L3- last of 'the tour' Flashcards
three types of junctions b/w a tooth and periodontal tissues
+ brief description
- gomphosis joint - via PDL, cementum and alveolar bone (bundle bone, cribriform plate, inner cortical plate
- Dentinocementum Junction (DCJ) - involves the hyaline layer of hopewell smith and cements the cementum to the mantle dentin
- CEJ - cementoenamel junction
- butt joint b/w cementum and enamel
- overlap of cementum onto enamel
- gap between cementum and enamel
what is cementum - general
principle function?
calcified covering over the dentin of the roots (50-200 um)
principle function = provide anchorage of tooth to alveolus through the collagen bundles of periodontal ligament SHARPEYS FIBERS
HARD AVASCULAR C.T.
- chemical structure more like bone
- mineralized outer layer - collagen fibers of periodontal ligament are inserted
T/F cementum becomes pathologically altered during Perio disease
TRUE – it can be lost following disease process and is associated with periodontal tx.
spontaneous and therapeutic regeneration of cementum has been difficult to achieve
major difference between bone and cementum
Cementum is AVASCULAR – so it NO OSTEON -LIKE STRUCTURES
- gets nutrition / vascular diffusion from PDL - not osteons
- relatively thin and limited repair /regeneration
is cementum a reservoir of minerals?
NO – therfore more static than bone
function of cementum
- attachment/ support via acellular cementum plus the hyaline layer
- adapation/ protection - during tooth movement and weating - via cellular cementum
- assist in mainting occlusal relationships - maintain width of PDL at apex
relationship between attirtion and cementum
attrition is the wear of the occlusal surfaces and with this there is continual erupting as a result which is termed ACTIVE ERUPTION – which is proportional to the amount of attrition – this process is accomplished via cementum deposits of cellular cementum at the apical ends of roots - which push tooth up
supraeruption
if no opposing force of tooth – continues to erupt via the deposition of cellular cementum at the apex of teeth with no antagonist tooth
which is less susceptible to resorption; alveolar bone or cementum?
cementum - so provides protection too
is cementum poorly mineralized?
composition?
yes - poorly mineralized.
60% inorganic (opposed to dentin which is 70% inorganic and enamel which is 95% inorganic)
bone composition
mineral
organic
water
mineral/ inorganic = 45%
organic = 30%
water = 25%
cementum vs bone
cementum contains ONLY TYPE I COLLAGEN
- more permeable
- no extensive remodeling like bone so DOES NOT TURN OVER – NOT RESORBED PHYSIOLOGICALLY
- 60% inorganic
- 27 % organic
ALVEOLAR bone
- 45 % inorganic
- 30% organic
- type I and type II collagen
resorption in cementum?
NOT PHYSIOLOGICALLY BUT IN PATHOLOGICAL CONDITIONS
- resorption due to inflammation
- resorption due to orthodontic tooth movement
cellular vs. acellular cementum
where?
turnover?
Cellular –> more towards apex and cementocytes get trapped in lacunae / in matrix as it calcifies (origin of cementocytes)
acellular –> covers coronal aspect of the root and has NO CEMENTOCYTES and after tooth errupts there is no longer any formation of this
two types of collagen in cementum
- intrinsic fibers – during initial formation and as the cementoblasts lay it down and calcification occurs – become trapped
- sharpeys fibers that get imbedded within the cementum from the PDL
- formed by fibroblasts
major cell types associated with cementum
- cementoblasts
- cementocytes
- PDL ligament fibroblasts
- odontoclasts/ cementoclasts
cementoblasts - origin and describe
from ectomesenchymal layer within the dental follicle – later on may come from undifferentiated cells in the PDL
- morphologically similar to fibroblasts - but located in close proximity to the cemental surface and extend cytoplasmic processes towards cementum
what do cementoblasts produce? how is this arranged
produce the intrinsic collagen fibers and their long axis is more/less parallel to tooth surface
(opposed to the extrinsic collagen fibers from PDL that are more/less perpendicular to tooth surface)
what secretes cementum matrix?
rate?
location?
cementoblasts do by apposition at the cemental surface
- grows slowly in thickess throughout life - but NOT REMODELED continuously (like bone)
cementocytes
how produced?
over rapid periods of cementogenesis - cementoblasts that become TRAPPED W/IN LUCUNAE – then have cytoplasmic processes extending toward cemental surface through canaliculi
- less organelles = less metabolic/ very little metabolic activity
periodontal fibroblasts considered cementum cells?
YES – b/c although not produced by them they become mineralized as they become incorporated into cementum - so they do contribute to cementogenesis
odontoclasts aka?
function?
type of cell?
aka –> cementoclasts
multi-nucleated giant cells
involved in the resorption process but are indistinguishable from osteoclasts
three relationships between cementum and enamel at the CEJ?
percentage of each?
can they co-exist?
30% = Butt joint – > do not overlap but meet up against each other
60-65% = OVERLAP (cementum overlaps enamel)
5-10% = GAP b/w the enamel and cementum - which can expose dentin on root - may have root sensativity problem
*these realtionships can co-exist on a single tooth
cementicles
describe + types?
implications
developmental anormality in which a clump of afibrillar or fibrillar cementum (or mixture) gets either attached/sessile to the cemental surface or lie free within the pdl adjacent to cementum – can mimick calculus and the attached ones may serve as a promoter of periodontal disease if exposed
imbedded ones have no clinical relevance
is cementum usually exposed?
clinical correlations
NO – usually covered by alveolar bone and gingiva
EXPOSED W/ GINGIVAL RECESSION OR PERIO POCKETS
PERMEABLE TO PLAQUE BACTERIA – so can get to the dentin subjacent to pathologically exposed cementum
can CT cells adhere to previously exposed cementum?
implication?
NO – cannot adhere to previously exposed OR toxin-containing cementum
clinical correlations to scaling and root planning relating to cementum
this process is aimed at removing claculus and bacterial deposits often removes the relatively thin layer of cementum — which leaves underlying surface with a ‘smear-layer’ and unknown findings whether or not this layer allows for new cementum formation – may be a clinically weaker junction now
new cementum formation? goal?
because cementum mediated attachment of the tooth to the PDL and bone this is a high sought out therapeutic measure - however limited repair and regeneration capacity
can alveolar bone fuse directly with cementum or dentin?
what is this called?
YES – ankylosis but this is undeserible b/c get increased resoprtion from osteoclast activity
function of the hyaline layer of cementum?
‘cements’ the cementum to the MANTLE dentin
acellular cementum primary function
attachment function
cellular secondary cementum function
ADAPTION
what makes PDL ligament ‘not’ a ligament in terms of its functions and characteristics
- rich vascular supply with array of cellular components for allowing homeostasis and repair
- hydrodynamic interactions is a key function
- vascular and lymphatic vessels to PDL supply nutrients and remove metabolic by-products
may be called PERIODONTAL MEMBRANE b/c ligament is a misnomer as a ligament is (usually) dense, avascular, band of connective tissue with limited ability to repair /heal
T/F the PDL contains the progenitor cells of the dental follicle necessary for regeneration of cementum and bone as well as PDL?
TRUE
five main key functions of the PDL?
- supportive
- nutritive
- sensory
- formative
- healing
extracellular fibers of PDL composition?
function?
composed mainly of collagens and associated molecules that CONNECT cementum with alveolar bone
cells in PDL that are responsible for maintenance and regeneration?
fibroblasts, neurovascualr elements of periodontal tissues like progenitor undifferentiated cells
how does PDL carry out adaption? via?
viscoelastic components
- designed primarily to withstand he considerable forces of mastication and/or bruxism & nocturnal grinding of teeth
how does PDL carry out attachement? via?
via tensile strengh components desginged to connect teeth to bone
how does PDL carry out sensory perception? via?
nerves – designed both to properly position the jaws during normal function and to withstanf the occlusal forces
how does PDL absorb light/moderate/ heavy forces?
light – ibtravascular fluid pushes out of blood vessels
moderate – extravascular fluids forced out of pdl space into adjacent marrow spaced
heavier– taken up by principle fibers
healing of bone grafts?
via the PDL
major blood supply for pdl
originating from dental arteries that enter ethe fundus of the alveoli
and major anastomoses exist b/w blood vessels in the adjacent marrow spaces and gingiva
are nerves of pdl myelinated?
the ones that perforate the fundus of the alveoli are but then they lose their myelination as they enter and branch to supply the pulp and pdl
nerve endings of pdl
primarily receptors for pain and pressure
describe the foramtive funciton of the pdl
provides cells that are able to form as well as absorb all the tissues that make up the attachment apparatus - bone (osteoblasts), pdl (fibroblasts), cementum (cementoblasts)
the undifferentiated ectomesenchymal cells are located around the blood vessels – can then differentitate into these cell types
bone and tooth -resorptive cells in pdl derived from?
ostecloasts and odontoclasts – generally multinucleated cells derived from blood-borne macrophages
principle fiber groups of pdl and compromised of?
all extend where
mainly type I collagen bundles
all extend from cementum to bne
- alveolar crest fibers
- horizontal fibers
- oblique fibers
- apical fibers
- interradicular fibers
60% of all pdl principle fibers are what type?
oblique fibers
alveolar crest fibers where
function?
run from the root to the osseous crest of bone
function – retain root in socket; oppose lateral forces - protect deeper periodontal ligament structures
horizontal fibers run where
function
horizontaly from bone to root
function - resist lateral forces
oblique fibers run where
function?
radiate from the apex of the tooth root to bone
function – resist axially directed forces
apical fibers where
function?
radiate from the apec of the tooth root to bone function - prevent tooth tipping and resisit luxation and protect blood, lymph and nerve supply to the tooth
interradicualr fibers where
function?
run from cementum in the bi-tri-furcations and spread APICALLY towards the furcal bone
function - aid in resisting tipping and torquing; resist luxation
mineralized vs. non mineralized portions of sharpeys fibers?
implication on names of these fibers
non-mineralized = what we actually call sharpeys fibers vs mineralized is the part in the ligament proper
diameter of type I and type III collagen mixture in PDL?
relatively big or small?
about 55nm
- considered relatively small
where are sharpeys fibers fully mineralized vs partially
fully –> acellular cementum
partially –> cellular cementum and bone
what type of elastic fibers are found within the PDL?
IMMATURE ELASTIC FIBERS
- Oxytalin & Elaunin molecules
Oxytalin & Elaunin molecules
IMMATURE ELASTIN FIBERS
- found within the PDL w/ extensive distribution
- running in an apico-coronal direction within the PDL
- forming a 3-D branching network that surrounds the root
- most likely functioning to regulate vascular flow in response to tooth function — viscoelastic shock absorber characteristics
main components of ground substance in PDL
Dermatan Sulfate is the main PG/GAG
PG and GAGS are most important in withstanding stress loads during normal function because of their high density of - charges and large water component (70% of mass in ground substance)
odontoclasts?
resemble?
resembling osteoclasts
resorbing cells include?
odontoclasts and mononuclear cells
mononuclear cells resemble?
macrophages
what serves as the main source of new cells? called what?
PDL is the primary source of the pluripotential cells (undifferentiated ectomesenchymal cells) that can be precursors to cementum, alveolar bone and fibroblasts
rests of mallasez?
where would they be?
can develop into?
in the PDL – remnants of hertwig’s epithelial root sheath
if present they are in the APICAL portion and have no known function
if proliferate they form LATERAL PERIODONTAL ROOT CYSTS
MAJOR VASCUALR SUPPLY TO PDL
THROUGH THE APICAL FORAMEN FROM THE BLOOD SUPPLY ORIGINATING FROM DENTAL ARTERIES
neural elements within PDL
myelinated vs unmyelinated?
responsible for the pressure and pain sensations as these are the associated free nerve endings
myelinated near the apical end and unmyelinated more coronally
closely following the distribution of the arterial supply
**these are what quantitate and locate the object when one bites down hard on something
mechanism of traction provided by the PDL?
compression and tension
- this is of the osseous socket wall during tooth eruption and orthodontic movement
what joint in pdl limits tooth movement during normal occlusal function?
gomphosis
what acts as a resoivor for the pluripotent cells recruited during periodontal wound healing?
PDL
repair and regeneration as it is a dynamic, biomechanical tissue
hypo and hyper function of the PDL
average width of pdl?
width is normally about .2mm – but alters based on the function of the loasds placed on the tooth
increases in width in hyperfunction
pdl decreases when not used for an extended period of time
major function of alveolar bone in the periodontium
- protection
- support
- reservoir of minerals – which reflects the dynamic status of bone
3 parts of the elveolar process
- cribriform plate
- supporting plate
- outer plate
cribriform plate
where? function? composition?
Closest to the pdl area and is of CORTICAL BONE which has the sharpeys fibers of the pdl inserted into it
supporting plate
where? function? composition?
between the cribriform plate and the outer plate
is of CANCELLOUS BONE –> has trabecular and marrow
- in children has marrow that is hematopetic
- in adults marrow is more fatty and converts to a fibrous state in periodontal inflammation
outer plate
where? function? composition?
what is special about this one?
THERE ARE TWO
- facial and lingual
- also composed of cortical bone and is covered with periosteum
*contious with the body of the maxilla and mandible
periosteum location?
layers?
function of layers?
covers outer plates and is composed of two layers
- outer fibroud layer
- inner cambium layer –> CONTAINS OSTEOBLASTS AND OSTEOCLASTS and their precuroses – so it is the active layer
three functions of the periostoeum
- attaches gingiva and alveolar mucosa to bone
- provides innervation, lymphatic drainage, and blood supply to bone
- participated in the healing of periodontal wounds
distinguish between alveolar process and alveolar bone
process –> portion of the jawbone that contains teeth and the alveoli in which they are suspended – RESTS ON BASAL BONE
bone –> lines the alveolus (or tooth housing) composed of a thin plate of cortical bone with numerous perforations (cribriform plate) that allows the passage of blood vessels b/w marrow and the pdl
proper development of alveolar process depends on?
tooth eruption and its maintenance on tooth retention
if adontia what fails to form?
when teeth fail to form –> the alveolar process fails to form
what happens to the alveolar process in edentoulism?
most of the process becomes INVOLUTED –> so leaves basal bone as the major constituent of the jawbone – therefor it is REDUCED in height
alveolar/ osseous crest
where the cribriform and outer plates MEET –> OSSEOUS CREST
- the most coronal portion of the alveolar process
interdental septum
portion of alveolar process that is located between the teeth
composed of the cribriform, outer, and supporting plates
position of osseous crest of bone
1 mm apical to the CEJ
*location is not altered by changes in the tooth position but can be changed via inflammation and trauma
bone morphology in relation to thickness
thickness of the cortical plates varies significantly from tooth to tooth
- labial and buccal plate generally thicer than lingual except in the incisor region
- palatal cortical plate is usually thicker than the facial plate of the maxilla
what is a major determinate for cortical plate thickness and contour
position of teeth in the arch
mesial distal sections - shape of the alveolar crest is determined by?
contour and width of the interdental space, degree of tooth eruption, and the position of adjacent teeth
CEJ relationship to alveolar crest
if CEJ’s are even - alveolar crest is more horizontal .. if they are on an uneven plane or inclined - then alveolar crest take on more of an oblique orientation
what appears light and dark on a radiograph?
what about the lamina dura?
non-mineralized tissues = dark
dense structures like teeth and bone appear LIGHT - like teeth and bone
LAMINA DURA – WHITE LINE that parallels the outline of the roots in a radiograph
radiographic term for line that parallels the outline of roots of the teeth
lamina dura
what does the pdl space look like on radiograph?
appears as dark line between the lamina dura and the root surface
trabecular pattern in which type of bone in alveolar process?
cancellous
bone produced by? origination of these cells?
osteoblasts – from a less differentiated precursor within the periosteum, endosteum and periodontal ligament
- ectomesenchymal differentiation
what is the system within the compact bone?
cylindrical units – osteons or haversian systems
- each osteon has a central haversian canal and linked to others via volkmans canal (which are perpendicular to them)
most of tooth support in center of jaw is provided by what type of bone?
cancellous bone
what does remodeling of alveolar process allow for?
normal migration of teeth in a MESIAL DIRECTION – or mesial drift (as interproximal sufaces ware down)
- also allows for orthodontic tooth movement and wound healing
a reversal line aka?
what does it identify?
REV
- dark staining scalloped line and outlines the resoprtion front created during the previous phase of bone resorption and the following it will be new bone deposited by osteoblasts within the PDL
fenestration in bone?
clinical variation which there is a hole in bone by totally circumscribed by bone
dehiscence in bone?
hole in bone with no coronal margin
where can holes be anticipated clinically?
in teeth which ahve prominant roots in the arch like maxillary cuspids and MB root of max first molar
difficult to see on radiographs
clinical importance of fenestrations and dehiscences
could worsen if go to do a gingival flap therapy
- surgical interventions could promote the conversion of fenestration to a dehiscences
also fenestrations can lead to dehiscences which in turn can lead to gingival recession
if root proximity is close what does this mean?
interdental space is narrow and the septjum may consist mostly of cortical bone –>
absence of any support between the teeth if a “window” b/w the teeth is found (connected at bottom then whole then reconnected)
resorption leads to?
mobility of teeth and the associated loss of function (Periodontal disease)
T/F bone is mineralized
TRUE – mineralized CT with a lot of type I collagen and other associated structures
what mechanism forms alveolar bone?
intramembranous
clinically, alveolar bone is manipulate during various types of what periodontal therapy
- resective surgery
- regenerative surgery
- implant surgery
