Development Of Occlusion

Question 1

When does preemergent eruption begin?

Answer 1

When root formation has started

Question 2

Emergence, the movement when a cusp or an incisal edge of a tooth first penetrates the gingiva, usually occurs when ___% of the final root length is established.

Answer 2

75%

Question 3

True or false… postemergent eruption haunts once it comes into occlusion.

Answer 3

False. It continues to to equal the rate of the vertical growth of the face.

Question 4

On average, a molar tooth erupts about __mm after having reached the occlusal contact

Answer 4

10mm

Question 5

Short-term eruption of teeth seems to follow a ___ rhythm, mainly occurring during the ___ hours of sleep. Tooth eruption and secretion of ___ and ___ hormones are correlated in its day-night pattern.

Answer 5

Circadian

Early

Growth and thyroid hormones

Question 6

Primary dentin is fully formed by the age of ___ with the calcificaiton of the primary roots completed ___ later

Answer 6

2.5 years old

1 year later

Question 7

The first primary tooth to erupt are the ____, which emerge at ___ months.

Answer 7

Lower central incisors

7 months

Question 8

Where are the primate spaces located in the primary dentition?

Answer 8

Between the upper primary laterals and canines

Between the lower primary canines and first molars

Question 9

It is estimated that if the total amount of space per dental arch is only 0-3mm, there is a ___% probability of crowding in the permanent dentition.

Answer 9

50%

Question 10

In about 80% of children with a mesial-step terminal plane less than 2mm, ___ results.

Answer 10

Angle Class 1 molar relationship

Question 11

If the mesial-step terminal plane is more than 2mm, a ___ molar relationship results in 20% of subjects.

Answer 11

Class 3

Question 12

A flush terminal plane results in either a class 1 (___% of subjects) or a class 2 (___% of subjects) molar relationship

Answer 12

56%

44%

Question 13

A distal-step terminal plane almost invariably results in a ___ molar relationship in the permanent dentition.

Answer 13

Class 2

Question 14

Define angle class 1 molar relationship. What is the difference between Class 1 normal occlusion, and class 1 malocclusion.

Answer 14

Mesiobuccal cusp of upper first molar occuldes with the buccal groove of the lower first molar.

They both have the same molar relationship, but the latter is also characterized by crowding, rotations, and other positional irregularities.

Question 15

Define angle class 2 molar relationship. What is the difference between division 1 and division 2?

Answer 15

MB cusp of the upper molar occludes anterior to the buccal groove of the lower first molar.

Division 1 - the upper incisors at labially tilted, creating significant overjet.

Division 2 - the upper central incisors are lingually inclined and the lateral incisors are labially inclined. When measured from the central incisors, overjet is within normal limits.

Question 16

As a general rule, a tooth should erupt once ___ of the root is formed.

Answer 16

2/3rds

Question 17

What occurs during the first transitional period?

Answer 17

First molars and all permanent incisors are present

Question 18

What is the second transitional period?

Answer 18

First period - lower canines with upper and lower first premolars.
Second period - upper and lower second premolars, followed shortly by maxillary canines
Third period - second molars erupt

Question 19

In both the maxilla and mandible, the permanent incisors develop and erupt on the ___ side of the roots of the primary incisors.

Answer 19

Lingual/palatal

Question 20

How is the space deficit between primary and permanent incisors solved?

Answer 20

First, the upper incisors generally erupt to a wider dental arch circumference than the primary incisors, which is the most effective way to gain space for these teeth.

Second, when the central permanent incisors erupt they push the lateral incisors distally. The same thing happens when the laterals erupt which pushes the canines distally.

The transverse growth of the maxilla at its midpalatal suture also allows for space-gaining.

In the mandible, pushing takes place as it does in the maxilla. However the lower anterior teeth do not generally erupt to a wider dental arch circumference than the primary teeth, and no transverse growth can take place. Crowding is commonly seen once the lower permanent incisors have erupted.

Question 21

If considerable spacing in the primary dentition (>5-6mm) does not exist, crowding is commonly seen once the permanent lower incisors have erupted. This is called ___

Answer 21

Physiological crowding

Question 22

Describe the “ugly duckling” stage.

Answer 22

A normal spacing condition seen in the upper front areas. This is due to lateral incisors tipped distally due to pressure of the erupting canines on their roots. Once the permanent canines erupt, the upper spaces usually close and uprighting of the lateral incisors can be seen.

Question 23

How is space secured for nonsuccedaneous teeth?

Answer 23

In the upper arch, space is created for the molars by bone apposition at the free posterior border of the maxilla. Also, the transverse palatal suture may make a contribution.

For the lower molars, bone apposition occurs on the posterior side of the mandibular ramus while bone resorption occurs on the anterior ramus.

Also, upper and lower first molars usually drift forward because of excess space due to the leeway space. This anterior drift of the first molars opens up space for the second molars to erupt.

Question 24

How much leeway space is typically provided?

Answer 24

1-1.5mm of space in each upper quadrant

2-2.5mm of space in each lower quadrant

Leeway space is provided due to the size discrepancy of primary molars and permanent premolars.

Question 25

The primary molars are on average ___mm larger than the second premolars

Answer 25

2mm

Question 26

Sometimes the lower second molars erupt before the second premolars. What can this cause?

Answer 26

This may cause anterior drift of the first permanent molars too early and, as a consequence, space loss for the second permanent premolars. Therefore, it is preferable that the second premolars erupt before the second permanent molars.

Question 27

Since the leeway’s space provides the space needed for the upper canines, they should erupt [after/before] the permanent first premolars. If not…

Answer 27

After

If not, lack of space may cause the upper canines to erupt too labially

Question 28

During the eruption of the maxillary permanent incisors, intercanine dimension increases on average by ___mm. Befor or at the time of eruption of the permanent canines another increase of __mm takes place in the canine-to-canine distance. This increase is caused by the distalizing pressure of the erupting permanent incisors on the permanent canines and growth in width of the maxilla at the midpalatal suture.

Answer 28

3mm

2mm

Question 29

What is different between the upper and lower arches in determining the intercanine distance?

Answer 29

In the lower dental arch, a comparable increase of the intercanine distance occurs during the eruption of the permanent incisors (3mm on average). However, unlike the upper arch, no additional increase in the canine-canine distance takes place in the lower arch during the later stages of dental development. This early establishment of the lower intercanine distance has an important clinical bearing in that attempts to increase lower intercanine distance by orthodontics usually results in relapse.

Question 30

How is dental arch width typically measured?

Answer 30

Distance between the corresponding contralateral teeth at the cusp tips.

Another measurement can be made at the palatal/lingual gingival level of the teeth; this measurement describes the width of the bony arch.

Question 31

What is secondary crowding?

Answer 31

Increase of existing crowding in the lower anterior area found in the late teens or early 20s. This crowding occurs before or simultaneously with the emergence of 3rd molars.

Question 32

What contributes to secondary crowding?

Answer 32

Maxillary and mandibular differential growth. Growth of the maxilla ceases earlier than growth of the mandible. Because of overbite, lower anterior teeth cannot move forward to the extent of the lower jaw growth but tilt lingually to a small circumference, which results in crowding.

in addition, the maturation of soft tissues that occurs during the teenage period may increase the pressure from lips, causing crowding.

More forward drift takes place in the lower dentition than in the upper arch, which also increases crowding.

Question 33

True or false… delayed tooth eruption is possible, but premature tooth eruption is more common.

Answer 33

False.. it is the other way around… premature tooth eruption is possible, but delayed tooth eruption is more common.

Question 34

Reasons for delayed tooth eruption bay be divided into rare systemic factors and more frequent local factors. What are some of local factors?

Answer 34

Supernumerary teeth

Heavy fibrous gingival tissue because of premature loss of a primary tooth

Crowding

Sclerotic alveolar bone

Ankylosis of a tooth

As a general rule, if a permanent tooth has erupted but its counterpart does not within 6 months, an eruption problem is evident and further investigation is recommended.

Question 35

True or false… ankylosis is more common in the primary teeth than the permanent

Answer 35

True (especially primary molars)

Question 36

What are the most common ectopically erupted teeth?

Answer 36

Upper first molars and canines followed by lower canines, upper premolars, lower premolars, and upper lateral incisors.

Question 37

Which teeth have the longest path of eruption?

Answer 37

Maxillary canines

Question 38

What percent of maxillary canines are impacted?

Answer 38

About 2%

Question 39

Interestingly, nearly 50% of patients with palatal located upper canines also present with ___.

Answer 39

Peg laterals or congenitally missing upper laterals

Question 40

What is the typical eruption problem of the second permanent molars?

Answer 40

If space is not adequate for the upper second molars, they often told buccally and distally before their emergence and eventually erupt too buccally. On the contrary, lower second molars tend to tilt lingually

Question 41

External forces on teeth (cheeks, lips, tongue) are not completely in balance. However, periodontally healthy teeth do not move, why?

Answer 41

The balancing factor is the PDL.

Thus, if if support from the alveolar bone and PDL is reduced, teeth are prone to move.

Question 42

During the period between 8 and 18 years of age, anterior and posterior face height increases by about ___mm.

Answer 42

20mm

Question 43

WHat happens if growth of anterior and posterior face is not in balance?

Answer 43

Either anterior or posterior growth rotation of the mandible occurs. This is followed by overeruption of posterior or anterior teeth in posterior or anterior rotation patterns respectively.

Question 44

It has been found that anterior facial height may continue to increase still between ages __ and ___

Answer 44

25 and 45 (and probably beyond in healthy individuals0

Question 45

True or false… It has been found that dental implants in the upper front area may exhibit major vertical steps in the same amount in persons with early (15-21 years) or late (40-55) implant placement .

Answer 45

True. Therefore, from the occlusal development point of view, placement of dental implants should be postponed as long as possible.

Question 46

What are the most common congenitally missing permanent teeth?

Answer 46

1) lower second premolars
2) upper laterals
3) upper second molars

Question 47

True or false… DAPs (Dental anomaly patterns) are commonly associated with each other.

Answer 47

True. Thus when one DAP is found, a closer look of the patient should be taken to see if there are any other DAPs

Question 48

Does variation in tooth size have an effect on occlusion?

Answer 48

Variation in tooth size is a relatively common finding and may have an effect on occlusion.

Question 49

What is the prevalence of “tooth size discrepancy”? Which teeth show the largest variation in size?

Answer 49

About 5%

Upper permanent laterals. If they are significantly smaller or larger than average, ideal occlusion is difficult to establish.