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1

What are the three types of problems that orthodontics treats?

1. Psychosocial
2. Oral Function
3. Trauma, periodontal disease, and tooth decay

2

Severe malocclusion is a social handicap. True or False?

True

3

What is the major reason why people seek ortho treatment?

To minimize psychosocial problems

4

Temperomandibular dysfunction patients are found in what four groups?

1. Masticatory muscle disorders
2. TM joint disorders
3. Chronic mandibular hypomobility
4. Growth disorders

5

Muscle spasms and fatigue should be fixed by orthodontics first. True or False?

False, simpler methods first

6

Orthodontics alone is rarely useful for patients with internal joint pathology. True or False?

True

7

What is disk displacement?

Trauma or aging of the ligaments that oppose the ac)on of the lateral pterygoid muscle are stretched or torn so when the muscle contracts the ligaments cannot return the disk to its proper position and a resulting pop upon opening and/or closure is seen.

8

TMD is no more prevalent in patients with severe malocclusion than in the general population. True or False?

True

9

What can splint therapy help identify?

Used to help identify if the malocclusion is a possible cause of the patients TMD.

10

Bite splints should always be full coverage of all the teeth, either maxillary or mandibular. True or False?

True

11

The disappearance of TMD during ortho treatment is often only temporary. True or False?

True

12

What types of problems can cross bites and traumatic occlusions cause?

Extreme wear, gingival recession, bone loss, influence growth, cause stress on the TMJ.
Early ortho intervention can fix these problems.

13

Long term studies show that ortho treatment increases chance of later periodontal problems. True or False?

False

14

What happens in dental age 6?

Mandibular central incisors
Mandibular first molars
Maxillary first molars

15

What happens in dental age 8?

Maxillary lateral incisors

16

What happens in dental age 11?

Mandibular canines
Mandibular first premolars
Maxillary first premolars

17

What happens in dental age 12?

Maxillary canine
Maxillary and mandibular second premolars
Maxillary and mandibular second molars

18

What happens in dental age 15?

Roots of all permanent teeth except third molars are done

19

When does the eruptive movement of the tooth begin?

The eruptive movement of the tooth begins soon after the root begins to form, and the roots emerge from the dental follicle.
– This supports the idea that metabolic activity within the periodontal ligament is necessary for eruption.
– But elongation of the tooth root is not.

20

What two processes are necessary for pre-emergent eruption?

– First, there must be resorption of the bone and the primary tooth roots, overlying the crown of the erupting tooth.
– Secondly, there must be a propulsive mechanism to move the tooth in the direction where the overlying path has been cleared.

21

What are some conditions that interfere with pre-emergent eruption?

In children with cleidocranial dysplasia the permanent teeth do not erupt because of abnormal resorption of both bone and the primary teeth.
• The eruption of the primary teeth is also delayed due to fibrotic gingiva
• Interestingly, if the mechanical obstruction of eruption is removed in these patients, the teeth may erupt spontaneously and can be brought into the arch with orthodontic force
• This is an example of a defect in the patients ability to remove the overlying structures during tooth eruption, which causes delayed eruption or the impaction of the involved teeth

22

The rate of bone resorption and the rate of tooth eruption, are controlled physiologically by the same mechanism. True or False?

False, they are not
• This means that the tooth's occlusal eruption movement, does not control the dissolution of the overlying bone and primary teeth.
• If an unerupted permanent tooth is wired (accidentaly) to the adjacent bone when a jaw fracture is repaired, eruption of the tooth is mechanically stopped.
• But in this situation, bone resorption to clear an eruption path through expansion of the dental follicle continues.
• This mechanism can go wrong in a follicular cyst.

23

What activates the signal for resorption of bone over the crown of a tooth?

The completion of the crown, which also removes the inhibition of the genes that are necessary for root formation

24

What is the rate limiting factor in pre-emergent eruption?

Because a tooth will continue to grow and form the tooth’s root regardless of whether the overlying bone and primary teeth are removed, It would seem clear therefore, that resorption of the overlying bone is the rate limiting factor in pre-emergent eruption
• Because resorption of the overlying bone is the controlling factor, a tooth that is still embedded in bone can continue to erupt after root formation is completed, but in this situation surgical orthodontic eruption is often necessary.
• Remember, active formation of the root, is not necessary for continued clearance of an eruption path, or for movement of a tooth along the eruption path.

25

Teeth will not continue to erupt if its apical area has been removed, as in an apicoectomy. True or False? And how is a dilaceration formed usually?

False, it still can. So the proliferation of cells associated with lengthening of the root, is not an essential part of the eruption mechanism.
• Normally, the rate of eruption is such that, the apical area remains at the same place while the crown moves occlusally.
• But if the eruption is mechanically blocked, the proliferating apical area will move in the opposite direction.
– This can cause a distortion of the root in an abnormal direction called a dilaceration.
• Despite many years of study, the precise mechanism through which the propulsive force is generated remains unknown.

26

What is primary failure of eruption?

It is a condition that is characterized by non syndromic eruption failure of permanent teeth in the absence of mechanical obstruction.
• This indicates that there is a defect in the propulsive mechanism of tooth eruption
• Typically in PFE patients the posterior teeth are more frequently affected, with the first and second molars being more frequently affected than the premolars and canines.
• If a tooth in a further anterior position presents with an eruption disturbance, the posterior teeth are usually, but not always, affected as well.
• The affected teeth resorb the alveolar bone above the crown, but erupt only partially or fail to erupt at all.
• Both deciduous and permanent teeth can be affected.
• This condition is usually asymmetrical, and primarily non-ankylosed teeth tend to become ankylosed as soon as orthodontic forces are applied. (Did the orthodontic force cause the ankylosis, or was the ankylosis identified after application of the orthodontic force). Application of a straight wire on these patients can be disastrous.

27

What did the UNC Ortho study conclude about treating PFE teeth orthodontically?

A PTH1R (parathyroid hormone receptor) mutation is strongly associated with failure of orthodontically assisted eruption or tooth movement and should therefore alert clinicians to treat PFE and ankylosed teeth with similar caution-ie, avoid orthodontic treatment with a continuous archwire

28

What is the juvenile post-emergent spurt?

• Once a tooth emerges into the mouth, it erupts rapidly until it approaches the occlusal level and is subjected to the forces of mastication.
• At that point, its eruption slows and then as it reaches the occlusal level of the other teeth, and is in complete function, eruption all but halts.
• The stage of relative rapid eruption from the time a tooth first penetrates the gingiva until it reaches the occlusal level is called the Juvenile post-emergent spurt.
• In the 1990’s the development of new instrumentation made it possible to track the short-term movements of teeth during the post emergent spurt, and this showed that eruption occurs only during a critical period between 8 PM and 1 AM.

29

Why does the post-emergent juvenile spurt happen at a specific time each night?

• This day time and night time eruption difference seems to reflect an underlying rhythm, which is probably related to the very similar cycle of growth hormone release.
• Experiments with the application of pressure
against an erupting premolar suggest that eruption is stopped by force for only one to three minutes.
– (Tongue pressures/Thrusting)

30

What forces oppose eruption of teeth?

– Chewing forces
– Soft tissue forces
• Lips
• Cheeks
• Tongue
• If eruption typically only occurs during the quiet periods between 8pm and -1am, the soft tissue pressures probably are more important in controlling eruption than the heavy pressures that occur during chewing
• Light pressures of long duration are more important in producing orthodontic tooth movement than heavy intermittent pressures like chewing.