Periodontium

Question 1

what are the parts of the periodontiium?

Answer 1

cementum (calcified), PDL (collagen fibers), bony socket housing tooth, sulcular and junctional epi
**all but sulcular epi are attachment apparatuses for the tooth

Question 2

what does the periodontium develop in snychrony with?

Answer 2

the roots

Question 3

timeline for periodontal development

Answer 3

root dentiogenesis slightly before periodontal development (inductive signals for HERS for ODB), once root dentin laid down, HERS separtes from root dentin and then osteoblasts, cementoblasts, PDL fibroblasts differentiate nd migrate from the dental follicle to appropriate locations

Question 4

formation of periodontal tissues overlaps…

Answer 4

cementoblasts and osteoblasts secrete organic collagen matrix (type 1 collagen) and then PDL fibroblasts secrete collagen. the organic matrices of the cementum and bone mineralize around the ends of the PDL fibers, securing an attachment between the tooth and alvelous

Question 5

periodontal development and eruption

Answer 5

happening during eruption, so collagen fiber bundles are added apically. During eruption, the orientation of the collagen fibers in the PDL goes from apical in the cementum to coronal in the cementum. After eruption the PDL thickens

Question 6

root development

Answer 6

strongly coordinated with periodontal development

**from CEJ to apex

Question 7

primary and secondary cementum

Answer 7

secondary doesn’t start until after eruption (atleast 1/2 root complete) and is cellular (cementoblasts trapped in the matrix)
**secondary and primary cementum overlap in the middle third of the tooth with secondary overlying primary

Question 8

which type of cementum is more important for attachment?

Answer 8

primary cementum

Question 9

why is there a firm attachment btwn cmentum and dentin?

Answer 9

collagen fibers of the two tissues intermingle before mineralization

Question 10

mineralization of the fiber fringe

Answer 10

occurs as discrete foci (small blackened areas)

Question 11

do cells get entrapped in primary cementum?

Answer 11

no, they retreat to the PDL

Question 12

from where does sulcular epi rise?

Answer 12

embyonic oral epi

Question 13

where do the CT of the periodontium originate?

Answer 13

dental follicle (boney socket and PDL) and possibly cementum?

Question 14

where do cementoblasts come from?

Answer 14

follicle - experiments say may be bone?
or epi-mesesenchyme transformation of the HERS - fewer number of cells showing the phenotype for evidence and subjective
maybe both??

Question 15

what molecules are involved in cementenogenesis?

Answer 15

growth factors to SIGNAL cementoblast induction (Bone morphgenic protein), TF to initiatie cementoblast differentiation (Runx) (also a master switch for osteoblats) and ECM molecules that are secreted during initial collagen secretion by CB to help mineralize - (bone sialoprotein and osteopontin)

Question 16

bone sialoprotien

Answer 16

AA sequence arg, gly, asp that attaches to cell membranes and another part that is a polyglutatmate that causes HAP binding. Molecule might play a role in CB adhesion to root dentin and in triggering the mineralization of dentin

Question 17

cementum function

Answer 17

attachment of tooth to jaw , protection of root dentin and adaptation to the physical mastication forces

Question 18

composition of cememtum

Answer 18

similar to bone - 45-50 organic and 50-55 inorganic CT

• inorganic is mainly HA
• type 1 and II collagen is the main organic component. Also contains proteoglycans and gags

Question 19

what are the differences cementum has from bone?

Answer 19

secreted throughout life, but does not remodel and is NOT vascularized

Question 20

between the ages of 16 and 70 there is how many times increase in cementum?

Answer 20

3X

Question 21

why is the CEJ so vulnerable?

Answer 21

because cementum is so thin at the CEJ, can easily wear away and expose dentin

Question 22

what are the types of joints at the CEJ?

Answer 22

overlap (60%), butt (30) and gap (10)

Question 23

acellular cementum or “acellular extrinsic fiber cememntum”

Answer 23

primary cementum is mainly this (PDL fibers mineralized ends in here as sharpey fibers) fibers at right angle to cementum surface

• *MAINLY FOR ATTACHMENT PURPOSES
• -canine and incisors are often composed of only acellular extrinsic fiber cememntum

Question 24

cellular intrinsic fiber cementum

Answer 24

-form of secondary cementum consists of collagne fibers parallel to cementum surface with no real attachment to the PDL

Question 25

cementocytes

Answer 25

what the CB are called after they are entrapped in mineralized matrix, no longer involved in synthesizing cementum

Question 26

mixed fiber cementum

Answer 26

• anther type of secondary cementum and comprises the bulk of the secondary cementum, contains both intrinsic parallel fibers and extrinsic perpindicular and continuous with the sharpey fibers and help with attachment.
• *secreted after and more slowly than the initial wave of secondary cementum, prominent apically and in interradicular region of multi-rooted teeth

Question 27

secondary cementum role

Answer 27

not as important of a role in attachment as primary cementum, but important for dentin protection and adaptation as it thickens most in response to occlusal forces

Question 28

cellular cementum

Answer 28

mixed fiber cementum and cellular intrinsic fiber cementum
less mineralized than primary
**both types of secondary cementum

Question 29

cementum is laid down throughout life, why?

Answer 29

(more slowly)

-dependent on environemental factors (attrition and perio disease, inflammation..)

Question 30

what can continued deposition of cementum cause?

Answer 30

apical foramen to become smaller

Question 31

how is cementum laid down throughout life, where are the active CB?

Answer 31

IN THE PDL, long axis parallel to CEJ

Question 32

cementoid

Answer 32

the outermost layer of cementum next to the CB in the PDL is sometimes unmineralized.

• analogous to predentin and osteoid (bone)
• *cementoid layer in mature tooth usually associated with cellular cementum

Question 33

are there growth lines in cementum?

Answer 33

YES

Question 34

hypercementosis

Answer 34

large amounts of cementum deposited around the root. difficulties for root canals and extractions **rare

Question 35

periodontal ligament

Answer 35

soft CT between cementum and the bony wall of the socket

• continuous with gingival CT cervically and apical foramen apically
• large collagen fiber bundles
• function is attachment-super thin, thinner with age

Question 36

cells of the PDL

Answer 36

fibroblasts are the most numerous, cementoblasts, osteoblasts, osteoclasts, epithelial cells (rests of mallasez), a variety of immune cells and undiff mesenchymal cells (stem cells)

Question 37

fibroblast of the PDL

Answer 37

• most numerous cell type in PDL
• secrete and degrade collagen
• large and well-defined cytoplasm (highly active cells)
• cell to cell contacts will desmosomes and gap junctions

Question 38

what do gap junctions do for the fibroblast?

Answer 38

synchronize collagen secretion

Question 39

fibroblast junciton with ECM

Answer 39

ex. fibronexus (fibroblast and fibronectin junction)
important because there is a functional link between oclusal forces that impinge on the ECM (can change FB orientation and speed or slow the produciton of collagne)

Question 40

where are fibroblasts most predominant?

Answer 40

in the central part of the PDL

Question 41

gingival vs. PDL fibroblasts

Answer 41

PDL fibroblasts have a 5X faster turnover, greater cell volume and higher proliferation rates

Question 42

junction interaction

Answer 42

all 3 are ultimately connecting the actin cytoskeleton of the FB to collagen in the ECM either through a transmembrane molecule or a complex of molecules

Question 43

how to tell a cementoclast in a histo section

Answer 43

has multiple nuclei!

Question 44

is cementum resistant to resorption?

Answer 44

yes (not like bone and PDL)

Question 45

when does resorption occur in cementum

Answer 45

shedding of deciduous teeth or trauma

**small regions of resorption are not uncommon in the roots of permanent teeth

Question 46

epithelial rest of mallasez

Answer 46

from HERS, closer to the cementum than alveolar bone in the PDL, lie in clusters, function is unclear, but when cell inflammed, can prolif and form cysts.
STEM CELL niche for periodontal regeneration??
**when sectioned perpendicular to collagen fibers they appear as a continuous network, not a cluster

Question 47

stem cells in the PDL

Answer 47

lie close to blood vessels, pluripotent that give rise to FB, CB and osteoblasts, maintain viability of peridontium
???can each cell differentiate into each of the cell types

Question 48

ECM PDL

Answer 48

collagen I and III (80:20 ratio) and turnover really fast, immautre (no mature) elastic fibers called oxytalin fibers (at right angles to colalgen). Ground substance is proteoglyc, gags, glycoproteins. gags help retain water, important for withstanding compressive loads (chewing)

Question 49

fibronectin

Answer 49

glycoprotein in PDL, ECM junction

Question 50

sharpeys fibers

Answer 50

ends of collagen fibers inserted into mineralized tissue

Question 51

cementicles

Answer 51

spherical calcified masses (like pulp stones)

Question 52

collagen fibers organized into bundles to attach adj alveolar bone to cementum are called

Answer 52

principal fiber groups

Question 53

what are the types of principal fibers?

Answer 53

alveolar crest, horizontal, oblique (most numerous), apical and interradicular (only in multirooted th)

Question 54

nearby group of collagen fibers that support the tooth and maintain integrity of the PDL

Answer 54

gingival ligament
ex. transeptal - cementum of one th , over alveolar crest to the cementum of adj th
others include circular, dentogingical, dentoperiosteal and alveologingival

Question 55

vascular supply PDL

Answer 55

profuse!

• superior and inferior alveolar a., also gingival arteries at the coronal PDL
• perforating arteries are terminal arteries that go through the foramina of the bony socket
• also near the apical foramen, branching

Question 56

what a. are less likely impacted by endodontic procedures?

Answer 56

perforating aa.

Question 57

aa. in the PDL lie close to?

Answer 57

the alveolar bone (surrounded by endothelial cells)

Question 58

PDL innervataion

Answer 58

• take same route as the blood vessles
• innervated by large Ab, Ad and C
• propri (Ab) and pain
• intertwined with principal fiber bundles

Question 59

Ab fibers in the PDL

Answer 59

each cell detects a different DIRECTION and FORCE, allowing a person to detect each
-sent to CNS to monitor chewing (diff food types)

Question 60

alveolar process

Answer 60

bone housing the sockets or “alveoli” of the teeth

Question 61

bone apical to the alveolar process is

Answer 61

basal bone

Question 62

where does the bony lining of the socket form from?

Answer 62

dental follicle

Question 63

what are the parts of the alveolar process?

Answer 63

outer cortical bone and central spongy (trabecular) bone and the bone lining the socket

Question 64

what are the names for the bone lining the socket?

Answer 64

-bundle bone (PDL inside), cribiform plate and lamina dura (radiopacity on radiograph) although its not more mineralized