Question 1

Enamel,dentin,and pulp develop from enamel organ.Enamel is derived from ectoderm whereas dentin and pulp are derived from mesoderm.

Accepted Answer

Enamel develops from enamel organ,which is derived from ectoderm.Dentin and pulp develop from the dental papilla,which is derived from mesoderm.

Question 2

Pulp tissue consists of blood vessels,lymphatic vessels,nerves,fibroblasts,and collagen fibers.The nerves of the pulp are primarily sensory and transmit both pain and thermal sensations.

Accepted Answer

While the nerves of the pulp are primarily sensory,the only type of sensation they transmit is pain.

Question 3

Each of the following is true of enamel lamellae EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

Lamellae are hairline cracks in enamel that may extend into dentin.An infrequent type is a developmental defect that results from cessation of enamel production by one or more ameloblasts.This defect leaves a space between enamel rods,which provides a potential pathway for bacteria.

Question 4

Each of the following accurately describes hypocalcified enamel EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

Hypocalcified enamel is less than 96% inorganic.It results from insufficient growth of enamel crystals or an insufficient number of crystals originally deposited in the matrix.

Question 5

Dentin matrix creates a barrier between the dental papilla and the preameloblasts.With the resulting fluid shift and change in polarity,the preameloblast becomes an ameloblast.

Accepted Answer

The barrier between dentin matrix and dental papilla adversely affects the nutrient supply of the preameloblast.To compensate,new vascular channels penetrate enamel organ,enabling fluid nutrients to access the preameloblasts.With the resulting change in polarity the preameloblast becomes an ameloblast and is ready to secrete enamel matrix.

Question 6

Following mild trauma,which type of dentin is formed?

Accepted Answer

Reparative dentin is formed in response to local trauma and is located immediately beneath the area of trauma.By radiographically examining patterns of dentin it is possible to distinguish various types of trauma because different types occur in somewhat predictable areas.Secondary dentin is formed inside the regular dentin throughout life.Sclerotic and interglobular dentin are abnormalities in dentin formation.

Question 7

For both primary and permanent teeth the process of tooth development is the same.Development occurs simultaneously in the anterior and posterior regions beginning at the cervical line and progresses toward the incisal/occlusal edges.

Accepted Answer

Tooth development is first seen in anterior teeth and later in posterior teeth.It begins at the tip of a cusp/incisal edge and progresses cervically.Also,development tends to occur slightly sooner in the mandibular arch.

Question 8

Enamel rod is somewhat parallel to the dentinoenamel junction (DEJ)because it runs all the way from the DEJ to the surface of the tooth.

Accepted Answer

Enamel rod is a column that runs all the way from the DEJ to the tooth surface in a direction perpendicular (90 degrees)to both the tooth surface and the DEJ.

Question 9

Each of the following is true of the cells of the inner enamel epithelium (IEE)during the bell stage EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

The number of mitochondria,cells responsible for energy production,increase.There is also an increase in endoplasmic reticulum,and a more obvious Golgi apparatus.

Question 10

An enamel spindle is an ameloblastic process that becomes trapped in dentin.Enamel spindles form in early development and are seen only histologically.

Accepted Answer

An enamel spindle is an odontoblastic process,a cellular extension of the odontoblast,that becomes trapped between ameloblasts and ends up in enamel.

Question 11

Each of the following is true of enamel EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

Enamel is developed from enamel organ,which is derived from ectoderm.

Question 12

The bulk of the dentinal material is called primary dentin or regular dentin.An area of higher crystalline content immediately surrounding the dentinal tubules is called sclerotic dentin.

Accepted Answer

The bulk of the dentinal material is called intertubular dentin.An area of higher crystalline content immediately surrounding the dentinal tubules is called peritubular dentin.(Hint: peri means around. )Regarding incorrect terminology,primary or regular dentin is the structure that exists when a tooth erupts into the oral cavity.In sclerotic dentin,a condition caused by occlusal trauma or decay,the empty dentinal tubules become filled with a dentin material.

Question 13

Young people are less susceptible to permanent pulpal damage than older people because with age the smaller pulp loses its reserve cells and is less able to resist trauma.

Accepted Answer

With age,the pulp becomes smaller due to accumulation of secondary and reparative dentin.The diminished size as well as increased concentration of fibers renders the older pulp more susceptible to permanent pulpal damage.

Question 14

Enamel is generally yellowish in color but usually appears white because of the reflection of the color of the underlying dentin.

Accepted Answer

Enamel is generally white but sometimes appears yellowish due to reflection of the color of the underlying dentin.

Question 15

After the ameloblast secretes the primary enamel cuticle it is called the reduced enamel epithelium because it becomes flattened and blends with outer enamel epithelial cells.

Accepted Answer

This statement correctly describes the final phase of the ameloblast.The term reduced enamel epithelium is appropriate because the ameloblast is "reduced," and it blends in with outer enamel epithelial cells.Note that the primary enamel cuticle,the final product of the ameloblast,is also called Nasmyth's membrane.

Question 16

The dental papilla is derived from the ectoderm.It determines the shape of the developing crown.

Accepted Answer

The dental papilla,which forms dentin and the pulp,is derived from mesoderm.The dental papilla seems to have genetic control over tooth shape (both crown and root).

Question 17

The portion of enamel rod that contains most of the fibrous organic substance is the

Accepted Answer

Enamel sheath,also called the rod sheath,contains most of the fibrous organic components of enamel.Enamel structure contains two parts: enamel sheath and enamel rod.Enamel matrix consists of mucopolysaccharides and organ fibers.Within enamel matrix is a glue like material called ground substance.

Question 18

During the mineralization stage of enamel rod calcification approximately half of the hydroxyapatite crystals are deposited because the remaining half are deposited during the maturation stage.

Accepted Answer

It is important to remember that all the hydroxyapatite crystal that will ever exist in a particular area of enamel rod is deposited during the mineralization stage of rod calcification.During the second stage of calcification,the maturation stage,the crystals grow in size and become packed together.Note that no crystals are deposited during the maturation stage.

Question 19

A sign that enamel production is completed is when

Accepted Answer

As the ameloblast moves away from the DEJ toward the OEE,it compresses the two middle layers-the stratum intermedium and the stellate reticulum.The sign for the ameloblast to cease enamel formation is when the ameloblast contacts the OEE.

Question 20

The multipointed cells that become dental papilla cells are called

Accepted Answer

Mesenchymal cells are large multipointed embryonic cells deep within the tooth bud.They are primitive cells of the mesodermal embryonic layer and have the ability to form a number of different tissues.During the cap stage,mesenchymal cells become cells of the dental papilla.

Quiz 20: Enamel, Dentin, and Pulp