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DMD3 > Ortho Level 2 Unit A > Flashcards

Ortho Level 2 Unit A Flashcards

1
Q

Which teeth are the “key to occlusion” what does that mean?

A

The maxillary first molars are the key to occlusion. This means their position at the base of the zygomatic arch, and that the mesiobuccal cusp of the upper first molar should occlude in the buccal groove of the lower first molar.

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2
Q

Where does Angle’s line of occlusion pass?

A

Through the central fossae of the maxillary posterior teeth and across the cingulum of the upper canines and incisors.

The same line also runs along the mandibular posterior teeth (the buccal cusps) and the incisal edges of the lower canines and incisors.

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3
Q

What are the types of occlusion?

A

Class 1: Normal relationship of the first molars but line of occlusion incorrect because of incorrectly aligned teeth

Class 2: Lower molar distally positioned compared to upper molar.

Class 3: Lower molar mesially positioned compared to upper molar.

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4
Q

What are the goals of orthodontic treatment?

A

To correct the alignment of teeth by correcting the relationship between oral and facial tissues.

Ideal soft tissue proportions and adaptation

Functional occlusion

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5
Q

Why can’t angle’s classification be used for malocclusion epidemiological studies?

A

There is a lack of consensus as to how much deviation from Angle’s normal occlusion could be tolerated before an individual could be said to have malocclusion.

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6
Q

What is used for epidemiological studies of malocclusion?

A

The irregularity index which takes into account:

The total of the distances between incisor contact points allowing a quantitative measurement of the extent of incisor irregularity.

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7
Q

What is overjet?

A

The horizontal overlap of the incisors.

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8
Q

What is the normal overjet?

A

Normally upper and lower incisors are in contact. The upper incisors ahead of the lower only by the thickness of their incisal edges.

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9
Q

What kind of molar and jaw relationship coincides with excessive overjet?

A

Class 2 molar and jaw relationships

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10
Q

What kind of molar and jaw relationship coincides with reverse overjet?

A

Class 3

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11
Q

What is overjet a good indicator of?

A

It is a better indicator of class II and III problems than molar relationships described by Angle.

Overjet is used as an indicator of Class II and III problems in population studies for this reason.

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12
Q

When is overjet considered a severe problem?

A

Overjet of 7mm or more can create severe problems as well as reverse overjet of -3mm or more.

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13
Q

Which type of overjet is most common?

A

Class 2

Reverse overjet is most common in people of Asian origin

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14
Q

What is overbite/open bite?

A

The amount of vertical overlap of the incisors.

Normally contact is between the lower incisal edges and at or above the cingulum.

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15
Q

Which is more common deep or open bite?

A

Moderate and severe deep bite or more common than morderate and severe open bite.

Extreme deep bite is only slightly more prevalent than extreme open bite.

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16
Q

What causes change of ideal alignment with age?

A

Mandibular growth

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17
Q

Which incisor relationships are most common in African americans?

A

Open bite is much more prevalent and deep bite less prevalent in African-Americans.

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18
Q

What are the common problems that malocclusion has for patients?

A

Psychosocial problems due to discrimination because of dental/facial appearance

Problems with oral function (difficulties in jaw movement, TMJ dysfunction, and problems with mastication, swallowing or speech)

Greater susceptibility to tooth decay, trauma, and periodontal disease.

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19
Q

What is the IOTN index?

A

Index Of Treatment Needed. It provides an indicator of the need for orthodontic treatment to fix a malocclusion.

It is composed of 5 categories that range from grade 1 (no need) to grade 5 (extreme need).

Children in grade 4 or 5 are a priority for treatment and they get priority treatment as well as potential financial help.

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20
Q

How common are crowded incisors according to the NHANES III?

A

33% crowded incisors, 15% very crowded

Gets worse with increasing age

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21
Q

What percentage of the US population have malocclusion?

A

65%

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22
Q

What causes malocclusion?

A

Almost always a distortion of normal development but it can be difficult to pinpoint the specific cause. It can be:

Hereditary

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23
Q

What hereditary factors cause malocclusion?

A

Evolution of smaller jaws

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24
Q

What are the lines of occlusion?

A

2 lines of occlusion:

Upper line runs in middle of central groove of teeth
Lower line runs buccally

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25
Q

What are the types of deviations from the line of occlusion?

A

Buccoversion

Linguoversion

Torsiversion

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26
Q

What lateral features are seen in ideal occlusion?

A

lateral overjet is desirable with upper teeth.

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27
Q

What additional features of the first maxillary molar are needed in angle’s classification?

A

Upper molar needs to be positioned underneath the zygomatic arch for ideal position

28
Q

What are the reasons for using angle’s classification?

A

Doesn’t use skeletal pattern

Doesn’t think about transverse or vertical problems

Makes it much more simple

29
Q

Why are orthodontics important?

A

Reduce psychosocial handicap

Improve oral function (TMD can result from 8 - 10% of cases)

Adjunct to disease control

30
Q

How does modern approach differ to the former paradigm?

A

Angle’s classification focused on ideal dental occlusion. Modern classification thinks f ideal soft tissue proportion and relationships.

31
Q

What proportion of people have normal occlusion and malocclusion?

A

1/3rd normal occlusion

1/3rd have malocclusion and seek treatment

1/3rd have malocclusion but don’t seek treatment

32
Q

Who seeks malocclusion?

A

65% of people

Dentists feel that 55% need treatment. Patients feel that 35% need treatment.

33
Q

What causes malocclusion?

A

Facial form and genetic abnormalities

Postnatal growth disturbances

Unknown

ONLY KNOWN IN 5% OF CASES

34
Q

Indicate 2 types of malocclusion related to facial dysproportion?

A

Class 3 jaw relationship can run in families leading to class 3 occlusion.

Long face is heritable

35
Q

What do studies show about the causes of malocclusion?

A

Studies have yet to show heritable factors for most forms of malocclusion.

Cutting condyle of an adolescent monkey caused the monkey to develop and asymmetry. When this was done to an adult this asymmetry did not present

36
Q

How does a condylar fracture result in asymmetry and malocclusion?

A

Lateral pterygoid pulls it medially and anteriorly causing it to move to the side.

Condyle can regenerate (in 75% of children the condyle regenerates leading to no growth deficit)

37
Q

What does the mandible need to grow following condylar fracture?

A

The mandible must be able to translate. Opening on a hinge is not good enough because it leads to ankylosis.

Function prevents ankylosis of the mandible.

Ankylosis results from: Fusion across the TMJ restricts motion restricting movement and inhibits growth.

38
Q

What is required for tooth movement to occur?

A

Moderate force + duration = tooth movement .

3g of force is known to impede eruption. 6 hours is needed for movement. If a force is applied 50% of the time it is the same as full time application of the force.

Intermittent light force affect the eruption of the rabbit incisor 50% of the time as often as full time.

39
Q

What effect did mouth breathing show on occlusion?

A

People that breathe more with their mouth tend to have a more straight posture. However, there is no effect it seems on occlusion or open bite.

40
Q

What are the proposed hereditary causes of malocclusion?

A

Evolution (Alignment of teeth was excellent until ~100k years ago)

Outbreeding (unlikely due to no independently inherited tooth and jaw characteristics that could produce malocclusion when mixed)

Familial characteristics (Skeletal characteristics are inherited more than dental characteristics. Example of this is familial mandibular prognathism however most aren’t inherited in this way.)

41
Q

Why did results of dog malocclusions when bred with different breeds not qualify as evidence of malocclusions caused by outbreeding?

A

Because they were caused by achondroplasia which has variable penetrance in the dog populations.

42
Q

What kind of relationship in eruption pattern is seen in twins?

A

In twins they have mirroring eruption. The opposite side teeth erupt equally in both twins.

43
Q

How heritable is malocclusion?

A

Controversiy around this topic:

Lundstorm up to 50% of malocclusions have their origin in hereditary factors.

Corrucini and Potter, using a different statistical approach saw no genetic contribution at all.

Evidence indicates that environmental factors play a larger role than hereditary factors.

44
Q

What kinds of pre-natal issues can cause malocclusion?

A

Foetal alcohol syndrome (alcohol first trimester)

Craniofacial microsomia (Early loss of neural crest cells at stage of origin and migration) = Underdeveloped side of the face

Intra-uterine molding (Pressure against developing face; eg arm against mid-face pushing maxilla back)

Pre-natal interferences with the dentition (Class 1 malocclusions, supernumerary teeth, congenitally missing teeth, distortions of tooth form)

Birth injuries that lead to interference growth. (rarely)

45
Q

What is the pierre robin sequence? Does it always cause malocclusion?

A

Aka anomolad, occures when there is a low volume of amniotic fluid leading to head flexing tightly against the chest.

This does not always cause malocclusion because when pressure is released from the mandible after birth some children have normal growth and complete recovery.

46
Q

Which teeth are most commonly congenitally missing?

A

Maxillary lateral incisor and/or mandibular 2nd premolars.

47
Q

How can soft tissue injuries affect occlusion?

A

The functional matrix theory explains that damage to the soft and facial tissues (particularly scarring) around the facial skeleton and dentition can have marked effects on the bone growth and tooth positions.

48
Q

How do hard tissue injuries affect occlusion?

A

Not as much as soft tissue. (Kid had a broken skull following tractor injury and recovered almost completely)

49
Q

What’s the difference between the children who grow normally following a condylar fracture and those who do not?

A

it’s largely whether there was enough soft tissue injury to create scarring around the TM joint that inhibited translation of the mandible as facial growth continued.

50
Q

How can trauma to dentition affect the teeth?

A

Scarring of labial or buccal tissue can push the teeth back. When cheek tissue is lost the opposite is true.

Direct trauma to the dentition can lead to loss of a tooth causing adjacent teeth to drift into the empty space. Premature loss of a primary tooth can lead to loss of space for its permanent successor.

Severe damage to the PDL can lead to ankylosis of the tooth.

51
Q

What habit can lead to malocclusion in children?

A

Thumb sucking (protruding upper incisors, anterior open bite, and maxillary constriction causing the child to shift into a unilateral posterior crossbite.)

52
Q

How can thumb sucking affect arch width?

A

Sucking motion tightens the cheeks leading to lingual movement of the teeth and narrowing of the arch.

53
Q

What is the most frequent location for a supernumerary tooth?

A

Maxillary midline

54
Q

What are the features of someone with foetal alcohol syndrome?

A

Short palpebral fissures

Flat midface

Short nose

Indistinct philtrum

Thin upper lip

Micrognathia

Minor ear anomalies

Epicanthal folds

Low nasal bridge

55
Q

What is ectodermal dysplasia commonly associated with?

A

Multiple congenitally missing teeth.

56
Q

Why doesnt chewing forces cause further movement of teeth if it is bent?

A

Because when chewing the tooth doesn’t really move so much as it pushes down on the PDL space which contains fluid and that pushes down on alveolar bone causing the bone to bend. If you bite down for too long fluid within the PDL space moves out and that causes pain.

57
Q

Why can’t teeth be moved as a result of always chewing a certain way?

A

The force isn’t maintained long enough to produce tooth movement.

58
Q

How long must force be applied to a tooth before it can cause displacement?

A

Must be at least 4 hours per day and perhaps a bit more than that, if it is to have any impact on the position of the teeth within the dental arches and thereby change the dental occlusion so that it could produce malocclusion.

59
Q

Why is there a need for force to be applied for an extended time for it to cause movement?

A

After about 4 hours upregulation of secondary messengers such as cAMP that trigger tooth movement begin to appear.

It takes 4 hours to induce cAMP production and other secondary messengers.

60
Q

Why do different degrees of movement occur in babies that suck their thumbs?

A

Different durations (not force)

61
Q

Where does equilibrium forces needed to move the teeth come from?

A

Not only swallowing, speech, and resting pressures alone.

The force in the PDL used for eruption is also important.

PDL has a stabilizing capacity that makes it appear like there is a threshold for movement to take place.

62
Q

What is tongue thrust swallow?

A

extension of the tip of the tongue between the incisor teeth during swallowing

63
Q

What are adenoid facies?

A

Large adenoids block the nose and so the mouth is used for breathing leading to a long narrow face.

64
Q

How does nasal vs oral respiration affect occlusion?

A

Impaired nasal respiration appears to be a risk factor in the growth of a long face pattern. Not a major determinant though.

Severe nasal obstruction can lead to severe malocclusion.

65
Q

How can mouth breathing be detected?

A

Open lips are a bad indication (rear of mouth can be closed off by tongue)

Nasal-oral ratio using a measuring device of air that passes the nasal and oral cavity. (nasal mask / body plethysmograph technique)

The data suggest that impaired nasal respiration may contribute to the development of long face / open bite problems, but this is not the sole or even the major cause.

DMD3 (53 decks)

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