ex2. Eruption and Shedding

Question 1

T/F Tooth movement halts after 10 years of ge

Answer 1

False. Tooth movement occurs throughout life

Question 2

What is the one direction that a tooth will not move?

Answer 2

A tooth will No move APICALLY (towards the direction of its root). Can’t even orthodontically move a tooth apically

Question 3

T/F cementoblasts are the most numerous kind of cell in the periodontal ligament (PDL)

Answer 3

False. FIBROBLASTS are the most abundant type of cell in the PDL. Fibroblasts have many func such as secreteing and breaking down (fibroclast) extracellular matrix, as well as possibly functioning as a fibromyocite where its contraction pulls on the attached collagen that causes a tooth to move

Question 4

T/F Presecretory, secretory, postsecretory, and terminal stages are the 4 stages of eruption

Answer 4

False. There are only 3 stages of eruption called:

pre-emergence, prefunctional, and functional.

Question 5

The structures of the dental lamina, epithelial bud-bell Hertwig’s sheath.. are all in which stage of eruption

Answer 5

The stages of odontogenesis occur during the pre-emergence stage of tooth Eruption

Question 6

During what stage does the reduced enamel epithelium (recall, enamel’s protective layer) merge with the oral epithelium of the jaw process?

Answer 6

The merger of reduced enamel epithelium and oral eoptihelium occurs first during the pre-functional stage .. after hte merger, the REE becomes the junctional epithelium (in the gingival sulcus)

Question 7

what is physiolocal mesial drift? In what stage of eruption is Mesial the main direction of motion?

Answer 7

Physiological mesial dirft is the physiological (natural) tendency the erupted and developed teeth to move mesially in the arch.

In the functional stage (post eruption) the main direction of tooth movement is mesially.// during the preemergence stage (odontogenensis) the main directionof movement was facially, and then during the prefuncitonal stage (merger) the main direction of motion is occlusal

Question 8

what cell types (-blast) can be found in the periodontal ligament?

Answer 8

fibroblasts (most numerous in PDL),
cementoblasts,
osteoblasts,
osteoClasts

Question 9

T/F The firbroblast, the most numerous cell type of the PDL, both acts as a -blast cell (secretes extracellular substnace) and a -clast cell (where it lysis/break-down the extracellular substance)

Answer 9

True. The fibroblast of the periodontal ligament both functions to secrete extracellular substance (-blast func) and to lyse/ break-down of the extracellular substance

Question 10

what is a fibromyocyte?

Answer 10

A fibromyocyte/ aka myofibroblast is a type of fibroblast that has the ability to contract. // The myofibroblast is a cell that connects to the Cartilage that spans from tooth to alveolar bone– so when myofibroblast contracts, te tooth is moved closer to the bone (( how orthodontics works..))

Question 11

what is the name of the eruption stage that spans the timeframe bt the appearnace of dental lamina through the developemnt of the reduced enamel epithelium/the second dental lamina/ Hertwig’s sheath?

Answer 11

The stage of eruption that spans the development of the tooth germ (odontogenesis) is the first stage of tooth eruption, called the pre-emergence stage.

Question 12

what is the main direction of motion of the teeth during the preemergence stage of tooth eruption

Answer 12

during the preemergence stage , odontogenesis is occuring, and the main direction of tooth movement is FACIALLY directed

Question 13

what are the components of the reduced enamel epithelium and when is it formed?

Answer 13

the reduced enamel epithelium is composed of the 4 layers of the enamel organ compressed into a protective layer (that will sheild the formed enamel through emergence)
the four layers are: the inner epithelial layer, stratum intermedium epi layer, the stellate reticulum layer, and the outer epithelial layer

Question 14

what forms Hertwig’s root sheath?

Answer 14

Hertwig’s root sheath is a double layer of epithelium formed where the inner and outer layers of eptithelium (of the enamel organ) meet and overlap

Question 15

are the stratum intermedium and the stallate reticulum eputhelial layers of the enamel bud a part of Hertwig’s sheath? A part of the reducued enamel eptihelial layer?

Answer 15

The stratum intermedium and stallate reticulum are Not a part of Hertwig’s root sheath (which is only inner and outer epithelial layers of enamel organ) but ARE a part of the reduced enamel epi. which is comprised of all 4 epithelial layers of the enamel organ

Question 16

T/F the ameloblasts secrete the entire length of the enamel rod BEFORE the enamel undergoes maturation (aka ful mineralization)

Answer 16

True. The ameloblasts secrete the entire length of the enamel rod before the enamels matures from partially to fully mineralzied

Question 17

What is the basal lamina and where is it located?

Answer 17

The basal lamina is the final (unmineralized) secretion of ameloblasts. It is located bt the outer rodless enamel layer and the reduced enamel epithelium. The basal lamina functions to attah the REE to the enamel

Question 18

What formation found during preemergence is responsible for 1)determining the number of root canals of the tooth and 2) determining the root-dentin outline of the tooth?

Answer 18

Hertwig’s epithelial root sheath is at the cervical loop of the enamel organ where the outer an inner peithlial layers of the enamel organ meet.

Hertwigs’s epithelial root sheath isthe structure found during preemergence that is responsible for 1) determining the number of root canals of the tooth and 2) determining the root-dentin outline of the tooth

Question 19

T/F The number of openings in the diaphragm of the reduced enamel epithelium determines the number of root canals in a tooth

Answer 19

False. The number of openings in the diaphragm of Hertwig’s epi. root sheath is what determines the number of root canals in a tooth BEFORE the dentin is formed

Question 20

Are the number of root canals of a tooth determined before or after root- dentin is formed?

Answer 20

The number of root canals of a tooth (via the # of openings in the diaphragm of Hertwig’s root sheath ) is determined BEFORE the root-dentin is formed

Question 21

In what stage of eruption do we see the appearnace of the pulp chamber?

Answer 21

The pulp chamber appears during the preemergene stage (same as the odontogenesis occurring)

Question 22

In what stage of eruption do cells differentiate into the formative cells: ameloblasts, odontoblasts, and fibroblasts?

Answer 22

The differentiation of cells into formative -blast cells occurs in the same stage as odontogenesis occurrin == the preemergence stage

Question 23

T/F In the premergence stage we see the enamel organ over the enamel become the reduced enamel epithelium that is attached to the enamel by a basal lamina

Answer 23

True. In the preemergene stage (pretty much the end of the preembergence stage..) the enamel organ located over (coronal) to the enaml compresses and beomes the reduced enamel eptithelium that is attached to the enamel via BASAL lamina

Question 24

T/F During the preemergence stage of eruption (the first stage) we see the forming of the bone crypts of the jaw remodel, becoming the alveolar process

Answer 24

True. During the first, preemergence stage of eruption, the bone crypts remodel as they becomes the alveolar processes

Question 25

What are the start and end points of the second stage of eruption, the prefunctional stage?

Answer 25

The second stage of eruption, the prefunctional stage, starts with the formation of root-dentin and ends with the tooth reaches the occlusal plane (ehere there is oppositiion.. if there is no occlusal plane opposition, the growing tooth will keep growing occlusally) == aka, by the end of the prefunctional stage, the tooth has erupted (has to to reach the occlusal plane))

Question 26

What is the main direction of tooth movement during the 2nd, prefunctional stage of eruption.

Answer 26

During the prefunctional stage of eruption the tooth mostly MOVES OCCLUSALLY as it develops until it reaches the occlusal plane

Question 27

During what stage of eruption does the merge between the reduced enamel eptiehlium and the oral epithelium occur? – what is the merged version of the REE called?

Answer 27

During the prefunctional stage of emergence (2nd) the reduced enamel epitehlium REE that protects abd covers the tooth merges with the surounding surface oral epithelium.

The REE merges and falls away as a cover, changing into the junctional epithelium surrounding the tooth (recall - juncitonal epitehlium reaches into the gingival sulcus)

Question 28

Does this correctly describe what happens to Hertwig’s root sheath?

1. Sheath diaphragm= # opening determind root canals #. Tooth erupts occlusally
2. Sheath elongates and determines root-dentin outline
3. Root dentin forms. The sheath breaks up and cementum forms on the exposed dentin until the root is completed

Answer 28

Yes. The following description is accurate regarding Hertwig’s root sheath.

1. Sheath diaphragm where # openings of sheath diaprhagm = # root canals
2. The hertwig sheat elongates and deermines the root-dentine outline
3. The root-dentin forms= the sheath breaks up and cementum forms on the exposed dentin until the root formation is complete.

Question 29

From what formation doe the eptithelial rest of Malassez form?

Answer 29

The epithelial rest of Malassez =remnants of epthelial cells in the periodontal ligament persisting form the origination formation, Hertwig’s root sheath

Question 30

during what stage of eruption do the epithlial rest of Malassez appear?

Answer 30

The epithelial rest of Malassez appears in the prefuncitonal stage (2nd) of eruption. The rest of Malassez are clusters of epithelial cells that clump up.. left over from the degraded Hertwig root sheath

Question 31

Is it possible for cysts to form in the epithelial rest of Malassez? Is this clinically significant?

Answer 31

Yes, it is possible for cysts (pockets, like a bubble of air or fluid) to form from the rest of Malassez .. and yes, these cysts would therefore be located in the periodontal ligament and Would be clinically significant

Question 32

Just before the tooth emerges, the reduced enamel epithelium merges with the oral epithelium.. though what opening does the tooth erupt?

Answer 32

During the prefunctional stage, reduced enamel epithelium and oral epithelium merge .. but the merger cells in the area occlusal to the tooth undergo apoptosis to form an opening for the tooth to emerge. The REE becomes the junctional epithelium around the tooth

Question 33

T/F the basal lamina attaches to enamel, dentin, cementum, and to implants

Answer 33

False. The basal lamina ((borders the junctional epithelium attaching the junctional epithelium to the tooth and to the CT =lamina propia of the gingiva)) does NOT attach to dentin nor implants. The basal lamina Only Attaches to Enamel and Cementum. ((imp in terms of gingival attachment))

Question 34

During what stage of eruption does cementogenesis occur?

Answer 34

Cementogenesis (formation of cementum) occurs during root formation which occurs during the 2nd stage of eruption: the prefunctional stage

Question 35

During hwat stage of eruption does the dental follicle mature?

Answer 35

The dental follicle forms the periodontal ligament. therefore, the dental follicle matures during the 2nd stage of eruption (along with the root formation) which is the prefunctional stage of eruption. The alveolar process (bone) is also maturing at this time.

Question 36

T/F Emergence of the tooth into the oral cavity occurs during the functional stage of emergence

Answer 36

False. The emergence of the tooth into the oral cavity occurs during the (2nd) prefunctionall stage of emergence. The prefunctional stage spans the time frame bt the beginning of root-dentin formation ((Hertwig’s root sheath forms the root outline, dentin forms, cementum forms, merging of epithelial, emergence) and ends when the tooth reaches the occlusal plane

Question 37

How is the junctional epithelium attached to the tooth surface? Wht would this make sense?

Answer 37

The jucntional epithelium is attached to the tooth surface via BASAL lamina. This makes sense bc the basal lamina attached the reduced enamel epithelium to the enamel.. and the REE becomes the junc epithelium.

Question 38

What is the time frame of the final stage of eruption- the functional stage?

Answer 38

The functional stage starts when the tooth has erupted to the level of the occlusal plane (where the opposing tooth stops its occlusally oriented growth) .. the functional stage lasts for the duration of the tooth life

Question 39

What is the major direction of tooth movement during the functional stage of eruption?

Answer 39

The functional stage of eruption is the 3rd/last stage of tooth eruption that lasts from time of ermegence to theocclusal plane for the remainder of tooth life. The major direction of tooth movment during the functional stage is MESIAL. called the physiological mesial drift.. all teeth want to move mesially ((clinically significant.. use spaces to maintain spaces, orthodontics, etc))

Question 40

T/F During the (2nd) prefunctional stage of tooth eruption, the collagen fibers of the periodontal ligaments attain their functional arrangement as groups/bundles of collagen

Answer 40

False. The collagen of the PDL does not attain its functional arrangement into groups until the FUNCTIONAL (3rd/last) stage of tooth eruption

during prefucntional stage, they are not in groups, but are arranged obliquely

Question 41

What changes about the junctional epithelium fduring the functional stage of tooth eruption

Answer 41

During the functional stage of tooth eruption (last/3rd) the junctional eptihelium (was REE) changes its location of attachment. The junctional epithelium starts as being attached to the enamel… (as the cementum devleops and final levels are reached) the juncrtional epithelium attaches to both the enaeml and cementum, and finally is only attached to the cementum == movement is called physiologic passive eruption

Question 42

What is the the junctional epitthelium attached to after development in the functional stage? ((the change process is called, physiologic passive eruption))

Answer 42

The junctional epithelium goes from being attached to only enamel (to both) to finally, only attached to cementum during the last stage of tooth eruption, the functional stage

Question 43

During what stage of tooth eruption do the signs of aging appear?

Answer 43

The signs of aging, including atrition, dead tracts. reduced pulp volume..) occur furing the 3rd/last stage of tooth eruption:: the functional stage – which lasts the length of the tooth’s life

Question 44

T/F Dentin formation ceases after the prefunctional stage of tooth eruption

Answer 44

False. Dentin formation does Not cease after the prefunctional stage (2nd) of tooth eruption.. dentin formation occurs throughout life.. as reparative, sclerotic, and normal growing in (causes the reduction of pulp size as tooth ages bc dentin still growing in)

Question 45

T/F it is possible for the primary teeth to be in the functional stage of eruption while permanent teeth are in the preemergene and prefunctioanl stages

Answer 45

True. Primary teeth develop and emerge before secondary/permanent teeth. As such, primary teeth can be in the funcational stage of toooth eruption while othe secondary teeth are in the earlier dtages of devlopment: the preemergence and prefunctional stages

Question 46

What is shedding in regards to primary teeth?

Answer 46

Shedding is::
The physiologic elimination of primary teeth caused by the resorptive ation of odontoClasts (which resorb all mineralzied tissues of the tooth – enamel, dentin, cementum)

Question 47

What do the odontoclasts do during shedding?

Answer 47

Odontoclasts RESORB all of the mineralzied tissue of the primary teeth during shedding (hence easy to pull out))

Question 48

Where do odontoclasts originate?

Answer 48

The odontoclasts originate in the BONE MARROW (just like OSteoclats that break down bone). The odontoclasts arrive to the tooth via blood vessels

Question 49

How do odontoclasts travel to the teeth?

Answer 49

Odontoclasts (like osteoclasts) that resorb the minerals of the teeth originate in the bone marrow and travel to the site of resorption (teeth) via BLOOD VESSELS

Question 50

T/F The secondary teeth have a reduced enamel epithelial covering

Answer 50

True! Secondary teeth also have enamel in need of protection- via the reduced enamel eptiehlium. The secondary teeth develop the same way as the primary

Question 51

Ameloclasts, dentinoclasts, and cementoclasts are all types of what cell?

Answer 51

Ameloclasts, dentinoclasts, and cementoclasts are all types of ODONTOCLASTS which break up the tissues of the tooth

Question 52

In a histology slide/pic.. how can you determine the areas of resorption?

Answer 52

To determine the area of resorption.., mostly occurs where there isw a primary tooth undergoing resorption and a secondary tooth visiblly emerging apical to the piramry. The scoendayr tooth has a reduced enamel eptihlial covering… the area of resoroption is on the priamry tooth (its root area) and looks like stippling along an otherwise definitive border ((the mineralized tissues have linear, clean lines as borders.. int he areas of resorption, there are lots of dots.. stippling, that is indicative of tissue being broken down))