Lesson 5

Question 1

Describe Successional dental lamina

Answer 1

1. Initially formed permanent teeth appears as an extension of the dental lamina into the ectomesenchyme lingual to the developing primary tooth germs.
2. Its site of origin is called the successional dental lamina.
3. Each primary tooth bud has a successional dental lamina
4. Successional dentinal laminas go through bud, cap and bell stages of development at a much slower rate than the primary teeth

Question 2

Because permanent molars are non-succedaneous, what do they form from?

Answer 2

Develop from a posterior extension of the dental lamina

Question 3

Describe the bell stage of permanent teeth

Answer 3

1. Crown morphology (shape of the crown) is expressed in the bell stage
2. Primarily differentiation four different types of cells are now found within the enamel organ.
3. the cap shape of the enamel organ assumes a bell shape.
4. Outer enamel epithelium (OEE) - protective barrier for the rest of the enamel organ during enamel production.
5. Inner enamel epithelium (IEE) - differentiate into enamel‑secreting cells: ameloblasts.
6. A basement membrane remains between the IEE and the adjacent dental papilla.

Question 4

During the bell stage, what 2 layers are between the outer and inner enamel epithelium?

Answer 4

1. stellate reticulum
2. stratum intermedium.
3. They support the production of enamel.

Question 5

During the bell stage, the dental papilla within the concavity of the enamel organ differentiates into two types of tissue in layers:

Answer 5

1. the outer cells differentiate into odontoblasts
2. the inner cells are the primordium of the pulp.

Question 6

Describe the dental sac (follicle) during the bell stage

Answer 6

1. The dental sac increases in the amount of collagen fibers but undergoes differentiation at a later time period than the enamel organ and dental papilla.
2. Dental sac follicle (cells) will form cementum, PDL and alveolar bone

Question 7

The late bell stage is also known as the __________

Answer 7

Apposition and maturation stage

Question 8

Describe apposition

Answer 8

1. Apposition: the enamel, dentin, and cementum are secreted in successive layers.
2. Initially secreted as a matrix
3. partially calcified
4. framework for later calcification.

Question 9

Describe maturation

Answer 9

Maturation is reached when the dental tissue types are fully mineralized - 96-97% mineralized

Question 10

Describe the Formation of Preameloblasts

Answer 10

1. IEE in the bell‑shaped enamel organ, differentiate into preameloblasts.
2. The preameloblasts induce dental papilla cells to differentiate into dentin-forming cells (odontoblasts) and then will differentiate themselves into cells that secrete enamel (ameloblasts).

Question 11

Describe the Formation of Odontoblasts and Dentin Matrix

Answer 11

1. Odontoblasts are lined up adjacent to the basement membrane but in a mirror‑image orientation compared with the preameloblasts.
2. The odontoblasts now begin dentinogenesis, which is the apposition of dentin matrix, or predentin, on their side of the basement membrane.

Question 12

What are the 2 phases of predentin turning into dentin?

Answer 12

1. collagen matrix formation
2. calcification with deposition of calcium phosphate (hydroxyapatite) crystals

*Thus the odontoblasts start their secretory activity some time before enamel matrix production begins.
* The dentin layer in any location in a developing tooth is slightly thicker than the corresponding layer of enamel matrix.

Question 13

Late bell stage: shape of the crown is determined beginning with ___________

Answer 13

cusp tips

Question 14

After the formation of predentin, the basement membrane between the preameloblasts and the odontoblasts _____________ and the preameloblasts to differentiate into ameloblasts.

Answer 14

disintegrates

*Ameloblasts then begin amelogenesis, or the apposition of enamel matrix, laying it down on their side of the now disintegrating basement membrane.

Question 15

Initial enamel matrix (amelogen) is _____ mineralized. During maturation, there is an influx of minerals and a loss of organic matter & water. _____ of enamel mineralization result of growth in size of crystals. Mature enamel is _____mineralized

Answer 15

1. 25%
2. 70%
3. 95%

Question 16

With the enamel matrix in contact with the predentin, mineralization of the disintegrating basement membrane now occurs, forming the __________

Answer 16

dentinoenamel junction (DEJ)

Question 17

Describe the odontoblastic process

Answer 17

1. The odontoblasts, leave attached cellular extensions in the length of the predentin called the odontoblastic process.
2. The odontoblastic process is contained in a mineralized cylinder, the dentinal tubule.
3. The cell bodies of odontoblasts will remain within pulp tissue.
4. The cell bodies of the ameloblasts will be involved in the eruption and mineralization process but will be lost after eruption.

Question 18

Describe Enamel dysplasia

Answer 18

1. Developmental disturbance of the apposition and maturation stage (late bell stage)
2. factors interfere with the metabolic processes of the Ameloblasts and/or Maturation of enamel
3. Local enamel dysplasia may result from trauma or infection occurring in a small group of ameloblasts.
4. Systemic enamel dysplasia involves larger numbers of ameloblasts and may result from traumatic birth, systemic infections, nutritional deficiencies, or dental fluorosis (excess systemic fluoride level).

Question 19

The types of Enamel dysplasia include ___________

Answer 19

1. Enamel Hypoplasia - Reduced quantity of enamel matrix (pitting, notches, grooves)
2. Enamel hypocalcification - Reduction in the quality of enamel maturation (opaque, yellow, staining)

Question 20

Describe dental fluorosis

Answer 20

Enamel hypoplasia and hypocalcification may occur together and affect entire dentition, a common finding in dental fluorosis.

Question 21

Describe Dentin Dysplasia

Answer 21

Dentin dysplasia, or the faulty development of dentin, can result from an interference with the metabolic processes of the odontoblasts during dentinogenesis.

Question 22

When does the process of root development take place?

Answer 22

After the crown has been completely shaped

Question 23

What structure is resposible for root development?

Answer 23

1. The structure responsible for root development is the cervical loop. The cervical loop is the most cervical part of the enamel organ, a bilayer rim that consists of only IEE and OEE.
2. The cervical loop begins to grow deeper into the surrounding ectomesenchyme of the dental sac, elongating and moving away from the newly completed crown area to enclose more of the dental papilla tissue and form Hertwig’s epithelial root sheath (HERS).

Question 24

What is the function of Hertwig’s epithelial root sheath (HERS)?

Answer 24

The function of the Hertwig’s epithelial root sheath (HERS) is to shape the root(s) and induce dentin formation in the root area, so that it is continuous with coronal dentin.

Question 25

Root dentin forms when the outer cells of the dental papilla undergo differentiation and become ___________.

Answer 25

odontoblasts

Question 26

After the differentiation of odontoblasts in the root area, these cells undergo dentinogenesis and begin to secrete ___________

Answer 26

predentin

Question 27

When root dentin formation is completed, there is disintegration of the root sheath, its cells may become the ___________

Answer 27

epithelial rests of Malassez (ERM).

Question 28

Describe Cementum and Pulp Formation

Answer 28

1. The cementoblasts move to cover the root dentin area and undergo cementogenesis, laying down cementum matrix, or cementoid. 2. Many cementoblasts become entrapped by the cementum they produce and become mature cementocytes. 3. As the cementoid surrounding the cementocytes becomes calcified, or matured, it is then considered cementum. 4. As a result of the apposition of cementum over the dentin, the dentinocemental junction (DCJ) is formed. 5. Also at this time, the central cells of the dental papilla are forming into the pulp. 6. The pulp tissue is surrounded by the newly formed dentin.

Question 29

What is concrescence

Answer 29

Excess cementum formation - rare

Question 30

Describe Periodontal Ligament and Alveolar Bone Development

Answer 30

1. The ectomesenchyme from the dental sac begins to form the periodontal ligament (PDL) adjacent to the newly formed cementum. 2. This process involves forming collagen fibers that are immediately organized into the fiber bundles of the PDL. 3. The ends of these fibers insert into the outer part of the cementum and the surrounding alveolar bone to support the tooth.

Question 31

Describe root development of multirooted teeth

Answer 31

1. Like anterior teeth, multirooted premolars and molars originate as a single root on the base of the crown. 2. This part on these posterior teeth is called the root trunk. 3. The cervical cross section of the root trunk initially follows the form of the crown. However, the root of a posterior tooth divides from the root trunk into the correct number of root branches for its tooth type. 4. Differential growth of HERS causes the root trunk of the multirooted teeth to divide into two or three roots.

Question 32

Describe enamel pearls

Answer 32

1. Developmental disturbance during root formation 2. In some cases, misplaced ameloblasts can migrate to the root area, causing enamel to be abnormally formed over the cemental root surface, which produces an enamel pearl.

Question 33

Describe dilaceration

Answer 33

1. Dilaceration results in either distorted root(s) or crown angulation in a formed tooth. 2. It is caused by a distortion of HERS due to an injury or pressure; it can occur in any tooth or group of teeth during tooth development.

Question 34

What is it called when a tooth has extra roots or canals?

Answer 34

1. accessory roots (or supernumerary roots) 2. accessory canals

Question 35

Eruption begins with __________

Answer 35

1. Root formation 2. With increase in root length, the tooth begins eruptive movements providing space for further root lengthening

Question 36

What eruptive forces do teeth experience?

Answer 36

1. Root growth 2. Changes in vascularity 3. Increased cellular activity around forming tooth 4. Endocrine factors (growth hormone) 5. Enzyme activity

Question 37

Describe active eruption

Answer 37

1. After enamel apposition ceases in the crown area of each primary or permanent tooth, the ameloblasts place an acellular dental cuticle on the new enamel surface. 2. AND, the layers of the enamel organ are compressed, forming the reduced enamel epithelium (REE). 3. The REE appears as a few layers of flattened cells overlying the new enamel surface. 4. As this formation of the REE occurs for a primary tooth, it can begin to erupt into the oral cavity. 5. To allow for the eruption process, the REE first has to fuse with the oral epithelium lining the oral cavity. 6. Second, enzymes from the REE then disintegrate the central part of the fused tissue, leaving an epithelial tunnel for the tooth to erupt through the surrounding oral epithelium into the oral cavity. 7. As a primary tooth actively erupts, the coronal part of the fused epithelial tissue peels back off the crown, leaving the cervical part still attached to the neck of the tooth. 8. This fused tissue that remains near the CEJ after the tooth erupts then serves as the initial junctional epithelium of the tooth and creates a seal between the tissue and the tooth surface. 9. This tissue is later replaced by a definitive junctional epithelium as the root is formed. 10. The primary tooth is then lost, exfoliated, or shed, as the succedaneous permanent tooth develops lingual to it.

Question 38

primary tooth consists of differentiation of ___________, which absorb the alveolar bone between the two teeth, and ____________, which cause resorption or removal of parts of the primary's root of dentin and cementum as well as small parts of the enamel crown.

Answer 38

1.osteoclasts 2. odontoclasts

Question 39

Permanent anteriors develop _________ to the incisal level of the forming primary teeth. Later development, as the primary teeth erupt: permanent successors are __________ of the primary tooth

Answer 39

1. lingual 2. lingual to apical third

Question 40

Permanent premolars shift from location near the ____________ area of primary molars to location enclosed within the ____________ of the primary molars. This change in position is result of __________ of the alveolar bone.

Answer 40

1. occlusal 2. roots 3. increased height

Question 41

Describe dentigerous cysts (follicular cysts)

Answer 41

An odontogenic cyst that forms from the REE after the crown has completely formed and matured is the dentigerous cyst, or follicular cyst.

Question 42

If a dentigerous cyst appears on a partially erupted tooth, it is considered an ___________ and appears as fluctuant, blue, vesicle‑like gingival lesion.

Answer 42

eruption cyst

Question 43

Describe Nasmyth's Membrane

Answer 43

1. A residue may form on newly erupted teeth of both dentitions that may leave the teeth extrinsically stained. 2. This residue, Nasmyth's membrane, consists of the fused tissue of the REE and oral epithelium as well as the dental cuticle placed by the ameloblasts on the new enamel surface.

Question 44

Describe Root Fragments

Answer 44

Root fragments from primary molars may be left from the process and create periodontal complications for the permanent dentition; panoramic radiographs of the mixed dentition are important in order to monitor tooth development.