Chronology of Dentitions

Question 1

What are lobes?

Answer 1

Tooth development center

Question 2

What is coalescence?

Answer 2

fusion of lobes

Question 3

What are mamelons?

Answer 3

3 labial development lobes on incisors

Question 4

What is the cusp of Carabelli?

Answer 4

5th cusp

Question 5

When are the earliest signs of tooth development? Where? What, exactly, is developing at this time?

Answer 5

5-6 week old embryo. anterior mandibular region. tiny tooth buds and tooth germs develop in the alveolar bone (tooth germs are clumps of cells that form tooth tissues: enamel, dentin, cementum, pulp)

Question 6

When does development of permanent teeth occur?

Answer 6

17th week of pregnancy

Question 7

How many teeth do babies have in development at birth?

Answer 7

44 teeth in various stages of development. enamel formation is well underway on all the primary dentition and the beginning of the permanent first molars

Question 8

What do primary and permanent dentitions develop from?

Answer 8

Both develop from buds

Question 9

When do primary teeth begin to calcify? When does this process end?

Answer 9

4th or 5th month of fetal life. this process continues until the 3rd or 4th year after birth for primary teeth, once all the roots have been fully formed

Question 10

What is calcification?

Answer 10

the hardening of tooth tissues by the deposition of mineral salts within the tissues

Question 11

What builds enamel?

Answer 11

Ameloblasts

Question 12

Where does enamel building start from?

Answer 12

Ameloblasts build enamel on the top of the crown at the dentinoenamel junction, and work its way down the sides layer by layer

Question 13

How long does the calcification process of permanent teeth take?

Answer 13

Begins soon after birth and continues until about 25 years of age, when the 3rd molar roots are fully formed

Question 14

During enamel and dentin formation, minerals are being deposited while the tooth buds or germs are forming. What can cause improper tooth formation or mineralization?

Answer 14

• high fever
• metabolic dysfuntion
• childhood or nutritional disease
• physical illness
• trauma during formation

Question 15

Primary eruption rule

Answer 15

begins with mandibular centrals at 6 months of age. mandibular teeth erupt first

Question 16

Sequence of eruption of primary teeth

Answer 16

A's -- 6-12 months
B's -- 9-16 months
D's -- 12-18 months
C's -- 16-23 months
E's -- 24-33 months
overall sequence: A, B, D, C, E
- usually 20 teeth by the age of 2.5, and all lost by the age of 12

Question 17

General rules: (not firm and always have exceptions)

Answer 17

• mandibular teeth before maxillary
• erupt in pairs on each arch (one right and one left either on mandible or maxilla)
• permanent teeth in girls erupt slightly earlier than boys. no evidence of difference in primary eruption between the sexes

Question 18

Primary teeth exfoliation

Answer 18

• mn centrals: erupt around 6 months and exfoliate at 6 years
• mx centrals: erupt 7-8 months and exfoliate 7-8 years
• man laterals: erupt 9 months, exfoliate 8 years
• mn 1st molars: erupts 12 months, exfoliates 10 years
• mx 1st molars: erupts after 12 months, exfoliates 10 years
• canines mx and mn: erupt at 16 months, exfoliates mx at 12, mn at 10 years
• 2nd molars: erupted by 2.5 years old, exfoliates at 12 years

Question 19

What will occur if a primary tooth is lost prematurely? Why is this?

Answer 19

One side of the jaw will develop differently than the other. Reason: exercise is not divided equally when a tooth is missing

Question 20

What is the first permanent tooth to erupt?

Answer 20

mandibular 1st molar

Question 21

What is mesial drift?

Answer 21

the tendency of the permanent molars to erupt towards the midline

Question 22

When does mesial drift occur? What will happen if this occurs?

Answer 22

• if the primary teeth are lost prematurely, space for permanent teeth will be lost
• the spaces between the primary teeth will close

Question 23

What does mesial drift cause overall?

Answer 23

Poor eruption of the permanent premolars and canines

Question 24

What must occur for permanent teeth to erupt?

Answer 24

the teeth of the primary dentition must exfoliate

Question 25

How does exfoliation occur?

Answer 25

the roots will resorb until the tooth falls out. resorption continues to take place as the permanent tooth erupts

Question 26

What do odontoclasts do?

Answer 26

destroy the root of the primary tooth

Question 27

How are odontoclasts activated?

Answer 27

by the pressure of the permanent tooth on the primary tooth

Question 28

Secondary eruption schedule

Answer 28

``` Mandibular teeth before maxillary - 1st molars (6): about 6-7 years - 1's: 7-8 years - 2's: 8-9 years - 4's: 10-11 years - 5's: 10-12 years - 3's: 9-12 years - 7's: 12 years - 8's: 17-21 years overall sequence: 6, 1, 2, 4, 5, 3, 7, 8 (mandibular canines may erupt before premolars, in which case the mn schedule is 6, 1, 2, 3, 4, 5, 7, 8 ```

Question 29

What can occur to stop eruption of 3rd molars?

Answer 29

- can be impacted (totally embedded in bone) - can be partially erupted (not completely erupted) - congenitally missing (the tooth bud never develops)

Question 30

What is attrition? What does it cause?

Answer 30

attrition is the wearing away of tooth surface through functional contact/occlusion. eruptive forces continue throughout the life of a tooth due to attrition

Question 31

What is the curve of spee?

Answer 31

as the teeth erupt, the meet their partner on the opposing arch and form what is called the occlusal plane. A curved plane is derived from the teeth in both arches occluding with one another and is called the Curve of Spee (anterior teeth are higher than posterior)

Question 32

When does the primary dentition start and end?

Answer 32

Starts with the eruption of the first primary tooth at 6-9 months and ends with the eruption of the first permanent tooth (around 6 years)

Question 33

When does the mixed dentition start and when does it end?

Answer 33

Starts with the eruption of the first permanent tooth (around 6 years) and ends with the loss of the last primary tooth

Question 34

When does the permanent dentition start?

Answer 34

When all primary teeth have been lost.

Question 35

What does the term edentulous mean?

Answer 35

no teeth