Unit C module 1

Question 1

What is dental age based on?

Answer 1

Developmental age scale, based on 3 things:

Amount of crown or root development of permanent teeth

The degree of root resorption of the primary teeth

Which teeth have erupted

Question 2

What does dental age 6 look like?

Answer 2

First appearance of permanent teeth. The first permanent tooth to erupt is the mandibular central incisor but it may occassionally be maxillary first permanent molar. Usually mandibular molar will precede the maxillary molar.

These teeth erupt at similar times.

Question 3

What stage of root development is seen prior to eruption of teeth?

Answer 3

Between 2/3rds and 3/4ths of their root development which is typical of root development of all permanent teeth at the time they first appear in the mouth.

Question 4

What happens to primary teeth at the time of permanent tooth eruption?

Answer 4

Resorption of primary roots begins about the time permanent root development starts so at age 6 the roots of maxillary primary centrals and laterals and mandibular primary lateral incisor roots.

Question 5

Which teeth erupt at dental age 6?

Answer 5

Mandibular central incisors

Mandibular first molars

Maxillary first molars

Question 6

Which teeth exhibit root development and resorption of primary teeth at age 6?

Answer 6

Maxillary central incisors

Maxillary and mandibular lateral incisors

Question 7

What happens at dental age 7?

Answer 7

In the second stage of eruption of permanent teeth:

The maxillary central incisors

Mandibular lateral incisors

At dental age 7 the maxillary lateral incisor has advanced root formation but has not yet erupted

Root development / resorption of primary roots occurs in the maxillary lateral incisors

Question 8

What occurs at dental age 8?

Answer 8

The eruption of the maxillary lateral incisors and the beginning of root formation of canines and premolars and the beginning of root resorption of primary canine and molars.

Question 9

What occurs at dental age 9 - 10?

Answer 9

After eruption of the maxillary lateral incisors at age 8 no permanent teeth erupt for 2 - 3 years.

Dental ages 9 - 10 are characterized by presence of permanent central and lateral incisors and permanent first and second molars on both arches.

At dental age 9 root development on premolars is occuring 1/3rd of the root of the mandibular canine and the mandibular 1st premolar are completed. Root development just beginning.

The difference in dental age 9 and 10 would be more resorption in the roots of the parimary canines and molars.

Question 10

What occurs at dental age 11?

Answer 10

Dental age 11 is characterized by the beginning of eruption of canines and premolars.

At this time, mandibular canine, mandibular first premolar, and maxillary first premolars but sometimes the canine is ahead

Question 11

What must be present at dental age 11?

Answer 11

Mandibular: The canine and first premolar

Maxillary arch: The first premolar. Primary canine and second molar are still present.

Question 12

What happens to the permanent canines at dental age 11?

Answer 12

Their root development has approached 2/3rds which indicates time for eruption.

Question 13

What happens at dental age 12?

Answer 13

The remaining succedaneous permanent teeth erupt into the mouth.

At dental age 12 the 2nd molars of both arches are near eruption.

Question 14

What does succedaneous mean?

Answer 14

Permanent teeth which have a primary predecessor (such as canines and premolars)

Question 15

Are permanent molars considered succedaenous?

Answer 15

No, they erupt after the 5s

Question 16

What happens at dental age 13 - 15?

Answer 16

More root formation in the maxillar and mandibular canines, second premolars, and second permanent molars.

By dental age 15 the roots of all permanent teeth except the third molars should be complete and third molars should be complete and third molars should be apparent on the radiographs even though they will not have erupted.

Question 17

Which tooth erupts first the first premolar or the canine in the maxillary arch?

Answer 17

The first premolar

Question 18

Which tooth erupts with the canine in the maxillary arch?

Answer 18

The second premolar.

Question 19

How are premolar and canine eruption rates compared in the mandibular arch?

Answer 19

Canine is slightly below the first premolar and both erupt at the same time.

Question 20

At what age to the primary mandibular canines start to exfoliate and have their roots resorbed?

Answer 20

At dental age 9

Question 21

How does the position of the maxillary canine change with time?

Answer 21

It begins development superiorly and moves downward and somewhat forward towards the position where it will emerge eventually.

Question 22

When does root completion usually take place?

Answer 22

Usually 2 years after tooth erupts into the mouth

Question 23

How long do teeth continue erupting after initial growth into the mouth?

Answer 23

Usually they continue to grow with the growth of the mandible and maxilla apart. They fill the space in.

Question 24

What are the common eruption variations encountered?

Answer 24

Eruption of second molars ahead of premolars in the mandibular arch

Eruption of canines ahead of premolars in the maxillary arch. (Maxillary canines and first premolars can also erupt simultaneously like the mandibular case)

Asymmetries in eruption between the right and the left sides

Question 25

What issue is caused by eruption of second molars before premolars?

Answer 25

The dental arch could have trouble accomodating the second premolar and may lead to impaction.

This can be solved using orthodontic appliances to hold molars back and to open up space for second premolars.

Question 26

What are the possible consequences of second molars erupting before premolars?

Answer 26

There must be enough mandibular growth to allow for third molar development. It can limit available space.

Question 27

What is the common outcome of maxillary canines and first premolars erupting simultaneously?

Answer 27

Maxillary canine is likely to be forced labially. This is because the premolars take up the room designed to accomodate the canine so the canine shifts labially.

Question 28

When should asymmetry between left and ride sides be checked?

Answer 28

More than 6 months difference can be clinically significant and should be investigated. Impaction of maxillary canines can often be prevented by timely intervention.

Question 29

What is the ugly ducklling stage of tooth development?

Answer 29

Incisor positioning early on during development can create a diastema which later corrects itself

Question 30

How does the diastema of early central incisor eruption during the “ugly duckling” stage correct itself?

Answer 30

The diastema in the midline tends to close with time as the lateral incisors erupt. This is further repaired by the eruption of the maxillary incisors.

This is because initially the lateral incisors point more distally and then when maxillary canines erupt this pushes them to follow occlusion more correctly.

Question 31

Do diastemas early in development always close up?

Answer 31

If the diastema is greater than 2mm

Question 32

Does the ugly duckling stage of development occur in all children?

Answer 32

No, it is common enough to be noted as a variation of the usual pattern of eruption.

Question 33

Where do the permanent tooth buds lie relative to the primary dentition?

Answer 33

Lingually and apically

Question 34

What is the problem of having lingual eruption of permanent teeth relative to the primary dentition?

Answer 34

A tendency for permanent lateral incisors to erupt lingually to their ideal position in the arch. (Permanent teeth erupt more lingually and move more labially)

Question 35

What other things can further accentuate the lingual deviation of mandibular and maxillary permanent incisors?

Answer 35

Severe shortage of space can lead to a tendency for the lateral incisors to be displaced lingually.

Question 36

What does absence of normal primary spacing indicate about permanent teeth?

Answer 36

There will be crowding.

Question 37

Where are the primate spaces located?

Answer 37

Behind the maxillary lateral incisors and the mandibular canines.

Question 38

How much primary space does each arch have?

Answer 38

On the average 28.8mm of space is available in the maxillary incisor segment from lateral incisor to lateral incisor. This is 2.6mm more than that needed to accomodate the primary teeth.

In mandibular incisor segment 22.3mm is available on average and is 1.1mm more than required.

When permanent central incisors erupt they are markedly larger than the primary central incisors.

Question 39

What is incisor liability?

Answer 39

The lack of adequate space across the incisors because the permanent incisors are likely to become at least slightly malaligned as they erupt.

Question 40

How is the incisor liability overcome?

Answer 40

As the permanent teeth erupt they force the canines distally into the primate spaces in the mandibular arch and the lateral incisors in the maxillary arch.

Question 41

Which arch is the spacing more favourable?

Answer 41

The maxillary arch

Question 42

What does eruption of first molar and the incisors do to the arch available spaces?

Answer 42

They decrease the available space significantly.

Question 43

What are moorees tables?

Answer 43

Table of available spaces as observed by Moorrees and other workers at Harvard.

They referred to the incisor crowding in the mandible as incisor liability.

Question 44

How is mandibular incisor liability overcome?

Answer 44

3 different sources:

Distal movement into the primate spaces.

Labial eruption

Increase in the width of the dental arch (transverse growth)

Question 45

At which dental age is eruption of teeth completed?

Answer 45

All teeth continue to erupt until age 15 even after they reach the occlusal plane to be consistent with facial growth.

Question 46

At dental age 7, where is the maxillary canine located?

Answer 46

The maxillary canines initially are very high above and only slightly distal to the lateral incisors. Their location almost in the floor of the orbit is why they’re sometimes called “eye teeth”.

Question 47

(A) Eruption of the maxillary canine coincident with the maxillary first premolar rarely is a problem because (B) the erupting canine tends to close spaces between the incisors and creates space in that way.

For A and B are they True or false?

Answer 47

The first statement is false and the second one true. Early eruption of the canine is likely to create a problem, even though its eruption tends to close spaces between the incisors and some space is gained in that way. Whether or not there’s incisor spacing, if the canine erupts along with the first premolar, before the second primary molar is lost and some additional space becomes available in that area, it’s likely to be displaced facially, and orthodontic treatment will be needed to get it back.

Question 48

How much additional space for the incisors is gained by the normal mechanisms to overcome incisor liability?

Answer 48

The normal mechanisms contribute about 3 mm, or half the width of a lower incisor. If more space than that would be needed to obtain incisor alignment, it probably won’t be forthcoming from normal development alone.

Question 49

Dental age 11 is characteried by eruption of:

Answer 49

Mandibular canine and all first premolars