Mechanical Properties of Bones

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Questions and Answers

What is the primary function of bone in the body?

To provide energy to muscles

To produce blood cells only

To serve as a fat storage area

To act as a system of rigid levers (correct)

According to Wolff’s law, how do mechanical stresses affect bones?

They only affect the internal structure of bones

They do not affect bone density or shape

They shape the density and dimensions of bones (correct)

They influence only the shape of bones, not density

What does the shear modulus represent in material science?

The ratio of shear stress to shear strain (correct)

The ratio of compressive stress to volume strain

The maximum stress a material can withstand before rupture

The ability to undergo plastic deformation under compression

What differentiates bone modeling from remodeling?

Modeling occurs without resorption, while remodeling involves it Signup and view all the answers

Which mechanical property describes a material's ability to deform under tension without fracture?

Ductility Signup and view all the answers

What are the consequences of dynamic mechanical loading on bones?

It results in bone deformation proportional to the load magnitude Signup and view all the answers

What does the bulk modulus measure?

The ratio of compressive stress to volume strain Signup and view all the answers

What defines the ultimate strength of a material?

The maximum stress a material can withstand before rupture Signup and view all the answers

What is the role of calcium hydroxyapatite in bone?

It impacts the mineral composition of the bone Signup and view all the answers

In which mode does remodeling occur without a change in bone mass?

Conservation mode Signup and view all the answers

How is toughness measured in materials?

By the amount of energy per unit volume required to fracture Signup and view all the answers

What defines a fracture in the context of bones?

A disruption in the continuity of a bone Signup and view all the answers

What does creep refer to in materials science?

The time-dependent plastic straining of a material Signup and view all the answers

What is a characteristic feature of mandibular and maxillary bone relevant to dental implants?

Their mechanical properties are vital for implant success Signup and view all the answers

Which property refers to a material's ability to be shaped into thin sheets without fracture?

Malleability Signup and view all the answers

What does the term fatigue mean in relation to materials?

Deformation resulting from cyclic stress Signup and view all the answers

What property describes the ability of a tissue to absorb energy and resist fracture?

Toughness Signup and view all the answers

Which of the following mechanical properties is characterized by a tissue's resistance to deformation?

Stiffness Signup and view all the answers

What describes the property of tissues that allows them to recover their original shape after deformation?

Resilience Signup and view all the answers

Which of the following tissues demonstrates viscoelastic behavior?

Muscles Signup and view all the answers

Which of these is a component of mammalian connective tissue that contributes to elasticity?

Elastic fibers Signup and view all the answers

Which property combines both viscosity and elasticity?

Viscoelasticity Signup and view all the answers

Which of the following tissues is NOT considered a hard tissue?

Pulp Signup and view all the answers

What best describes the elasticity of tissues?

Capacity to stretch and recoil Signup and view all the answers

What type of fracture is classified as simple?

When bone ends remain within surrounding soft tissues Signup and view all the answers

Which property defines elastic materials?

They return to original shape after stress removal Signup and view all the answers

What is the unit of stress in materials?

N/m2 Signup and view all the answers

What kind of stress is applied when a long bar is subjected to a tension force along its axis?

Tensile stress Signup and view all the answers

What is the definition of shearing stress?

Tangential force per unit surface area Signup and view all the answers

What does the elastic modulus measure?

The ratio of stress to strain in a material Signup and view all the answers

What is Young's modulus used to calculate?

The ratio of longitudinal stress to longitudinal strain Signup and view all the answers

What happens during torsion of a structure?

It twists about its longitudinal axis Signup and view all the answers

Study Notes

Mechanical Properties of Materials

The lecture is about mechanical properties of materials, specifically focusing on bone.
The lecture outline includes bone modeling and remodeling, mechanical stresses, elastic moduli, general stress-strain curves, and definitions of mechanical features of materials.
The learning objectives (ILOs) include understanding the difference between bone modeling and remodeling, analyzing different types of mechanical stresses, understanding elastic moduli, analyzing general stress-strain curves, understanding mechanical properties of materials, and applying these properties to dental materials, tissues, and oral tissues.

Bones

Bone is a vital, dynamic tissue supporting and protecting other body tissues.
Bone strength and fracture resistance depend on its material composition and structure.
Mandibular and maxillary bones are important for dental implants.
Bone is a specialized connective tissue with an organic matrix containing poorly crystallized calcium hydroxyapatite.
Bone has a higher organic content compared to other dental hard tissues.

Bone Structure

The diagram shows a long bone with labeled sections: epiphysis, diaphysis, articular cartilage, trabecular bone, cortical bone, medullary cavity, yellow marrow, red marrow, and periosteum.

Bone Modeling and Remodeling

According to Wolff's law, bone density and shape depend on the magnitude and direction of mechanical stresses.
Dynamic loading causes bone deformation (strain).
Remodeling is a process where fatigue-damaged older bone is resorbed and replaced with new bone.
Remodeling can occur in conservation or disuse modes. With conservation mode, there is no change in bone mass. But with disuse mode, there is a net loss of bone mass characterized by an enlarged marrow cavity and thinned cortex.
Bone modeling creates new bone without prior resorption. It's involved in the growth of immature bones.

Fractures

A fracture involves disruption in the continuity of a bone.
Fracture nature depends on the direction, magnitude, rate, and duration of the sustained mechanical load.
Fractures are classified as simple (bone ends within soft tissues) or compound (one or both ends protruding from skin).

Mechanical Stresses

Compressive, tensile, and shear stresses concern the direction of the squeezing force.
Tensile stress occurs when a force is applied along a bar perpendicular to its cross-section, equal to the perpendicular force per unit cross-sectional area.
Compression stress occurs when a force is applied along a bar perpendicular to its cross-section, equal to the perpendicular force per unit cross-sectional area.
Shear stress occurs when a tangential force applies on a material's surface, equal to the tangential force per unit surface area.

Elastic Moduli

Elastic moduli quantify the relationship between stress and strain.
Young's modulus(Y) quantifies the ratio between longitudinal stress and strain.
Shear modulus(G) quantifies the ratio of shear stress to shear strain.
Bulk modulus(B) quantifies the ratio between compressive stress and volume strain.

General Stress-Strain Curve

The stress-strain curve shows the relationship between stress and strain during material deformation.
Elastic region, proportional limit, elastic limit, and yield point are key properties.
Ultimate tensile stress(UTS) marks the highest stress before rupture.
Fracture point marks the stress level before the material fracture.

Material Properties

Ductility: The ability of a material to undergo plastic deformation under tension.
Malleability: The ability of a material to undergo plastic deformation under compression.
Resilience: Energy absorbed per unit volume before reaching elastic limit.
Toughness: Energy absorbed per unit volume up to fracture point.
Fatigue: Deformation due to cyclic stress. Important for dental restorations that experience alternating forces.
Hardness: Resistance to penetration by a point under a specific load.

Mechanical Properties of Human Tissues

Biological tissues are specialized cells working together in organisms.
Tissues' mechanical properties describe their physical characteristics and behaviors.
These properties include elasticity, stiffness, strength, toughness, viscoelasticity, and resilience.
These properties illustrate how tissue respond to stress, strain, compression, tension, and deformation

Mechanical properties of human Tissues (continued)

The lack of knowledge on human tissues limits applications in surgical planning, ballistic testing, implantable medical devices, and the assessment of traumatic injuries.
Elasticity describes how tissue deforms and recovers its shape.
Examples of elastic tissues include elastic fibers (important for cardiovascular, pulmonary, and intestinal function in mammals)
Stiffness is a tissue's resistance to deformation; stiffer tissues require more force to deform the same amount.

Types of Muscle Cells (Illustrative, No Detailed Notes)

Different types of muscle (skeletal, cardiac, and smooth) are depicted in diagrams.

Toughness and Viscoelasticity

Toughness is the ability of a tissue to absorb energy before fracture.
Viscoelasticity involves time-dependent behavior of tissues, influenced by stress or strain rates.
Examples include ligaments, tendons, muscles, and skin.

Mechanical Properties of Connective Tissues

Connective tissues often contain protein fibulins.

Mechanical Properties of Oral Tissues

Teeth consist of hard tissues (enamel, dentin, and cementum).
Pulp (the center of the tooth) is a soft (non-calcified) tissue containing nerves and blood vessels.