Second Semester Flashcards
(238 cards)
1
Q
Which types of external root resorption is a potential complication of orthodontic treatment?
A
Transient inflammatory resorption
Surface resorption
2
Q
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.
A
higher
3
Q
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.
A
thickness
mesiodistal
faciolingual
4
Q
What are the compensations for first order bends in the contemporary edgewise appliance?
A
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.
5
Q
What are the compensations for second order bends in the contemporary edgewise appliance?
A
Angulating the bracket or bracket slot decreases or removes the necessity for these bends
6
Q
What are the compensations for third order bends in the contemporary edgewise appliance?
A
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
7
Q
Why is it most critical to place a bracket with built-in tip correctly?
A
to maintain proper bone thickness between roots
8
Q
GAC In-Ovation R I a/an [active/passive] self-ligating bracket system
A
active
9
Q
Damon is a/an [active/passive] self-ligating bracket system
A
passive
10
Q
When was self-ligation first introduced?
A
1930s
11
Q
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
A
efficient
provide reduced chair time
12
Q
Are conventional brackets less hygienic than self-ligating brackets?
A
Insufficient evidence that self-ligating brackets are more hygienic than conventional
13
Q
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?
A
Reduced chair time and control of mandibular incisor inclination
14
Q
What is the moment of force for a tooth in which 200gm of force is applied 10mm away from the center of resistance?
A
2000gm/mm
15
Q
What is the moment of force of a tooth in which 200gm of force is applied 12mm away from the center of resistance?
A
12mm
16
Q
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 ___.
A
8-10 weeks
6 months
17
Q
When using crossbite elastics, why is it important to use them only for a short time?
A
Crossbite elastics also cause extrusion, which can cause an open bite if used for too long
18
Q
Extrusion can be as rapid as __ mm per week without damage to the PDL
A
1
19
Q
What side effects would be expected to result if a continuous wire were used for canine eruption?
A
incisor intrusion and anterior open bite
20
Q
An anterior extrusion arch is shown in the image. After activation, what forces/couples are expected at the molar and at the anterior segment?
A
Intrusion and mesial crown tip at the molar and extrusion at the anterior segment
21
Q
What forces/moments would you expect to see on the molars from a continuous arch wire system used to intrude a second molar?
A
intrusion of the second molar
extrusion of the first molar
crown mesial tip of both molars
22
Q
How does a round wire cause labial tipping of incisors when an intrusive force is applied?
A
The intrusive force acts labial to the center of resistance
23
Q
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?
A
Distal
Lingual
The moment of the molar is significantly larger, essentially over-riding the opposing moment of the incisor and pulls the wire back.
24
Q
true or false…
Mini-implants used for molar uprighting are osseointegrated
true or false… mini-implants are easily removed after treatment
A
false
true
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
true
26
True or false... using a tip back bend, in both a round wire and a rectangular wire, the incisors will intrude
true
27
What are some disadvantages of conventional molar uprighting when compared with molar uprighting with tads?
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
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
C) correct OB, OJ
29
How many mm of space total can be gained by derotating the molars with a TPA?
6mm
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?
extrusion and distalization
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
b) distalization of the lower premolars
32
how many grams of force is ideal for the intrusion of upper incisors?
20 grams
33
According to Parking et al., Can orthodontists and laypeople generally identify operated canines?
orthodontists generally can (60.7% of the time P < 0.01)
Laypersons generally cannot (49.7% of the time, P > 0.05)
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?
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
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?
Gingival health
Alignment
Torque (most common)
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?
open exposure was associated with reduced treatment time to initial alignment
closed exposure was associated with greater risk of canine ankylosis
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?
Laypersons found OSC images more attractive than PR images
Laypersons preferred OSC images over PR images
38
Rank the following arch wires in order of highest to lowest formability: NiTi, SS, B-Ti
SS = TMA > NiTi
39
What are the advantages of NiTi wires compared to others and at what stage might you use these?
high springiness
low formability
high springback
low stiffness
ideal for initial stages of leveling and alignment
40
Which type of NiTi wire is considered to have true shape memory effect?
thermoelastic
41
Which NiTi wire(s) undergoes a phase change from austenite to martensite in response to stress?
pseudoelastic
stress-induced martensite
austenitic active
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?
Coaxial
greater flexibility
reduced load deflection rate
more mean tooth movement in the first 12 weeks
43
Which technique is the most effective for incisor retraction and anchorage preservation according to Rizk et al?
En masse retraction with miniscrews
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
C) both are statistically similar
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
C) there was no statistically significant difference between the two
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
C) there was no statistically significant difference between the two
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?
controlled tipping
35-60 grams
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
E) two of the above
tipping and bodily movement
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
C) closing loop alone
closing loops need to have gable bends to produce ideal M/F ratio for bodily space closure
50
True or false...
| elastomeric power chain is an efficient way to close extraction spaces that is cost-effective
true
51
True or false.. there is strong evidence to suggest that NiTi coil springs are significantly more efficient and are therefore always recommended
false
52
what is the ideal force for closing spaces using sliding mechanics?
100-200g
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
B) Bands
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?
10-2 anchorage system
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
D) excessive OB present
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
A) denture planning
57
True or false.. according to the Janson et al., systematic review:
Class 2 elastics are effective in correcting class 2 malocclusions
true
58
True or false.. according to the Janson et al., systematic review:
overall, class 2 elastics produced correction primarily with dentoalveoarl effects
true
59
True or false.. according to the Janson et al., systematic review:
Class 2 effects include mandibular molar intrusion
false....
class 2 elastics include mandibular molar EXTRUSION
60
True or false.. according to the Janson et al., systematic review:
Class 2 effects include lower mandibular incisor intrusion
true
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
true
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
d) Herbst
the Herbst appliance achieved greater skeletal changes in the short-term treatment compared to class 2 elastics
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
C) increase in overjet
remember there was an overjet reduction of 5.8mm and an overbitre reduction of 3mm
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?
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 )
65
If a patient is expected to be noncompliant should you use a Forsus or elastics for class correction?
Forsus
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
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
67
Profit defines the threshold for Bolton significant as ___mm
2mm
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
D) all of the above
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
```
true
70
True or false.. because of the tendency of relapse it is important to slightly overcorrect occlusal relationships
true
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
b) rotations
72
How much is recommended for overcorrection of class 2 or 3 malocclusion or a crossbite?
1-2mm
73
True or false... retainers should be worn full time for at least the first 3-4 months
true
74
true or false... fixed retainers should be rigid, not allowing for any displacement of individual teeth upon mastication
false
75
True or false.... gingival elastic fibers take longer than PDL fibers to reorganize, requiring up to 1 year
true
76
true or false...
Gingival elastic fibers can cause rotational relapse so supracrestal fiberotomoy may be indicated in cases with severe rotations
true
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
d) all of the above
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
F) all except third molar eruption
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
B) Flattens the contact area, enhancing stability
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
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
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
E
82
postoveraptive infections are less probable following CSF with a laser because the laser ___ the irradiated area
sterilizes
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)
true
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
false
the opposite is true. conventional CSF reported twice as much pain as laser-aided CSF
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
true
86
According to Burstone, why would you use a TPA for rotation before placing a buccal arch wire?
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
87
Besides using a TPA for rotation of the upper 6s how else could you rotate the molars to get them parallel?
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
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?
none. equal and opposite coupes rotate teeth without side effects (like a centric V-bend)
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?
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.
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?
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.
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?
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)
92
If you want to torque upper incisors using a torquing arch as described by Isaacson, what else would you expect to happen?
counterclockwise couple at the incisors
extrusive at the incisor
intrusive at the molar
unwanted tooth movement: buccal crown movement down; incisor crown lingual
93
If you cinch a torquing arch behind the first molars, what would you expect to happen?
"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
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?
50g extrusion force on the molars
intrusion at incisors, extrusion at molars
distal rotation on molar crown, mesial rotation of roots
95
If you cinch a base arch (as described by Isaacson) behind the first molars, what would you expect to happen?
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
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.
- 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
97
What are the limits of expansion for stability in the lower arch:
How much can the incisors go forward?
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
98
What are the limits of expansion for stability in the lower arch:
Expansion at the canines?
0-1mm
Expansion across the canines is NOT STABLE
99
What are the limits of expansion for stability in the lower arch:
At the 4s?
2mm
Expansion across the premolars and molars can be stale if not overdone
100
What are the limits of expansion for stability in the lower arch:
at the 5s?
2-3mm
101
What are the limits of expansion for stability in the lower arch:
At the 6s?
3mm
102
How much transverse expansion can be accomplished before an increasing risk of fenestration occurs?
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
103
How should we choose an arch form for an individual patient?
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
104
If the maxillary and mandibular arch forms are incompatible, how should we choose an arch form?
The mandibular arch form should be used as a basic guide. This guideline does not apply if the mandibular arch is distorted
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.'
lower
106
How do untreated lower arch width measures change in younger subjects?
Decrease of... inter canine width, inter first premolar width, arch length, anterior space, and total space,
increase of irregularity
107
How do untreated lower arch width measures change in older subjects?
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
108
How do lower canines and bicuspids change with age?
in both adults and children, the canines and premolars get more narrow over time
109
How do lower molars change with age?
lower molars do not change much overtime
110
True or false... even if a patient did not have ortho treatment there is a chance for more crowding as they age
true
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
relapse: -1.6 (total change -.2)
relapse -.8 (total change 0.9)
relapse: -2 (total change -1.1)
relapse: -.9 (total change 1.3)
112
What happens after treatment if you expand upper canines?
overtime the inter canine width either decreased from post-treatment width (maxilla) or decreased to less than pre-treatment width (mandible)
113
What do the authors (De La Cruz 1995) believe is the best guide to stability of the arch form after treatment?
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
114
How do you perform an irregularity index?
distance between the contacts and add them up
115
In a study from Riedel, Little 1992, what is the % of patients with an irregularity index of II <3.5mm?
More than 50% of patients had minimal/acceptable irregularity
116
In Reidel, Little 1992 study, ___ had the worse stability, and ___ had the best.
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
117
____ of arch width and length is normal until age 30-40.
___ of the length is the least stable movement
constriction
expansion
118
What does Dr. Little believe about selecting an arch form?
"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."
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
true
120
Does Kokich support the extraction of primary maxillary canines for labially-intra-alveoalr and/or palatally impacted canines?
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.
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
8-9
122
What are the guidelines for early extraction of primary maxillary Canines for palatally displaced permanent canines?
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.
123
What are some of the mechanical options for extruding/positioning impacted canines that Kokich illustrates/discuses?
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)
124
What are the three options for labial and intra-alveolar impactions?
excisional uncovering
apically positioned flap
closed exposure
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?
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)
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?
All 3 could be used (excisional uncovering, apically positioned flap, closed) because labial bone should be thin so easy access with limited risks
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?
could: apical positioned flap and closed eruption technique
should not: excisional uncovering (will result in no gingiva on labial surface of tooth)
128
If you have a labially displaced canine that is significantly apical to the MGJ - which options could be used, which should not, why?
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)
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?
could: apically positioned flap (only technique that would produce more gingiva)
should not: closed and exicisonal
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?
could: apically positioned flap (difficult to move tooth through alveolus unless completely exposed with this technique)
should not: closed and excisional
131
What are the two options for palatally impacted canines?
Early uncovering with auto-eruption
uncover after preparation and place orthodontic tractictiogn to erupt tooth
132
What are the pros and cons of uncovery of palatally displaced canine after prep?
pro: less discomfort for patient??
con: root resorption, bone levels on M of canine and D of lateral are more apical, longer treatment time
133
What are pros and cons of early uncovering with auto eruption of a palatally displaced canine?
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?
134
What is the likely problem if it appears that a canine is not moving and perhaps may be ankylosed?
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)
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
periodontal
surgical technique (open vs closed exposure)
136
What is the treatment technique per Wick Alexander for canine substitution? (bracket placement)
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)
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.
true
the findings have implications for advising patients about the best aesthetic outcome when both maxillary lateral incisors are missing
138
Define anchorage
resistance to unwanted tooth movement
139
Define anchorage value
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
140
Define reinforced anchorage
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
141
What happens if you use MORE force than what is needed to move the anterior teeth?
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
142
___, not ___ is the major component of resistance to sliding mechanics
binding
friction
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.
elastic
up
144
The amount of force between the wire and the bracket strongly influences the amount of resistance to ___
sliding
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.
friction
walls
elastic or inelastic
corners
146
What is elastic binding and how is it generated?
What is inelastic binding and how is it generated?
Elastics: when the wire contacts the corners of the bracket
Inelastic: when notching occurs on the bracket and the wire is contacting it
147
When a tooth is pulled along an AW, the resistance to sliding will be only ___ until...
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.
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.
narrow
greater
149
___ brackets have greater elastic binding
narrow
150
Why are wider brackets better for sliding mechanics?
they don't let the tooth tip as far. shorter inter bracket span (less springy wire).
151
What is inelastic binding?
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)
152
How are notches typically released if inelastic binding occurs?
due to PDL movement during masticatory function
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?
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
154
Why is friction independent of the apparent area of contact?
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
155
What are asperities?
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
156
What is frictional resistance?
the force to produce the plastic deformation of shearing asperities
157
Why does TMA have the highest friction?
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
158
True or false... surface roughness makes a material have significantly more friction
false.. it is less about surface roughness and more about composition and reactivity involved
159
Why do ceramic brackets (without a metal slot) produce a lot of friction?
The irregularity of the surface of the crystal structure. Ceramic brackets can damage wires during sliding, which increases resistance to sliding.
160
Which is rougher, polycrystalline or mono crystalline alumina?
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
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?
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
162
True or false... the problem with resistance to sliding is not so much its presence but the difficulty of knowing its magnitude.
true
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?
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)
164
how can friction be avoided?
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
165
What are 6 ways of altering the stress on anchor teeth to minimize their movement?
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
166
What is the main disadvantage to independent canine retraction technique?
takes nearly twice as long
167
What is the disadvantage of closing springs?
constant forces
168
what is the disadvantage with elastics for anchorage?
they are intermittent
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.
50
tipping
170
True or false... arch wires for alignment should be able to move freely within the brackets.
true
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
2mil
4mil
172
Why should rectangular AWs not be used for initial AWs?
It is better to tip crowns to position during initial alignment rather than displacing the root apices.
Round wires are preferred for alignment
173
What is the ideal amount of force for intrusion?
15g
174
What is the ideal amount of force for extrusion, rotation, or tipping?
50g
175
What is the ideal amount of force for root uprighting?
75g
176
What is the ideal amount of force for translation?
100g
177
What is the recommended procedure to the treatment of asymmetric crowding?
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.
178
What is the most straightforward way to proline incisors to alleviate crowding?
crimp a stop on a round superelastic wire at the molar tubes so the wire is proud to the incisor brackets.
179
What are the possible ways to level a lower arch with an excessive curve of spee?
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.
180
What does burstone recommend for absolute intrusion of the maxillary incisors?
segmented arch
segmentation allows for absolute intrusive movement of anterior teeth compared to continuous arches where the wires run continuously
181
What is the definition of intrusion?
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
182
If the orthodontist desires to intrude four incisors, ___gm of force would be required
100g (25g per tooth)
183
What happens if you provide too much force when intruding teeth?
you won't get intrusion, you will get root resorption and burn posterior anchorage
184
In order to accomplish intrusion, should the force be delivered continuously or intermittently?
continuously
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?
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
186
What movements of the molars would you predict when using an intrusion arch?
extrusion and clockwise rotation
187
Does burstone recommend tying the intrusion arch directly into the incisor bracket? why or why not?
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 .
188
What are two additional reasons why burstone does not recommend placing an intrusion arch into the anterior bracket slots?
1) produces a statically indeterminate system
| 2) undesirable curvatures are formed in the wire during activation
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?
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
190
Discuss two ways to prevent proclination of teeth with an intrusion arch
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
191
If all 6 anterior teeth needed to be intruded, should you do them all at the same time or do it segmentally?
segmentally
incisors first, then canine
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)?
Favorable growth allows for both:
1) restraint of maxillary growth
2) differential forward mandibular growth
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)?
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)
194
How do functional appliances influence tooth position? What are the pros and cons of these movements?
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
195
If your patient is ready to start comprehensive treatment and growth modification, which type of appliance is more compatible with full fixed appliances?
Headgear is more compatible with full fixed appliances.
Herbst works well too, but introduces side effects: forward displacement of mandibular teeth
196
True or false... we are unlikely to get growth modification with elastics/flexible spring appliances
true
197
Is the final profile significantly more attractive when the patient is treated with a Herbst or with headgear?
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
198
Where does the generation of a moment occur in either sliding teeth on a arch wire or when closing loop between segments?
sliding teeth - automatic (bracket width)
Closing loop - gable bend (approximately 45 degrees)
199
What is the major advantage and major disadvantage of sliding mechanics?
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
200
The wire on which sliding occurs must have two properties. what are they?
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
201
Which is better for sliding mechanics, a 16x25 in an 18 slot or a 19x25 in a 22 slot? Why?
19x25 in a 22 slot. It is a stiffer wire and brackets are wider
202
A single wing bracket (18 slot) is better for ___ whereas a double wing (22 slot) is better for ___. Why?
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)
203
Why is A-NiTi (superelastic) coil better than elastomeric chain for closing space?
the springs provide ideal levels of force and changes minimally as the space closes. (chain has a force degradation over time)
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 ___
retracted
forward force on the posterior anchorage
Therefore, when closing spac, maximum anchorage is necessary until you are sure its not.
205
With closing loop mechanics should you use a round or rectangular wire?
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.
206
How much force is desired for a continuous arch to closing space?
250g per mm activation
207
What affects the force level?
1) wire size
2) length of wire
3) inter-bracket distance
4) configurations (more or less wire in your segment between 2 brackets)
208
How tall should a loop be?
7-8mm tall while incorporating 10-12mm or more of wire
209
If you do not place the closing loop in the center what will happen?
you will get vertical forces
The loop should be placed where the center of the embrasure will be once the space is closed.
210
For routine use with fail-safe loops in continuous arch wires, where should the loop be located and why?
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.
211
Which type of loop is more fail-safe, opening or closing loop?
opening loop (the one you activate by opening)
212
What are the two ways to hold the arch wire in its activated position when using a closing loop?
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.
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)?
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
214
According to the study by Dixon, did inter arch elastics influence the rate of space closure?
no
215
What is the first step in class 2 treatment of almost every type?
correct molar rotations
216
What are some of the appliance options for placing a rotating couple on both upper molars?
TPA
Auxiliary labial arch
inner bow of a facebow
217
Distal movement of upper molars requires more anchorage than can be supplied by just the other teeth. How can you accomplish this?
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
218
`The major use of class2 elastics to a sliding jig (motion appliance) would be to...
accentuate rotation of the upper molar as a component of correcting the molar relationship
It is not a great device for molar distalizing
219
Why would class 2 elastics in a camouflage case with u4 extraction be contraindicated?
it is contraindicated unless the lower incisors need to be moved forward
220
Class 2 elastics produce molar correction largely by _____ with only a small amount of ____. Class 2 elastics can produce far too much ____
mesial movement of the mandibular arch
distal positioning of the maxillary arch
protrusion of lower incisors
221
How much force does Profit recommend per side to displace one arch relative to the other?
250gms
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?
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
223
Why are class 2 elastics contraindicated in non growing patients with a long LAFH?
When the lower molar extrudes, the mandible will be rotated down and back
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.
posterior
maxillary incisors
225
True or false... the forsus is an acceptable substitute for class 2 elastics for patients who appear to be non-compliant
true
226
How much force decay of elastomeric chains occur in 24 hours?
elastomeric chains generally lose 50-70% of their initial force during the first day of load application
227
How much force decay of elastomeric chains occur in 3-4 weeks?
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
228
Which has less force decay over time, closed chains, short filament, or long filaments?
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
229
Chains tested in water at 24 hours have ___% force loss
50%
230
true or false... closed chains are more stable than open chains
true
231
What wire should you use with class two treatment?
well-fitting rectangular wire
round wire doesn't give you as much control over the vertical and can cause lower anterior to flare out
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.
3-4
233
Most manufacterers recommend stretching elastics __x the slack diameter of the lumen to obtain the strength of force advertised.
3
234
How often should elastics be changed?
2x per day (for hygiene and convenience reasons)
1x per day for force decay reasons.
235
how much force in coil springs is typically lost at 24 hours?
not much (about 10% +/= 10%)
236
How much force in elastomeric chains is lost at 3-4 weeks (standard chains)?
What about RMO energy chains?
2/3rds loss
1/3rd loss
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?
15-27%
20-35%
20-40%
Synthetic
238
According to Burstone, why would you use a TPA for rotation BEFORE placing a buccal archwire?
to avoid mesial force side effect of the buccal wires
