Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Orthodontics > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Most dental trauma occurs in what age range? What is the most common location?

A

7-10

Anterior incisor region

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

True or false… avulsed primary teeth should not be replanted.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Avulsed permanent teeth that are replanted require follow-up evaluations for a minimum of ___ to determine outcome of therapy

A

2-3 years

Look for periapical abscess, internal root resorption, ankylosis and tooth submergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What should you do with an avulsed permanent tooth?

A

Replant immediately if possible

If contaminated, rinse with water before replanting

When immediate replantation is not possible, place tooth in the best transport medium available

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some transport media to keep a permanent avulsed tooth in?

A

Hank’s balanced salt solution

Milk

Saline

Saliva (buccal vestibule)

Saliva (spit in cup)

If none are available, use water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

You should replant the tooth immediately if…

A

Extraoral dry time is less than one hour with or without storage in transport media

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How should you manage the root surface of an avulsed tooth?

A

Keep the tooth moist at all times

Do not handle the root surface. (Hold tooth by crown)

Do not scrape or brush the root surface or remove the tip of the root

If the root appears clean, replant as is after rinsing with saline

If the root surface is contaminated, rinse with HBSS or saline (or water if necessary)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What should you do if extraoral dry time is over 60 minutes?

A

Soak tooth in an accepted dental fluoride solution for 20 minutes. Rinse with saline and replant

(Research shows that ankylosis is prevented by applying the root surface to a medium that favors regeneration of injured parts of the PDL)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How should you manage the socket in an avulsed tooth?

A

Gently aspirate without entering them socket

Do not curette the socket
Do not vent socket
Do not make a surgical flap unless bony fragments prevent reimplantation
If the alveolar bone is collapsed and prevents reimplantation, carefully insert a blunt instrument into the socket to reposition the bone to its original position
After reimplantion, manually impress facial and lingual bony plates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What should you do to manage the soft tissues in a dental traumatic event?

A

Tightly suture any soft tissue lacerations, particularly in the cervical region

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Splints should extend how far?

A

Distally to at least two non-involved teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How long should splints remain in place?

A

7-10 days

However, if tooth demonstrates excessive mobility, splint should be replaced until mobility is within acceptable limits (<1mm)

Bony fractures resulting in mobility require longer splinting periods of 2-8 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why should rigid composite splints be avoided when possible?

A

Difficult to maintain patients oral hygiene

Difficult to remove

Extremely rigid and doesn’t allow for minor tooth movement to stimulate normal PDL development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the steps for an avulsed tooth that has been lingually displaced with a fracture of the alveolar bone?

A

Bend wire to touch passively on non-involved teeth, while approximating the anterior arc of the wire to position the avulsed teeth in their prior positions

Prepare all teeth for bonding

Bond the wire to the non involved teeth using composite

Place composite on the labial surface of the involved teeth and press/pull the teeth forward until they are in their proper position and the composite has surrounded the arch wire (cure composite)

Squeeze alveolar bone together Bucal and lingually

Place any necessary sutures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are some adjunctive drug therapy considerations?

A

Systemic antibiotics

Referral to physician for tetanus consultation within 48 hours

Chlorhexidine rinses

Analgesics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define force

A

A load applied to an object that will tend to move it to a different position in space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Define center of resistance

A

A point at which resistance to movement can be concentrated for mathematical analysis. For an object free in space, the center of resistance is the same as the center of mass

(If an object is partially restrained as is the case for a tooth root embedded in bone, the center of resistance is located approximately halfway (6/10ths between the root apex and crest of alveolar bone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where is the center of resistance found in a tooth?

A

6/10ths between root apex and crest of alveolar bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define moment

A

A measure of the tendency of a force to rotate an object around some point

A moment is generated by a force acting at a distance to the center of resistance

Quantitatively it is the product of the force times the perpendicular distance from the point of force application to the center of resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Define couple

A

Two forces equal in magnitude and opposite in direction

A couple will produce pure rotation, spinning the object around its center of resistance

while the combination of a force and a couple can change the way an object rotates while it is being moved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define center of rotation

A

The point around which rotation actually occurs when an object is being moved

When two forces are applied simultaneously to an object, th econeter of rotation can be controlled and made to have any desired location

The application of a force and a couple to the crown of a tooth, in fact, is the mechanism by which bodily movement of a tooth, or even greater movement of the root than the crown can be produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

If a single force is applied to the crown of a tooth the tooth with rotate around the center of ___

A

Resistance

(In this case, the center of rotation and center of resistance are identical because a moment is created by applying a force at a distance from center of resistance without a couple)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The perpendicular distance from the point of force application to the center of resistance is the ___

A

Moment arm

24
Q

Pressure in the PDL will greatest in which locations?

A

Alveolar crest

Opposite the root apex

25
Q

Describe how rectangular archwires work

A

The wire fits into a rectangular slot and can generate the moment of a couple necessary to control root position. The wire is placed into torsion as it is put into the bracket slot.

The moment arm is therefor quite small but the force is large to generate the necessary moment

26
Q

The ratio between _____ and ___ determines the type of tooth movement

A

The moment produced by the force applied to move a tooth (Mf)

Counterbalancing moment produced by the couple used to control root position (Mc)

27
Q

The ____ determines where the center of rotation will be on the tooth and thus what type of tooth movement will occur

A

Moment couple ratios

28
Q

What happens when there is no Mc?

A

The tooth rotates around the center of resistance which equals the center of rotation, creating a pure tipping movement

29
Q

What happens as the moment-to-force ratio increases? (More Mc and less Mf)

A

The center of rotation is displaced further and further apically, away from the center of resistance to produces controlled tipping

30
Q

What happens when Mc/Mf = 1?

A

The center of rotation is displaced to infinity apically and bodily movement occurs with no tipping

31
Q

What happens when Mc/Mf >1?

A

The center of rotation is displaced incisally and the root apex will move more than the crown, producing lingual root torque. It causes tipping in the opposite direction

32
Q

The center of resistance of a single-rooted tooth lies approximately ___ of the distance between the apex of the tooth and the crest of the alveolar bone

A

6/10ths

33
Q

Loss of alveolar bone height moves the center of resistance in which direction?

A

Closer to the root apex. (6/10ths rule still applies)

34
Q

Magnitude of the tipping moment produced by a force is equal to ___ times ___ from the point of force application to the center of resistance

A

Force

Distance

35
Q

What happens to Mf when bone loss occurs?

A

The center of resistance moves apically, thus the tipping moment increases because the moment arm is longer

36
Q

True or false… in moving teeth that have had bone loss a larger countervailing moment produced by a couple is necessary to produce bodily movement

A

True

37
Q

For all practical purposes, a ___ is required if root movement is the goal in patients who have experienced loss of alveolar bone height

A

Fixed appliance

Removable appliances dont work

38
Q

True or false.. although heavy pressure is felt at the root apex and crest of the alveolar bone, the pressure decreases to zero at the center of resistance in a tipping motion

A

True

39
Q

What is the optimal force to create a rotational movement of a tooth?

A

35-60 grams (lower number for incisors and higher number for molars)

40
Q

Tipping movements create an ___ movement if the tooth is moved lingually and an ___ moment if the tooth is moved bucally

A

Extrusive

Intrusive

It is important to anticipate intrusive and extrusive movements when tipping forces are used

41
Q

True or false… Translation or bodily movement of a tooth requires that the PDL space be loaded uniformly from alveolar crest to apex

A

True

42
Q

____ as much force must be applied to the crown of the tooth to produce the same pressure within the PDL for bodily movement when compared to tipping movements

A

Twice

43
Q

What is the optimal force to create a translational movement?

A

70-120grams

44
Q

When a tooth is intruded, the force is concentrated over a small area at the apex. What is the significance of this?

A

Extremely light forces are needed to produce appropriate pressure within the PDL during intrusion

45
Q

What are the optimal forces for intrusion and extrusion?

A

Intrusion = 10-20 grams

Extrusion = 35-60 grams

46
Q

What is the difference between ideal springs and real springs?

A

An ideal spring would maintain the same amount of force regardless of distance a tooth had moved

But with real springs the force decays at least somewhat as tooth movement occurs

47
Q

Forces that are maintained between activations of an orthodontic appliance, even though the force declines are defined as ____ (such as ___)

A

Continuous forces

Nickel titanium arch wire

48
Q

In contrast to continuous forces, ____ forces drop to zero between activations (such as ___)

A

Interrupted

Stainless steel arch wire bends

49
Q

Intermittent forces fall to zero when …

A

A removable appliance is taken out, only to resume when the appliance is reinserted into the mouth.

These forces also decay as tooth movement occurs

50
Q

In a typically force-deflection curve for an elastic material like an orthodontic arch-wire, define stiffness

A

The stiffness of the material is given by the slope of the linear portion of the curve

(The greater the slope or steeper the line the stiffer the material)

51
Q

In regards to a typical force-deflection curve, define the range

A

The range is the distance along the X-axis to the point at which permanent deformation occurs, usually taken as the yield point, at which -.1% permanent deformation has occurred)

52
Q

In regards to a typical force-deflection curve, define strength and proportional limit

A

The strength of a wire is a mathematical calculation of the stiffness times the range

The proportional limit is the point below which the force placed on the wire creates a proportional deflection in the wire (the graph remains linear)

53
Q

In regards to a force-deflection curve, define spring back and the point of arbitrary clinical loading, and the failure point

A

Spring back is the position the wire will return to after it has been deflected. If deflection has exceeded the proportional limit to the yield point, the spring back will not return the wire to its original position

The point of arbitrary clinical loading is a point at which increasing deflection causes minimal changes in force to occur (the wires force has been maxed out)

The failure point is when the wire breaks

54
Q

Each of the major elastic properties of an orthodontic wire (strength, stiffness, springiness, range, etc) is affected by…

A

A change in length, shape, and cross section area of a wire

55
Q

True or false… smaller brackets means increased length of the wire between teeth which means less force is required

A

True

Orthodontics (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions