Second Semester

Question 1

Which types of external root resorption is a potential complication of orthodontic treatment?

Answer 1

Transient inflammatory resorption

Surface resorption

Question 2

During your consultation, your patient is curious if she might be susceptible to root resorption during treatment. You tell her the risk of root resorption is ___ in adults, completely formed roots, and patients with a history of root resorption, and habits like nail biting.

Answer 2

higher

Question 3

In Angle’s edgewise appliance, first order bends were used to compensate for differences in tooth ___, second-order bends to position roots correctly in a ___ direction, and third-order bends to position roots in a ___ direction.

Answer 3

thickness

mesiodistal

faciolingual

Question 4

What are the compensations for first order bends in the contemporary edgewise appliance?

Answer 4

1st order bends - this compensation is built into the base of the bracket itself, by varying the thickness of the base depending on which tooth it will be attached to.

Question 5

What are the compensations for second order bends in the contemporary edgewise appliance?

Answer 5

Angulating the bracket or bracket slot decreases or removes the necessity for these bends

Question 6

What are the compensations for third order bends in the contemporary edgewise appliance?

Answer 6

The bracket slots in the contemporary edgewise appliance are inclined to compensate for the inclination of the facial surface, so that third-order bends are less necessary

Question 7

Why is it most critical to place a bracket with built-in tip correctly?

Answer 7

to maintain proper bone thickness between roots

Question 8

GAC In-Ovation R I a/an [active/passive] self-ligating bracket system

Answer 8

active

Question 9

Damon is a/an [active/passive] self-ligating bracket system

Answer 9

passive

Question 10

When was self-ligation first introduced?

Answer 10

1930s

Question 11

Self-ligating brackets are more ___ than conventional brackets because they….

a) provide reduced chair time
b) improve rate of mandibular incisor alignment
c) decrease total treatment time
d) decrease rate of bracket failure

Answer 11

efficient

provide reduced chair time

Question 12

Are conventional brackets less hygienic than self-ligating brackets?

Answer 12

Insufficient evidence that self-ligating brackets are more hygienic than conventional

Question 13

Your local general dentist just watched the Damon Forum 2021 and is demanding treatment with self-ligating brackets only. Unfortunately, your practice in rural Alaska only has access to 3M Victory brackets. What are the only two assertions in favor of self-ligating brackets that was found to be supported by current evidence?

Answer 13

Reduced chair time and control of mandibular incisor inclination

Question 14

What is the moment of force for a tooth in which 200gm of force is applied 10mm away from the center of resistance?

Answer 14

2000gm/mm

Question 15

What is the moment of force of a tooth in which 200gm of force is applied 12mm away from the center of resistance?

Answer 15

12mm

Question 16

Uprighting one second molar by distal crown tipping occurs quicker than mesial root movement. Simple cases involving uprighting one molar should take ___, but uprighting two molars in the same quadrant could take ___.

Answer 16

8-10 weeks

6 months

Question 17

When using crossbite elastics, why is it important to use them only for a short time?

Answer 17

Crossbite elastics also cause extrusion, which can cause an open bite if used for too long

Question 18

Extrusion can be as rapid as __ mm per week without damage to the PDL

Answer 18

1

Question 19

What side effects would be expected to result if a continuous wire were used for canine eruption?

Answer 19

incisor intrusion and anterior open bite

Question 20

An anterior extrusion arch is shown in the image. After activation, what forces/couples are expected at the molar and at the anterior segment?

Answer 20

Intrusion and mesial crown tip at the molar and extrusion at the anterior segment

Question 21

What forces/moments would you expect to see on the molars from a continuous arch wire system used to intrude a second molar?

Answer 21

intrusion of the second molar

extrusion of the first molar

crown mesial tip of both molars

Question 22

How does a round wire cause labial tipping of incisors when an intrusive force is applied?

Answer 22

The intrusive force acts labial to the center of resistance

Question 23

A tip-back bend (or wire with curve of speed) with a round wire will cause ___ movement of the maxillary arch and ___ tipping of the incisors. Why?

Answer 23

Distal

Lingual

The moment of the molar is significantly larger, essentially over-riding the opposing moment of the incisor and pulls the wire back.

Question 24

true or false…

Mini-implants used for molar uprighting are osseointegrated

true or false… mini-implants are easily removed after treatment

Answer 24

false

true

Question 25

True or false…

When a tip-back bend is used…

In a round wire, the incisors will tip labially, whereas in a rectangular wire the incisors will tip lingually

Answer 25

true

Question 26

True or false… using a tip back bend, in both a round wire and a rectangular wire, the incisors will intrude

Answer 26

true

Question 27

What are some disadvantages of conventional molar uprighting when compared with molar uprighting with tads?

Answer 27

1) extrusion of target molar
2) unwanted reciprocal movements of anchor teeth
3) long treatment duration
4) some molar uprighting appliances are bulky
5) surgical uprighting has risk of pulpal necrosis, ankylosis, external root resorption
6) osseointegrated implants are costly, need sufficient bone space, and are difficult to remove

Question 28

Which is NOT a goal during phase 1 of non-extraction treatment?

a) increase space and distalize molars into super class-1
b) correct molar rotations, inclination and crossbones
c) correct OB, OJ
d) level curve of spee

Answer 28

C) correct OB, OJ

Question 29

How many mm of space total can be gained by derotating the molars with a TPA?

Answer 29

6mm

Question 30

While treating a non-extraction patient, you decide to use cervical pull headgear. if the point of force application and the line of force are above the center of resistance of the upper first molar, what will the resulting effect be on the molars?

Answer 30

extrusion and distalization

Question 31

Which is NOT an expected outcome of using a lip bumper?

a) change in the transverse of the mandibular basal bone
b) distalization of the lower premolars
c) space created by lateral dentoalveoalr growth
d) spontaneous reduction of lower crowding

Answer 31

b) distalization of the lower premolars

Question 32

how many grams of force is ideal for the intrusion of upper incisors?

Answer 32

20 grams

Question 33

According to Parking et al., Can orthodontists and laypeople generally identify operated canines?

Answer 33

orthodontists generally can (60.7% of the time P < 0.01)

Laypersons generally cannot (49.7% of the time, P > 0.05)

Question 34

According to Parkin et al., Does surgical technique (open vs closed) affect the frequency orthodontists and laypersons identify operated canines or how they rate canine length and gum health?

Answer 34

surgical technique does not significantly affect the frequency orthodontists and laypersons identify operated canines

surgical technique does not significantly affect how orthodontists or laypersons assess gum health or crown length

Question 35

What are the main reasons orthodontists and residents gave for identifying previously impacted canines (Schmidt and Kokich cited by Parkin et al.)? Which was the most common?

Answer 35

Gingival health
Alignment
Torque (most common)

Question 36

According to Cassina et al., which exposure technique was associated with reduced treatment time to initial alignment? Which exposure technique was associated with greater risk of canine ankylosis?

Answer 36

open exposure was associated with reduced treatment time to initial alignment

closed exposure was associated with greater risk of canine ankylosis

Question 37

According to Qadri et al., did laypeople find images of orthodontic space closure with canine substitution (OSC) or opening space for prosthetic replacement (PR) more attractive? Did they prefer either one more than the other?

Answer 37

Laypersons found OSC images more attractive than PR images

Laypersons preferred OSC images over PR images

Question 38

Rank the following arch wires in order of highest to lowest formability: NiTi, SS, B-Ti

Answer 38

SS = TMA > NiTi

Question 39

What are the advantages of NiTi wires compared to others and at what stage might you use these?

Answer 39

high springiness
low formability
high springback
low stiffness

ideal for initial stages of leveling and alignment

Question 40

Which type of NiTi wire is considered to have true shape memory effect?

Answer 40

thermoelastic

Question 41

Which NiTi wire(s) undergoes a phase change from austenite to martensite in response to stress?

Answer 41

pseudoelastic

stress-induced martensite

austenitic active

Question 42

According Sebastian, would a superelastic, coaxial or single-stranded NiTi arch wire be best for initial alignment in cases of severe lower anterior crowding? Why?

Answer 42

Coaxial

greater flexibility

reduced load deflection rate

more mean tooth movement in the first 12 weeks

Question 43

Which technique is the most effective for incisor retraction and anchorage preservation according to Rizk et al?

Answer 43

En masse retraction with miniscrews

Question 44

According to Xu et al, which space closing technique had the least amount of anchorage loss?

a) en masse retraction technique
b) two-step retraction technique
c) both are statistically similar

Answer 44

C) both are statistically similar

Question 45

According to Rizk et al., which statement is true about root resorption?

a) en-masse retraction causes more apical root resorption
b) Two-step retraction causes more apical root resorption
c) there was no statistically significant difference between the two

Answer 45

C) there was no statistically significant difference between the two

Question 46

According to Xu et al., which retraction technique had less mesial molar displacement?

a) en-masse technique
b) two-step technique
c) there was no statistically significant difference between the two

Answer 46

C) there was no statistically significant difference between the two

Question 47

According to Xu et al., retraction of the incisor in both en-masse and 2-stage retraction was accomplished almost entirely by ____. How much force is required for this movement?

Answer 47

controlled tipping

35-60 grams

Question 48

Closing extraction spaces using fixed orthodontic appliances is mainly accomplished using:

a) tipping mechanics
b) rotation mechanics
c) bodily movement
d) all of the above
e) Two of the above

Answer 48

E) two of the above

tipping and bodily movement

Question 49

Which of the following does not cause bodily space closure?

a) lace back
b) tie back
c) closed loop alone
d) NiTi coil spring

Answer 49

C) closing loop alone

closing loops need to have gable bends to produce ideal M/F ratio for bodily space closure

Question 50

True or false…

elastomeric power chain is an efficient way to close extraction spaces that is cost-effective

Answer 50

true

Question 51

True or false.. there is strong evidence to suggest that NiTi coil springs are significantly more efficient and are therefore always recommended

Answer 51

false

Question 52

what is the ideal force for closing spaces using sliding mechanics?

Answer 52

100-200g

Question 53

all of the following are part of the Tweed-Merrifield edgewise appliance except which one?

a) brackets and tubes
b) bands
c) archwires
d) bends
e) auxillary appliances

Answer 53

B) Bands

Question 54

Sequential mandibular anchorage preparation places a progressive tip on the mandibular posterior teeth; what is the method merrifield used to create these angulation and minimize the unwanted movements in the surrounding teeth?

Answer 54

10-2 anchorage system

Question 55

All of the following should be attained during the “denture completion”, stage of the tweed-merifield technique except which one?

a) maxillary Caines and 2nd premolars locked into class 1 relationship
b) distal cusps of the first molars and second molars are out of occlusion
c) incisors must be aligned
d) excessive OB present
e) all spaces must be closed from 2nd premolar and forward

Answer 55

D) excessive OB present

Question 56

The four steps of treatment with the Tweed-Merrifield technique include all of the following except:

a) denture planning
b) denture preparation
c) denture correction
d) denture completion
e) denture recovery

Answer 56

A) denture planning

Question 57

True or false.. according to the Janson et al., systematic review:

Class 2 elastics are effective in correcting class 2 malocclusions

Answer 57

true

Question 58

True or false.. according to the Janson et al., systematic review:

overall, class 2 elastics produced correction primarily with dentoalveoarl effects

Answer 58

true

Question 59

True or false.. according to the Janson et al., systematic review:
Class 2 effects include mandibular molar intrusion

Answer 59

false….

class 2 elastics include mandibular molar EXTRUSION

Question 60

True or false.. according to the Janson et al., systematic review:

Class 2 effects include lower mandibular incisor intrusion

Answer 60

true

Question 61

True or false.. according to the Janson et al., systematic review:

on a long-term basis, there are NO significant differences between the effects of class 2 elastics and other removable or fixed functional appliances in class 2 malocclusion treatment

Answer 61

true

Question 62

According to the Janson et al. systematic review, when comparing class 2 elastics to various functional appliances, which of the following displayed differences in the changes produced by the two various approaches in the short term?

a) Frankel function regulator
b) forsus
c) headgear/reciprocal mini chin-cup
d) herbst
e) all of the above

Answer 62

d) Herbst

the Herbst appliance achieved greater skeletal changes in the short-term treatment compared to class 2 elastics

Question 63

According to the Janson et al systematic review, which of the following were NOT dentoalvoealr effects produced by class 2 elastics?

a) mandibular incisor proclination
b) overbite reduction
c) increase in overjet
d) forward growth of the mandible
e) all of the above are correct

Answer 63

C) increase in overjet

remember there was an overjet reduction of 5.8mm and an overbitre reduction of 3mm

Question 64

According to the Cacciatore et al study, while using the Forsus appliance, the most relevant dental changes still ovvured in the lower arch with the lower incisors demonstrating significant protrusion (+1.5mm), intrusion (-1.6mm) and a large amount of proclination (+5.6). In order to prevent this incisor proclination from occurring, Cacciatore et al. suggested what possibilities that the orthodontist should consider?

Answer 64

1) The use of a mandibular rectangular AW of greater size (21x25 or 17x25 (018 slot))
2) The addition of a negative torque in the lower incisor region of the archwire
3) the use of miniscrew anchorage in the lower anterior region which has been recently studied and showed to effectively minimize the proclination of the mandibular incisors (although this study was only recorded during a short interval of 6 months )

Question 65

If a patient is expected to be noncompliant should you use a Forsus or elastics for class correction?

Answer 65

Forsus

Question 66

According to Cacciatore et al., the purpose of their study was to evaluate the treatment and post-treatment outcomes in terms of dent-skeletal effects that are induced by the Forsus appliance in growing patients that possess a class 2 malocclusion. When examining the post-treatment results, which of the following was NOT one of the dent-skeletal effects induced by the forays appliance?

a) upper molar extrusion
b) upper incisor retroclination
c) lower incisor proclination
d) lower incisor intrusion
e) all of the above

Answer 66

A ( upper molar extrusion)

it results in lower molar extrusion

results showed significant retrusion of upper incisors; proclination, protrusion, and intrusion of the lower incisors; extrusion of the lower first molars; and no significant changes in the horizontal or vertical position of the upper molars

Question 67

Profit defines the threshold for Bolton significant as ___mm

Answer 67

2mm

Question 68

What factors determine expression of torque by rectangular AW?

a) Torsional stiffness in wire
b) inclination of bracket slot in relation to AW
c) Tightness of fit between AW and bracket
d) all of the above

Answer 68

D) all of the above

Question 69

true or false... 
After class 2 and class 3 correction, the teeth tend to rebound back toward their initial position despite the presence of rectangular arch wires

Answer 69

true

Question 70

True or false.. because of the tendency of relapse it is important to slightly overcorrect occlusal relationships

Answer 70

true

Question 71

CSF and Papilla split are procedures performed to help prevent relapse in which of the following?

a) crowding
b) rotations
c) anterior deep bite
d) none of the above

Answer 71

b) rotations

Question 72

How much is recommended for overcorrection of class 2 or 3 malocclusion or a crossbite?

Answer 72

1-2mm

Question 73

True or false… retainers should be worn full time for at least the first 3-4 months

Answer 73

true

Question 74

true or false… fixed retainers should be rigid, not allowing for any displacement of individual teeth upon mastication

Answer 74

false

Question 75

True or false…. gingival elastic fibers take longer than PDL fibers to reorganize, requiring up to 1 year

Answer 75

true

Question 76

true or false…

Gingival elastic fibers can cause rotational relapse so supracrestal fiberotomoy may be indicated in cases with severe rotations

Answer 76

true

Question 77

Fixed retainers…

a) require regular observation
b) may seem passive when placed but actually be active
c) can be inspected by general dentists after a couple years
d) all of the above
e) none of the above

Answer 77

d) all of the above

Question 78

The causes of lower incisor relapse are:

a) late mandibular growth
b) gingival fiber recoil
c) soft tissue pressures
d) third molar eruption
e) all of the aboce
f) all except D

Answer 78

F) all except third molar eruption

Question 79

IPR for lower incisor correction:

a) can be safely done up to 1.5mm per side without removing too much enamel
b) flattens the contact area, enhancing stability
c) should never be followed by topical fluoride application
d) will be unnecessary if the third molars have been removed

Answer 79

B) Flattens the contact area, enhancing stability

Question 80

Which of the following is correct concerning the circumferential supracrestal fiberotomy procedure?
a) should be completed during active movement of rotated teeth to encourage derogation
b) incising the epithelial attachment is not recommended on the mid-labial portion of any tooth with a narrow zone of attached gingiva
c) following CSF, a surgical dressing should be placed at the site and retention with a removable retainer should be postponed until healing has occurred after 7-10 days
d) B and C
E) all of the above

Answer 80

B) incising the epithelial attachment is not recommended on the mid-labial portion of any tooth with a narrow zone of attached gingiva

Reasoning:
A: should NOT be completed until malalignment of teeth has been corrected and the teeth have been held in their new position for several months (can be done several weeks prior to debond or at debond)

C) no surgical dressing is needed and if done at debond, then a retainer must be delivered immediately

Question 81

CSF is more stable in:
A) maxillary teeth than mandibular
B) teeth with severe irregularity (6mm+)than those with mild irregularity (<3mm)
C) teeth with pure rotational malposition than those with labiolingual malposiiton
d) A and B
E) A, B, and C

Answer 81

E

Question 82

postoveraptive infections are less probable following CSF with a laser because the laser ___ the irradiated area

Answer 82

sterilizes

Question 83

True or false… both laser-aided CSFj and LLLT were as effective as the conventional CSF surgery in alleviating relapse of rotated maxillary incisors within a short observational period (1 month)

Answer 83

true

Question 84

true or false… patient reported pain within the first 24 hours was twice as high in patients who received laser-aided CSF than conventional CSF

Answer 84

false

the opposite is true. conventional CSF reported twice as much pain as laser-aided CSF

Question 85

True or false…
pocket depth increase and gingival recession for both the laser-aided group and conventional group was small and the difference was not statistically significant

Answer 85

true

Question 86

According to Burstone, why would you use a TPA for rotation before placing a buccal arch wire?

Answer 86

avoid mesial force

Can also get class 2 corrected to some degree (1-3mm) by rotating the molars (usually the mesial is rotated in on class 2 cases). As it rotates around the palatal cusp it creates more space and helps correct the class 2

Question 87

Besides using a TPA for rotation of the upper 6s how else could you rotate the molars to get them parallel?

Answer 87

you could do it with an ideally placed bracket (with pre-adjustment) and arch wire. could use a toe end bend to get the ideal prescription out of the bracket. you can skip the 5s and use that extra length to give you more springiness to rotate the molar

Question 88

If you were to use a TPA to rotate your patient’s upper first molars mesial-to-buccal, and you placed equal and opposite couples, what movements would you predict other than equal and opposite rotations?

Answer 88

none. equal and opposite coupes rotate teeth without side effects (like a centric V-bend)

Question 89

If you were to use a TPA to rotate one upper first molar mesial-to-buccal by placing a bend on one side only, what movements would you predict other than that rotation?

Answer 89

The unilateral couple to rotate mesial out, distal in in will also produce a slight mesial force on that molar. A distal force will be applied on the opposite side.

Question 90

If you want to tip the crown of one upper molar to the buccal with a torque bend (or twist) in a TPA, what other movements would you predict?

Answer 90

extrusive force on the molar being torqued and intrusive force on the opposite molar.

there will be a short couple to get it into the bracket (on the rotated molar) then a long couple to get it into the other side.

Question 91

If you have a crossbite on your patient’s right first molars primarily caused by buccal tipped lower molar… how can you address this problem with a lingual arch?

What other movements would you predict?

Answer 91

Unilateral torque can be used

• counterclockwise couple on the tipped molar and intrusive force; opposite side will have extrusive force on molar
• small side effect of vertical movement (intrusion of the tipped molar and extrusion of the opposite molar)

Question 92

If you want to torque upper incisors using a torquing arch as described by Isaacson, what else would you expect to happen?

Answer 92

counterclockwise couple at the incisors

extrusive at the incisor

intrusive at the molar

unwanted tooth movement: buccal crown movement down; incisor crown lingual

Question 93

If you cinch a torquing arch behind the first molars, what would you expect to happen?

Answer 93

“rowboat effect”

• when the torquing arch is cinched at the molar, facial moment of the incisor crown is restrained, but the lingual root force results in lingual movement of the incisor center of resistance

Question 94

If you are using a base arch as described by Isaacson to intrude a patient’s incisors, what else would you expect to happen?

Answer 94

50g extrusion force on the molars

intrusion at incisors, extrusion at molars

distal rotation on molar crown, mesial rotation of roots

Question 95

If you cinch a base arch (as described by Isaacson) behind the first molars, what would you expect to happen?

Answer 95

posterior displacement of the incisor center of rotation

molar restricted from distal crown rotation but mesial rotations of molar roots still occurs

lingual moment of incisor roots

Question 96

If using a base arch to intrude incisors, does it matter where you tie the intrusion arch to the anterior segment, and if so, describe what changes depending on where you tie it.

Answer 96

• if tied at central incisors you get the maximum moment of force because you are further from the center of resistance
• if tied at lateral incisors you reduce the moment of the force because you are closer to the center of resistance

Question 97

What are the limits of expansion for stability in the lower arch:

How much can the incisors go forward?

Answer 97

2mm

If teeth are expanded more than 2mm, the teeth occupy the space where the lip resides, so lip pressures will increase on teeth. This also depends on the initial position though. If teeth were retroclined to start then you may be able to move them more than 2mm

Question 98

What are the limits of expansion for stability in the lower arch:

Expansion at the canines?

Answer 98

0-1mm

Expansion across the canines is NOT STABLE

Question 99

What are the limits of expansion for stability in the lower arch:

At the 4s?

Answer 99

2mm

Expansion across the premolars and molars can be stale if not overdone

Question 100

What are the limits of expansion for stability in the lower arch:

at the 5s?

Answer 100

2-3mm

Question 101

What are the limits of expansion for stability in the lower arch:

At the 6s?

Answer 101

3mm

Question 102

How much transverse expansion can be accomplished before an increasing risk of fenestration occurs?

Answer 102

3mm

Excessive expansion carries the risk of fenestration of premolar and molar roots through the alveolar bone. There is an increasing risk of fenestration beyond 3mm of transverse tooth movement

Question 103

How should we choose an arch form for an individual patient?

Answer 103

The patient’s ORIGINAL arch form should be maintained. This would place teeth in a position of maximum stability and long-term retention

Not ideal to produce dental arches of a single ideal size and shape for everyone

long-term retention studies show that post-treatment changes are greater when the patients arch form is altered

Question 104

If the maxillary and mandibular arch forms are incompatible, how should we choose an arch form?

Answer 104

The mandibular arch form should be used as a basic guide. This guideline does not apply if the mandibular arch is distorted

Question 105

Proffit states that ‘transverse expansion across the canines is almost never maintained, especially in the ___ arch. In fact, it typically decreases whether or not they had treatment.’

Answer 105

lower

Question 106

How do untreated lower arch width measures change in younger subjects?

Answer 106

Decrease of… inter canine width, inter first premolar width, arch length, anterior space, and total space,

increase of irregularity

Question 107

How do untreated lower arch width measures change in older subjects?

Answer 107

Decrease of.. inter canine width, inter first premolar width, arch length, anterior space, and total space

increase of irregularity and overjet

tendency: things constrict overtime

Question 108

How do lower canines and bicuspids change with age?

Answer 108

in both adults and children, the canines and premolars get more narrow over time

Question 109

How do lower molars change with age?

Answer 109

lower molars do not change much overtime

Question 110

True or false… even if a patient did not have ortho treatment there is a chance for more crowding as they age

Answer 110

true

Question 111

In a study by De La Cruz (1995) what happened to class 1 lower canines when expanded 1.4mm

class 1 upper canines expanded 1.7mm

class 2 lower canines expand 0.9mm

class 2 upper canines expanded 2.2 mm

Answer 111

relapse: -1.6 (total change -.2)

relapse -.8 (total change 0.9)

relapse: -2 (total change -1.1)
relapse: -.9 (total change 1.3)

Question 112

What happens after treatment if you expand upper canines?

Answer 112

overtime the inter canine width either decreased from post-treatment width (maxilla) or decreased to less than pre-treatment width (mandible)

Question 113

What do the authors (De La Cruz 1995) believe is the best guide to stability of the arch form after treatment?

Answer 113

The patient’s pretreatment arch form appeared to be the best guide to future arch form stability, but minimizing treatment change was no guarantee of post-retention stability

Your best shot of having stability is by staying close to the lower arch form but this is not guaranteed. this is why we need long-term retention

Question 114

How do you perform an irregularity index?

Answer 114

distance between the contacts and add them up

Question 115

In a study from Riedel, Little 1992, what is the % of patients with an irregularity index of II <3.5mm?

Answer 115

More than 50% of patients had minimal/acceptable irregularity

Question 116

In Reidel, Little 1992 study, ___ had the worse stability, and ___ had the best.

Answer 116

expansion (extraction of PMs also not that great)

incisor extraction (pts with spacing had good stability too)

Incisor ext > spacing > premolar = serial exts > arch length expansion

Question 117

____ of arch width and length is normal until age 30-40.

___ of the length is the least stable movement

Answer 117

constriction

expansion

Question 118

What does Dr. Little believe about selecting an arch form?

Answer 118

“The pretreatment arch form seems to be a better guide to future arch form stability. The greater the treatment change, the greater the tendency for relapse.”

Question 119

True or false.. there is no difference in incisor alignment and future crowding between patients with missing thirds and those with them present or extracted, and no difference in mandibular growth

Answer 119

true

Question 120

Does Kokich support the extraction of primary maxillary canines for labially-intra-alveoalr and/or palatally impacted canines?

Answer 120

yes

For palatal impactions, if the permanent tooth is position not more than half-way over the root of the maxillary lateral incisor; however if it extends beyond the mesial surface of the lateral self-correction is not probable.

Question 121

For labial and intra-alveolar canine impaction: extraction of the primary canines at ___ years of age will enhance eruption and self-correction of a labialr or intra-alveolar maxillary canine impaction

Answer 121

8-9

Question 122

What are the guidelines for early extraction of primary maxillary Canines for palatally displaced permanent canines?

Answer 122

If PA radiographs show that the crown of permanent canine were positioned over the root of the maxillary lateral incisor but not past the mesial surface of the root, self-correction of the ectopic canine occurred with high predictability if the primary canine were removed.

however, if a permanent canine positioned well beyond the mesial surface of the lateral incisor root, self correction does NOT occur with extraction of deciduous canine and must be uncovered.

Question 123

What are some of the mechanical options for extruding/positioning impacted canines that Kokich illustrates/discuses?

Answer 123

1) button and elastomeric chain directed toward the center of the edentulous alveolar ridge to gradually guide the canine into the dental arch
2) Bracket and flexible AW
3) Ballista loop (aplies a vertical force vector)
4) open exposure until cusp tip at occlusal plane level, the bond with bracket and move into dental arch (ideal)

Question 124

What are the three options for labial and intra-alveolar impactions?

Answer 124

excisional uncovering

apically positioned flap

closed exposure

Question 125

If you have a canine crown that is in the center of the alveolus - which options could be used, which should not, and why?

Answer 125

Could: closed eruption technique

should not: excisions uncovering and apical positioned flap (extensive bone might be needed to be removed from labial surface of crown)

Question 126

If you have a canine crown that is positionally labially and is mostly coronal to the mucogingival junction, which options could be used, which should not and why?

Answer 126

All 3 could be used (excisional uncovering, apically positioned flap, closed) because labial bone should be thin so easy access with limited risks

Question 127

If you have a labially displaced canine that is mildly apical to the MGJ, which options could be used and which should not? why?

Answer 127

could: apical positioned flap and closed eruption technique

should not: excisional uncovering (will result in no gingiva on labial surface of tooth)

Question 128

If you have a labially displaced canine that is significantly apical to the MGJ - which options could be used, which should not, why?

Answer 128

could: closed eruption technique (will provide adequate gingiva and does not lead to reintrusion)

should not: apical flap (will lead to reintrusion) or excisional uncovering (will result in inadequate gingiva)

Question 129

If you have a labially displaced canine that does not have sufficient gingiva (but is mostly coronal to the MGJ) which could be used, which should not?

Answer 129

could: apically positioned flap (only technique that would produce more gingiva)

should not: closed and exicisonal

Question 130

If you have a canine that is mesial and over the root of the lateral incisor. which options could be used, which should not, why?

Answer 130

could: apically positioned flap (difficult to move tooth through alveolus unless completely exposed with this technique)

should not: closed and excisional

Question 131

What are the two options for palatally impacted canines?

Answer 131

Early uncovering with auto-eruption

uncover after preparation and place orthodontic tractictiogn to erupt tooth

Question 132

What are the pros and cons of uncovery of palatally displaced canine after prep?

Answer 132

pro: less discomfort for patient??
con: root resorption, bone levels on M of canine and D of lateral are more apical, longer treatment time

Question 133

What are pros and cons of early uncovering with auto eruption of a palatally displaced canine?

Answer 133

pro: tooth with erupted and at the level of the occlusal plane at time of bonding, bone and attachment levels are improved compared to other option, little to no root resorption, reduced treatment time, periodontal and esthetic results are superior
con: none listed in study guide. more uncomfortable at first? less control?

Question 134

What is the likely problem if it appears that a canine is not moving and perhaps may be ankylosed?

Answer 134

1) insufficient bone removal over the crown (causes dental follicle to deflate and be removed = no cells remaining to perform resorption of overlying bone. Then bone will resorb due to pressure necrosis from tooth (very slow process)

Question 135

Exposure and alignment of PDC has a small impact on ___ health. The magnitude of this impaction is not influenced by ____ and is so small that it unlikely to influence the prognosis of a tooth in the long term in most patients

Answer 135

periodontal

surgical technique (open vs closed exposure)

Question 136

What is the treatment technique per Wick Alexander for canine substitution? (bracket placement)

Answer 136

use the same canine bracket but invert it

place bracket gingival to allow cusp reduction

decrease distal root angulation 3-4 degrees

place 0.5mm distal to normal

use cuspid bracket on bicuspid

Offset bend in arch wire may be necessary

Enamel reduction (cuspid cusp tip, cuspid lingual surface, first bicuspid lingual cusp)

Question 137

True or false… according to a study by Quadri, space closing (canine substitution) was perceived to be more attractive than space opening (for prosthetic replacement) by laypeople.

Answer 137

true

the findings have implications for advising patients about the best aesthetic outcome when both maxillary lateral incisors are missing

Question 138

Define anchorage

Answer 138

resistance to unwanted tooth movement

Question 139

Define anchorage value

Answer 139

The anchorage value of any tooth is roughly equivalent to its root surface area. Anchorage value is its resistance to movement. can be thought of as a function of its root surface area, which is the same as its PDL area. The larger the root, the greater the area over which a force can be distributed and vice versa

Question 140

Define reinforced anchorage

Answer 140

reinforcing anchorage by adding more resistance units is effective because with more teeth (or extra oral structures) in the anchorage, the reaction force is distributed over a larger area. if it desired to differentially retract the anterior teeth, the anchorage of the posterior teeth could be reinforced by adding the second molar to the posterior unit. This would change the ratio of the root surface areas so that there would be relatively more pressure in the PDL of the anterior teeth and therefore relatively more retraction of the anterior segment than forward movement of the posterior segment

Question 141

What happens if you use MORE force than what is needed to move the anterior teeth?

Answer 141

it will destroy the effectiveness of reinforced anchorage. too much force destroys the effectiveness of reinforced anchorage by pulling the anchor teeth (posterior segment) up onto the flatter portion of the pressure-response curve. Then the clinician is said to have slipped, burned, or blown the anchorage by moving the anchor teeth too much

Question 142

___, not ___ is the major component of resistance to sliding mechanics

Answer 142

binding

friction

Question 143

Resistance to sliding includes ___ binding almost immediately when tooth movement begins and goes [up/down] rapidly as the angle between the bracket and the wire increases.

Answer 143

elastic

up

Question 144

The amount of force between the wire and the bracket strongly influences the amount of resistance to ___

Answer 144

sliding

Question 145

The resistance to sliding is determined primarily by two things: ___ as the wire contacts the ___ of the bracket, and ___ or ____ as the wire contacts the ___ of the bracket.

Answer 145

friction

walls

elastic or inelastic

corners

Question 146

What is elastic binding and how is it generated?

What is inelastic binding and how is it generated?

Answer 146

Elastics: when the wire contacts the corners of the bracket

Inelastic: when notching occurs on the bracket and the wire is contacting it

Question 147

When a tooth is pulled along an AW, the resistance to sliding will be only ___ until…

Answer 147

friction

the tooth tips enough to bring the corners of the bracket into contact with the wire. The tooth tips because the force is applied to a bracket on its crown, and the center of resistance is halfway down the root

As soon as the corners of the bracket engage the wire, which happens after a very small movement of the tooth, a moment is generated that opposes further tipping. This generates elastic binding between the bracket and wire.

Question 148

Greater resistance to sliding occurs with ___ than ___ brackets. The [greater/less] the angle at which the wire contacts the corners of the bracket, the greater the force between the wire and the bracket.

Answer 148

narrow

greater

Question 149

___ brackets have greater elastic binding

Answer 149

narrow

Question 150

Why are wider brackets better for sliding mechanics?

Answer 150

they don’t let the tooth tip as far. shorter inter bracket span (less springy wire).

Question 151

What is inelastic binding?

Answer 151

inelastic binding occurs when notching of the edge of the wire occurs. When a notch encounters the edge of the bracket, tooth movement stops until displacement of the tooth during function releases the notch (like when shoveling snow and hit a divot in pavement)

Question 152

How are notches typically released if inelastic binding occurs?

Answer 152

due to PDL movement during masticatory function

Question 153

Friction is ultimately derived from ____ forces between atoms. Is friction more related to the force with which the contacting surfaces are pressed together or to the area of contact of the surfaces? why?

Answer 153

electromagnetic

Friction is proportional to the force with which the contacting surfaces are pressed together and is affected by the nature of the surface at the interface.

It is INDEPENDENT of the apparent area of contact

Question 154

Why is friction independent of the apparent area of contact?

Answer 154

all surfaces, no matter how smooth, have irregularities that are large on a molecular scale, and real contact occurs only at a limited number of small spots at the peaks of the surface irregularities, which are called asperities

Question 155

What are asperities?

Answer 155

small spots at the peaks of surface irregulariteis

they carry all the load between the two surfaces. even under light loads, local pressure at the asperities may cause appreciable plastic deformation of this small areas. Because of this, the true contact area is to a considerable extent determined by the applied load and is directly proporitanl to it

Question 156

What is frictional resistance?

Answer 156

the force to produce the plastic deformation of shearing asperities

Question 157

Why does TMA have the highest friction?

Answer 157

as Ti content of an alloy increases, its surface reactivity increases. There is enough Ti reactivity for the wire to “cold-weld” to itself to a steel bracket under some circumstances, making sliding impossible

Question 158

True or false… surface roughness makes a material have significantly more friction

Answer 158

false.. it is less about surface roughness and more about composition and reactivity involved

Question 159

Why do ceramic brackets (without a metal slot) produce a lot of friction?

Answer 159

The irregularity of the surface of the crystal structure. Ceramic brackets can damage wires during sliding, which increases resistance to sliding.

Question 160

Which is rougher, polycrystalline or mono crystalline alumina?

Answer 160

polycrystalline alumina

In mono crystalline alumina, even though it is as smooth as steel, it does not display good sliding possible due to chemical interactions between the wire and the bracket

Question 161

If you want to retract a canine with sliding mechanics, what is the ideal magnitude of force for tooth movement and what amount of force is needed to overcome resistance to sliding?

Answer 161

if a canine is to slide along an AW as part of the closure of an extraction space, and a 100g net force is needed for tooth movement, ANOTHER 100g will be needed to overcome the effects of binding nd friction. Therefore = 200g

Amount of force needed to overcome resistance to sliding = amount of force needed to move the tooth

Question 162

True or false… the problem with resistance to sliding is not so much its presence but the difficulty of knowing its magnitude.

Answer 162

true

Question 163

It is difficult to avoid the temptation to estimate the resistance to sliding generously and add enough force to be certain that tooth movement will occur. What is the effect of this?

Answer 163

The effect of any force beyond what was really needed to overcome resistance to sliding is to bring the anchor teeth up onto the plateau of the tooth movement curve. Then either unnecessary movement of the anchor teeth occurs or additional steps to maintain anchorage are necessary (such as headgear or TADs)

Question 164

how can friction be avoided?

Answer 164

Closing loops (connect two arch wires segments)

retraction springs (attach to only one tooth)

Incorporating springs into the arch wire makes the appliance more complex to fabricate and use clinically but eliminates the difficulty in predicting resistance to sliding

Question 165

What are 6 ways of altering the stress on anchor teeth to minimize their movement?

Answer 165

1) anchorage reinforcement
2) subdivision of desired movement (independent canine retraction)
3) anchorage control in space closure
4) closing loops
5) tipping/uprighting
6) Skeletal anchorage

Question 166

What is the main disadvantage to independent canine retraction technique?

Answer 166

takes nearly twice as long

Question 167

What is the disadvantage of closing springs?

Answer 167

constant forces

Question 168

what is the disadvantage with elastics for anchorage?

Answer 168

they are intermittent

Question 169

The initial arch wire for alignment should provide light, continuous force of approximately __grams to produce the most efficient ___ tooth movement. heavy forces should be avoided.

Answer 169

50

tipping

Question 170

True or false… arch wires for alignment should be able to move freely within the brackets.

Answer 170

true

Question 171

For MD sliding along an arch wire at least ___ of clearance between the arch wire and the bracket is needed, ___ of clearance is desirable, and more than that provides no advantage

Answer 171

2mil

4mil

Question 172

Why should rectangular AWs not be used for initial AWs?

Answer 172

It is better to tip crowns to position during initial alignment rather than displacing the root apices.

Round wires are preferred for alignment

Question 173

What is the ideal amount of force for intrusion?

Answer 173

15g

Question 174

What is the ideal amount of force for extrusion, rotation, or tipping?

Answer 174

50g

Question 175

What is the ideal amount of force for root uprighting?

Answer 175

75g

Question 176

What is the ideal amount of force for translation?

Answer 176

100g

Question 177

What is the recommended procedure to the treatment of asymmetric crowding?

Answer 177

Start alignment without being attached to the tooth that is very misaligned, create space for it with open coil spring, then work up to rectangular to stabilize the other teeth when using a piggy back wire.

Question 178

What is the most straightforward way to proline incisors to alleviate crowding?

Answer 178

crimp a stop on a round superelastic wire at the molar tubes so the wire is proud to the incisor brackets.

Question 179

What are the possible ways to level a lower arch with an excessive curve of spee?

Answer 179

Absolute intrusion: pushing teeth into alveolar bone

Relative intrusion: achieved by preventing eruption of the incisors while growth provides vertical space into which the posterior teeth erupt

Extrusion of posterior teeth: causes mandible to rotate down and back in the absence of growth.

Question 180

What does burstone recommend for absolute intrusion of the maxillary incisors?

Answer 180

segmented arch

segmentation allows for absolute intrusive movement of anterior teeth compared to continuous arches where the wires run continuously

Question 181

What is the definition of intrusion?

Answer 181

intrusion referes to the apical movement of the geometric center of the root in respect to the occlusal plane or a plane based on the long axis of the tooth

labial tipping around its geometric center which would produce pseudo-intrusion

Question 182

If the orthodontist desires to intrude four incisors, ___gm of force would be required

Answer 182

100g (25g per tooth)

Question 183

What happens if you provide too much force when intruding teeth?

Answer 183

you won’t get intrusion, you will get root resorption and burn posterior anchorage

Question 184

In order to accomplish intrusion, should the force be delivered continuously or intermittently?

Answer 184

continuously

Question 185

Why does burstone recommend when using an intrusion arch to use a large cross-sectional wire with a 2.5 turn helix instead of using a smaller cross-sectional wire without a helix?

Answer 185

The helix lowers the force and delivers it more constantly without reducing the arches ability to withstand permanent deformation

helix increases springiness and distance but also prevents deformation

Question 186

What movements of the molars would you predict when using an intrusion arch?

Answer 186

extrusion and clockwise rotation

Question 187

Does burstone recommend tying the intrusion arch directly into the incisor bracket? why or why not?

Answer 187

No, it is not placed directly into the slots.

Major reason is because it may cause anterior torque. If labial root torque is introduced, the intrusive forces are increased and may cause anchorage loss of the posterior segment. If lingual root torque is present, it will have the effect of reducing the magnitude of intrusion on the incisors. if the lingual root torque is large enough, the direction of the force could reverse and the incisors could actually extrude .

Question 188

What are two additional reasons why burstone does not recommend placing an intrusion arch into the anterior bracket slots?

Answer 188

1) produces a statically indeterminate system

2) undesirable curvatures are formed in the wire during activation

Question 189

What other movements of the incisors could be predicted if they started with excessively flared incisors and an intrusion arch was used? how can you prevent this effect?

Answer 189

lingual root movement and additional flaring of the incisors (force off-center). cinch the wire behind the molar to minimize this effect

Similarly, if the tooth was perfectly upright, no tipping would occur

Question 190

Discuss two ways to prevent proclination of teeth with an intrusion arch

Answer 190

1) cinch the intrusive arch back to prevent incisors from protruding
2) use a posterior extension so that the force can be directed through the center of resistance of the incisors

Question 191

If all 6 anterior teeth needed to be intruded, should you do them all at the same time or do it segmentally?

Answer 191

segmentally

incisors first, then canine

Question 192

What is a favorable response when class 2 patients are treated with headgear (conceptually used to restrain maxillary growth) or a functional appliance (conceptually used to hold the mandible forward and increase mandibular growth)?

Answer 192

Favorable growth allows for both:

1) restraint of maxillary growth
2) differential forward mandibular growth

Question 193

Do most studies find that functional appliances result in acceleration of growth with later slowing (such that the ultimate size of the mandible intreated and untreated patients is similar) or true stimulation of mandibular growth (such that the ultimate size of the mandible is larger than found in untreated patients)?

Answer 193

Most studies find that functional appliances result in acceleration of growth with later slowing such that the ultimate size of the mandible in treated and untreated patients is similar (barely any difference)

Question 194

How do functional appliances influence tooth position? What are the pros and cons of these movements?

Answer 194

1) maxillary posterior intrusion - good for pts with long LAFH
2) maxillary and dental retraction and mandibular dental protrusion - good for pts with maxillary dental protrusion and mandibular dental retrusion. (not good for patients with mx dental retrusion and mn dental protrusion)
4) mandilbar posterior extrusion and forward movement - good for fixing the class 2 by rotation of occlusal plane

Question 195

If your patient is ready to start comprehensive treatment and growth modification, which type of appliance is more compatible with full fixed appliances?

Answer 195

Headgear is more compatible with full fixed appliances.

Herbst works well too, but introduces side effects: forward displacement of mandibular teeth

Question 196

True or false… we are unlikely to get growth modification with elastics/flexible spring appliances

Answer 196

true

Question 197

Is the final profile significantly more attractive when the patient is treated with a Herbst or with headgear?

Answer 197

1) Both headgear and Herbst treatment groups had significant profile improvements with treatment
2) Both headgear and Herbst treatment groups finished with similarly attractive profiles
3) despite close matching of the groups, the head groups subjects had lower initial scores and experienced greater percentage changes

Question 198

Where does the generation of a moment occur in either sliding teeth on a arch wire or when closing loop between segments?

Answer 198

sliding teeth - automatic (bracket width)

Closing loop - gable bend (approximately 45 degrees)

Question 199

What is the major advantage and major disadvantage of sliding mechanics?

Answer 199

advantage - automatic generation of root-paralleling moments at the extraction site. easier than bending closing loops

disadvantage - significant resistance to sliding in form of binding and friction

Question 200

The wire on which sliding occurs must have two properties. what are they?

Answer 200

1) The wire must be undersized relative to the bracket

2) the wire must be strong enough to not bend significantly when force is applied

Question 201

Which is better for sliding mechanics, a 16x25 in an 18 slot or a 19x25 in a 22 slot? Why?

Answer 201

19x25 in a 22 slot. It is a stiffer wire and brackets are wider

Question 202

A single wing bracket (18 slot) is better for ___ whereas a double wing (22 slot) is better for ___. Why?

Answer 202

aligning (wire is more springy with increased inter bracket space)

sliding (keeps angle of wire to corner of bracket lower to minimize binding forces when sliding)

Question 203

Why is A-NiTi (superelastic) coil better than elastomeric chain for closing space?

Answer 203

the springs provide ideal levels of force and changes minimally as the space closes. (chain has a force degradation over time)

Question 204

Torque in the incisor brackets is often needed as the teeth are ___ to keep them from becoming too upright. The reciprocal for insider torque is ___ force on ___

Answer 204

retracted

forward force on the posterior anchorage

Therefore, when closing spac, maximum anchorage is necessary until you are sure its not.

Question 205

With closing loop mechanics should you use a round or rectangular wire?

Answer 205

rectangular wire to prevent the wire from rolling in the bracket slots.

The frictionless design of closing loops has the potential to reduce anchorage problems and decrease the time for space closure.

Question 206

How much force is desired for a continuous arch to closing space?

Answer 206

250g per mm activation

Question 207

What affects the force level?

Answer 207

1) wire size
2) length of wire
3) inter-bracket distance
4) configurations (more or less wire in your segment between 2 brackets)

Question 208

How tall should a loop be?

Answer 208

7-8mm tall while incorporating 10-12mm or more of wire

Question 209

If you do not place the closing loop in the center what will happen?

Answer 209

you will get vertical forces

The loop should be placed where the center of the embrasure will be once the space is closed.

Question 210

For routine use with fail-safe loops in continuous arch wires, where should the loop be located and why?

Answer 210

if it is a continuous arch wire, the preferred location for a closing loop is at the spot that will be the center of the embrasure when the space is closed. Put it at the distal end of the anterior segment.

Question 211

Which type of loop is more fail-safe, opening or closing loop?

Answer 211

opening loop (the one you activate by opening)

Question 212

What are the two ways to hold the arch wire in its activated position when using a closing loop?

Answer 212

1) bending the end of the archwire gingival behind the last molar tube
2) place an attachement (soldered tieback) on the posterior part of the archwire so that a ligature can be used to tie the wire in its activated position.

Question 213

According to a study by Dixon, which method produces the most rapid rate of sliding space closure (active ligatures, power chains, or NiTi springs)?

Answer 213

NiTi springs gave the most rapid rate of space closure and may be considered the treatment of choice.

However, power chain provides a cheaper treatment option that is as effective as NiTi springs

Question 214

According to the study by Dixon, did inter arch elastics influence the rate of space closure?

Answer 214

no

Question 215

What is the first step in class 2 treatment of almost every type?

Answer 215

correct molar rotations

Question 216

What are some of the appliance options for placing a rotating couple on both upper molars?

Answer 216

TPA

Auxiliary labial arch

inner bow of a facebow

Question 217

Distal movement of upper molars requires more anchorage than can be supplied by just the other teeth. How can you accomplish this?

Answer 217

headgear

problem is though that you need moderate intensity with long duration. headgear is only medium duration even in cooperative patients.

distal movement of first molars is more effective in cervical pull headgear, however it can result in down and back rotation of the mandible

Question 218

`The major use of class2 elastics to a sliding jig (motion appliance) would be to…

Answer 218

accentuate rotation of the upper molar as a component of correcting the molar relationship

It is not a great device for molar distalizing

Question 219

Why would class 2 elastics in a camouflage case with u4 extraction be contraindicated?

Answer 219

it is contraindicated unless the lower incisors need to be moved forward

Question 220

Class 2 elastics produce molar correction largely by _____ with only a small amount of ____. Class 2 elastics can produce far too much ____

Answer 220

mesial movement of the mandibular arch

distal positioning of the maxillary arch

protrusion of lower incisors

Question 221

How much force does Profit recommend per side to displace one arch relative to the other?

Answer 221

250gms

Question 222

The vertical force of class 2 elastics will extrude mandibular molars and maxillary incisors, rotating the occlusal plane __ posteriorly and ___ anteriorly. What would happen if the molar extrudes more than the ramus grows vertically?

Answer 222

up

down

if the molar extrudes more than the ramus grows vertically, the mandible will be rotated downward

Therefore, class 2 elastics are contraindicated in non growing patients who cannot tolerate some down and back rotation of the mandible

Question 223

Why are class 2 elastics contraindicated in non growing patients with a long LAFH?

Answer 223

When the lower molar extrudes, the mandible will be rotated down and back

Question 224

The rotation of the occlusal plane with class 2 elastics (up posteriorly, down anteriorly) facilitates the desired correction of the ___ occlusion, but even if elongation of the lower molars can be tolerated because of good growth, the corresponding extrusion of the ___ can be unsightly.

Answer 224

posterior

maxillary incisors

Question 225

True or false… the forsus is an acceptable substitute for class 2 elastics for patients who appear to be non-compliant

Answer 225

true

Question 226

How much force decay of elastomeric chains occur in 24 hours?

Answer 226

elastomeric chains generally lose 50-70% of their initial force during the first day of load application

Question 227

How much force decay of elastomeric chains occur in 3-4 weeks?

Answer 227

At 3 weeks, retention of original force is only 30-40%

Elastomeric chains should be initially extended 75-100% of their original length and have the initial force level verified with a force gauge

Question 228

Which has less force decay over time, closed chains, short filament, or long filaments?

Answer 228

Longer filament chains will deliver a lower initial force at the same extension and exhibit a greater rate of force decay under load than the closed loop chain

Question 229

Chains tested in water at 24 hours have ___% force loss

Answer 229

50%

Question 230

true or false… closed chains are more stable than open chains

Answer 230

true

Question 231

What wire should you use with class two treatment?

Answer 231

well-fitting rectangular wire

round wire doesn’t give you as much control over the vertical and can cause lower anterior to flare out

Question 232

Using heavy class 2 elastics for 9-12 months as the major method for correcting a class 2 malocclusion rarely produces an acceptable result. Using class 2 elastics for __-___ months at the completion of treatment, however will obtain good posterior interdigitation and the result is often acceptable.

Answer 232

3-4

Question 233

Most manufacterers recommend stretching elastics __x the slack diameter of the lumen to obtain the strength of force advertised.

Answer 233

3

Question 234

How often should elastics be changed?

Answer 234

2x per day (for hygiene and convenience reasons)

1x per day for force decay reasons.

Question 235

how much force in coil springs is typically lost at 24 hours?

Answer 235

not much (about 10% +/= 10%)

Question 236

How much force in elastomeric chains is lost at 3-4 weeks (standard chains)?

What about RMO energy chains?

Answer 236

2/3rds loss

1/3rd loss

Question 237

Interarch elastics lose about __% of their force in 1 hour, ___% in 12 hours, and ___% at 24 hours. which loses force faster, latex or synthetic?

Answer 237

15-27%

20-35%

20-40%

Synthetic

Question 238

According to Burstone, why would you use a TPA for rotation BEFORE placing a buccal archwire?

Answer 238

to avoid mesial force side effect of the buccal wires