ex.2 periodontium

Question 1

cementum, periodontal ligament, the bony socket, junctional and sulcular epithelium are all a part of what group of tissues?

Answer 1

the PERIODONTIUM = the cementum, PDL, boney socket, junc. and sulc. epi.

these are all tissues that SURROUND the tooth

Question 2

what collagenous fiber spans between the bony socket and the cementum of the tooth?

Answer 2

The periodontal ligament spans bt the cementum and the bony socket that houses the tooth. The PDL is mostly collagen fibers

Question 3

Of thhe periodontium (cementum, bony socket, PDL, junctional epi., sulcular epithelium, ) which of the components does NOT function to anchor/ attach tooth to the jaw?

Answer 3

of the periodontium, the sulcular epithelium does Not function to attach the tooth to the jaw. All the other components - the cementum, PDL, bony socket, and junctional epithelium ALL function to attach the tooth to the jaw.

• ths sulcular epithelium = (the gingiva in the sulcus surrounding the tooth)
• • the junctional epithelium = was the former reduced enamel epithelium (recall, 4 layer blanket that protected the enamel during emergence)

Question 4

T/F All of the periodontum is considered as connective tissue

Answer 4

False. The junctional and sulcular epitheliums are NOT considered to be CT.

The cementum, PDL, and alveolus (bony socket) ARE considered to be connective tissue

Question 5

Does the root develop before or after the crown?

Answer 5

The root develops AFTER the crown

Question 6

T/F The root develops before the crown

Answer 6

False. The crown develops before the root

** recall, Hertwig’s root sheath ((at th cervical loop of the enamel organ– the crown predecessor)) guides the growth fo the root (via Hertwig’s epithelial root sheath)

Question 7

place the following in chronological order:

1. HERS (Hertwig’s epithelial root sheath) separates from the root dentin
2. Osteoblasts, cementoblasts, PDL fibroblasts differntiate and migrate to their appropriate locations
3. Root dentinogenesis starts.. then periodontal development starts a little after

Answer 7

In summary: the chronological order is the following:
(3) Root dentinogenesis starts, then periodontal development starts a little after (( basically, root dentinogenesis starts bf the periodontium development does)

(1) Hertwig’s epithelial root sheath separates from the root dentin ((first step of periodontium devleopment))
(2) osteoblasts, cementoblasts, PDL, and fibroblasts migrate to their appropriate locations

Question 8

T/F The periodontium develops in ‘synchrony’ with the root

Answer 8

True. The development of the root dentin starts a little before the deelopmental start of periodontium development ( whose start is heralded by Hertwig’s root sheath separating from the root dentin_

Question 9

What inductive signal does Hertwig’s root sheath deliver to odontoblasts to start root dentin formation? (be specific)

Answer 9

Specifically, TGFb and lamiin5 are the signals from HERS (epithelium) to the odontoblasts to begin root dentin formation. .. then, the mesenchymal dentin inductively signals HERS (Hertiwg’s root sheath) to seprate from the root sdentin - and this is hte first step of periodontium development

Question 10

What are the 3 formative cell types that lead to the periodontium evvelopment?

Answer 10

The cementoblasts, osteoblasts, and fibroblasts are the 3 formative ecll lines that lead to periodontium formation

Question 11

T/F It is necessary for the devlopment of the osteoblasts, cementum, and PDL to occur in a very precise way

Answer 11

True. The development of hte periodontium responsible for tooth attachment to the jaw must occur in a very precise way for attachment to be achieved. //
the order of things:

1. the cemento and osteoblasts secrete ORGANIC MATRIX ..
2. PDL formation lags slightly behind the O matrix
3. After PDL is in place, the bone and cementum mineralize

Question 12

T/F the organic matrix secreted by teh cemento and osteo-blasts contains type 3 collagen

Answer 12

False. The organic matrix secreted by the cemnto and osteo-blasts contains type 1 collagen

Question 13

regarding the periodontal ligament, some of the following events occur during tooth eruption and some occur after. which is which?

• collagen fiber bundles increase in thickness
• the number of collagen fibers increase as they are added apically
• the collagen fibers change their orientation

Answer 13

The PDL development: During tooth eruption, the number of collagen fiber bundles increases (added apically) AND the orientation of the collagen bundles changes.

After eruption, the collagen fibers increase in thickness
** recall, the periodontal ligament is mostly Type 1 collagen

Question 14

T/F eruption occurs before periodontium development

Answer 14

False. Eruption is simultaneous w periodontium devlopment – they are coordinated events

Question 15

T/F Like the root, the periodontium forms from the CEJ to the apex.

Answer 15

True. The development of the root and the periodontium occurs from CEJ to root

Question 16

T/F Root formation and periodontium formation is considered to be a slow process

Answer 16

True. DEvelopment of hte periodontium and the root take years, and is considered a slow process

Question 17

T/F there is a primary and secondary type of cementum

Answer 17

True/ both primary and secondary cementum exist.. they are diferent in a few ways

Question 18

When does secondary dentin form?

Answer 18

secndary dentin forms after at least half of the tooth is formed.. which is about the time the tooth erupts into the oral cavity

Question 19

Assign the following characterisitics to primary and/or secondary as appropriate:

cellular, acellular, located in apical 2/3 of root, located in coronal 2/3 of tooth, more important role in attachment of tooth to jaw, forms prior to tooth eruption, forms after half of the root is formed

Answer 19

Primary cementum:

• forms before the apprx time of tooth eruption, is ACELLULAR, and located in the coronal 2/3 of the root ((recall, cememntum develops from coornal CEJ to apical))
• • primary cementum is more important than secondary in Attachment of the tooth

SECONDary cementum forms after at least half of the root has formed (about time of tooth eruption).. secondary is CELLULAR and located in the apicla 2/3 of the root

Question 20

T/F Primary cementum is cellular

Answer 20

False. Primary cementum is ACELLULAR, secondary cementum is cellular

Question 21

T/F Primary and secondary cementum overlap

Answer 21

true. Primary cementum is the coronal 2/3 of the root while secondary is the apical 2/3 of the root.. so they likely overlap about the middle 1/3 of the tooth – the secondary cementum overlies the primary in th middle 1/3 (logical, the primary was there first)

Question 22

T/F Predentin is located near the pulp and non-mineralized dentin is located near the DCJ– both are unminerlaized

Answer 22

True. Predentin is found near the pulp and non-minerlaized dentin is near the DCJ.. these unminerlaized dentins are noticeable as hte dentin starts to minerlize

Question 23

Are the fibers of hte initial cementum organic matrix oriented parallel or perpendicular to the DCJ?

Answer 23

The collagen fibers of the cementum are laid PERPENDICULAR to the DCJ. ..As the neighboring dentin is not yet completely mineralized, nor is the devloping cementum, the colagen fibers (‘fiber fringe) function to attach cememntum to dentin as both minerlaize

Question 24

T/F The firm attachment between the cemnetum and dentin is a consequence of the hydroxyapatite crystals intermingling bt the 2 tissues during minerlaization

Answer 24

False. The firm attachment bt the cementum and dentin is a consequence of the COLLAGEN FIBERS intermingling bt the two tissues Before either of them minerlaize

Question 25

Does the dentin minerlaize before, after, or same time as the cementum?

Answer 25

The dentin minerlaizes completely to the DCJ before the cementum minerlaizes.\– histologically, the minerlaization appears to be a darker stain

Question 26

T/F The minerlization of the cementum starts in the fiber fringe and occurs in layers

Answer 26

False. The fiber fringe begins to mineralie in descrte foci (looks like dark, scattered patches through out the fiber fringe )

Question 27

what is the fiber fringe?

Answer 27

the fiber fringe is the intial cementum matrix that is laid down. it is dense, collagen fibers oriented perpendicular to the DCJ. The fiber fringe extends into the unmineralized dentin and is important in attaching the cementum to the dentin

Question 28

what is it called when the fiber fringe completley minerlaizes?

Answer 28

The fiber fringe is called CEMENTUM (primary cementum!) when it totally mineralizes . this is visible as the discrete foci of initial fringe minerlaization coalese into a larger solid region of minerlaization

Question 29

T/F Primary cementum stops being added once minerlaization starts at the DCJ (most coronal)

Answer 29

False. Primary cementum continues to be laid down and gets thicker as the primary cementum minerlaizes at the DCJ.. cementum devleopment (like all periodontium) is from coronal to apical

Question 30

Primary cementum is acellular – so what happens to the cementoblasts that form the cementum?

Answer 30

The cementoblast cells that form the cementum migrate to the PDL rather than get trapped in minerlaizing matrix. Hence, primary cementum is considered to be acellular

Question 31

What strucutre was the predecessor of the fragmented Hertwig’s root sheath islands?

Answer 31

The fragments of HERS that persisted in the PDL persist as the Eptihelial Rests of Mallasez

Question 32

T/F the PDL houses both the cementoblasts as well as the eptihelial rests of Mallasez

Answer 32

True. The PDL houses the cementoblasts that formed the acellular primary cementum (coronal 2.3 tooth) as well as the epithelial rests of Mallasez (= the remnants of HERS)

Question 33

Primary and secondary cementogenesis both share the feature of having a fiber fringe where the collagen fibers intermingle w unminerlaized dentin. – Name a difference regarding cementoblasts :

Answer 33

It is true that the primarh and secondary cementogenesis anchor to the dentin via collagen fibers that interact prior to minerlaization and then embed in minerlaized matrix for supremem attachment ((like how the PDL attaches later into the cementum and alvelous)) //

However, primary cementum is ACELLULAR while seocndary is CELLULAR. the cementoblasts of hte primary cementum migrate to the PDL, while the cementoblasts of the seocndary cementum stay put and get trapped/ embedded in the minerlaized cementum matrix ((now, cementocytes))

Question 34

where are cementocytes located?

Answer 34

cementocytes are located in secondary cementum, in the mninerlaized matrix (called cementoblasts formerly to being trapped in the minerlaized cementum)

Question 35

does the primary or secondary cementum form more rapidly?

Answer 35

The second cememtum forms faster.. explains paritially why the cementoblasts get trapped in the mineralized matrix and beocme cementocytes

Question 36

T/F Both the sulcular and junctional epithelliums are from the reduced enamel epithelium

Answer 36

False. The junctional epithelium is from the reduced enamel eputhelium (recall- the protetive sheath of the enamel, from the enamel organ!) .

the sulcular epithelium is from the embryonic oral epithelium

Question 37

T/F both the sulcular and junctional epithelium function in attaching the tooth

Answer 37

False. the junctionals epithelium DOES attach the tooth (along w the cementum, PDL, and bony socket), the suluclar epithelium has NO attaching action.

Question 38

T/F The sulcular epithelium is from embryonic oral eptihelium

Answer 38

True. The sulcular epithelium (found in hthe sulcus surrounding the tooth) is from the embryonic oral epithelium

Question 39

Which part of the tooth germ (dental folklicle, dentla papilla, enamel organ) gives rise to cementoblasts?

Answer 39

origin of cementoblasts:: is debateable.

–RECENT EVIDENCE and CONVINCING MODERN TECHNIQUES – suggests that cementoblasts may have cells from BOTH the dental follicle and HERS.

• could be the dental follicle (since the other connective tissue components of the periodomtium are from the dental follicle..)) ……but it is debatable . –could also be from the ectodermal germ layer- the epithelia cells and HERS could be the orignin of cementoblasts …

Question 40

What part of the tooth germ gives rise to the PDL, and the bony socket lining of the tooth socket?

Answer 40

The dental follicle is ectomesenchymal (Neural crest cells) that is the part of the tooth germs tht gives rise to the bony socket and the periodontal ligament

Question 41

Bone morphogenic proteins are secreted growth factors invovled w cementogenesis (induce cementogenesis) – what superfamily do they belong to?

Answer 41

Bone morphogenic proteins (BMP) belong to the TGFb (transforming growth factor beta) superfamly – induce cemntoblast differentiation

Question 42

what is Runx?

Answer 42

Runx is a transcription factor that hypothesied to upregulate prtns that help form cementoblasts (differntiation). Runx is well known for differentiating osteoblasts

Question 43

What role do bone sialoprotein and osteopontin pla in cementogenesis?

Answer 43

BSP (bone sialoprotein) and osteopontin are both secreted from cemetoblasts (these are extracellular proteins) and are secreted during initial collagen matrix (fiber fringe) and are importnat for minerlazation

Question 44

T/F Bone sialoprotein and osteopontin are importnat for cementoblast differnetiation

Answer 44

False. Cementoblasts secrete the extracellular protiens BSP (bone sialoprotein) and osteopontin. These proteins are secreted initially as collagen and ASSIST W MINERALization. both proteins also bind to collagen