Question 1

The enamel organ originates from the

Accepted Answer

Cells of the enamel organ originate from ectodermal tissue. Note that as the enamel organ develops, the stellate reticulum forms between the inner enamel epithelium (IEE) and the outer enamel epithelium (OEE). Stellate reticulum is also ectodermal in origin.

Question 2

The cap stage begins when the concavity of the tooth buds becomes slightly concave.

Accepted Answer

As tooth buds develop they seem to stretch from the dental lamina, with the deepest parts becoming slightly concave. It is at this point that the developing enamel organ progresses from the bud stage to the cap stage.

Question 3

The clefting that occurs in the thickened vestibular lamina eventually becomes a mucogingival groove. The vestibular lamina is a thickening of oral epithelium in a lingual direction.

Accepted Answer

The vestibular lamina forms the area of the mucobuccal or mucolabial fold in the future vestibule. As the epithelium of the vestibular thickens in a facial or buccal direction, a clefting or splitting occurs. This is a key event in the formation of the fold within the vestibule. Without these events the vestibule would end at the level of the alveolar ridge.

Question 4

Without thickening of the vestibular lamina in an occlusal direction the vestibule would not exist because clefting or splitting of the epithelium would not occur.

Accepted Answer

Formation of the vestibule is dependent upon thickening of the epithelium in a facial or buccal direction from the lamina dura. This is followed by an epithelial clefting or splitting, which is critical to formation of the area of the mucobuccal or mucolabial fold in the future vestibule. Without formation of this vestibular lamina , the vestibule would end at the level of the alveolar ridge.

Question 5

The cells between the dental papilla and the outer enamel epithelium (OEE) compose the stellate reticulum. Originating from deep layers of the oral epithelium, cells of the stellate reticulum are mesenchymal in origin.

Accepted Answer

The stellate reticulum lies between the inner enamel epithelium (IEE) and the outer enamel epithelium (OEE). Although cells of the stellate reticulum originate from superficial embryonic layers and appear mesenchymal, they are actually ectodermal cells. All other parts of the enamel organ are also ectodermal. The dental papilla is a small area of condensed cells arising from mesoderm and located next to or deep to the IEE.

Question 6

Premolars are successional because they develop from a posterior growth of the dental, or general, lamina.

Accepted Answer

Note that premolars replace primary molars; premolars do not exist in the primary dentition. While it is True that premolars are successional, they develop from a lingual extension to the general dental lamina. This is also True of permanent incisors and canines, the remaining successional teeth. (A synonymous term is succedaneous.) Contrast this with the permanent molars, which do not have primary precursors. The permanent molars develop from a posterior growth of the dental, or general, lamina.

Question 7

The earliest signs of tooth development are seen during the tenth week in utero.

Accepted Answer

ALSE
During the eighth week in utero, starting at the midline and spreading posteriorly, the dental lamina continues its thickening process. Twenty localized thickenings are formed as precursors to the twenty teeth of the primary dentition.

Question 8

The dental papilla is first seen in the _____ stage.

Accepted Answer

The dental papilla, a small area of condensed cells arising from mesoderm and located near the inner enamel epithelium, is first seen in the late bud stage. It becomes more pronounced as it goes through the bell stage. The dental papilla forms both the dentin and the pulp.

Question 9

At about the sixth embryonic week, there is a continued thickening in the dental lamina. These localized thickenings correspond to the positions of the twenty teeth of the future primary dentition.

Accepted Answer

The thickening of the lamina dura that forms the twenty positions for the future primary dentition begins to occur at about the eighth embryonic week.

Question 10

The outermost part of the structure of the cap stage is the outer enamel epithelium (OEE). This tissue, a continuation of the basal layer of oral epithelium, is composed of predominately pyramidal and conical-shaped cells.

Accepted Answer

The OEE is a direct continuation of the basal layer of oral epithelium. These are low columnar or cuboidal cells.

Question 11

The stratum intermedium develops during which stage?

Accepted Answer

The appearance of the stratum intermedium, a fourth layer of epithelium within the enamel organ, marks the transition from the cap to the bell stage.

Question 12

The cells of the outer enamel epithelium (OEE) are indirectly responsible for enamel formation because they elongate and become ameloblasts.

Accepted Answer

After elongating and changing internally, the cells of the inner enamel epithelium (IEE) become ameloblasts. This transformation makes the cells of the IEE indirectly responsible for enamel formation by ameloblasts.

Question 13

The successional lamina forms all permanent teeth EXCEPT for one type. Which type is the EXCEPTION?

Accepted Answer

The successional lamina, a lingual extension to the side of each primary tooth, forms permanent incisors, canines, and premolars. These teeth are preceded, respectively, by the primary incisors, canines, and molars. Permanent molars develop from a posterior growth of the dental, or general, lamina and are nonsuccessional.

Question 14

Skin, hair, enamel, and cementum can be adversely affected by ectodermal dysplasia because this condition causes poor development of structures arising from ectoderm.

Accepted Answer

Although ectodermal dysplasia can adversely affect tissues arising from ectoderm, cementum is not affected by this condition. Cementum is formed by the dental sac, which arises from mesoderm.

Question 15

Cells of the outer enamel organ (OEE) constrict and morph into ameloblasts. Stellate reticulum, in conjunction with ameloblasts, is responsible for enamel formation.

Accepted Answer

Cells of the inner enamel organ (IEE) elongate and change internally to become ameloblasts. Ameloblasts are responsible for enamel formation. The stellate reticulum does not produce enamel.

Question 16

The dental sac is composed of several layers of flat mesodermal cells that partially surround the dental papilla and the enamel organ. The dental sac is another name for the dental lamina.

Accepted Answer

The dental sac is another name for the dental follicle. The dental sac is comprised of several rows of flattened cells that surround the portion of the dental papilla not in contact with the inner enamel epithelium (IEE). The dental sac also surrounds part of the enamel organ. Both the dental sac and dental papilla arise from mesoderm.

Question 17

The cells of the inner enamel epithelium (IEE) are structurally similar to the cells of the outer enamel epithelium (OEE) because they both originate from the basal layer of the oral epithelium.

Accepted Answer

Both the outer enamel epithelium (OEE) and the inner enamel epithelium (IEE) originate from low columnar or cuboidal cells of the basal layer of the oral epithelium. Appearance of these tissues, along with the stellate reticulum, is indicative of the cap stage of tooth development.

Question 18

Each of the following statements accurately describes aspects of the development of the enamel organ EXCEPT one. Which one is the EXCEPTION?

Accepted Answer

The enamel organ will eventually form the enamel. Cementum is formed by another embryonic component, the dental sac.

Question 19

The appearance of the stratum intermedium differentiates the cap stage from the bell stage. The stratum epithelium, the fourth layer of epithelium, lies between the inner enamel epithelium and the outer enamel epithelium.

Accepted Answer

The stratum epithelium, comprised of several layers of flattened squamous cells, lies between the internal enamel epithelium and the stellate reticulum. It is the stellate reticulum that lies between the inner and outer enamel epithelium. All other aspects of the statements are correct.

Question 20

The vestibular lamina forms in a lingual direction from the dental lamina.

Accepted Answer

The vestibular lamina is a thickening of oral epithelium in a facial or buccal direction from the dental lamina.

Quiz 19: Dental Lamina and Enamel Organ