ex.2 periodontium Flashcards
cementum, periodontal ligament, the bony socket, junctional and sulcular epithelium are all a part of what group of tissues?
the PERIODONTIUM = the cementum, PDL, boney socket, junc. and sulc. epi.
these are all tissues that SURROUND the tooth
what collagenous fiber spans between the bony socket and the cementum of the tooth?
The periodontal ligament spans bt the cementum and the bony socket that houses the tooth. The PDL is mostly collagen fibers
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?
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)
T/F All of the periodontum is considered as connective tissue
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
Does the root develop before or after the crown?
The root develops AFTER the crown
T/F The root develops before the crown
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)
place the following in chronological order:
- HERS (Hertwig’s epithelial root sheath) separates from the root dentin
- Osteoblasts, cementoblasts, PDL fibroblasts differntiate and migrate to their appropriate locations
- Root dentinogenesis starts.. then periodontal development starts a little after
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
T/F The periodontium develops in ‘synchrony’ with the root
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_
What inductive signal does Hertwig’s root sheath deliver to odontoblasts to start root dentin formation? (be specific)
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
What are the 3 formative cell types that lead to the periodontium evvelopment?
The cementoblasts, osteoblasts, and fibroblasts are the 3 formative ecll lines that lead to periodontium formation
T/F It is necessary for the devlopment of the osteoblasts, cementum, and PDL to occur in a very precise way
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:
- the cemento and osteoblasts secrete ORGANIC MATRIX ..
- PDL formation lags slightly behind the O matrix
- After PDL is in place, the bone and cementum mineralize
T/F the organic matrix secreted by teh cemento and osteo-blasts contains type 3 collagen
False. The organic matrix secreted by the cemnto and osteo-blasts contains type 1 collagen
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
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
T/F eruption occurs before periodontium development
False. Eruption is simultaneous w periodontium devlopment – they are coordinated events
T/F Like the root, the periodontium forms from the CEJ to the apex.
True. The development of the root and the periodontium occurs from CEJ to root
T/F Root formation and periodontium formation is considered to be a slow process
True. DEvelopment of hte periodontium and the root take years, and is considered a slow process
T/F there is a primary and secondary type of cementum
True/ both primary and secondary cementum exist.. they are diferent in a few ways
When does secondary dentin form?
secndary dentin forms after at least half of the tooth is formed.. which is about the time the tooth erupts into the oral cavity
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
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
T/F Primary cementum is cellular
False. Primary cementum is ACELLULAR, secondary cementum is cellular
T/F Primary and secondary cementum overlap
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)
T/F Predentin is located near the pulp and non-mineralized dentin is located near the DCJ– both are unminerlaized
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
Are the fibers of hte initial cementum organic matrix oriented parallel or perpendicular to the DCJ?
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
T/F The firm attachment between the cemnetum and dentin is a consequence of the hydroxyapatite crystals intermingling bt the 2 tissues during minerlaization
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
Does the dentin minerlaize before, after, or same time as the cementum?
The dentin minerlaizes completely to the DCJ before the cementum minerlaizes.\– histologically, the minerlaization appears to be a darker stain
T/F The minerlization of the cementum starts in the fiber fringe and occurs in layers
False. The fiber fringe begins to mineralie in descrte foci (looks like dark, scattered patches through out the fiber fringe )
what is the fiber fringe?
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
what is it called when the fiber fringe completley minerlaizes?
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
T/F Primary cementum stops being added once minerlaization starts at the DCJ (most coronal)
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
Primary cementum is acellular – so what happens to the cementoblasts that form the cementum?
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
What strucutre was the predecessor of the fragmented Hertwig’s root sheath islands?
The fragments of HERS that persisted in the PDL persist as the Eptihelial Rests of Mallasez
T/F the PDL houses both the cementoblasts as well as the eptihelial rests of Mallasez
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)
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 :
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))
where are cementocytes located?
cementocytes are located in secondary cementum, in the mninerlaized matrix (called cementoblasts formerly to being trapped in the minerlaized cementum)
does the primary or secondary cementum form more rapidly?
The second cememtum forms faster.. explains paritially why the cementoblasts get trapped in the mineralized matrix and beocme cementocytes
T/F Both the sulcular and junctional epithelliums are from the reduced enamel epithelium
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
T/F both the sulcular and junctional epithelium function in attaching the tooth
False. the junctionals epithelium DOES attach the tooth (along w the cementum, PDL, and bony socket), the suluclar epithelium has NO attaching action.
T/F The sulcular epithelium is from embryonic oral eptihelium
True. The sulcular epithelium (found in hthe sulcus surrounding the tooth) is from the embryonic oral epithelium
Which part of the tooth germ (dental folklicle, dentla papilla, enamel organ) gives rise to cementoblasts?
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 …
What part of the tooth germ gives rise to the PDL, and the bony socket lining of the tooth socket?
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
Bone morphogenic proteins are secreted growth factors invovled w cementogenesis (induce cementogenesis) – what superfamily do they belong to?
Bone morphogenic proteins (BMP) belong to the TGFb (transforming growth factor beta) superfamly – induce cemntoblast differentiation
what is Runx?
Runx is a transcription factor that hypothesied to upregulate prtns that help form cementoblasts (differntiation). Runx is well known for differentiating osteoblasts
What role do bone sialoprotein and osteopontin pla in cementogenesis?
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
T/F Bone sialoprotein and osteopontin are importnat for cementoblast differnetiation
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
