01.30 development of dentition

Question 1

when do the primary teeth begin to calcify?

Answer 1

In utero

-about 3.5-4.5 months in utero

Question 2

what is the typical eruption sequence of primary teeth, and when does it start/end?

Answer 2

beings around 6-7th month (mandibular incisors) and ends about the 26th month (maxillary 2nd molars)

Question 3

when do the teeth start moving occlusally (towards eruption)?

Answer 3

after the crown formation is complete

Question 4

dental arch circumference decreases…

Answer 4

during the late transitional and early permanent dentition (maybe after 4 years old)
-so basically a 4 years old has a longer arch length than kids that are older

Question 5

how soon after eruption is the root completely formed for both primary and permanent teeth?

Answer 5

• primary: 18 months post eruption

- permanent: 3 years post eruption

Question 6

how many teeth does a typical one year old have?

Answer 6

6-8, rarely less than 2 or more than 10

Question 7

teeth present at birth are called?

Answer 7

Natal teeth

Question 8

teeth present within the first 30 days of life are called?

Answer 8

Neonatal teeth

Question 9

which is more prevalent, Natal or neonatal teeth, and what is the ratio?

Answer 9

Natal 3:1 Neonatal
incidence 1:2000-3000
-90% are true primary teeth

Question 10

characteristics of ideal primary dentition

Answer 10

• spaced anteriors
• primate spaces (around canines, distal in mandibular, mesial in maxillary)
• shallow overbite and overjet
• flush or mesial step terminal plane
• class I canine relationship
• almost vertical inclination of anterior teeth
• ovoid arch form

Question 11

structures in newborns that are often confused with premature teeth

Answer 11

• dental lamina cysts: crest of ridge
• Bohn’s Nodules: buccal and lingual aspects of ridge palate (away from midline raphe)
• epstein’s pearls: midpalatal raphe

Question 12

primate spaces

Answer 12

wide spaces mesial to the maxillary canines and distal to mandibular canines
-important during canine and bicuspid eruption

Question 13

if a child has a distal step, what will likely be the permanent classificaiton?

Answer 13

class II

Question 14

what is the desired inclination for permanent and primary teeth

Answer 14

primary incisors are upright with little overbite and overjet
-permanent incisors have labial angulation and greater overbite and overjet

Question 15

mandibular intercanine width changes

Answer 15

-the intercanine width increases only slightly with the eruption of the permanent incisors due to divergent nature of the distal movement of the primary canine into the primate spaces

Question 16

how big is the Leeway space?

Answer 16

0. 9 mm in maxilla per side (1.8 total)

1. 7 mm in mandible (3.4 mm total)

Question 17

early mesial shift

Answer 17

• the eruptive force of the permanent molar causes generalized spaces to close allowing the permanent molar to shift into a class I occlusion
• about 6 yrs old, primate space closed

Question 18

late mesial shift

Answer 18

when no primate spaces exist, the permanent molar shift occurs when the second primary molar exfoliates in the mandible before the maxilla
-usually around 12 yr old

Question 19

Histopathology: initiation

Answer 19

problems of tooth #, congenitally missing is more common than super numerary

Question 20

Histopathology: proliferation

Answer 20

problems of tooth #, size, proportion, twinning

Question 21

what is the most common congenitally missing permanent tooth?

Answer 21

mandibular second premolars

Question 22

Histopathology: histodifferentiation

Answer 22

problems of enamel (AI 1 &4) and Dentin (DI)

Question 23

Histopathology:morphodifferentiation

Answer 23

problems of size, shape

Question 24

Histopathology: appostion

Answer 24

enamel hypoplasia, dentin dysplasia, hypercementosis, enamel pearly

Question 25

Histopathology: mineralizaiton and maturation (post eruptive)

Answer 25

AI (2,3,4), flourosis, localized hypomineralization, intergolbular dentin

Question 26

what is the sequence of clacification of primary teeth?

Answer 26

A, D, B, C, E

Question 27

what is the first permanent tooth to begin calcification, and when does that occur?

Answer 27

1st molar, birth

Question 28

eruption sequence of primary teeth

Answer 28

A, B, D, C, E