Embryology_Ch 4 And 5

Front 1

Tooth development is called?

Back 1

Odontogenesis

Front 2

Are the stages of development the same or different for primary vs. permanent dentitions?

Back 2

same

Front 3

What are the general development patterns? MN vs. MX, ant vs. post

Back 3

Anterior develop before posterior to allow jaws time to grow. MN usually before MX

Front 4

What is unique about the length of development of teeth?

Back 4

Teeth have the longest developmental perios of any set of organs in the body

Front 5

At what age is the first eveident of hard tissue calcification for

Back 5

3-4 months

Front 6

Name the 6 stages of odontogenesis and when they occur

Back 6

Initiation-6-7th week, Bud stage-8th week, Cap stage-9-10th week, Bell 11-12 weeks, Apposition stage and Maturation stage--vary per tooth

Front 7

When does odontogenesis start?

Back 7

6-7th week prenatal

Front 8

What lines the stomodeum and what does it give rise to?

Back 8

ectoderm (gives rise to the oral epithelium)

Front 9

The 2 horsechoe-shaped bands of tissue on the surface of the stomodeum in areas of each future dental arch are called?

Back 9

Oral epithelium

Front 10

What forms the enamel organ?

Back 10

Oral epithelial cells. Enamel forms from the enamel organ

Front 11

What forms the dental papilla? What forms from the dental papilla?

Back 11

Mesenchymal cells form the denal papilla, Dentin forms from the dental papilla

Front 12

What happens at the end of the initiation stage (end of week 7)

Back 12

Growth of oral epithelium gives rise to the Dental lamina

Front 13

What is the dental lamina and when does it appear?

Back 13

layer of epithelial cells that gives rise to 20 primary tooth buds. It begins to form at the end of the 7th week

Front 14

How does the oral vestibule form?

Back 14

vestibular lamina cells enlarge at the end of the initiation stage and then degenerate forming a cleft

Front 15

What characterizes the bud stage?

Back 15

rounded, localized growth of epitherium surrounded by mesenchymal cells

Front 16

During the Bud stage different types of dental lamina give rise to different types of teeth…name the three types and which teeth they form

Back 16

1. Primary Lamina-Deciduous teeth, 2: Successional Lamina-Succedaneous teeth, 3: General Lamina-Non-succedaneous teeth

Front 17

When does the enamel organ form?

Back 17

Cap stage weeks 9-10

Front 18

When does the dental papilla form?

Back 18

Cap stage weeks 9-10

Front 19

What forms the future DEJ during the cap stage of development?

Back 19

The basement membrane-this usually dissolves and the enamel and dentil lock to form the DEJ

Front 20

What does the dental papilla form?

Back 20

future dentin and pulp tissue

Front 21

What does the enamel organ form?

Back 21

Enamel

Front 22

What is the dental sac or follicle and what does it form?

Back 22

Connective tissue that surrounds part of the enamel organ and papill. It forms the PDL, cementum, and alveolar bone

Front 23

What does the tooth germ consist of?

Back 23

Enamel organ, dental papilla and the dental sac/follicle

Front 24

Which dentition do the tooth germs develop?

Back 24

Primary dentition, successional dental lamina will develop the permanent dentition, this also begins during the cap stage

Front 25

When does the Bell stage occur?

Back 25

weeks 11-12

Front 26

what happens during the bell stage?

Back 26

tooth germ grows and changes to a bell0shape and there are 4 distinguishable enamel organ layers at this time

Front 27

During the bell stage what are the four layers of the enamel organ and what do they do?

Back 27

1. Outer enamel epithelium--layer of cuboidal cells, that oraganizes a netwrok of capillaries that brings nutrition to the ameloblasts. 2:Stellage reticulum-just inside the OEE, loose network of star shaped epithelial cells. 3:Stratum intermedium between the stellate reticulum and IEE-closely packed, flat epithelial cells. ASSIST the ameloblasts in the formation of enamel. 4. Inner enamel epithelium-lines inside of the enamel organ-single layer of cuboidal cells which become AMELOBLASTS that form the enamel.

Front 28

What happens to the dental papilla during the bell stage?

Back 28

Differentiates into two types of tissue layers. 1:Outer cell-Odontoblasts (dentin secreting cells), 2:Central cells of the dental papilla-become dental pulp

Front 29

When the enamel organ's inner and outer epithelial cells layers meet are are continuous with each other what is formed? When is this formed? What else happens at this time?

Back 29

Cervical loop is formed during the end of the Bell Stage. At this time, Mesenchymal cells migrate from the periphery of the enamel organ to start development of the future periodontium.

Front 30

What are the two main cellular players during the Appositional Stage? What separates these two cell types initially? What happens during the Appositional Stage?

Back 30

Ameloblasts are formed by the inner enamel epithelium when cuboidal cells elongate into columnar cells. Odontoblasts are formed by peripheral cells of the dental papilla changing into columnar cells. The Basement membrane separates the two. During this stage after the cells have differentiated, formation of the partially hard tissue begins--enamel and dentin.

Front 31

What else is forming during the appositional Stage when enamel and dentin are forming?

Back 31

mandible and maxilla bones

Front 32

What do ameloblasts form?

Back 32

Enamel matrix

Front 33

What do Odontoblasts form?

Back 33

predentin

Front 34

During dentinogenesis/appositional stage, what is the first cell to differentiate?

Back 34

The inner enamel epithelium cells elongate and differentiate into PREAMELOBLASTS.

Front 35

What dos preameloblasts induce?

Back 35

The dental papilla cells to differnetiate into odontoblasts and then they differentiate into ameloblasts

Front 36

What is dentinogenesis? Does it happen before or after amelogenesis?

Back 36

Apposition of dentin matrix or predentin on their side of the basement membrane. This always happens before amelogenesis (but it starts almost immediately after)

Front 37

when does the basement membrane dissolve?

Back 37

During dentinogenesis. After the odontoblasts form predentin it disolves and allows the preameloblasts to come into contact with the newly formed predentin

Front 38

What induces the preameloblasts to differentiate into ameloblasts?

Back 38

The dissolving of the basement membrane and subsequent contact with the newly formed predentin

Front 39

Where is the initial formation of dentin?

Back 39

At the cusp tips

Front 40

what are the attached cellular extensions that odontoblasts leave in the predentin called?

Back 40

Odontoblastic processes

Front 41

What are odnontoblastic processes contained in?

Back 41

A mineralized cylinder or dentinal tubule

Front 42

Where do the cell bodies of odontoblasts reside?

Back 42

They remain in the pulp tissue and retain the ability to repair

Front 43

Do ameloblasts remain functional throughout life?

Back 43

No. These cells will be involved in the eruption and mineralizastion process but are lost after eruption. Enamel can't be replaced

Front 44

What is the apposition of enamel matrix or laying down enamel on the side of the disintigrating basement membrane called?

Back 44

Amelogenesis. This always starts after dentinogenesis

Front 45

What cells are active during amelogenesis?

Back 45

Ameloblasts

Front 46

Where is the enamel matrix secreted from on an ameloblast? What direction is the enamil matrix secreted towards?

Back 46

Tomes' process (an angled part of each ameloblast that faces the disintegrating basement membrane created as the ameloblasts move away from the dentin interface)

Front 47

What happens when the dintegrating basement membrane begins to mineralize?

Back 47

The dentinoenamel junction is formed (DEJ)

Front 48

What appears at the junction of the cell body and tomes' processes to maintain contact of the ameloblasts?

Back 48

Terminal bar apparatus

Front 49

During what stage do the dental tissues fully mineralize?

Back 49

During the maturation stage which varies according to the tooth

Front 50

What happens during the maturation stage? Where does this begin?

Back 50

Minerals are deposited shortly after the matrix is formed001st mineralized at the DEJ

Front 51

What is the mineral content of enamel? Dentin?

Back 51

enamel is 95% mineral content (the most highly calcified tissue in the body), Dentin-70%

Front 52

What happens after the protective stage? Which cells are important during this time?

Back 52

Ameloblasts secrete an organic cuticle on the surface of the enamel

Front 53

What is the cellular organic covering that covers newly formed enamel surfaces called? What forms it?

Back 53

Reduced enamel epithelium

Front 54

What aids in tissue disintegration giving way to the eruption pathway?

Back 54

Enzymes from the reduced enamel epithelium

Front 55

What forms the junctional epithelium near the CEJ during eruption?

Back 55

The REE (reduced enamel epithelium)

Front 56

When do roots form?

Back 56

As the crown is compteley shaped and the tooth begins to erupt. (A tooth froms from the "top down")

Front 57

Where does root formation begin>?

Back 57

through the formation of a cervical loop--the most cervical portion of the enamel/dental organ

Front 58

What are the two layers of the cervical loop and what is each layer involved in the formation of?

Back 58

Inner Enamel Epithelium-forms the inner cell layer of the root sheath wich form odontoblasts/dentin and The Outer Enamel Epithelium-which forms the outer cell layer which funcions in the deposition of intermediate cementum.

Front 59

What layer of the root sheath forms dentin? Cementum?

Back 59

Inner enamel epithelium-dentin. Outer enamel epithelium-cementum.

Front 60

When the cervical loop begins to grow down into the dental sac what is formed?

Back 60

Hertwig's Root Sheath

Front 61

Which cells in the root sheath function in depositing intermediate cementum? What do these do after depositing intermediate dentin?

Back 61

Outer root sheath cells, then they move away from the root surface as epithelial rests.

Front 62

What is the 45 degree angle at the end of the root sheath know as?

Back 62

Epithelial diaphragm

Front 63

What is the function of the pulp proliferation zone?

Back 63

Produces cell for root lenthening

Front 64

what is present during the later stages of root development?

Back 64

Cementoblasts, PDL fibers, and epithelial rests

Front 65

When does cementogenesis begin, how does it begin, and what cells are involved?

Back 65

Occurs upon degradation of the root sheath which allows contact of the dental sace cells with the dentin surface--this inducted the formation of cementoblast cells

Front 66

What is cementogenesis? Do they lay down calcified cementum?

Back 66

When cementoblasts cover the root dentin and lay down non-calcified cementoid on the intermediate cementum (from the outer enamel epithelium)

Front 67

When Is cementiod converted to cementum?

Back 67

Upon mineralizion of the cementoid

Front 68

During root formation what forms the pulp?

Back 68

The central cells of the dental papilla

Front 69

Which tissue do cementoblasts arise from?

Back 69

the dental sac cells

Front 70

Where is the cemntum less cellular?

Back 70

Towards the CEJ

Front 71

How are multi-rooted teeth formed? What is the rol of the epithelial diaphragm

Back 71

All teeth begin as a single root-root trunk, then due to differential growth of the root sheath there is a division of the root trunk into 2 or 3 roots. The epithelial diaphragm grows,makes contact and fuses to develop 2 or 3 roots

Front 72

What forms the PDL and alveolar bone?

Back 72

The mesenchymal cells from the dental sac or follicle

Front 73

Where do the PDL fibers insert into?

Back 73

The outer layer of cementum and alveolar bone

Front 74

What are the islands of epithelial cells that develop from the disintegrating of the root sheath? What is their funcion?

Back 74

Rests of Malessez. No known function but are responsible for the formation of radicular cysts

Front 75

When does the PDL reach full maturation?

Back 75

Not until the teeth reach functional occlusion

Front 76

Bone between the root is called?

Back 76

Interradicular bone

Front 77

What type of bone lines the tooth socket?

Back 77

Alveolar bone proper

Front 78

What type of bone covers the mandible?

Back 78

Supporting bone which is composed of cancellous and compact bone

Front 79

What type of cells form the PDL?

Back 79

Fibroblast (originate from mesenchymal cells in the dental sac/follicle)

Front 80

What type of cells form the alveolar process?

Back 80

Osteoblasts (originate from mesenchymal cells in the dental sac/follicle)

Front 81

What is the difference between active and passive eruption?

Back 81

Active-vertical movement of the tooth, Passive-occurs with aging, recession-no actual tooth movement

Front 82

What are some examples of passive eruption?

Back 82

supereruption, mesial drift and eruption due to attrition

Front 83

What are the 3 phases involved in eruption

Back 83

1. Pre-eruptive phase 2. Pre-functional phase 3. Functional phase

Front 84

Is eruption a static process?

Back 84

Eruption is a continuous process that ends only with tooth loss

Front 85

Which phase of tooth eruption includes the time of tooth initiation until the time of crown completion?

Back 85

Pre-eruptive phase

Front 86

What is happening during the pre-eruptive phase?-primary teeth, jaws, permanent teeth?

Back 86

crowns are forming, jaws lengthern, teeth make mesial and distal movements AND permanent teeth adjust their position to the resorptive roots of the primary teeth

Front 87

What marks the beginning and end of the pre-functional eruptive phase?

Back 87

Starts with root formation and ends when teeth reach occlusal contact

Front 88

What four major events mark the pre-funcional eruptive stage?

Back 88

1. Root formation (proliferation of the root sheath and root dentin and pulp inside) 2. Movement (Incisal or occlusal movement due to the need for space of the enlarging roots-reduced enamel epithelium fuses with oral epithelium) 3. Penetration (into oral cavity) 4. Intraoral occlusal or incisal movement (until clinical contact with the opposing crown occurs, apical shift of gingival attachment).

Front 89

During what event does the reduced enamel epithelium fuse with the oral epithelium? What is formed by this?

Back 89

Movement (of Pre-Functional Eruptive Phase). REE forms juncional epithelium

Front 90

What happens to the gingival attachment during the intraoral occlusal or incisal movement of the pre-functional eruptive phase?

Back 90

It shifts apically

Front 91

What forms the eruption pathway>

Back 91

The dental follicle. An inverted triangular area of degenerating connective tissue forms

Front 92

The follicular fibers that guide teeth movements during eruption are called?

Back 92

Gubernacular cord

Front 93

What two types of cells are involved in breaking down the tissues so that teeth can erupt?

Back 93

Macrophages-release enzymes that help with the tissue destruction. Osteoclasts are between the teeth ard the bone that will be resorbed.

Front 94

How is primary teeth root dentin resporbed?

Back 94

Similar to bone resorption

Front 95

What do Osteoclasts do during the pre-functional eruption phase? How do they achieve this? What do they do to maximize their efficiency?

Back 95

Resorb hard tissue by secreting hydrolytic enzymes. They become modified (enfolded) producing a ruffled border which increases their surface area and maximizes their resorption function

Front 96

What are the two phases of hard tissue resorption?

Back 96

1. Extracellular-mineral is separated from collagen 2. Intracellular-osteoclasts ingest these fragments

Front 97

Which cells help to dissolve the remaining collagen fibers and then utilize the amino acids from the breakdown to form new bone?

Back 97

Fibroblast-fibroclast cells during the pre-functional phase

Front 98

What is happening around the teeth during the prefunctional phase (ligaments and bone)?

Back 98

As roots develop fibers begin to attach to the cervical area, as the root lengthens more fibers appear. Which root formation, alveolar bone accommodates. Once in occlusion the fibers organize and increase in density forming the periodontal ligament.

Front 99

When is the periodontal ligament formed

Back 99

starts during the prefunctional phase of eruption but doesn't complete until the tooth is in occlusion

Front 100

What is the region at the root apex that accommodates the growing root with changes in the surrounding soft tissue and bone?

Back 100

The fundic region

Front 101

What type of cells are abundant in the fundic region and what do they do?

Back 101

Fibroblasts-form collagen fibers and calcified trabeculae at the apex. Network helps to support tooth

Front 102

Which eruptive stage are our teeth currently in?

Back 102

The functional eruptive phase which occurs after the teeth are functioning and as long as they are present

Front 103

When does root completion occur?

Back 103

Continues after occlusion. About 1-1.5 years for primary and 2-3 years for permanent

Front 104

What happens once roots are complete (bone and PDL)?

Back 104

Bone increases density and the PDL fibers increase in dimension and mature orientation

Front 105

With attrition, teeth lose height…what mechanism compensates for this loss?

Back 105

Teeth erupt more. Cementum is deposited at the root apex and the furcation area in multirooted teeth

Front 106

What are the 4 types of tooth movement?

Back 106

1. Occlusal 2. Horizontal 3. Rotational & Lateral 4. mesial drift

Front 107

What is mesial drift? Explain what is going on when this happens

Back 107

lateral movement of teeth on both sides of the mouth towards the midline. Contacts wear due to mastication. Pressure on the mesial side of the socket causes resrption of lamina dura and tension of the PDL on the distal side causes growth--this causes a shift in position of the tooth socket.

Front 108

How are 1st molars different in their eruption than 2nd and 3rd molars (permanent)? Why?

Back 108

!st molar develop in approximately the same position as where they erupt. 2nd and 3rd molars have to rotate to emergin in correct relationship of other teeth. The mandible and maxilla are too small to accommodate these during the time of development.

Front 109

Where do MN 2nd and 3rd molars develop? MX molars?

Back 109

MN-develop in ramus of the mandible with occlusal surfaces towards the mesial (Impaction is when there is inadequate jaw development and improper rotation). MX-develop in the MX tuberosity with their occlusal surfaces directed buccally and distally

Front 110

Having 2 dentitions

Back 110

Diphyodont

Front 111

Loss of primary dentition by the physiologic resprption of their roots

Back 111

Shedding

Front 112

How are primary teeth different that permanent in terms of enamel, dentin, pulp and nerves?

Back 112

Primary enamel-prismless (hard to etch for sealants), 1/2 thickness, less pigmented--whiter. Primary dentin-softer Primary pupls are larger and Primary teeth have less nerves