Histow Flashcards
% composition of enamel? What is the main mineral component?
96% inorganic
Calcium phosphate aka Hydroxyapatite arranged in prisms
1% amelogenins (main protein) and enamelins contained in enamel tuft
3% water
*Dentin: 70% inorg
*cementum: 55% inorg (calcium salts)
Enamel prisms are arranged…
Approximately PERPENDICULAR to the dentin at the dentinoenamel junction following a wavy course towards enamel surface
Gnarled enamel vs straight enamel
Gnarled enamel - prisms are twisted in a random manner, located over cusps and ridges of premolars and molars, rarely fractures
Shallow, transverse, wavelike grooves visible under reflected light parallel to the CEJ, surface manifestation of the lines of Retzius
Perikymata / imbrication line of Pickerill
- encircles the surface of enamel on anatomic crown
Some sources: perikymata - cervical ridges
Imbrication lines - grooves between
Brown lines seen in ground sections at the enamel
Incremental striae (lines of Retzius)
-indicate variations in deposition of organic matter in enamel which later calcifies
Hypomineralized area
Line where enamel is being deposited at birth
Neonatal line
- represents accentuated lines of Retzius
- reflects metabolif changes at birth
-present in dentin
Enamel Internal to it: formed before birth and has fewer defects
Enamel External to it: formed after birth
Alternating light and dark bands seen under oblique reflected light in longitudinal ground sections
Hunter-Schreger bands - DEJ to external surface of enamel / inner 2/3 of enamel (due to periodic changes in the enamel prism direction)
LIGHT ZONE: PARAZONE
DARK ZONE: DIAZONE
Area of poorly calcified enamel that extend from outer surface into the tissue for variable distances
Enamel lamellae - sometimes completely through underlying dentin
Extension of adjacent odontoblastic processes that continue into enamel (left behind kasi)
Enamel spindles - various terminations (pointed, sharp, rounded)
Areas of hypocalcification in prisms and interprismatic material (calcification imperfections in enamel prisms) that starts at DEJ and penetrates into enamel
Enamel tufts - start at DEJ and penetrate into enamel about 1/3 of its thickness
Enamelin: organic material in enamel tufts
Some patients experience pain on tooth may be due to:
A. Enamel Tufts
B. Enamel lamellae
C. Enamel spindles
D. Striae of Retzius
C
Cause of sclerosis in dentinal tubules
Increase formation of peritubular dentin = decrease permeability
Optical phenomenon due to cyclic activity of the odontoblasts during dentin formation
Incremental lines of von Ebner (perpendicular to the dentinal tubules)
Sa DENTIN TO!!
Completion of radicular dentin formation
(closure of apex)
Primary: 18months after eruption
Permanent: 2-3yrs after eruption
Tomes fiber vs tomes process
Odontoblastic process: tomes fiber
Ameloblast extension: tomes process (responsible for enamel secretion)
Main bulk of dentin?
Intertubular dentin
Immediate wall material which is the peritubular dentin was previously called?
Sheath of Neumann
Type of dentin that lines the pulp?
Secondary dentin -can sometimes obliterate the pulp
Type of dentin that develops at localized sites stimulated by local irritation
Tertiary or reparative or irregular dentin
Type of dentin resulting from stimuli that causes calcification of the odontoblastic process
Sclerotic or transparent dentin - hypercalcification = harder and denser dentin
Seen where tome’s process has disintegrated
Dead tracts in dentin - black in transmitted light, white in reflected light
Location of cellular and acellular cementum
Acellular deposited slowly from CEJ to 2/3 of root
Cellular rapidly forms and predominantly in apical 3rd and furcations
Two types mingle in the apical 3rd of the root
Most common type of CEJ
Acellular cementum overlaps the cervical enamel (60%)
Cementum and enamel meet at a sharpt point (30%)
No direct connection (10%)
Involved in dentin formation that originates in the pulp
First sign of mantle dentin formation
Von Korff’s fibers - type 3 collagen fibers (reticular) + fibronectin
Calcospherites failed to fuse completely will result to?
Areas of dentin matrix with tubules that are incompletely calcified (interglobular dentin frequently near DEJ)
Principal fibers that can prevent rotation of the tooth and preclude occlusal displacement
Alveloar crest fibers - cervical cementum to alveolar crest
**Horizontal fibers can also check rotation of the tooth (cervical cementum horizontally to alveolar bone)
Principal fiber that prevents tooth from being forced into the socket
Oblique fibers - cementum occlusally to alveolar bone (obliquely), largest group
Fibers that prevent rotation of tooth by radiating out like a fan from the apical region of root
Apical fibers
Fibers that maintain the mesiodistal relations
Transseptal fibers
Alveolar process two regions: internal cancellous layer and lamina dura. Other name for lamina dura?
Cribriform plate - it contains many apertures for vessels coursing between the marrow cavities and the PDL
Type of bone that lines the socket after teeth have been subjected to stress
Bundle bone
periods of prenatal development
proliferative (0-2 weeks IU) least vulnerable
embryonic (2-8 weeks IU) most vulnerable
fetal (8 weeks-9 months)
16 cell zygote
morula
blastocysts is when there is a fluid filled center (yolk sac)
lines the primary yolk sac and aids implantation (becomes placenta)
trophoblast cells -digests endometrial cells
embryoblast will form bilaminar germ disk or embryonic disk (embryo proper)
two-layered disk
bilaminar germ disk or embryonic disk
becomes:
ectodermal layer: lines amniotic cavity
endodermal: lines yolk sac
before placenta forms, what provides nutrition of embryo? … through??
yolk sac through vitelline arteries
week when bilaminar becomes trilaminar disk? what is it called?
period of gastrulation
3rd week of gestation
gastrulation and neurulation events
3rd week
ectodermal layer thickens (neural plate) –> neural folds –> neural groove –> meets at the middle –> neural tube (brain and spinal cord)
migration of neural crest cells/ ectomesenchyme (from ectoderm) becomes face and teeth EXCEPT ENAMEL; gives rise to neural, endocrine, pigment cells, skeleton, CT of head and neck
when: heart begins to beat?
4th week
derivatives of ectoderm, mesoderm, endoderm
ectoderm
nervous system
sensory epithelium of eye, ear, nose
mammary and cutaneous glands
epithelium of the sinuses, oral and nasal cavities, intraoral glands
tooth enamel
CT of head and neck
mesoderm
muscles
CT derivatives (bone, cartilage, blood, PDL, cementum, pulp etc)
endoderm
GI tracct
lungs
liver, gallbladder, pancreas
urinary bladder
when is the neural tube formed/fused?
18 days - 20 days
when: facial development
3rd to 7th week IU
four major tissue masses for facial development
frontonasal process
LEFT AND RIGHT maxillary processes (PA1)
mandibular process (PA1)
3rd Week IU
rapidly developing brain + heart = embryo folds
*stomodeum - primitive mouth; bounded by frontal prominence and PA1
*presence of buccopharyngeal membrane (ectoderm and endoderm)
end of 3rd week: first PA has divided into right and left Maxillary process and mandibular process
separates the primitive mouth from the foregut
buccopharyngeal membrane - ecto and endoderm
4th week IU
buccopharyngeal membrane disintegrates
nasal pits on the frontonasal process –> median nasal process, left and right lateral process
heart begins to beat
tongue begins to develop
5th week IU
fusion of medial nasal process –> philtrum, middle of upper lip, **globular process* –> primary palate/premaxilla
lateral nasal process forms the ala of nose
eyes become prominent at the side
Md arch loses midline constriction
6th week IU
lateral growth of brain
broadening of face
upper lip forms (MxP + MNP)
6 auricular hillocks (hillocks of His) - from BA1 and BA2 (pharyngeal grooves?) –> external ear
7th week IU
eyes approach front of face
development of the secondary palate –> completed by 3rd month
maxi process –> two palatine shelves develop –> secondary palate
palatine shelves + nasal septum –> separation of oral and nasal cavities
PALATE DEVELOPMENT
what forms the upper lip??
Maxillary process + median nasal process
*failure of fusion = cleft lip
when and how: palate development
starts 7 weeks IU
palatal closure: approx 12 weeks
from globular process of MNP –> premaxilla/primary palate
from palatine shelves of L&R maxi process –> secondary palate
*FUSION OF PRIMARY is from posterior to anterior
*FUSION OF SECONDARY is from anterior to posterior
**may contact sa gitna kasii tas dun magstart magfuse
when and how: development of tongue
4 weeks IU
anterior 2/3
-right and left lateral swellings + tuberculum impar of (BA1)
posterior 1/3 - posterior to old buccopharyngeal membrane
-Copula (BA2) + hyprobranchial eminence (BA3 and BA4) –> eminence grows OVER copula (matatakpan)
-epiglottal swelling (BA4)
marks the development of epiglottis
posterior part of the 4th BA (epiglottal swelling
former location of thyroid gland
foramen cecum –> bababa thyroid with thyroglossal duct (parang string then mawawala)
facial and palatal clefts: critical period?
6th and 7th week IU
oblique facial cleft is the failure of fusion of?
lateral nasal process and maxillary process
bilateral cleft lip is the failure of fusion of?
median nasal process and left and right maxillary process
median cleft lip is the failure of fusion of?
left and right median nasal process at midline
*magkalayo ang median nasal process before kasi
lateral facial cleft is the failure of fusion of?
maxillary process and mandibular process
only BA that extend to the midline??
BA1 and BA2
How was the smooth surface of neck formed? when?
fusion of BA2 and BA5 to eliminate features of 2, 3, 4 BA
5th week!
BA1 structures?? (Mandibular arch)
Maxillary artery
Trigeminal nerve
MOMs
tensor tympani and tensor veli palatini
mylohyoid
anterior belly of digastric
malleus, incus, sphenomandibular, Meckel’s
external ear, middle ear, eustachean tube
BA2 structures?? (hyoid)
hyoid artery, stapedial artery
facial nerve
MOF
stapedius, stylohyoid, POSTERIOR digastric
stylohyoid ligament
LESSER horn of hyoid
supratonsillar fossa
BA3 structures
internal carotid artery
glossopharyngeal nerve
stylopharyngeus
GREATER horn of the hyoid
INFERIOR parathyroid gland
thymus
BA4 structures
right subclavian artery
aorta
Vagus nerve
levator veli palatini
palatoglossus
pharyngeal constrictors
cricothyroid
SUPERIOR parathyroid gland
from what B.A is the parafollicular cells from?
parafollicular cells of thyroid gland (calcitonin) is from BA5
BA: hyoid??
both BA2 (lesser) and BA3 (greater horn)
horseshoe shape that will correspond in position to the future dental arches (week??)
Primary epithelial band (6th week IU)
-invagination of the thickened band of oral epithelium into the ectomesenchyme (NCC)
primary epithelial band will divide into?? contribute to?? (week??)
7th week
1. dental lamina - development of teeth
2. vestibular lamina - vestibule of mouth
local thickening that develop within the dental lamina corresponding to the positions of the 20 primary teeth?
dental placodes - will proceed to the bud, cap, bell stage
*successional lamina - LINGUAL extensionn that will give rise to the succedaneous teeth
three parts of tooth germ in the cap stage
enamel organ (from dental lamina) - enamel
dental papilla (from ectomesenchyme) - pulp-dentin complex
dental follicle (from ectomesenchyme) - cementum, pdl, alveolar process
3 layers of enamel organ
outer enamel epithelium
inner enamel epithelium
stellate reticulum - between IEE OEE
*cap stage
bell stage histodifferentation
IEE –> becomes pre-ameloblast –> urges adjacent cell to become pre-odontoblast –> mature odontoblast –> lays down uncalcified pre-dentin –> calcification of dentin induces –> maturation of ameloblast –> enamel deposition
site of CEJ
Cervical loop - formed when IEE and OEE meets; gives rise to Hertwig’s and epithelial diaphragm
seen in Bell stage
remnant of dental lamina entrapped within gingiva; important in pathology
cell rests of Serres
signals site of future cusp tips
enamel knot
First dentin formed is found at?
Incisal or cusp area
Towards cervical loop
new layer of collagenous dentinal matrix laid down not yet mineralized
Predentin
How many microns of dentin is deposited and mineralized?
During crown development and eruption:
4microns deposited in a 24 hr period
2microns mineralized in a 12 hr period
Period of function:
Less that 1 micron deposited per day
First and outermost layer of dentin
Mantle dentin mineralized by globular mineralization aka calcospheric mineralization
Succeeding layers formed after mantle dentin
Circumpulpal dentin (linear mineralization)
Picket fence or saw tooth appearance between enamel and ameloblast
Tome’s process –> rod and interrod structure of enamel
**Ameloblastoma
Very first and very last layer of enamel to be laid down
Prismless enamel
Responsible for Maturation of enamel
Ruffle ended ameloblast: adds calcium
Smooth ended ameloblast: removes organic part
Globular mineralization of mantle dentin
Von korff’s -> odontoblast secrete matrix vesicles which contain HAP crystals –> increase size of HAP –> HAP breaks out from vesicle –> touch each other pero may gaps (interglobular dentin)
Contributes to the reduced enamel epithelium
IEE
OEE
*Stellate reticulum
*S. Intermedium
How was hertwig’s root sheath formed
Aka epithelial root sheath
*Cells in the cervical loop (IEE + OEE) proliferate
Acellular cementum that covers the ends of dentinal tubules and seals root surface
Intermediate cementum
Remnants of HERS in PDL
Epitheloal cell rests of Malassez
Uncalcified cementum? Secreted by?
Cementoid secreted by cementoblast that differentiated due to tooth follicle being in contact with the exposed root surface
Area where root sheath bends at 45-degree angle
Epithelial diaphragm
Responsible for the formation of multi-rooted teeth
Epithelial diaphragm -encircles apical opening of the dental pulp during root development
Development of root
Cervical loop - HERS - odontoblast differentiation (inner) to form dentin - HERS deposit intermediate cementum - root sheath cells disperse away (Malassez) - mesenchymal cells differentiate to cementoblast - cementoid - cementum
Eruptive movements phases
- Pre eruptive - movement made by primary and permanent tooth germs w/in tissues of jaw
- Eruptive - within crypt to functional position
- Functional eruptive /post eruptive
Pre-eruptive movement of primary and permanent teeth (direction/location)
Primary - facial and occlusal or with growth of face
Developing permanent anterior - lingually near apical 3rd of primary
Developing permanent premolars - furcation of primary molars
Developing permanent molars
-upper molars: develop in Mx tuberosities occlusal surfaces slanting distally
-lower molars: develop in the base of mandibular rami withsurface slanting mesially
When does the eruptive phase begin? First clinical sign?
Begins with the initiation of root formation and ends when the teeth reach occlusal contact
Emergence is the first clinical sign
Contributes to the junctional epithelium
REE + oral epithelium
Believed to guide teeth towards complete tooth eruption
Gubernacular cord aka gubernacular dentis contained in gubernacular canals
present on succedaneous teeth
Delicate membrane that covers the entire crown of newly eruptive teeth (2 names and from what structure??)
Primary enamel cuticle aka Nasmyth’s membrane from reduced enamel epithelium. Removed by mastication
Causes for functional eruptive / posteruptive phase
Accommodation of growth
Compensation for occlusal wear
Accommodation for interproximal wear
Factors that can cause mesial drift (functional eruptive)
Anterior component of occlusal force
Contraction of transseptal ligament
Soft tissue pressures
Contributes to the ruffled-border appearance that suggests resorption of primary tooth
Odontoclast
Causes of exfoliation: odontoclast and pressure from erupting successional teeth
Submerged teeth successional tooth does not exist
Boundrary between rod and interrod enamel is delimited by a narrow space containing organic material called?
Rod sheath
Predominant form of human enamel (cross section)
Pattern III: Keyhole pattern
Pattern I: Circular
Pattern II: aligned in parallel rows
Represents 24-hour cycle of incremental growth of enamel
Cross striations (short term apposition)
Represents incremental growth pattern of enamel over a week or 5-10 days (longitudinal and cross section???)
Enamel striae aka incremental lines of Retzius -Longer apposition
Longitudinal: oblique lines from DEJ to surface
Cross-sectional: concentric lines
initiation
bud stage
cap stage
bell stage
appositional stage
happens in what week?
initiation = 6th week
bud = 8th week
cap = 9th week
bell = 11th week
appositional = 14th week
defects that can occur due to abnormalities during the initiation stage?
anodontia or supernumerary
defects that can occur due to abnormalities during the cap stage?
dens in dente, gemination, fusion, tubercles
defects that can occur due to abnormalities during the appositional stage?
enamel dysplasia, concrescence, enamel pearls
last layer of enamel secreted by ameloblast
Nasmyth membrane / primary enamel cuticle
membrane between enamel organ and dental papilla, makes the DEJ
membrane performativa
-gives rise to shape of crown
defects that can occur due to abnormalities during the bell stage?
dentinogenesis and amelogenesis imperfecta, micro/macrodontia
mineralization stage takes ___ to complete
2 years; it starts at DEJ = first enamel and dentin is formed here
composition of dentin
70% inorganic calcium hydroxyapatite crystals
20% organic (mostly type 1 collagen)
10% water
directly underlies mantle dentin and comprises the bulk of the tooth’s primary dentin
circumpulpal dentin - contains smaller in diameter and more randomly oriented collagen fibers
*more mineralized than mantle dentin.
reactionary vs reparative dentin
both are tertiary type of dentin
reactionary - from preexisting odontoblast and due to mild injury. tubular and continuous with primary and secondary dentin
reparative / osteodentin - newly differentiated odontoblast, more severe pulpal incure, atubular, deposited immediatedly adjacent to it
path of dentinal tubules seen in ground sections
crown: S shaped
root: straight
*dentinal tubules are larger near the pulp, more surface area of dentin, and there’s increased number of tubules
primary content of the dentinal tubule
Tome’s process
*if it dies or distintegrates, = empty dentinal tubules = dead tracts
band of newly formed unmineralized matrix of dentin at the pulpal border of dentin adjacent to odontoblast
predentin
dentin matrix that immediately surrounds the dentinal tubule (hyper or hypomineralized?)
peritubular dentin / intratubular dentin
hypermineralized collar –> if completely fills the tubules –> sclerotic dentin / transparent dentin / calcified dentin
type of dentin located between and around the dentinal tubules
intertubular dentin (it is less calcified than peritubular dentin)
zone between the peritubular and intertubular dentin (hyper or hypomineralized?
Sheath of Neuman
represents the daily deposition of 4 micros of dentin. what is the counterpart in enamel and cementum?
incremental lines of von ebner
enamel - IL of retzius
cementum - IL of Salter
results from the coincidence of secondary curvatures between dentinal tubules
contour lines of Owen
hypomineralized region of dentin only present in the root; looping of terminal tubules
Granular layer of tomes
four distinct zones of the pulp
- odontoblastic zone - processes extend into dentin; zone is more pronounced in the coronal pulp;
in the rad pulp and furcation areas, odontoblasts are more cuboidal rather than columnar - cell-free zone of Weil - contains capillaries, unmyelinated fibers; subodontoblastic plexus of Raschkow - present in coronal pulp
- cell-rich zone - contains lymphocytes, dendritic, macrophages
- pulp proper - blood vessels of the pulp, nerve endings
most abuntant cells found in the dental pulp (and all cells found in the pulp)
fibroblast
odontoblast
undifferentiated ectomesenchymal cells
macrophages (histiocytes or wandering cells) and dendritic cells
Pain theories and the pulp-dentin complex
- direct innervation theory - nerves extend to DEJ
- transduction theory - odontoblastic process is the pain receptor that conducts pain to nerve endings presend in the pulp
- hydrodynamic theory / Brannstrom - pain is caused by stimuli that produce fluid movement and disturbs the odontoblastic processes within the dentinal tubules
pulp changes with age
DECREASE in pulp size, cellularity, capability of repair
INCREASE in fibrosis, pulp stones/denticles (pulp chamber), diffuse calcifications (root canal)
true denticles - with dentinal tubules
false denticles - concentric layers of calcified tissue
marker for areas where resorption may have occurred but cementum repair takes place to reverse effects
reversal lines
first cementum to be deposited on the root
intermediate cementum / Hyaline layer of Hopewell Smith
formed by IEE of HERS
located between tome’s granular layer and primary cementum
types of cementum
acellular cementum / primary cementum - initial layer of cementum deposited on the intermediate cementum - cervical 3rd
cellular/ secondary cementum - apical 3rd and interradicular regions of premolars and molars - associated with repair!!
processes of the cementocytes that extend through narrow channels
canaliculi
extrinsic fibers embedded into the cementum which run perpendicular to root surface
Sharpey’s fibers
intrinsic fiber - runs parallel to root surface produced by cementoblasts
composition of alveolar bone
60% inorganic (hydroxyapatite crystals
25% organic (type 1 collagen)
5% water
Alveolar process type of bone absent in the anterior region
trabecular or spongy bone
*red marrow - mostly in mandi
*yellow marrow - mostly in the maxi
bone that lines the socket
bundle bone or cribriform plate
-XR: lamina dura
width of the alveolar crest
determined by shape of adjacent teeth
narrow crest: between teeth with relatively flat surface
widened crest - teeth with convex surface or teeth with diastema
principal collagen fibers embedded in the alveolar proper (bundle bone)
sharpey’s fibers
composition of PDL
mostly collagen fibers
mostly type 1; some oxytalan fibers = regulation of vascular flow
gingival fiber group that resists gingival displacement
circular / circumferential fibers - extends around the tooth at the level of the CEJ
gingival fiber group that causes the relapse of rotated teeth
transseptal fibers - from cementum of one tooth to the adjacent tooth
peridontal fiber group that resists vertical
interradicular group (furcation to alveolar bone proper)
apical group to resist extrusion / vertical
–
alveolar crest and oblique group - resist vertical and intrusive
-
Horizontal group to resist horizontal and tipping forces
lamina propria layers
papillary layer - collagen are thin and loosely arranged with many capillary loops
reticular layer - deeper, thicker layer; collagen fibers are arranged in thick bundles
orthokeratinized vs parakeratinized
ortho - no nucleus in s. CORNEUM
para - pyknotic nuclei in s CORNEUM
Oral mucosa: areas covered with lining mucosa, masticatory mucosa, and specialized mucosa
lining mucosa: FOM, buccal mucosa, alveolar mucosa, lips, soft palate, ventral surface of tongue (epithelial ridges are fewer)
masticatory: hard palate, alveolar ridges, gingiva
specialized: dorsum of tongue
only kind of specialized mucosa that is lined with keratinized epithelium
filiform papillae - tough, abrasive surface
location of taste buds
trench of circumvallate
lateral walls of foliate
fungiform
mucosa of soft palate
epiglottis
types of cells located in the taste bud
supporting cells / sustentacular cells - periphery of tase buds
neuroepithelial cells / gustatory cells / taset cells - elongated microvilli that project into the tase pore or shortened villi into the base of the pore; assoc with nerves
contractile cells that surronds the ducs and acini. it contains myofilaments similar to smooth muscle fibers
myoepithelial cells aka basket cells
differentiate serous cells, mucous cells, serous demilunes (other name)
serous - secretes zymogen granules - amylase - watery consistency
mucous - secretes muciin - viscous - lubricant
serous demilunes /Demilunes of Gianuzzi - terminal mucous cells with a cap of serous demilunes will secrete a mixed product
INTRAlobular duct system
intercalated ducts - receives secretions from acini, simple cuboidal, saliva is isotonic, contributes lactoferrin and lysozyme
striated - main intralobular ductal component, simple columnar, receives secretions from intercalated, hypotonic (sodium reabsorption + K excretion)
interlobular excretory ducts - pseudostratified columnar cells (excretory ducts)
acini is simple cuboidal
minor salivary glands in the peritonsillar region and type of secretion
weber’s gland - mucous
minor salivary glands in the retromolar area
carmalt’s gland
contents of dentinal tubules
odontoblastic process, periodontoblastic space (contains dentinal fluid), intratubular nerve (from plexus of Rashkow)
nerve supply of pulp
rashkow’s plexus, sympathetic and afferent
nerve supply, vascular, lymphatics of PDL
maxillary artery
trigeminal nerve
submandibular lymph nodes
collagen type in the basement membrane
type IV and laminin
areas in the oral mucosa where submucosa is not present
attached gingiva, hard palate, tongue
The amount of collagen in a tissue can be determined by its?
Hydroxyglycine
Collagen contains AA: glycine, proline, hydroxylysine, hydroxyproline
Smallest neuron in the brain
Granule cells
