ex1 amelogenesis

Question 1

T/F

Enamel tissue is a composite biological mineral with apatite crystals oriented in a 3D pattern

Answer 1

True. Enamel is a composite BIOLOGICAL mineral with apatite crystals oriented in a complex 3D pattern – in the form of enamel RODS

Question 2

A whole lot about the apatite mineral::

Answer 2

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, named for high concentrations of OH−, F− and Cl− ions, respectively, in the crystal.

Apatite is one of a few minerals produced and used by biological micro-environmental systems

. Apatite is the defining mineral for 5 on the Mohs scale ((a scale for hardness bases on one mineral’s ability to scratch another. Mohs is a 1-10 scale with talc = soft =1 and diamond=10))

. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate (CO3 ^-2))) and acid phosphate substitutions is a large component of bone material.

Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite; in the mid-20th century, it was discovered that communities whose water supply naturally contained fluorine had lower rates of dental caries.[3] Fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate). Too much fluoride results in dental fluorosis and/or skeletal fluorosis.

Question 3

T/F Dentinogenesis (formation of dentin) occurs before amelogenesis (formation of enamel) during the crown stage of odontogenesis

Answer 3

True. Dentinogenesis occurs before amelogenesis (aka, first the dentin forms, and then the enamel is formed.) during the crown stage of odontogenesis (formaiton of teeth)

Question 4

a side foray: some info about the tongue (anatomy review)

Answer 4

Blood supply[edit]
The tongue receives its blood supply primarily from the lingual artery, a branch of the external carotid artery. Veins of the tongue, the lingual veins, drain into internal jugular vein. The floor of mouth also receives its blood supply from the lingual artery.[4]:993–994 There is also secondary blood supply to the tongue from the tonsillar branch of the facial artery and the ascending pharyngeal artery.

The triangle formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and the hypoglossal nerve is sometimes called Pirogov’s, Pirogoff’s, or Pirogov-Belclard’s triangle.[5][6] The lingual artery is a good place to stop severe hemorrage from the tongue.

Innervation[edit]
Nerves which supply the sensation and taste of the tongue differ between the anterior and posterior parts.[4]:994–5

Anteriorly 2/3 , the sensation of taste is passed along the chorda tympani, a branch of the facial nerve **
**(The facial nerve is the seventh cranial nerve, or simply cranial nerve VII. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity. It also supplies preganglionic parasympathetic fibers to several head and neck ganglion//
Intracranial branches[edit]

Greater petrosal nerve - provides parasympathetic innervation to several glands, including the nasal gland, palatine gland, lacrimal gland, and pharyngeal gland. It also provides parasympathetic innervation to the sphenoid sinus, frontal sinus, maxillary sinus, ethmoid sinus and nasal cavity.

Nerve to stapedius - provides motor innervation for stapedius muscle in middle ear
Chorda tympani
Submandibular gland
Sublingual gland
Special sensory taste fibers for the anterior 2/3 of the tongue.

Extracranial branches[edit]
Distal to stylomastoid foramen, the following nerves branch off the facial nerve:

Posterior auricular nerve - controls movements of some of the scalp muscles around the ear
Branch to Posterior belly of Digastric muscle as well as the Stylohyoid muscle
Five major facial branches (in parotid gland) - from top to bottom (a helpful mnemonic being To Zanzibar By Motor Car):
Temporal branch of the facial nerve
Zygomatic branch of the facial nerve
Buccal branch of the facial nerve
Marginal mandibular branch of the facial nerve
Cervical branch of the facial nerve

People to Zanzibar by Motor Car :: posterior auricular, temporal zygomatic, buccal, mandibular, cervical , . Sensation is passed along the lingual nerve, a branch of the trigeminal nerve.
Posteriorly, both taste and sensation are passed along the glossopharyngeal nerve.
All intrinsic and extrinsic muscles of the tongue are supplied by the hypoglossal nerve, with the exception of the palatoglossus. The palatoglossus is innervated by the vagus nerve.[4]:995

Question 5

how is the formation of enamel and dentin an example of reciprocal induction?

Answer 5

the epithelial tissue of the enamel organ and the ectomesenchymal tissue of the dental papilla interact to form enamel and dentin mineralzied tissues.

While dentin forms before enamel, ameloblasts (formative cells of enamel ) Must be present for dentinogenesis to occur.. then the presence of dentin spurs amelogenesis..
ameloblasts induces > dentinogenesis induces> amelogenesis
== this interaction = reciprocal induction

Question 6

what are the 4 mineralized tissues of the oral cavity?

Answer 6

bone, enamel, dentin, and cementum are the 4 mineralized tissues of the oral cvity

Question 7

which of the mineralized tissues of the oral cavity does NOT have an unmineralized pre- stage?

Answer 7

Enamel! Enamel does not have an unmineralized pre-enamel stage

Question 8

What occurs in the 2 steps of enamel formation?

Answer 8

Enamel formation is a 2-step process. The first step lays out a partially-mineralzied framework (30% inorganic, 70% water)
- the second step replaces the water with a high concentration of mineralzied inorganic material ((notice, the pre-enamel first stage is still mineralized))

Question 9

T/F For all mineralized tissues, you need a specialized cell

Answer 9

True. For all mineralized tissues, you need a specialized cell (ex/ the - blast cells, ie ameloblast, odontoblast, cementoblast, osteoblast)

Question 10

in what layer of epithelial tissue of the enamel organ is alkaline phosphatase located?

Answer 10

The alkaline phosphatase os located in the stratum intermedium epithelial layer of the enamel organ (located bt the inner layer ad the stellate reticular eptithelial layers)

Question 11

T/F the tooth germ is avascular

Answer 11

False. The enamel organ (epithelial) portion of the tooth germ is avascular. Botht he detnal papilla and dental follcle are vascular.

Question 12

What part of the tooth germ supplies the blood during amelogenesis?

Answer 12

The dental follicle has the blood that supplies amelogenesis. Since dentinoenesis occurs first, the dental papilla is blocked off and only the dental follicle is accessible for blood

Question 13

What is the progression of ameloblast formation along hte tooth germ?

Answer 13

Ameloblast formation occurs in the enamel organ portion of the tooth germ. The coronal-most inner portion of the enamel organ is the first area to diferentiate into ameloblasts.. successively, ameloblast formation continues apicaly toward the cervical loop (recall, where the inner and outer epithelial layers of the enamel organ meet in a double layer of epithelium ((in the enamel organ– the 2 lateral, inferiorally reaching tips))

Question 14

Name the 3 main stages of amelogenesis and the # of phases associated with each stage

Answer 14

There are 3 main stages with (#) phases associated:

1) presecretory stage (2)
2) secretory stage (6)
3) postsecretory stage (1)

Question 15

rods, rod sheath, and interrod substance are structurally identifying components of what tissue?

Answer 15

Rods, rod sheath, and interrod substance are structurally identifying components of enamel

Question 16

what are the two major steps involved in forming the structurally identifiable part of enamel ?= describe what happens in each step.

Answer 16

preamble:: (step 1, tooth germ> dentinogenesis> amelogenesis AKA first phase = tooth germ development, the Presecretory stage)

ANSWER::
then, Enamel formation happens in 2 steps: the secretory phase and post secretory phase .

The first step invovles the secretion of a 30% inorganic/ 70% organic enamel substance. This pre-enamel is paritally mineralized and at first, rodless/structureless. the ameloblast hten chages configuation to Tome’s process such that it secretes INTERORD substance that Encircles the Tome’s process. Tom’es process occupies a space called Tom’es pit.. As this material is laid down around the process/ the pit, it leaves a honey-comb like framework. The interrod substance of enamel surrounds the wall of Tom’es pits. There is one enamel rod per Tom’es pit (the space occupied by the ameloblast modified into Tome’s process) As the ameloblasts move on, they secrete partially mineralized enamel rod into the pit created. This continues until the length of the pit, built up by interrod substance, is filled with rod. ..

AFTER the width of enamel has been deposited, then the enamel modifies from being paritally mineralized to 96% mineralized by process of a big influx of minerals simultaneously with removal of organic content and water

there is the 2nd post secretory stage after this previous secretory stage. ..this is the protective stage where the reduced enamel epithelium- remnant enamel organ= protects the enamel until it reaches the oral cavity (enamel only wants to be touched by saliva)

Question 17

T/F – A specialized cell is necessary for all mineralized tissue

Answer 17

True. A specialized cell is needed for the formation of all mineralized tissue:
ex// osteoblasts (bone) , odontoblasts (dentin), ameloblasts (enamel) and cementoblasts (cementum)

Question 18

What are the 3 main things that all mineralzied tissues need (including enamel formation) . State generall and the counterpart regarding enamel formation.

Answer 18

All mineralized tissues need 3 things ::

• A specialized cell: for enamel = ameloblast
• alkaline phosphate– for enamel, located in the stratum intermedium
• rich blood supply- for enamel, supplied by the dental follicle portion of the tooth germ

Question 19

There are 6 phases to the II Secretory stage -((after the presecretory stage and before the postsecretory phase of amelogenesis

Answer 19

There are 6 phases in the Secretory stage of amelogenesis
basically, innerord subtance and then rod are laid down by ameloblasts (inovled are Tome’s process and pit), these start out partially mineralized and then o through the maturation phase (4th) where io. material influx and efflux of organic and water.
the order of layers laid down (corresponding in-part to phases):

1) inner rodless enamel layer =immediately mineralized secretion
2) interrod substance secretion (initially immature/partially mineralized .. apprx 30% IO, 70% organic + water )
3) rod secretion (““initially immature/ partialy mineralized “”)
4_ MATURATION PHASE - the interrod substane and rods become mature/ fully mineralized VIA removal of organic substance (=1%) and water (3%), Influx of mineral salts (= inorganic) to 96%
5) outer rodless enamel layer (= immediately mineralized) secretion
6) basal lamina = nonmineralized, = the final ameloblast secretion (last secretion phase)

Question 20

The reduced enamel epithelium is important to which stage of amelogenesis (( choose: presecretory stage, secreory stage, postsecretory stage))?

Answer 20

The reduced enamel eputhelium is important to the postsecreotry stage = which has the functional purpose of protecting the enamel. ((Enamel only wants to touch saliva ))

Question 21

Which of the layers/ secretions during amelogensis is not mineralized?

Answer 21

The final ameloblast secretion (phase 6 of the secretory stage), is of NON-mineralized basal lamina.

Question 22

what is the first layer;secretion laid down during the secretory phase of amelogenesis?

Answer 22

the first layer/secretion laid down during the secretory phase of amelogenesis is the inner rodless enamel layer. this layer is IMMEDIATELY mineraled upon secretion (( as in, no immature/mature phase as seen witht he intterrod substance and the rods)

Question 23

which secretions of the Secretory phase of amelogenesis are mineralzied immediately upons secretion?

Answer 23

Both the 1st layer, the inner rodless enamel, and the second-to-last layer - the outer rodless enamel ((located after the maturation of hte interrods/rods and before the nonminerlized basal lamina)
both the inner and outer rodless layers of enamel are mineralized upon secretion ( no immature-maturation change)

Question 24

T/F cells are the coronal most area of the inner layer of enaeml organ are the first to differentiate into ameloblasts

Answer 24

True. CElls found at the coronal-most area of the inner layer ((recall, the inner layer is the coast of the bay, in terms of shape location)) .. are the 1st to differentiate into ameloblasts.

ameloblast differentiation continiues on down apically (to what looks like 2 lateral tips

Question 25

T/F Cells at the cervical loop of the enamel organ are the first to differentiate into ameloblasts

Answer 25

False. CElls at the CORONAL -most location of the INNER eptiehlial layer of the enamel organ are the first to differentiate into ameloblasts.

the cervical loop is the location on the 2 lateral apical locations where the outer and inner epithelial layers meet and form a double epithelial layer called Hertwig’s epithelial root sheath ((which is covered in Eruption and shedding, as Hertwig’s is invovled in determining the number of root canals a tooth will have))

Question 26

T/F the most coronal part of the dental folicle will be be cusp tip/ incisal height?

Answer 26

False. The most coronal part(s) of the DENTAL PAPILLA will be a cusp tip/ incisal edge

Question 27

What formative cell type is located amongst the peripheral cells of the dental papilla?

Answer 27

Odontoblasts (form dentin) is the formative cell type that is located with the peropheral cells of the dental papilla (future pulp)

Question 28

Histolologically, between what layer is the clear / acellular layer located in the tooth gernm?
((((((– fyi, this clear space is found during the morphogenic phase (1st) of the presecretory stage of amelogenesis… the clear space is present before inner epi layer specailization into -blast cells ))))

Answer 28

The clear/ acellular area is found between the inner epithelial layer ((recall, the coast of the bay)) and the peripheral cells of dental papilla (the water in the bay). ((odontoblasts are located along these peropheral dentla papilla ectomesenchyme cells)) /// as the ameloblasts mature and form, they grow into the clear space/ Tome’s process/pit so that the clear space is filled w ameloblast

– where the clear space disappears bt the dentin and enemal is the DEJ = dentino-enamel junction

Question 29

what is the importance of the stellate reticular epithelial layer to amelogenesis?

Answer 29

The stratum intermedium epithelial layer of hte enamel organ (inner epi layer, stratum intermedium epi layer, stellate reticular epi layer, outer epi layer)) contributes ALKALINE PHOSPHATE to amelogenesis = important.
alkaline phosphatase is a necessary component of minerlaized tissues ((all mineralzied tissues, along witht he need of a specialized formative cell -blast, and rich blood supply))

Question 30

• where does ameloblast formation start?

Answer 30

Ameloblast formation starts in the inner epithelial layer of the enamel organ. Specifically, ameloblast fomation starts in the coronal-most part of the inner epithelial layer of the enamel organ, and formtation continues down apically / cervically

Question 31

T/F The 4 stages of amelogenesis are synthesis, presecretory, secretory, and terminal stages

Answer 31

False. There are 3 main stages in amelogenesis, hte presecretory, secretory, and postsecreotry phases.

Question 32

What is the main happenng in the presecretory stage of amelogenesis?

Answer 32

During hte presecreotry stage, first there is a clear space bt the inner epi layer of the enamel organ and the peripheral dental papilla… with histodifferntiation, the inner epithelial cells differentiate into specialized ameloblasts and odontoblast, etc. and the clear space disappears.

Question 33

If there is a histological clear space visible bt the dentla papilla and the inner pithelial layer of the enamel organ, - has histodifferentiation (as described by the presecretory stage of amelogenesis) occurred yet?

Answer 33

No! The clear space disappears if histodifferentiation has occurred.
- histodifferntiation refers to the differentiation of the inbner eithelial layer of the enaml organ into sepcialized ameloblasts and the odontoblasts in the dental papila.

• the clear space disappears as the ameloblasts develop. The clear space becomes the DEJ- the dentinoenamel junction

Question 34

where does the necessary alkaline phospahte come from during amelogenesis

Answer 34

The stratum intermedium contributes the necessary alkaline phosphate during amelogenesis

Question 35

where does the necessary blood supply come from necessary to amelogeneisis (enamel formation)

Answer 35

the necessary blood is supplied by the dental follicel during amelogenesis

Question 36

How does the dentin have retention with the enamel?

Answer 36

Dentin and enamel have MECHANICAL retention. Dentin is laid down first (recall, odontogenesis occurs bf amelogeneisis) and the perimeter along hte clear space is ragged with dentin mineralized (crystal) ends. The ameloblasts lay down enamel over this – the first layer layed down is the inner rodless (srucutureless) layer.. these 2 layers interact and have mechanical retention,

No adhesives!

Question 37

What enamel layer has direct contact (layers on top of) the dentin layer

Answer 37

The inner rodless (strucutureless) enamel layer laid down by the ameloblasts in the enamellayer that interacts with dentin.

the inner rodless layer (as well as the outer “”) is mineralized upon secretion (immediately)

Question 38

What secretes interrod substance?

Answer 38

Ameloblasts secrete interrd substance. Sepcifically, neighbor Tom’es processes secrete the interrod substance that surrounds the pit space of itself and neighbors (forming a honecomb around the pits.. and with added hieght from further interrods secretions AND ROD secretion..3D these honeycombs become the enamel rods surrounded by the interrod substance

Question 39

What is Tome’s process? And Tom’es pit. Describe

Answer 39

Tome’s process configuration that the ameloblast adopsts after laying down the smooth, inner rodless eptihelium. The ameloblasts modify their distal ends to be Tome’s process that now secretes interrod substance and rod substance .. these tom’es pocesses occupy a space called Tome’s pit. As the ameloblasts travel coronally while secreting differnt layers as they go (inner rodless, interrod, rod, outer rodless, basal lamina)) Tome’s process goes too (bxc distal end of ameloblast.. follows ameloblast as a tail)) and Tom’es pit remains unoccupied.. and is filled with rod substance during the (4th part of) secretory phase of amelogenesis)

Question 40

What ameloblast secretion surrounds the Tome’s pits?

Answer 40

The interrod substance surrounds Tome’s pits. Layer upon layer ((looks like honeycomb cross-sectionally, or like long rods when built up.. will be filled w enamel rod))

Question 41

Is interrod substance immediately mineralized like the inner and outer rodless enamel layers?

Answer 41

No. The interrod layer, like the enamel rod layer, is initially only PARITALLY mineralized.. only during the maturation phase of the secretory stage of amelogenesis are the interrod and enamel rod layers matured into fully 96% mineralized enamel.

Question 42

T/F there is a rod sheath layer that is between the enamel rod and the interrod subsance.

Answer 42

True. From when the rod is first laid down (after the interrod substnace has already started layering) there is a rod sheath layer bt the rod and interrod substnave ((aka from inital secretion of rod there is a rod sheath present))

Question 43

T/F Tome’s pit is always occupied by Tome’s process

Answer 43

False. As the ameloblast moves away from the DEJ coronally, its distal end- Tome’s process, moves away with it. Tome’s pit no longer contains Tome’s process.
– Tome’s pit is surrounded by interrod substance and filled with enamel rod all secreted by the ameloblast.

Question 44

When does the enamel compleltely mineralize?

Answer 44

The enamel completley mineralized suring the maturation phase of the secretory stage of amelogeneisis. This maturation phase does not occur until the ameloblasts reach the end of the rod (created by the interrod substance)

Question 45

The presence of tome’s processes and partially mineralized enamel (rod) indicates that the ameloblasts are in which phase

Answer 45

That Tome’s process is present and the enamel is partially mineralized means that we are in the rod secretory phase (during the secreotry stage of amelogenesis)

Question 46

Is Tome’s process present in the interrod secretion phase of the secretor stage of amelogeneisis

Answer 46

Yes. Tome’s process is present during the interrod stage, however during the interrod seceotry phase, Tome’s porcess is still in Tome’s pit. As Tome’s process leaves TOme’s pit, the rod secreotry phase is reached

Question 47

What changes occur to the distal end of the ameloblast during the maturation pahse (of the secretory stage of amelogenesis)?

Answer 47

During the maturation phase, the distal end of the ameloblast alternates bt eve/smooth ANd uneven/ruffled. – and the ameloblast has a differnt func assoc with the differntly shaped ends::: (((think: prev smooth for the inner rodless enamel, uneven for the interrod/rod secretion phase))) :::

– when the distal end of the ameloblast is smooth, the ameloblast is UPTAKING/resrobing/removing organic materal and water (efflux from the paritally minerlaized od and interrod enamel)

– when the distal end of the ameloblast is uneven/ruffled, the ameloblast SECRETES MINERAL SALTS (INORGANIC) into the partially matured enamel interrods and rods.
initial composition = 70% organic + water, 30% inorganic
final comp: 1% organic, 3% water, 96% inorganic

Question 48

what is the initial and final material composition of interrod/rod enamels prior and after maturation?

Answer 48

MAturation = mineralization
initial composition = 30% inorganic, 70% organic + water
final composition= 96% inorganic, 1% organic, 3% water

Question 49

Is the inner rodless enamel secreted by Tome’s process?

Answer 49

No. Neither the inner nor outer rodless enamel layers are secreted by Tome’s process.== the inner and outer rodless enamel layers do not contain enamel rods therefore not sereted by Tome’s process

Question 50

how does the outer rodless enamel layer adhere to the mineralized rod layer? what is the role of the outer rodless layer

Answer 50

The mineralized rod layer is rough on the surface. The rod/ struvcutureless enamel layer is laid by ameloblasts and adheres via mechanical retention (( the rods are uneven edges and are covered by the outer rodless enamel like a coat))

– one role of the outer rodless layer is to seal off the ends of the enamel rods

Question 51

what is the last layer to be secreted by the ameloblasts?

Answer 51

the last layer the ameloblasts secrete is the basal lamina = a nonmineralized secretion == an organic layer

Question 52

what is the last mineralized layer secreted by ameloblasts

Answer 52

the last MINERALIZED layer secreted by the ameloblasts is the outer rodless enamel layer which is immediately mineralzied (and has no enamel rods) = inorganic layer

Question 53

/is the basal lamina an organic or inorganic layer

Answer 53

the basal lamina is the final secretion of the ameloblasts, it is non-mneralized = it is ORGANIC

Question 54

When is Tome’s process present (indicate all)?

• inner rodless phase
• interrod enamel
• rod enamel
• outer rodless enamel

Answer 54

Tome’s process is involved w enamel rods – so Tomne’s process is present during the interrod and rod enamel secretions and NOT present during the inner and outer rodless enamel secretions

Question 55

what is the last phase of amelogenesis? (name it, and describe what happens)

Answer 55

The last stage of amelogeneisis is the postsecretory stage = which is the protective phase . The reduced enamel epithelium ((= superfiical and attached to the final ameloblast secretion of the basal lamina)) is the remnant of the enamel organ and serve to protect the enamel until it enters the oral cavity

((if exposed, things like odontoclasts, etc can break down the enamel… recall– enamel ONLY wants to be touched by SALIVA)))

Question 56

how is the reduced enamel epithelium (the protective cover) attached to the enamel?

Answer 56

the reduced enamel epithelium is attached to the enamel via the basal lamina ((the lat secreted, organic, nonmineralized layer scretreted by ameloblasts))

Question 57

what does the protective layer- the reduced enamel epithelium- become as the tooth emerges?

Answer 57

the protective layer, the reduced enamel epithelium becomes the JUNCTIONAL EPITHELIUM dueing emergence of the tooth into th oral cavity

junctional epithelium::
The junctional epithelium (JE) is that epithelium which lies at, and in health also defines, the base of the gingival sulcus. The probing depth of the gingival sulcus is measured by a calibrated periodontal probe

Question 58

where is the junctional epithelium found? and what forms it?

Answer 58

junctional epithelium::
The junctional epithelium (JE) is that epithelium which lies at, and in health also defines, the base of the gingival sulcus. The probing depth of the gingival sulcus is measured by a calibrated periodontal probe
- the reduced enamel epithelium (protective cover) turns itnot he junctional epithelium as the otooth emerges into the oral cavity

Question 59

how long does the maturation pahse take for each tooth? what does the maturation phase mean?

Answer 59

the maturation phase means the enamel of interrods and rods changes to mineralized tissue ((away from paritally mineralized )).

The process for all of the enamel of 1 tooth to mature takes about 5 years. The porcess starts coronal-most and continues apically

Question 60

what is a line of Retizius?

Answer 60

A line of Retizius is found in maturing/ secreted enamel – is the line due to differnt layers being secreted at different times (like the rings of a tree))

Question 61

what is the pattern of immature enamel secretion? (starts and ends where?)

Answer 61

enamel secretion started at the coronal tips/ cusps and extends apically ((same progression of the next step of maturation where the enamel fully mineralizes.. atarts coronally and continueis apically until all of the enamel is mature)) ((aka, top–>down))

Question 62

for all primary teeth- when do they initially mineralize and when do they complete mineralization (post maturation)) =– provide a timeframe for each

Answer 62

for all primary teeth::
initial mineralization occurs bt weeks 15-19 in UTERO
completed minerlazation occurs 2-11 months post natally

Question 63

for all permanent teeth: provide time frames for when they initially mineralzie and when they all complete mineralziation

Answer 63

for all permanent teeth:
initial mineralzation = birth=9 years
completed mineralzation = 5-14 years

Question 64

what is the first adult permanent tooth to erupt? when does it complete maturation

Answer 64

the first adult tooth is the 1st molars of Max and Mand, and this erupts at birth. COmpleted mineralization occur at 5 years.

Question 65

what is the first primary tooth to develop?

Answer 65

The central incisors and then the 1st max and mand molars are the first teeth to develop –showing up at 15 weeks IU and finishing mneralziation by 2months for the central insicosrs,,, and 6 months for the 1st pirmary molars

Question 66

name the 6 phases of the secretory stage of amelogenesis

Answer 66

the 6 phases of the secretory stage of amelogenesis are::

1) initial minerlaized phase (inner rodless enamel via ameloblasts = mineralized but no enamel rods)
2) interrod substance secretion phase (interrod substance via Tome’s process. mineralzied)
3) rod secretion phase (enamel rods into the Tome’s pits surrounded by interrod substance as a framing matrix..) minerlaized , secreted by tome’s process
4) maturation phase (( enamel rod layers change from partialy to completely mineralized w 96% inorganic material compostion))
5) final minerlaized stage (last minerlaized layer is secreted by ameloblasts = outer rodless enamel
6) final ameloblast secretion = basal lamina = nonminerlaized ((basal lamina attaches to the reduced enamel epithelium that protects the enamel until emergence, and then forms the junctional epithelium))

Question 67

(recall reciprocal induction)) what does the ameloblast need before it will begin to secrete enamel?

Answer 67

the ameloblast needs the presence of dentin before it will secrete enamal – reciprocal induction example

Question 68

name a few of the reciprocal induction needs of tooth formation

Answer 68

in order for dentin to form, there must be ameloblasts present ((inner epithelial layer of hte enamel organ dofferentiates into a specialized ameloblast during the prescretory stage of amelogenesis) /// .. dentin must then be present PRIOR to the formation of enamel – ameloblasts will not secrfete enamel unless dentin is present ((and recall, the first inner rodless enamel is secreted right on top of the rough-hewn dentin allowing for mechanical retention)

Question 69

T/F the presence of the clear layer in the enamel organ indicates that the ameloblasts have not yet matured

Answer 69

True. The presence of the clear layer(acellular) indicates the ameloblasts have not yet matured (no enamel secreted yet) .. once maturing, the ameoloblasts will grown via the Tome’s pits into the clear space which will then be the DEJ boundary

Question 70

what is enamel dysplasia

Answer 70

enamel dysplasia is the condition of abnormal growht or development of the enamel

Question 71

if there is enamel dysplasia evident in the cusp tips/ incisal edges of the teeth, did the dysplasia occur early or later in amelogenesis?

Answer 71

If there are issues of development (dyspolasia) in the incisal 1/3 of the teeth,. likely that the dysplaisa occurred early in developemnt ((as the cusps/ incisal edges are the first part of the tooth to initially minealze and to mature))

Question 72

you presented with teeth were many of the teeth seem pock-marked with tiny holes/divots

Answer 72

The presence of many tiny divots on the teeth may be an idication that there was dysplasia involving the reduced enamel epithelium (where the 4 epithelial layers of the enamel organ come together and form aprotective cover for the enamel)). without an adequate protection, gactors likle the presence of osteolasts etc could have harmed the enamel and caused the dysplasia as the tooth developed and emerged into the oral cavity