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orthodontics 2 > Midterm > Flashcards

Midterm Flashcards

1
Q

PDL occupies how much space?

A

.5mm

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2
Q

Main cell in PDL

A

undifferentiated mesenchymal cells that turn into fibroblasts and osteoblasts

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3
Q

collagenous fibers do what?

A

resist displacement in normal function. They attach to lamina dura and cementum

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4
Q

can orthodontic forces displace sutures?

A

yes, especially in kids

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5
Q

T/f, as the tooth moves away the PDL moves with it?

A

T, tooth movement is primarily a PDL phenomenon.

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6
Q

_____ & _____ forces squeezes out PDL fluid causing remodeling of adjacent bone

A

light, continuous

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7
Q

> 1 second of pressure on the PDL

A

PDL fluid to compress and alveolar bone bends

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8
Q

1-2 seconds of pressure on PDL causes

A

PDL fluid expressed, tooth moves within the PDL space

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9
Q

3-5 seconds seconds of pressure on PDL causes

A

PDL fluid squeezed out, tissue compressed, immediate pain if pressure is heavy.

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10
Q

which area of the mouth is affected by tongue thrusting?

A

lower anteriors. tongue produces ~10gm and lip produces 5gm

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11
Q

T/F, fibers within the PDL can cause movement themselves?

A

T, Collagen fibers continue to change even after tooth eruption and can cause extraetruded teeth.

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12
Q

whats hyalinization?

A

form of tissue degeneration. Denotes a compressed and locally degenerated pdl. Reversible process. Occurs in almost all forms of orthodontics

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13
Q

whats tipping?

A

simplest form of orthodontic tooth movement. Center of resistance is usually ½ way between the apex and alveolar crest.

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14
Q

strain

A

internal distortion produced by the load( defined as deflection perunit length)

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15
Q

whats translation?

A

2 forces applied simultaneously. AKA bodily movement. Has a rectangular diagram

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16
Q

translation requires__ times as much force as tipping?

A

2

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17
Q

whats intrusion?

A

one of the hardest movements in orthodontics. You have a very small loading area. This requires very little force. Movement is back into the alveolar bone.

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18
Q

____ hours of force is the minimum for beginning of tooth movement?

A

6

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19
Q

(on F&D diagram)

elastic limit

A

space between yield point and proportional limit, Its the greates amount of stress without permanently deforming

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20
Q

force decay

A

reduction in force magnitude as is seen in springs after a tooth has moved.

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21
Q

3 stages in tooth movement are…

A

initial compression and alterations in blood flow associated with pressure within the PDL, formation and release of chemical messengers, activation of cells

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22
Q

( on stress-strain diagram)

the more vertical the slope, the more ____ the wire

A

stiffer

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23
Q

intermittent forces

A

when magnitude of force drops to zero in one shot. ( like when removing the braces)

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24
Q

stress

A

internal distribution of the load (defined as force per unit area)

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25
Q

strain

A

internal distortion produced by the load( defined as deflection perunit length)

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26
Q

load deflection

A

degree to which a structural element is displaced under a load

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27
Q

3 major properties of water are

A

strength, stiffness, range

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28
Q

(on F&D diagram)

proportional limit

A

highest point stress and strain has linear relationship

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29
Q

(on F&D diagram)

yield point

A

intersection of stress-strain curve with parallel line offset at .1% strain

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30
Q

(on F&D diagram)

elastic limit

A

space between yield point and proportional limit

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31
Q

(on F&D diagram)

point of arbitrary clinical loading

A

clinically useful springback

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32
Q

( on stress-strain diagram)

the more horizonal the slope, the more ___ the wire

A

springier

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33
Q

( on stress-strain diagram)

the more vertical the slope, the more ____ the wire

A

stiffer

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34
Q

modulus of elasticity

A

the ratio of the stress applied to a body or substance to the resulting strain within the elastic limit

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35
Q

stationary anchorage

A

refers to the advantage of putting bodily movement of one group of teeth against tipping of another group.

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36
Q

nickel titanium alloy ( nitinol) properites

A

provides light force of large range.

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37
Q

Beta-titanium properties

A

TMA?????

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38
Q

2 different forms of Nitinol

A

martensitic- stable at low temp and high stress

austenitic- stable at high temp and low stress

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39
Q

what happens when you double the length of Niti wire?

A
  • Cuts strength by ½
  • 8X more springy
  • 4X the range
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40
Q

what happens when you double the thickness of the niti wire?

A
  • 8X as strong
  • 1/16 as springy
  • ½ the range
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41
Q

Anchorage

A

resistance to unwanted movement

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42
Q

what can be used for anchorage?

A

teeth, palate, head, neck, screws..

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43
Q

reciprocal tooth movement

A

forces applied to teeth and arch segment are all equal.

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44
Q

Which teeth are better anchors and why?

A

posteriors because they have a bigger PDL area

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45
Q

reinforced anchorage

A

you add another tooth into the system to anchor that side more so the other side moves more.

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46
Q

define moment

A

measure of tendency to rotate an object around some point

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47
Q

Orthodontic pain

A

caused by ischemic areas in the PDL that undergo sterile necrosis

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48
Q

what should be used for ortho pain?

A

acetaminophen ( tylenol)

49
Q

tissue inflammation with ortho treatment

A

very rare but is usually caused by latex allergy and or nickel from the brackets

50
Q

what happens when incisor is tipped to far lingually?

A

vitality is lost via root exposure

51
Q

what did Rygh and his coworkers discover for root effects?

A

where PDL necrosis occurs, the underlying cementum is remodeled as well. Root length is decreased( mostly incisors)

52
Q

what factors play into root resoprtion?

A

treatment length, and heavy forces

53
Q

what were elastics made of in the past and what are they made out of now?

A

gum elastic, it degraded pretty fast so they switched to latex elastics which last 4-6 times as long

54
Q

ortho magnets

A

not good. Follow inverse law which means they dont provide consistant force.

55
Q

define force

A

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

56
Q

define center of resistance

A

point at which resistance to movement can be concentrated for mathematical analysis. On a tooth it is at the approximate midpoint of the embedded portion of the root

57
Q

define moment

A

measure of tendency to rotate an object around some point

58
Q

plastic brackets

A

stain, poor stability, friction between plastic an wire makes it difficult to slide teeth into new positions ( some have metal sliding material but they still suck)

59
Q

define couple

A

when 2 forces equal in magnitude and opposite in direction

60
Q

define center of rotation

A

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

61
Q

MC/MF ratios and control of root resorption

A
  • A simple way to determine how a tooth will move is to look at the MC/MF ratio
  • MF- the moment of the force
  • MC- moment of the couple
62
Q

(MC/MF ratios and control of root resorption)

=0

A

pure tipping

63
Q

(MC/MF ratios and control of root resorption)

=1

A

bodily movement

64
Q

(MC/MF ratios and control of root resorption)

>1

A

torque( root apex moves further than crown)

65
Q

what year did Dr. angle make edgewise appliances?

A

1928

66
Q

ribbon arch vest

A

whent all around the tooth with a vertical slot

67
Q

edge wise appliance

A

slot size .22X.28”
horizontal slot
90 degree angle of insertion

68
Q

what is a good alternative for someone who is allergic to stainless steel brackets? ( it has nickel)

A

titanium brackets

69
Q

ceramic brackets

A

very strong and can cause abrasion problems with enamel ( why they put them on maxillary usually). Very stable but can fracture easily.

70
Q

first order bends

A

used to compensate for differences in tooth thickness
o Upper molars should have at least 10 degree offset
o Lower molars should be 5-7 degrees

71
Q

second order bends

A

used to position roots correctly mesiodistally

o Also called artistic positioning bends

72
Q

third order bends

A

torque bends to position roots in faciolingual direction
o Failure to add third order bends makes the anterior teeth become too upright. Posteriorly buccal cusps of molars would be depressed and lingual cusps elevated

73
Q

3 types of self ligating brackets

A

springy latching cap, springy retaining clips, and rigid latching caps.
Save time during ligating but thats it.

74
Q

customized brackets

A
  • This technology is used to precisely cut each bracket using CAD/CAM so that each slot for each bracket has the appropriate thickness, inclination, and torque needed for positioning that specific tooth.
  • Treatment time is reduced in comparison to conventional brackets
  • Minor adjustments to wires still needed
75
Q

lingual appliances

A

wire bending is done via “wire bending robot”.

2nd molars arent positioned as precisely as others.

76
Q

what kind of archwires should be used when nickel-titantium and beta titanium wires are needed?

A

preformed archwires because theyre difficult to bend without special tools.

77
Q

If both arches are incompatible during beginning of treatment, which arch should you use as a basic guide?

A

mandiublar

78
Q

Whats a catenary curve

A

shape that a loop of chain would take if it were suspended from 2 hooks.

79
Q

Brader arch form

A

based on trifocal ellipse. This provides the posterior constriction that the catenary curve does not.
So this is good for 2nd and 3rd molars.

80
Q

benefits of polymer clear wires

A

esthetic, as strong as metal, round or rectangular, can be corporated into retainers

81
Q

AAO recommends children to have their first ortho apt at what age?

A

7
Reasons: the posterior occlusion is established when the first molars erupt. At the time one can evaluate the antero- posterior n transverse relationships of occlusion, as well as discover any functional shift or crossbites.

82
Q

TADs

Bone screws

A

o Mostly titanium due to better biocompatibility than stainless steel.
o Stability- short term and long term is determined by mechanical retention of screw in bone, which depends on bone properties, design of screw, placement technique.
o Long term ( secondarily stability)- defined by biologic union of screw to surrounding bone. Determined by implant surface, bone characteristics, bone turnover, and implant surface mechanical system
• Primary stability
o Decreases over time while secondary increases

83
Q

what factors into the stability/success of TADs

A

pitch, lenght, diameter, taper , form of tip.

84
Q

pitch of screw

A

how close the threads are. For dense bone you want a tight pitch.

85
Q

length of screw

A

the amount of contact with the cortical bone is the main determining factor of stability

86
Q

diameter of scew

A

needs to be narrow enough to fit between teeth. ( current scews are 1.3-2mm wide)

87
Q

form of tip

A

2 types
thread forming- compasses bone around the threads of the screw as it advances which is better bone to scew contact
self-tapering-

88
Q

TADs

miniplates are usually placed where?

A

base of zygomatic arch( but can be elsewhere)

89
Q

what are the determinates for stability for miniplates?

A

o Number of screws used- 3 is best, anything more doesn’t add additional stability
o Patient age- failure occurs more often in young pts. Bone maturity doesn’t reach a good level until around age 11

90
Q

what are some indications for miniplates?

A

positioning groups of teeth- distalization of entire maxillary or mandibular arch, intrusion anterior and posterior teeth

Growth modification- class 3 elastics, maxillary deficient child

91
Q

can canine interference cause a posterior crossbite?

A

you bet it can! This is why its important to make sure the pt is in CO when diagnosing.

92
Q

what appliace can you use for a mxed dentition patient?

A

2x4 or 2x6

93
Q

whats somthing to watch out for when treating someone in mixed dentition?

A

unerupted teeth

94
Q

T/F, early treated ortho patients frequently need a phase 2 treatment?

A

true

95
Q

In early treated patients, can class 2 or 3 pts be delayed?

A 
class 2 can
class 3 needs to be addressed early because there may be skeletal deformities.
96
Q

which permanent teeth are most commonly missing?

A

upper laterals and lower 2nd premolars

97
Q

90% of supernumerary teeth are what ?

A

maxillary anteriors

98
Q

what must you watch when using the cross-elastic technique for single posterior teeth?

A

o Must monitor carefully especially in children with increased lower facial height. When lingual cusp drops down and contacts molar it will make face even longer, 1mm in post is 3 mm in anterior

99
Q

what % of kids have posterior crossbites?

A

7.1

100
Q

how do palatal expanders work?

A

( w-arches, quad helix) they prevent the fusion of the suture and open it up

101
Q

can canine interference cause a posterior crossbite?

A

you bet it can! This is why its important to make sure the pt is in CR when diagnosing.

102
Q

niti wire in aiding with anterior crossbites

A

The niti wire pushes the teeth out but doesnt align. This method is good for thumb suckersand tongue thrusters

103
Q

what appliacne can be used for someone with unilateral maxillary constriction?

A

W- arch with one side longer than the other. The longer side is the anchored side and the shorter is the one doing the pushing. ( he said both sides moves so its not a good appliance)

104
Q

how can you adjust a W-arch?

A

with a 3 pronged plier. It can be adjusted without removal.

105
Q

which appliace can be used to stopt thumb sucking and tongue thrusting?

A

thumb crib, this makes a mark on the tongue but will disappear. Its affective in about 85-90% of cases. It does cause hygiene problems becasue it traps food.

106
Q

whats an example of reminder therapy for thumb suckers.

A

put a bandaid on their finger

107
Q

how far should you over correct maxillary constricions?

A

until maxillary posterior lingual cusps occlude with lingual incline of buccal cusps of mandibular posteriors
You want to retain this for 3 months

108
Q

how do you fix a single molar thats in crossbite?

A

cross-elastic with welded buttons on bands

109
Q

what must you watch when using the cross-elastic technique for single teeth?

A

o Must monitor carefully especially in children with increased lower facial height. When lingual cusp drops down and contacts molar it will make face even longer, 1mm in post is 3 mm in anterior

110
Q

what can you do if a cross bite is forming in the anterior area druing mixed dentition?

A

extract primary cuspids to provide more room. sometime spontaneous correction occurs

111
Q

removable appliace in aiding anterior crossbites

A

its a retainer with a double helical fingerspring thats activated 1.5-2mm per month to produce 1mm per month of tooth movement

112
Q

anterior crossbite with the fingerspring

A

has bands on the posterior teeth with the helical wire pushing on the anterior teeth. This can be modified into a retainer to maintain the position after treatment.

113
Q

niti wire in aiding with anterior crossbites

A

The niti wire pushes the teeth out but doesnt align. This method is good for thumb suckersand tongue thrusters

114
Q

when does it start to become a problem with tongue thrusters?

A

as soon as incisors start o erupt. If habit ceases while theyre erupting the incisors autocorrect.

115
Q

which method provides the best success to stop thumb sucking?

A

reward system
child must be motivated
parants must be willing to give reward, child must go 3 days without sucking for reward

116
Q

which appliace can be used to stopt thumb sucking and tongue thrusting?

A

thumb crib, this makes a mark on the tongue but will disappear

117
Q

whats an example of reminder therapy for thumb suckers.

A

put a bandaid on their finger

118
Q

thumb suckers maxillary incisor are usually tipped ______ and mandibular are ______

A

facially

lingually

orthodontics 2 (1 decks)

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