental material one must understand its properties. Knowledge of the properties of the material predicts its behavior, functioning in the mouth and longevity. Accordingly, one can optimize design and techniques in order to get the best out of a particular material. A mechanical property is the behavior of the material when it s linked to the application of force. The mechanical properties of a material describe how it will react to physical forces.
Stress When an external force tends to cause a body to deform, the body develops a resistance to that external force which is equal in intensity and opposite in direction. It is defined as the force per unit area induced in a body in response to some externally applied force.
Stress Force Unit area Stress ( ) = Stress: measured in pascals (Pa) Force: measured in Newton (N) Unit area: measured in square meter (m2) (1 Pa = 1 N/m2 = 1 MN/mm2)
Types of stress Tensile stress: results from two forces directed away from each other in the same line or when one end is constrained and the other end is subjected to a force directed away from the constraint, it is accompanied by tensile strain.
Types of stress Compressive stress:results from two forces directed toward each other in the same line or when one surface is constrained and the other is subjected to a force directed toward the constraint. It is accompanied by compressive strain.
Types of stress Shear stress: is the result of two forces directed parallel to each other, one force is applied to one part of the body while the other force is applied on the opposite direction which results in sliding molecules over each other. It is accompanied by shear strain. Shear force is the force which causes tearing a paper or a card.
Types of stress Flexural stress (bending stress):it is the force per unit area of a material that is subjected to flexural stress. It results from an applied bending moment. usually, three types of stresses occur at the same time. If a piece of metal is being bended it will exhibit tensile stress on the outer surface, compressive stress on the inner surface and shear stress in the middle.
Types of stress Torsion stress: Force per unit area of a material subjected to twisting of a body.
Strain Strain is the change in length per unit length caused by external force. Strain is denoted as . It has no measurement unit.
Strain Strain under tensile stress is an elongation in the direction of loading. Strain under compression is shortening in the direction of loading. a, elongation. b, shortening
Strain Elongation: deformation results from application of tensile stress. Ex.An alloy with high percent of elongation can be adjusted without danger of fracture.
Strain Types of the strain 1. Temporary or elastic or recoverable strain: the material is returned to its original length after removal of force. 2. Permanent or plastic or unrecoverable strain: the material is not returned to its original length after removal of force. The material may remain deformed.
