Oral Biology - bds Flashcards
when do the pharyngeal arches begin development?
4th and 5th week i.u
what does the 1st pharyngeal arch give rise to?
meckels cartilage
MOM
body of tongue
what is treacher collins syndrome?
failure of nerual crest migration, facial bone hypoplasia, ear abnormalities, clefts, tooth deformities
what does the 2nd pharyngeal arch give rise to?
facial muscles
how does fusion between the medial nasal processes happen?
by elimination of a furrow
how does fusion between the medial and nasal processes happen?
true fusion of seperate processes
when does the palate form and what does it do?
6-12 weeks
sperates oral and nasal cavities
how does the palate form?
at week 7 - the lateral palatal shelves are vertical because there is no space because of the tongue
at week 8 they flip into horizintal direction/contact each other at midline to form the secondary palate
what ossification takes place between the 6-7th week?
mandible
what ossification takes place at the 8th week?
maxilla
palate
nasal capsule
how does facial growth happen?
surface deposition and resorption
what is a cleft lip?
failure of fusion of maxillary and medial nasal processes
what forms in the 8th week i.u?
the palate
how does the mandible form?
6 weeks i.u meckels cartilage forms
7 weeks - bone formation starts at the mental foramen and spreads back and forward and up
symphis mentis fuses at 2 years after birth
what happens at 6 weeks i.u?
first sign of tooth development
condensation of mesenchymal cells
ectodermal epithelium thickens and protrudes into mesenchymal cells - primary epithelial band
what happens at 7 weeks i.u?
primary epithelial band becomes venstibular band and dental lamina
vestibular band - buccally - becomes vestibule
dental lamina - lingually - arch shape where tooth germ develps
what happens during 8 weeks i.u?
bud stage
enamel organs form for each tooth
what happens during 12 weeks i.u
cap stage inner layer - IEE outer layer - OEE under inner - dental papilla = pulp around = fibrous capsule = PDL
what happens during 14 weeks i.u?
bell stage
IEE - columnar cells - defines crown shape, become ameolblasts
SI - gives nutrients to and from ameloblasts
SR - protects tissues, maintains tooth shape
OEE - ccuboidal cells - joins IEE at cervical loop = hertwigs sheath of root formation = maps root shape
what is the process of dentinogenesis?
- IEE becomes the odontoblasts and secrete an unmineralised dentine matrix
- odontoblasts retreat as matrix is deposited and leave a process behind
- predentine is laid down at surface of pulp
- mineralisation starts at over 5um
- spherical zones of HA = calcospherites fuse together
- odontoblasts retreat in an s shape towards the papilla
what is the name of the 1st mineralised layer of dentine?
mantle dentine
what is the name of the rest of the mineralised dentine?
circumpulpal dentine
what are the stages of amelogenesis?
- ameolblasts form after deninte matrix
- calcium and phosphate ions secreted into the matrix and mineralisation starts
- cells move away from matrix and crystals form
- enamel prisms run from ADj to surface
- tomes process flattens and and the REE becomes the JE
what is the tomes process?
pyramidal secretory extension of ameolblast which secretes the enamel matrix at the ADJ
when does the root form?
and how does it happen?
after crown completion
HRS induces odontoblasts cells = cementoblasts
how does the pdl form?
the dental follicle is acted on by fibroblasts and collagen produced, becomes principle fibres of the pdl
how does eruption happen?
root formation begins and eruption starts
overlying bone is resorbed by osteoclasts
REE fuses with oral epithelium and becomes the epihelial attachment
- eruption continues until occlusion is met
what is the chemical composition of dentine?
70% inorganic - HA
20% - organic - collagen
10% water
where are dentinal tubules situated?
what do they contain?
run parallel to each other from pulp to ADJ
odontoblast process
what is peritubular dentine?
highly mineralised inside the tubules
what is interglobular dentine?
unmineralised dentine
what are incremental lines?
contour lines of owen due to pattern of dentinogenesis
what are neonatal lines?
primary teeth
1st perm molars
what is the granular layer of tomes?
narrow layer of dentine in root under cementum
what is secondary dentine?
laid down throughout life at pulp - decreases pulp chamber
what is translucent or sclerotic dentine?
obliterated tubules become translucent
what is reparative dentine?
laid down at pulp in response to stimulus
severe stimulus - process can be destroyed and contents of the tubule necrose = dead tract
what are the 3 theories of sensitivity and what are they?
innervation theory - nerve fibres pass into tubules
odontoblast theory - odontoblasts transmit nerve impulses
brannstomrs hydrodynamic theory - fluid movement
what is the composition of cementum?
65% inorganic - HA
23% organic - collagen
water
what is acellular cementum?
primary cementum
covers root dentine from CEJ to root apex
what is cellular cementum?
thin layer at apical third
secondary cementum
cementoblasts are embedded in matrix/inactivated
where does the CEJ sit?
60% of teeth - cementum overlaps enamel
30% of teeth cementum and enamel meet exactly
10% of teeth cementum and enamel do not meet
when does cementum resorption happen?
excessive masticatory stress or ortho loading
what is hypercementosis?
inreased thickening of cellular cementum bc chronic periapical inflammation/ excessive occlusal attrition. pagets disease
what is ankylosis?
cementum fibres fuse with alveolar bone of socket
what is concresece?
2 teeth fused by cementum
what is the job of pulp?
forms odontoblasts
nutrients to odontoblasts
sensory organ
defence cells
what is pulp?
a soft vascular connective tissue
at the apex of the root - blood vessels, nerves, lymphatics
where are odontoblasts found?
at the periphery of the pulp
what is the plexus of raschkow?
nerve fibres branching towards periphery of pulp beneath cell free of layer of weil
what is the marginal plexus?
situated around odontoblasts
with age - decreases volume of the chamber, increased collagen , decreased cellular content and nerve supply
what is the PDL and what is its role?
specialized fibrous connective tissue, collagenous fibres
- support
- maintains functional position
- forms, maintains and repairs alveolar bone and cementum
- proprioception
- rich blood supply - nutrients to cementoblasts
- proprioception
what are cell rests of malassez?
remnants of HR sheath found between collagen fibres of pdl
what are the gingival fibres of the PDL?
dentogingival - attached to cementum/fan out into gingival tissues
trans septal fibres - run horizontal from cervical area of one tooth to adjacent
alveogingival - alveolar crest to free gingiva
circular - encircle neck of tooth
alveolar crest - cervical cementum to alveolar crest
what are the principal fibres of the PDL?
oblique - alveolar bone to tooth
apical - apex of tooth adjacent to alveolar bone
horizontal - horizontal from cementum to adj alveolar bone
inter radicular - between roots of multirooted teeth and adj alveolar bone
what part of the periodontium is touch felt by?
PDL
what part of the periodontium is pain felt by?
dentine and pulp
PDL
what part of the periodontium is cold felt by?
gingiva
dentine
pulp
how is pulp innervated?
plexus of rashkow
marginal plexus
what are the layers of non keratinised mucosa?
superificial layer
intermediate layer
prickle cell layer
basal cell layer
what are prickle cells?
membrane coating granules discharge contents into the intermediate layer
how a gtn spray works
what is the form of non keratinised mucosa?
epithelium
lamina propria
submucosa
bone/muscle
what are the layers of keratinised mucosa?
keratinised layer
granular layer
prickle cell layer
basal cell layer
what types of cells are non keratinocytes?
merkel cells
melanocytes
langerhans
inflammatory
what are salivary glands made up of?
lobules
basic secretory unite of acini
what are the 2 types of acinous epithelial cells?
seruous cells
mucous cells
describe seruous cells?
polyhedral, thin watery secretions
describe mucous cells?
cuboidal. viscous secretion rich in mucous
when mixed what happens to mucous and seruous cells?
serous cells form a cap around the periphery of mucous cells - demilune
what are secretions controlled by?
autonomic nervous system
how does saliva reach the oral cavity?
passes through intercalated ducts to striated ducts tp excretory ducts to the oral cavity
what is the composition of saliva?
99.5% water.
0.5% =
glycoproteins - lubrication, pellicle, protection
amylase - starch to maltose
lactoferrins - antimicrobial
lysozymes - attack cell wall of bacteria
sialoperoxidase - conrols bacterial metabolism
histatins - inhibits candida
statheirn - inhibits calcium and phosphate precipitaion
PRP’s - encourage adhesion of bacteria and inhibit calcium and phosphate adhesion
immunoglobulins - antibodies to prevent infection
what inorganic ions are found in saliva?
bicarb and phosphate ions - buffer/regulate pH
calcium and phosphate maintain tooth integrity
what gasses are found in saliva?
dissolved oxygen, carbon dioxide, nitrogen
what is compact bone?
cortical/lamellar bone
outer layer of bone
haversian canals run along long axis of bone
osteoblasts deposit bone in concentric layers = lamellae
what are lacunae?
as matrix is deposited osteoclasts become trapped in hollows = lacunae = become inactive and osteocytes
what are canalliculi?
osteocytes have small processes which extend into lacunae which form small channels called cannaliculi
what is compact bone covered bone?
surrounded by dense connective tissue = periosteum
what is trabecular bone?
cancellous/spongy
delicate bony bars and sheets of bone = trabeculae which branch and intersect to form spongy network
how is bone remodelling done?
osteoclastic and osteoblastic activity
how does the bone of the maxilla differ to the mandible?
is more vascular and less dense than that of the mandible
what is the enamel pellicle made up of?
acidic prp's statherin amylase lysozyme albumin immunoglobulins gtf's glucose
what are mucins?
tissue coating found on hard and soft tissues
concentrates anti microbial molecules at the mucosal surface
lubrication, aligned by direction of flow
antimicrobial
what are prp’s?
acidic - affinity for HA - important for calcium and phosphate levesl
antibacterial
what is statherin?
prevents calcium and phosphate deposition
what is amylase?
digestive
bacterial repair
what is GTF?
encourages bacterial adhesion
what are immunoglobulins?
IgA/IgG in pellicle
inhibits growth of some species
what are cystatins?
inhibit proteases - some control in perio disease
what are hisatins?
antifungal
antibacterial - against s mutans
how does the pellicle form?
molecules attach immediately
1-2ums thick before bacteria attach
s.sanguinis attach and pellicle becomes plaque
rapid increase in 2 hours
what is found in the pellicle that has antibacterial properties?
amylases/cystatins/histatins/mucins/peroxidases
what is found in the pellicle that is antiviral?
cystatins
mucins
what is found in the pellicle that is antifungal?
histatins
what is found in the pellicle that is tissue coating?
amylase cystatins mucins prps statherin
what is found in the pellicle that is lubricating?
mucins
statherin
what is found in the pellicle that is mineralising?
cystatins
histatins
prps
satherins
what digests in the pellicle?
amylase
mucins
lipase
what buffers in the pellicle?
histatins
carbonic anhydrases
what is the job of the pellicle?
selective absorption
diffusion barrier
renwable lubrication - protects from attrition and abrasion
what are strong calcium phosphate inhibitors?
moderate?
weak?
satherin, acidic prps
histatins, cystatins
mucins and amylase
where does lingual lipase come from?
serous glands of von ebner
1st phase fat digestion
what are the components of the periodontium?
PDL
alveolar bone
gingiva
what is the role of bone in the periodontium?
rigidity
attachment of muscles and teeth
what is the composition of bone?
65% - largely HA
25% - organic - 90% type 1 10% ground substance
10% water
how often is bone completely replaced?
every 10 years
how is bone arranged in alveolar bone?
lamina dura fills socket
surrounded by cortical and contact bone
filled with trabeculous bine
what is the role of calcium?
decreased membrane permeability
decreased cell excitability
hard tissue formation
blood clotting
what is the role of the parathyroid gland?
PTH released in response to reduced calcium,withdraws calcium from bone
what is the role of calcitonin?
released from c cells
prevent high levels of calcium
what is the role of vitamin d?
increased calcium absorption in the intestine
what are the eruption push theories?
root formation
pulp proliferation
bone formation
fluid pressure
what are the eruption of pull theories?
pdl - collagen contraction
fibroblast contraction
fibroblast migration