Lecture 5 & 6 Flashcards
Thickness of cementum?
20um at CEJ, 200um at apex
T/F - Dentine is covered by cementum in cervical region of tooth
False - it covers dentine in roots of teeth
Cementum is vascular like bone
False - it is avascular
Cementum has a nerve supply
False - does not have nerves
T/F - Cementum has similar consistency and hardness to bone
True
Is cementum sporadically cellular
True
T/F - Cementum readily remodels
False, it does not readily remodel. But it can remodel on a very small scale (applied in orthodontic treatments) to accommodate reattachment of periodontal collagen (Sharpey’s fibres)
Sharpey’s fibres are periodontal collagen
True
Cementum is formed quickly throughout life T/F
False
Cementum life formation can result in a gradual thickening that is approximately two-fold
False, it results in thickening of approximately three-fold.
What are the features of cementum?
Matrix and cells
What does matrix consist of?
Ground substance and collagen
T/F - some collagen is intrinsic in fully-formed cementum, some is extrinsic
True
Extrinsic cementum are ends of collagen fibres which do not extend into PDL
True
Ground substance is dissimilar to bone
False
Cementoblasts are located within cementum, which produces cementum
False, they are located on surface of cementum
Cementocytes are located on surface, and breakdown cementum
False, they are located within cementum, and produce cementum
Cementoclasts/odontoclasts are located on surface of cementum and produce cementum
False, they are located on surface of cementum but they breakdown cementum
Cementoblasts produce matrix T/F
True
Matrix consists of inorganic ground substance and intrinsic collagen
False - it’s organic ground substance!
T/F - Some collagen in cementum is derived from periodontal ligament fibroblasts which are intrinsic fibres
True in first half, false for fibroblasts - they are extrinsic fibres.
T/F - Cementoblasts produce matrix vesicles which are not involved in mineralization.
False, they do play in mineralization.
Cavities in cementum are called ?
Lacunae
Long processes in cementum are called?
Canaliculi
Lacunae and canaliculi are directed towards source of nutrition - T/F
True, the blood vessels in the periodontal ligament
Adjacent canaliculi are often connected - T/F
True
Gap junctions exist between processes of adjacent cells
True
Cementocytes in deeper parts of cementum do not degenerate normally and die
False
Osteocytes in deeper parts of bone remain viable
True
Lacunae are variable in size and shape but usually 10-30um
False, they are usually 7-20um.
Cementoclasts are single nucleate cells derived from blood monocytes as are other phagocytic cells
False - Cementoclasts are multinucleate
T/F - Cementoclasts/odontoclasts exist on cementum surface, and are comparatively common since cementum readily undergoes remodelling.
False - cementoclasts are uncommon, since cementum does not readily undergo remodelling
Most roots of permanent teeth show small areas of ________ which may extend into dentine. Cause unknown but may be result of _______
FOCAL CEMENTUM RESORPTION. local microtrauma
Regions of focal resorption may be subsequently be repaired by _________
cementoblasts
___________ extends from periodontal ligament into cementum.
Extrinsic collagen
Extrinsic collagen is formed by ____________
periodontal fibroblasts, collagen forms first, cementoid/cementum is laid down around it
Coarse fibres of extrinsic collagen are ________ (diameter)
5-7um diameter
__________ is a general term for collagen which is partly embedded in mineralised tissue and partly in general connective tissue
Sharpey’s fibres
___________ is totally within cementum. It is formed by cementoblasts/cytes. It’s ____ fibres are _____ (diameter)
Intrinsic collagen. Fine, 1-2 um diameter
Cementum is classified on the basis of three factors:
1) whether it incorporates cells (cementocytes)
2) whether it contains collagen fibres
3) whether collagen within cementum consists of large or smaller fibres
1) acellular/cellular
2) fibrillar/afibrillar
3) extrinsic fibres/intrinsic fibres
What are the two common types of cementum in humans?
acellular extrinsic fibre cementum + cellular intrinsic fibre cementum
Summarise acellular extrinsic fibre cementum (AEFC)
No cells,
sharpeys fibres only (can be seen in LM),
cervical 2/3 of root
Summarise cellular intrinsic fibre cementum
contains cementocytes,
intrinsic fibres only (not visible in LM without special staining,
in apical part of root
When does cellular intrinsic fibre cementum form?
During latter part of root development.
When does acellular extrinsic fibre cementum form?
Forms during earlier part of root development, usually found in apical part of root
AEFC forms comparatively _____ and consists of closely packed ____________ Sharpey’s fibres embedded in _______
slowly, fully calcified, cementum matrix
CIFC forms during the _____ part of root development and is usually found in ______ part of root and is often interspersed with ________________
latter, apical, cellular mixed fibre cementum
Cellular mixed fibre cementum consists of _________ containing ___________ oriented mostly parallel to the surface, plus _______ containing cementocytes. Their __________ processes are contained within ________ which are mostly oriented towards the ________ ligament. Cellular _______ may not be present in ______ rooted teeth.
cementum matrix, fine intrinsic collagen, lacunae, long cytoplasmic, canaliculi, periodontal, cementum, single
Summarise CELLULAR MIXED FIBRE CEMENTUM
Contains:
1) cells
2) both extrinsic and intrinsic fibres
3) identify in LM by presence of both cells and extrinsic fibres
4) apex and bifurcation of root
CMFC usually forms later at the _____ & ______ of the root & is often interpersed with other types of cementum. Consists of cementum matrix containing a mix of ___________ oriented obliquely or at right angles to the surface plus _________ plus ________ and their canaliculi and lacunae.
Apex, bifurcation, large extrinsic fibres, small intrinsic fibres, cementocytes
Summarise ACELLULAR AFIBRILLAR
- no cells
- probably no collagen
- very restricted in location - cemento-enamel junction
Acellular fibrillar cementum can only be recognised with certainty in EM, but is generally described as being mostly restricted to the _________. This type of cementum is reported as lacking __________
Cementoenamel junction (CEJ), collagen fibres
Alternative terminology for cementum. _______ is restricted to first formed cementum, and others to describe cementum formed prior to formation of some or all of the root.
primary and secondary cementum
T/F - Cementum is laid down slowly throughout life but does readily remodel.
False - it does not readily remodel
Cementodentinal junction can be recognized by adjacent __________________ in _______. There is also a very thin structureless, highly layer of mineralized tissue between cementum and dentine - ______________.
granular layer of Tomes, root dentine, hyaline layer of Hopewell-Smith
Hyaline layer of hopewell-smith is _____ thick. It is the product of ___________ not cementoblasts. It is an organic matrix more like ______ than dentine (amelogenins). It is more mineralized than _____ and mineralizes later than the adjacent _______. Its function is adhesion of _______ and ______. It can sometimes be recognized on demineralized sections as ______ or poorly stained line between ______ &_____.
10-20 um, epithelial root sheath cells, enamel, dentine, mantle dentine, cementum, dentine, thin unstained, root dentine, cementum
___________ can form in cementum but do not have the regular pattern or specific names of ______ in other parts of tooth.
Incremental lines
About 35% of human roots incorporate small globular masses of cementum called _________, either in the ______ ligament or attached to or wholly within cementum.
cementicles, periodontal
In some instances, cementum may thicken excessively forming ________ on surface of normal cementum which may complicate _______
hypercementosis, extractions
Hypercementosis thickenings are usually ______, but in some abnormal conditions, e.g. _______ may be quite extensive
local, Paget’s disease
Orthodontic movements & Mesial drift:
bone is resorbed on the side of pressure, either due to an orthodontic device or to _____ forces, which cause teeth to drift ______ with time
occlusal, mesially (move inwards)
What are the features of periodontal ligament?
Connective tissue attachment between tooth and aveolar bone,
consists of general connective tissue
provides mechanical protection against excessive occlusal load,
has proprioreceptors which play a role in regulating jaw reflexes
Fibroblasts are involved in _________ - laying down, maintenance, breakdown.
Collagen remodelling - allows for tooth movements and eruption
Fibroblasts have ________ nuclei which are mostly aligned with direction of __________ which are best seen in the light microscope, however there are an extensive ______________ as well.
elongated, collagen fibres, branches cytoplasm
Undifferentiated cells can differentiate into ______, ______ or _______
fibroblasts, osteoblasts, cementoblasts
_____________ are groups of epithelial cells in the periodontal ligament, which are remnants of Hertwigs Epithelial Root Sheath (this is part of _______ which is involved in root formation. Hertwig’s epithelial root sheath mostly breaks down after root formation, but some remnants are normal.
Rests of Malassez, enamel organ
Rests of Malassez are recognized as tightly packed groups of _____________. If viewed three dimensionally, often forms a network of ______ with a dense nucleus, joined by _______ & _________.
deeply staining nuclei, small dark cells, desmosomes, gap junctions,
Rests of Malassez are surrounded by a ___________ - not visible in light microscope without special staining
basal lamina
T/F - Rests of Malassez have a close relationship with nerve endings and small blood vessels
True
T/F - there is evidence that rests of Malassez are involved in BOTH periodontal pathologies and in normal maintenance of periodontium.
True
T/F - Periodontal ligament fibres are comprised of collagen and mature and functional elastin called ________
False, its immature, and its called oxytalin fibres
T/F - Collagen of periodontal ligament is not highly oriented
False
Periodontal ligament: gaps between collagen bundles are _________
Interstitial tissue (sometimes interstitial spaces, but they are areas of loose CT
T/F - Collagen fibres insert into bone at one end and cementum at the other. Inserted fibres are called sharpey’s fibres!
True
T/F - Sharpey’s fibres in cementum are not finer than bone
False
T/F - Collagen has a slow turnover, fine collagen fibrils intertwined like the fibres which form the subunits of a rope.
False, they have a rapid turnover
What is the average width of collagen bundles/fibres?
About 5um, but can be very variable between teeth, within a tooth and with age
What is oxytalin?
Immature elastin
What is oxytalin produced by?
Fibroblasts
How is oxytalin oriented?
It is mostly oriented longitudinal in the periodontal ligament.
Can oxytalin attach to bone?
Rarely, and it may attach to cementum
T/F - Oxytalin is closely associated with periodontal blood vessels, and may play a role in regulating blood flow.
True
T/F - Fibre groups of periodontal ligament function to retain tooth in socket and resist lateral, vertical and shearing forces
True
T/F - Alveolar crest group exists between cementum to bone in a coronal direction, and are the most numerous
False, they exist between cementum and rim of alveolus, just below CEJ. Alveolar crest group resists horizontal movement.
T/F - Horizontal group exists between cementum to bone just below alveolar crest
True, resists horizontal movement.
T/F - Oblique group exists between apex of root to bone of socket.
False, it exists between cementum to bone in a coronal direction and is the most numerous.
T/F - Oblique group of periodontal ligament fibres resists horizontal pressure/movement
False, they resist vertical pressure which could drive root into socket.
T/F - Interradicular group is located at the bifurcation of root to interradicular septum.
True
T/F - Apical and interradicular group of fibres both help to stabilise tooth in socket.
True.
T/F - Venous and lymph drainage is into the bone of the alveolus
True
T/F - Minor arteries supply the maxillary and mandibular teeth
False, superior and inferior alveolar arteries supply the teeth.
T/F - Branches of superior and inferior alveolar arteries pass within the alveolar bone and through foramina vertically into the periodontal ligament, but they do not form a capillary plexus.
False, they pass horizontally into the ligament and they do form a capillary plexus.
T/F - Both blood and lymph vessels have an endothelial lining and lumen
True
T/F - periodontal ligament have mechanoreceptors, both free-endings (schwann cells without fibrous capsule) and encapsulated endings
True
____________ generally have a collagen capsule - the axon within branches to form fine _________ with interspersed collagen. _________ displaces the collagen and the axon terminals respond.
encapsulated endings, intertwined endings, mechanical stress
T/F - periodontal ligament nerves are sympathetic (vasomotor) and parasympathetic
True
T/F - Periodontal ligament does not narrow with age
False, it does narrow.
