Histology Test 2-w18 Flashcards
What does enamel cover
Anatomical crown
Composition of enamel
96% inorganic material MAINLY HYDROXYAPETITE
3% water
1% organic ENAMELIN
The hardest calcified/mineralized tissue in the human body
Enamel
Is enamel avascular
Yes it is non vital- no nerves
Colour of enamel
Translucent, greyish/bluish white
**BUT appears yellow due to underlying dentin
The process of enamel matrix formation and mineralization
Amelogenesis
Enamel matrix is ____ derived from _____ of the enamel organ
Ectodermal ; inner enamel epithelium
Anelogenisis occurs during what stage of tooth development
Appositional (formation of enamel/dentin matrix)
Enamel matrix is initially composed of protein, carbohydrates and small amounts of calcium hydroxyapatite but DOES NOT CONTAIN
Collagen
In order for Amelogenesis to occur what must be present
Dentin
Enamel is first formed on
Cusp/tip
Enamel matrix is produced by?
Secreted by?
Produced by ameloblasts; secreted by tomes process
Ameloblasts are not differentiated on what area?
Therefore there is no enamel on ??
Root area; therefore no enamel on roots
Enamel mineralization is
Complete and immediate
What pumps calcium hydroxyapatite into the forming enamel matrix?
Ameloblasts
When ameloblasts are finished they become part of the reduced enamel epithelium fusing with
The oral mucosa
Ameloblasts are lost post tooth eruption; therefore
No new enamel is deposited
A newly erupted tooth will continue to?
Mineralized post eruption (minerals from saliva)
Developmental disturbances: What is an enamel pearl
Small, spherical enamel projections on root surface
Developmental disturbances: what is enamel dysplasia
Faulty development of enamel
What causes deep pits and fissures
Ameloblasts back into one another during apposition; cutting off their source of nutrition
= incomplete maturation of enamel matrix
What can be placed to seal off deep pits and fissures
Sealants
Enamel rods are composed of (3)
Head- enamel rod core
Tail- interrod enamel
Rod sheath- microscopic spaces btwn rods
How are enamel rods aligned?
What is the exception
Perpendicular to the DEJ
EXCEPTION: in the cervical regions of permanent teeth
Shape of enamel rods?
Key hole shaped
What PATTERN are rods aligned in
Interlocking pattern
-this adds strength and durability
What are lines of retzius
hint growth lines
Series of bands on the enamel rods
Represent incremental growth lines that extend from dej
What is neonatal line
Pronounced line of retzius marked by trauma/stress experienced by ameloblasts at birth
What is nasmyths membrane
Primary enamel cuticle- delicate membrane covers entire crown of newly erupted tooth
(Green or yellow easily worn away)
What are hunter shreger bands
Change in the direction of rods
What is perykimata
(Cervical 2/3rds of crown) Raised grooves on enamel surfaces- represent line of retzius externally
What is enamel spindles
(Found beneath the cusps and incisal tips of teeth)
Odontoblastic processes (sentinel tubules) that passed across dej and became trapped
What are enamel tufts
Small dark “brushes”
Represent areas of less mineralization
What is enamel lamella/lamellae
*hint transverse cracks
Partially mineralized vertical sheets of enamel matrix
-transverse cracks from occlusal surface of enamel to dej
Defects of enamel: hypocalcification
Chalky areas
Enamel didn’t form properly due to mineral deficiency (Ca)
Defects of enamel: decalcification
Decalcified chalky areas due to acids or poor oral hygiene
Defects of enamel: dental fluorosis
Mottled enamel
Exposure to more than 2ppm for 1st 8 years
Loss of enamel: attrition
Wearing away of tooth structure from ordinary forces of occlusion (tooth to tooth contact)
Loss of enamel: abrasion
Abnormal wear caused by friction due to excessive tooth brushing or use of abrasive toothpastes
Loss of enamel: erosion
Tooth structure lost through chemical means : Acid reflux, acidic foods/drinks, vomiting
Loss of enamel: abfraction
Wedge shaped legions
Loss of tooth structure at the cervical neck area of teeth due to compressive and tensile forces during tooth flexure
Denton makes up
The bulk of the tooth
T/F. Denton is avascular and vital; has nerves
True
Denton is ___ in colour
Yellow
Mature dentin composition
70% inorganic (calcium hydroxyapatite)
20% organic
10% water
Crystals in dentin are “_____” like and ____ than those in enamel
“Plate like” and are smaller
The process of dentin formation
Dentinogenesis
Denton forms from the ___ of the tooth germ
Dental papilla (mesenchymal)
Predentin is the initial layer of dentin matrix laid down by Odontoblasts containing
Collagen fibers
As organic matrix forms, Odontoblasts move away from the dej producing
Predentin in layers (apposition)
Apposition of the dentin occurs throughout the life of a tooth, why?
Odontoblasts remain in the tooth along the outer pulpal wall
Maturation of dentin or mineralization of predentin occurs when
Soon after its apposition
What forms during the primary phase of dentin maturation that allows for expansion and fusion
Hydroxyapatite crystals form as globules in the collagen fibers of primary dentin
Describe secondary phase of dentin maturation
Further mineralization (secondary dentin) will occur as globules form in partially mineralized areas
What is mantle dentin
Outermost layer
First predentin
What is circumpulpal dentin
Surrounds outer layer of the pulp
Bulk of the dentin
Primary dentin is present before completion of the
Apical foramen
After completion of the apical foramen what is present
Secondary dentin
forms throughout the life of the tooth!
Tertiary dentin is aka
Reparative dentin
Dentin Mineralization occurs by
Budding
Formation and calcification start at the
*hint same as enamel
Cusp
Small odontoblastic buds provide location of crystallizations which join and grow in _____ process to form___
3 dimensional process to form mantle dentin
Long tubes in the dentin that extend from the DEJ to the outer wall of pulp
Dentinal tubules
Dentinal tubules contain (3)
Odontoblastic process
Dentinal fluid
Sensory (afferent) axon (pain)
What is pertibular dentin
Wall of the tubules
What is intertubular dentin
In between the tubules (main body of dentin)
Dentinal tubules may become open due to caries, recession, attrition and cavity preparation causing
Dentinal hypersensitivity
What may trigger dentinal hypersensitivity (4)
Thermal
Mechanical (ultrasonic)
Dehydration
Chemical exposure ( acidic foods, teeth whitening)
What is the hydrodynamic theory of dentinal hypersensitivity
Pain is due to changes in the dentinal fluid associated with the odontoblastic process
How can we help clients with dentinal hypersensitivity
Desensitizing toothpastes
Fluoride varnishes
Dentin histology: What is the incremental lines of Von ebner
*growth lines
Similar to lines of retzius in enamel
Dentin Histology: what is tomes granular layer
Hint spotted areas
Found in ROOT AREA
Thin hypomineralized spotted areas giving it a granular appearance
What is dentinogenesis imperfecta?
Is it hereditary?
Shiny opalescent dentin
Hereditary
Dentinal defects: empty tubules resulting from loss of the Odontoblastic processes or odontoblast death
Dead tracts
Dentinal defects: sclerotic dentin
Form of tertiary dentin
Aka transparent dentin
Often found in areas with chronic injury of caries
Pulp is connective tissue derived from the
Dental papilla
What are the 4 pulp zones
Odontoblastic zone
Cell free zone/ zone of weil
Cell rich layer
Pulp core
Pulp zones: the Odontoblastic zone is closest to the dentin and consists of
Cell bodies of Odontoblasts
Capable of forming secondary/tertiary dentin
Pulp zones: cell free zone contains ___ cells than Odontoblastic zone
Fewer
-Nerve and capillary plexus located here
Pulp zones: cell rich layer contains many cells but fewer than what zone
Odontoblastic zone
-extensive vascular supply
Pulp zones: pulp core is the ___ of the pulp chamber
Centre
-major vessels and nerves similar to cell rich layer
Blood supply of pulp: large ____ vessels. Nutrition is obtained through?
Large cylindrical vessels
Nutrition is obtained through the tubules and their connection to the Odontoblasts
Nerve supply of pulp: cell bodies of afferent axons lie in the
Dentinal tubules
Nerve supply pulp: changes in what 3 things are perceived ONLY as PAIN
Temperatures
Vibrations
Chemical changes
What is pupal mode of entry
Apex
Lateral/accessory canals
What is pulpitis
Injury to the pull from caries, cavity prep, or other trauma. May result in pulpal infection or periapical abscess
What can happen to the pulp with age?
Vascularity and cells decrease
CT fibers and pulp stones (denticles) increase
What does the periodontium consist of
Consists of cementum, alveolar bone and PDL
Function of the periodontium
- supports the tooth in its relationship to the alveolar bone
What is cementum
Specialized connective tissue
Can cementum form throughout the life of a tooth
Yes
Where is cementum the thickest
Where is it the thinnest
Thickest at apex/interradicular areas
Thinnest at CEJ
What is the function of cementum
Covering for the root surface
Mechanical attachment (PDL to bone)
Compensates occlusal wear/attrition
Where is cementum located
On top of the tomes granular layer in dentin
Cementum forms shortly after the
Disintegration of HERS (hertwigs epithelial root sheath)
Cementum forms from
Undifferentiated cells of the dental sac
After HERS disintegrates, undifferentiated cells of the dental sac contact what and differentiate into what
Contact the root dentin surface
Differentiate into cementoblasts
Cementoblasts spread over the ____ and start laying down ____
Spread over the root dentin and start laying down cementoid
Cementoblasts can also become trapped in the cementum. These cells are called
Cementocytes
Cemetogenesis: once the cementoid is formed and reached its proper thickness it starts to
Calcify
Formation of cementum is
ONGOING
Composition of cementum
(Composed of fibrous matrix and cells)
65% inorganic
23% organic
12% water
What does the fibrous matrix of cementum consist of
Sharpeys fibers
Intrinsic non periodontal fibers
Sharpeys fibers function as a ligament between
The bone and cementum
Sharpeys fibers are part of the collagen fibers from the PDL which are partially inserted into what at one end and what at the other
Partially inserted into the cementum at one and end and part of the alveolar bone at the other end (at a right angle)
The intrinsic non PDL fibers of the cementum are collagen fibers made by the
Cementoblasts
The cementoblasts that do not get trapped in cementum line up along? And do what?
Line up along the cemental surface
And repair the tooth if it is injured
What are the 2 cementum types
Acellular (primary) and cellular (secondary)
4 characteristics of acellular (primary) cementum
-1st layer deposited at DCJ
-laid down slowly and regularly
-no embedded cementocytes
-width never changes
4 characteristics of cellular (secondary) cementum
-on the surface of acellular cementum
-laid down quickly
-cementoblasts and cementocytes present
-width may change
What are the 3 types of CEJ’s
(OMG)
15% overlap
52% meet
33% gap
What is Hypercementosis
Excessive production of cellular cementum mainly at apices
What are the causes of Hypercementosis (3)
-Chronic periapical inflammation
-Occlusal trauma
-Compensatory mechanism in response to attrition to increase occlusal tooth height
Hypercementosis may result in pulpal necrosis by blocking
Blood supply via the apical foramen
What is concrescence
Fused roots (2 separate crowns)
Mineralized spherical bodies of cementum in PDL caused by apposition of cementum around cellular debris
Cementicles
What are the 3 types of cementicles
Free
Attached
Embedded
Free cementicles are found in the
Ligament
Attached cementicles are attached to the
Surface of cementum
Embedded cementicles are found within
The cementum
What is the PDL
Fibrous connective tissue btwn alveolar bone and cementum that supports teeth
The PDL acts as a
Shock absorber
PDL is composed of
Fibers, cells and intercellular substance
The PDL contains
Blood vessels (nutrition)
Nerves (pain, touch pressure and temp changes)
What are the 2 types of nerves in the PDL
Afferent (sensory, myelinated)
Autonomic (sympathetic)
Afferent nerves transmit _____ that occur within the PDL
Sensations
Autonomic nerve of PDL regulates
Blood vessels
Gingival fiber group of the PDL is around the ___ and supports only the ____
Around the necks of the teeth
Supports only the marginal gingiva
Alveodental ligament surrounds the
Roots of the teeth (main group)
Interdental ligament or transseptal ligament is found
Cervical surface of adjacent teeth
Cementum to cementum
NO BONY ATTACHMENT
Alveolar bone is part of the maxilla and mandible that contains the
Roots of the teeth
Alveolar bone includes what (4)
Cortical plate
Alveolar crest
Trabecular bone
Alveolar bone proper
Alveolar bone proper/lamina dura is a thin layer of compact bone that forms the
Tooth socket
(* known as lamina dura on radiographs)
Alveolar crest is the highest point on the _____. It joins what 2 things
Alveolar ridge
Joins the facial and lingual cortical plates
Supporting compact bone is aka
Cortical bone/plate
Supporting cortical bone extends over what surfaces of the maxilla and mandible
Lingual and buccal surfaces
Supporting compact bone is dense and provides
Strength and protection
Supporting cancellous bone is aka
Spongy bone/ trabecular bone
Supporting cancellous bone is located between
ABP and the plates of cortical bone
Fenestration: the area of bone loss where an apical root
Penetrates the cortical bone, opening through the bone
window like defect
Dehiscence: bone loss in the
Coronal area of the root, bone splits open
Leeway space is created in the arches by replacement of
Larger primary molars by smaller permanent premolars
Ortho movement: pressure on the ____ causes movement in that direction
ABP
Compression zone = ?
-pressure applied to PDL, osetoclasts resorb bone
Bone resorption
Tension zone = ?
* tension applied to PDL, osteoblasts resorb bone
Bone deposition
With age, if there are no longer present alveolar bone undergoes ? Because?
Resorption. Because it needs roots to remain viable
Prenatal development begins and ends when
Begins at conception and ends at birth
3 periods of prenatal development
Pre implantation period (1st trimester)
Embryonic period (1st trimester)
Fetal period (2nd and 3rd trimester)
Embryonic period occurs when
2nd-8th week
During the embryonic period developmental processes occur which are?
Induction
Proliferation
Differentiation
Morphogenesis
Maturation
What is Bilaminar embryonic disc
3D flattened, circular plate with bilayered cells that developed from a blastocyst
What are the bilaminar embryonic disc layers
Superior epiblast layer
Inferior hypoblast layer
Primitive streak forms during the beginning of the
3rd week within the bilaminar disc
Formation of the primary streak: cells from the _____ will move toward the _____ in the area of the primitive streak
Epiblast layer; hypoblast layer
Formation of the primitive streak: these migratory cells move to the ____ between epiblast and hypoblast layers and become _____ and _____
Middle; mesoderm and endoderm
With 3 layers present, the bilaminar embryonic disc is now called
Trilaminar embryonic disc
Epiblast layer =
Migrated cells =
Hypoblast layer =
Epiblast layer= Ectoderm
Migrated cells= mesoderm
Hypoblast= endoderm
Development of the face begins during the ___ week, with formation of primitive mouth called ?
4th week; stomodeum
How many branchial arches form below stomodeum
6
What is another name of 1st and 2nd branchial arches
1st aka mandibular arches
2nd aka hyoid arches
What cartilage is associated with 1st and 2nd branchial arches
1st- Meckels cartilage
important in formation of the mandible
2nd - reicherts cartilage
What is Ectodermal dysplasia? What does it look like?
Abnormal development of one or more structures from ectoderm
* may be partial or complete anodontia
What is rubella
Causes cataracts, deafness or damage to heart or brain in the unborn infant
How does fetal alcohol syndrome look
Crowding of teeth, mouth breathing, anterior open bite
Syphilis produces defects in the ?
Incisors and molar (hutchinsons incisor, mulberry molar)
How does tetracycline staining look?
Intrinsic yellow/brown stain
* chemically bound to dentin and becomes transparent in the enamel
Development of the face: frontonasal process gives rise to?
What is included in this process
Gives rise to medial nasal processes and lateral nasal processes
Forehead, bridge of nose, philtrum of upper lip, primary palate, nasal septum
Development of the face: maxillary processes: bilateral. What is included?
Sides of upper lip
Cheeks
Secondary palate
Posterior part of maxilla
Development of the face: mandibular processes, bilateral. What is included in this process
Lowe jaw- mandible
Lower lip
Sides of the mandible and lower face to the lateral borders of the lips
Development of the face: median nasal processes: bilateral
What is included in this process?
Intermaxillary segment (globular process)
Centre of the upper lip
Philtrum
Middle part of the nose
Development of the face: lateral nasal processes, bilateral. What is included in this process
Side of the nose
Palate development starts during the 5th week of prenatal development and arises from 3 sources which are
2 maxillary processes
Globular process (aka Intermaxillary segment)
Intermaxillary segment (5/6th week) forms from the fusing of the?
Gives rise to the?
2 medial basal processes
Gives rise to the primary palate (anterior 1/3rd of hard palate)
Lateral palatine processes (2 palatal shelves- 6-12th week) form from?
Gives rise to?
Form from the bilateral maxillary processes
Gives rise to the secondary palate (posterior 2/3rd of hard palate, soft palate, uvula)
Final palate (12th week) what occurs?
Primary palate fuses with the secondary palate (Y shaped pattern)
The fusion of primary and secondary palate gives rise to (2)
The median palatine raphe within mucosal lining and deeper median palatine suture where palatal shelves/bones fuse
Cleft lip results from
Partial or complete failure of fusion of 1 or both maxillary processes with the medial nasal processes
During the 4th week, the tissue around the_____ on the frontonasal process undergoes growth, creating ____
Nasal placodes; nasal pits
The medial nasal processes fuse together to form the
Middle part of the nose
Tubercle of upper lip
Philtrum
Nasal septum (5-12th week) part of the frontonasal process forms the nasal septum by
Growing backwards and down until the inferior border fuses with the center of the hard palate
Lateral nasal processes form the
Alae (side) of the nose
Fusion of lateral nasal, maxillary and medial nasal processes forms the
Nares
At __ weeks in utero, the tongue begins to develop from the
4 weeks; anterior wall of the primitive throat and protrudes upward and anterior
The body of the tongue develops from the ______ and the base/root of the tongue develops later from the _____
1st brachial arch
2nd, 3rd, and 4th brachial arch
The developing tongue: tuberculum impar
Swelling begins
The developing tongue: lateral lingual swellings
Develop on each side of the tuberculum impar
Developing tongue: the 2 swellings overgrow and encompass the disappearing tuberculum impar to form the
Anterior 2/3rd of tongue (body of tongue)
Developing tongue: median lingual sulcus
Line of demarcation of fusion of the two lateral swellings
Developing tongue: just behind the fused anterior swellings is the _____. This will form the ?
Copula; forms the base of the tongue (posterior 1/3rd)
Development of tongue: even more posterior to the copula there is
Epiglottis swelling. Site of future epiglottis
Macroglossia
Large tongue
Ankyloglossia
Tongue tied; short attachment of lingual frenum
Macrostomia: what is it? What is it a result of ?
Extremely large mouth opening resulting from a failure of fusion of the maxillary process and mandibular arch at the corners of the mouth
Microstomia: what is it and what is it a result of?
Extremely small mouth opening resulting of the merging of the maxillary process and mandibular arch at the corners of the mouth
Odontogenesis; development of the primary dentition begins at about the __th week of embryonic life
6th
What is the first stage of odontogenesis and involves the physiological process of induction
Initiation stage (6-7th week)
At the beginning of the 6th week the embryos stomodeum is lined by?
Ectoderm
Initiation stage: The outer part of the ectoderm gives rise to
Oral epithelium
Initiation stage: below oral epithelium, connective tissue called ___ develops
Ectomesenchyme
Initiation stage: oral epithelium grows deeper into the ectomesenchyme to produce
Dental Lamina
Lack of initiation results in the absence of
A single tooth or multiple teeth (hypodontia or anodontia) or extra teeth (hyperdontia)
What is the second stage of odontogenesis occurring at the beginning of the 8th week
Bud stage
Main physiological process of bud stage is
Proliferation
Bud stage: dental lamina proliferates (grows) into
Tooth buds (primary 10 buds)
Tooth buds for all permanent teeth, except molars, arise from _____ which is lingual to the dental lamina of primary teeth
Successional lamina
What are the developmental disturbances that can occur during bud stage
Macrodontia
Microdontia
3rd stage of odontogenesis occurring during the 9/10th week
Cap stage
What are the physiological processes of the cap stage
Proliferation
Differentiation
Morphogenesis
Cap stage: dental lamina has proliferated and differentiated into the ______ of a primary tooth
Tooth germ
Tooth germ consists of
Enamel organ (with enamel knot)
Dental papilla
Dental sac
Enamel organ produces future
Crown form and enamel
Connective tissue within the cap becomes the dental papilla; dental papilla gives rise to
Pulp and dentin
The dental sac will produce the periodontium which includes?
Cementum
PDL
Alveolar bone
Succedaneous refers to permanent teeth that develop from ?
What do they replace
Develop from successional dental lamina and they replace primary teeth
(Primary Anteriors and primary molars- perm anterior and perm premolars)
Nonsuccedaneous refers to permanent teeth that
Don’t develop from successional dental lamina and don’t replace any primary teeth (permanent molars only)
The 4th stage of odontogenesis occurring during the 11-12th week
Bell stage
Bell stage: Enamel organ has 4 cell layers
Inner enamel epithelium
Stratum intermedium
Stellate reticulum
Outer enamel epithelium
Inner enamel epithelium is the innermost columnar cells. This will differentiate into?
Ameloblasts
What cell layer(s) of the enamel organ support the production of enamel
Stratum intermedium
Stellate reticulum
Outer enamel epithelium is outer cuboidal cells and provides a
Protective barrier
Cells of the dental papilla are (2) and what are they associated with
Outer cells- differentiate into odontoblast
Central cells- pull
Describe apposition stage
Enamel, dentin and cementum are secreted in successive layers
Describe maturation stage
Dental tissue types fully mineralize
Ameloblasts develop from
Inner enamel epithelium (IEE)
Odontoblasts produce a layer of
Predentin
1st enamel is deposited on surface of _____. It establishes what?
Dentin; establishes DEJ
Developmental disturbances that can occur during the cap stage include
Dens in dente
Gemination
Fusion
Tubercles
Once enamel is formed, layers of enamel organ condense to? What is it? What is its function?
Reduced enamel epithelium (REE)
-REE is a thin membrane on the entire surface of the crown
- protects enamel until tooth erupts
As the tooth erupts, REE fuses with epithelial lining and forms
Epithelial attachment
Root formation begins after
The crown is completely formed
What is the cervical loop and what is its function
Most cervical part of the enamel organ. Responsible for root development
Innermost and outermost enamel organs merge in a cervical loop and grows down as a double row of cells called
Hertwigs epithelial root sheath
What is the function of HERS and what does it consist of ?
Molds the shape of the root and initiates dentin formation from the cells of the dental papilla.
-consists of ONLY inner and outer enamel epithelium
After the first layer of dentin is formed what disintegrates? This disintegration leaves behind ?
HERS disintegrates
Leaves behind epithelial rests of malaassez
Cementoblasts cover root dentin and lay down?
Cementoid
*cementoblasts differentiate from the cells of the dental sac
Cementum and pulp formation: central cells of the dental papilla are condensing to form
The pulp
Remaining ectomesenchyme from the dental sac forms the
PDL and mineralized to form the tooth socket of the alveolar bone
Anodontia
Congenital absence of all primary or permanent teeth (initiation stage)
Hypodontia
Less than the normal amount of teeth (initiation stage)
Oligodontia
Absence of 6 or more teeth
(Initiation stage)
Hyperdontia
Having supernumerary (extra teeth) (initiation teeth)
Microdontia
Small teeth (bud stage)
Macrodontia
Large teeth (bud stage)
Dens in dente
Tooth within a tooth (cap stage)
Gemination
2 crowns develop from 1 bud
(Cal stage)
Fusion
2 developing teeth fuse into 1 tooth (cap stage)
Tubercle
Outgrowth or projection (cap stage)
Enamel pearl
Misplaced ameloblasts during root formation (A and M stage)
Concrescence
Fusion of cementum (A&M stage)
Dilacerations
Disturbance during root formation; crown or root showing angular distortion (A&M stage)
Amelogenesis imperfecta
Hereditary enamel dysplasia with thin or absent enamel
Dentinogenesis imperfecta
Dentin dysplasia with hereditary basis and blue gray or brown teeth with opalescent sheen
Enamel dysplasia
Faulty development of enamel
