First Semester Flashcards
(244 cards)
1
Q
What is was the problem they were trying to address in the ABO objective grading system article (1998)?
A
They were trying to address a way to make all phase 3 examination more objective with the grading system. Also tried establishing validity and reliability within the indexes used for grading.
Furthermore, diplomates may use this scoring system at anytime in their career to determine if they are producing “board quality” results for self-evaluation.
This would help with repeatability, accuracy, and standardized evaluation of candidates
2
Q
What was known prior to the 1994 ABO committee? Were the indices that had been used valid? were they reliable?
A
Prior to the 1994 ABO committee several indices existed aiming to evaluate the outcome of orthodontic treatment. The PAR (peer assessment rating) index is reliable and valid, however it is not precise enough to discriminate between the minor inadequacies of tooth position that are found in ABO case reports.
The occlusal index has been used to determine treatment quality, but this method is tedious and is more appropriate for pre-treatment records rather than post-treatment
3
Q
How did the ABO conduct their first study (1995) and what was the level of evidence (RCT, prospective, restrospective, etc?)
A
100 cases were evaluated, series of 15 criteria measured on final dental casts and pano
LOE = retrospective without controls, no selection criteria
Results = 85% of the inadequacies occurred in 7 of the 15 criteria (alignment, marginal ridges, BL inclination, OJ, occlusal relationships, occlusal contacts, root angulation)
4
Q
In the ABO 1995 study, 85% of the inadequacies occurred in 7 of the 15 criteria. What were the 7?
A
Alignment marginal ridges BL inclination OJ Occlusal relationship Occlusal contacts Root angulation
5
Q
How did the ABO conduct their second study (1996)? What did they find?
A
300 cases were evaluated by a subcommittee of four directors. This test was intended to verify the results of the previous test to determine if multiple examiners could score the records reliably and consistently. Again, the majority of inadequacies occurred in the same 7 categories. But the committee had difficulty establishing adequate inter examiner reliability. Thus, they suggested creating a measuring instrument to make the process more reliable.
6
Q
What was different in ABO’s third study conducted in 1997? What did they find?
A
third field test was performed with a modified scoring system and the addition of an instrument to measure the various criteria more accurately. 832 cases were analyzed by all the directors. This time, a calibration session preceded the examination to establish increased reliability of the directors. Again, the results showed that the overwhelming majority of inadequacies occurred in the same 7 categories. however, this time, they added inter proximal contacts to the scoring system
7
Q
Describe the 1998 ABO study
A
all directors participated in the evaluation process. the new and improved measuring instrument was used, extensive calibration of directors was performe.d. this study reaffirmed the benefits of using an objective grading system for grading the dental casts and pano, and also established standards for successful completion of this portion of the phase 3 examination. 8 criteria: alignment, marginal ridges, BL inclination, occlusal relationship, occlusal contacts, overjet, inter proximal contacts, root angulation
8
Q
How does the ABO assess ideal alignment of maxillary anterior teeth?
A
incisal edges and lingual surface of maxillary anterior teeth (functioning surfaces and they effect esthetics)
9
Q
how does the ABO assess ideal alignment of mandibular anterior teeth?
A
incisal edges and labial incisal surfaces
10
Q
How does the ABO assess ideal alignment for maxillary posterior teeth?
A
MD central groove of the premolars and molars
11
Q
How does the ABO assess ideal alignment for mandibular posterior teeth?
A
Buccal cusps of the premolars and molars
12
Q
How do we achieve ideal alignment with bracket placement?
A
Incisal/gingival alignment determined by incisal/gingival position of brackets. BL alignment determined by the bracket prescription (and ensuring bracket is fully seated against the teeth). M/D tip determined by angling the bracket slot.
13
Q
Why should the marginal ridges be at the same level according to ABO?
A
if marginal ridges are at the same relative height, the CEJ will be at the same lee. In a periodontally healthy individual, this will result in flat bone levels between adjacent teeth. Additionally, if marginal ridges are at the same height, it will be easier to establish proper occlusal contacts.
14
Q
How are marginal ridges positioned at the same level by bracket placement?
A
The slot should be parallel with the plane extending from the mesial to distal marginal ridges
15
Q
Describe the vertical placement of brackets following Alexander’s protocol.
A
Upper: central = X Lateral = X -0.5 Canine = X + 0.5 Bicuspids = X First molar = X -0.5 Second molar = X - 1
Lower: incisors = X -0.5 Canine = X +0.5 Bicuspids = X First molar = X -0.5 Second molar = X - 1
16
Q
In regards to BL inclination, there should not be a significant difference between the heights of the buccal and lingual cusps of the molars and premolars. why? (per ABO)
A
In order to establish proper occlusion in maximum intercuspation and avoiding balancing interferences, there should not be a significant difference between the heights of the B and L cusps of the maxillary and mandibular molars and premolars.
17
Q
How do the brackets help achieve correct BL inclination?
A
third order compensations (torque) prescribed into brackets(slots).
18
Q
What are the four main factors to consider in placement of brackets in regards to BL inclination (torque)?
A
1) prescriptions in different appliances vary considerably.
2) Brackets must be placed occluso-gingivally at the correct height of contour given the chosen torque prescription
3) consider the expected “play” between the wire and slot
4) consider the resistance to unwanted tooth movements (EG resistance to negative torque of lower incisors in non extraction cases)
19
Q
In regards to root angulation, there should be sufficient bone present between adjacent roots. Why?
A
if roots are properly angulated, then sufficient bone will be present between the adjacent roots, which could be important if the patient were susceptible to perio bone loss at some point in time.
20
Q
how do brackets influence root angulation?
A
the guiding line in the bracket should be in line with the long axis of the tooth in order to achieve the proper MD root position prescribed in the bracket. Also, visualize the angulation of the bracket slot
21
Q
How do we get to a well-finished case as efficiently as possible (minimal wire-bending)?
A
proper initial bracket placement
22
Q
Prior to Andrew’s straight wire appliance, bends needed to be placed for 1st, 2nd, and 3rd order movements. Describe the first order dimension.
A
B/L. B/L bends placed in arch wires necessary to compensate for variation in the contour /thickness of labial surfaces of individual teeth. With a contemporary appliance, the compensation is built into the base of the bracket itself, by varying the thickness of the base depending on which tooth it is attached to. This reduces the need of first order bends.
23
Q
Prior to Andrew’s straight wire appliance, bends needed to be placed for 1st, 2nd, and 3rd order movements. Describe the second order dimension.
A
Incisal/gingival (vertical plane). Originally, M/D root tipping required angled bends called second order bends. (step up and step down also second order because its incisal/gingivla bend). Now, prescription of the angle of the bracket slot decreases the need for these angled bends.correct bracket placement is necessary to avoid step-up and step-down bends.
24
Q
Prior to Andrew’s straight wire appliance, bends needed to be placed for 1st, 2nd, and 3rd order movements. Describe the third order dimension.
A
B/L (root torque)
Originally, it was necessary to place a twist/torque in rectangular wires to move/control roots buccally or lingually. Now, prescription brackets are inclined to compensate for the inclination of the facial surface so the third-order bends are less necessary.
25
In Andrew's article (1972) about the six keys to normal occlusion, what was the problem he was trying to address? What was known prior to his study?
improper cusp-embrasure relationship existed even after ortho treatment. he was trying to identify "ideal" parameters to orthodontically treat patients. prior to his study, Angle's classes of malocclusion were the gold standard
26
In Andrew's first study (1960-4), what was the study design and what was the level of evidence?
LOE = retrospective observational w/o controls
120 non orthodontic normal models were acquired and the crowns were examined to ascertain characteristics of ideal occlusion. inclusion criteria = never had ortho tx, straight and pleasing in appearance, bite looked generally good, Andrew's judgment would not benefit from ortho tx.
27
In Andrew's first study, how did he study and what did he find?
he gathered data because there was no standardization for what was confirmed successful orthodontic treatment (it was very subjective). Recognizing conditions in treated cases that were less than ideal was simple, but wasn't enough. We needed criteria found through a deliberate approach to determine what was naturally ideal where its required no ortho tx and to use that for ortho tx goals.
28
What was different in Andrew's second study (1965-71)?
Much greater population sample size (1,150 cases) and cases were treated by orthodontists following criteria for ideal occlusion.
This was used to learn to what degree the 6 keys were present and whether the absence of any one permitted prediction of other error factors.
29
Why did Andrews think his results from his second study (1965-71) were valid?
the six keys were present in each of the 120 normals, but also even the LACK of even one of the six was predictive of an incomplete end result in treated model.
30
What did Andrews find about molar relationship and how did it influence his bracket preadjustment?
- distal surface of the DB cusp of the U6s made contact and occluded with mesial surface of MB cusp of L7s.
- MB cusp of U6 fell within buccal groove of L6s
- only person to pre-tip the bracket to gain MD tipping of the U6s (5 degrees on first molar, none on second)
31
What did Andrews find about crown angulation and how did it influence his bracket preadjustment?
gingival portion of crown should be distal to the incisal portion, varying with individual tooth height. This is the reason why Andrews prescription has a positive tip on all teeth (highest for upper 3s)
32
What did Andrews find about crown torque for the incisors?
anterior inclination of uppers - only upper incisors exhibit positive torque in Andrews prescription
33
What did Andrews find about crown torque for the upper posteriors?
lingual inclination similar in degree from canines to second molars. Andrews Rx - similar negative torque for upper canines-molars
34
What did Andrews find about crown torque for lower posteriors?
lingual inclination increasing from canine to second molars. Andrews Rx - increasingly negative torque from lower canines to molars
35
According to Andrews, there should be [no/some] rotations in the teeth.
no
| rotated molar takes up more MD space
36
How do you know if you have the correct band when placing on a tooth?
the hook is attached to the Mesial-gingval portion of the bracket (end of hook points distally)
37
What are some considerations when adjusting the vertical position of bands?
when viewed from buccal, the tube and band should be parallel with the buccal cusps
when viewed from occlusal, the upper molar tube should straddle the buccal groove. The lower molar tube should also straddle the buccal groove.
38
What are some considerations when adjusting the MD position of the bracket attached to the band?
mesial border of the buccal tube should bisect the MB cusp as seen from the occlusal view
39
What is the best technique to find the right size of band?
start with band that is too big, then work down to the smallest size that meets positioning criteria. (if you can position it with only finger pressure, it is still too large!)
40
In regards to bonded bracket placement, how do you achieve ideal alignment (rotation)?
if the tooth is not rotated, place the bracket in the center of the tooth MD to prevent rotation
On a rotated tooth, bond the bracket slightly towards the end (M/D) of the tooth that needs to be rotated out to aid in correction of the rotation.
41
In regards to bonded bracket placement, how do you achieve ideal vertical tooth relations and marginal ridges?
can use a measuring device or visually eyeball the vertical placement to the center of the tooth
Important to consider adjacent and contralateral teeth
pay attention to gingival height (fractured/worn teeth can throw you off)
maxillary laterals should be slightly shorter than centrals
don't seat molar bands too far gingival
42
In regards to bonded bracket placement, how do you achieve ideal angulation of the crowns/roots?
use a mirror to visualize long axis of crown from facial and occlusal view
use the most prominent portion of the buccal surface as a guide
pano will help visualize long axis to see root angulation
43
What are the two different types of ceramic brackets?
monocrystalline
polycrystalline
44
What are the differences between mono crystalline and polycrystalline ceramic brackets?
Mono- offers greater strength (until bracket surface is scratched), scratches/cracks tend to spread and reduces fracture resistance to below the level of poly crystalline (scratches are likely to occur during treatment)
Poly - relatively rougher surfaces (not good for sliding and could cause more enamel damage), some of these brackets have an integrated metal slot
45
What're are the two most common ways that fractures occur in ceramic brackets?
loss of part of the brackets (tie wings) during arch wire changes or eating
cracking of bracket when torque forces are applied
46
What are some ways that ceramic brackets compensate for their tendency to fracture?
bulkier brackets than steel
design is much closer to a wide single bracket than is usual in steel brackets
47
Define fracture toughness
ability to resist fracture
48
True or false.. the fracture toughness of ceramic brackets is greater than steel
false, it is much lower than steel.
fractures occur easier in ceramic, especially when scratched
49
What are some problems associated with ceramic brackets? (name 4)
fractures of brackets
resistance to sliding (some use metal slot to decrease friction)
enamel wear (risk is avoided if ceramic is only placed on upper anterior teeth)
Enamel damage from bracket removal
50
How can enamel damage from removal of ceramic brackets be minimized?
use debonding pliers from the manufacturers of the ceramic bracket (some brackets manufactured to break in a way to avoid enamel damage)
use thermal or laser instrument to weaken the adhesive by heating it (to induce failure whin bonding agent itself (reduces risk of enamel damage but increases risk of pulpal damage)
51
Ceramic brackets can be bonded chemically and/or mechanically. ceramic brackets are composed of aluminum oxide which is inert, so ____ is used to promote chemical retention
silane (coupling agent)
52
What are the ceramic bracket debonding techniques recommended for Clarity from 3M unitek?
Utilize the Unitek SL bracket debonding instrument preferably while brackets remain on AW
brackets are retained with mechanical retention, not chemical
concentrate stress on base side of slot so when you squeeze wings together, it creates a peeling force
53
What are the ceramic bracket debonding recommendations for Inspire ICE from Ormco?
Brackets utilize a ball-base design. Utilize their bracket removal plier to ensure the brackets come off easily and consistently
54
What are the ceramic bracket debonding recommendations for InVu from TP orthodontics?
No special instrument required, brackets use a molded polymer mesh base
step 1: after removing any flash, squeeze MD edges of mesh base with a SHARP 2-jawed instrument
step 2: the base will flex and release from the tooth, retaining most of the adhesive. the bracket should remain intact with no breaking or shattering
55
What are the ceramic bracket removal recommendations for the In-ovation C brackets from GAC?
place ligature cutter incisally and gingival and use to remove bracket
be careful not to cut the enamel
claims base design of bracket allows for easy debonding
56
What are the ceramic bracket removal recommendations for Fascination 2 brackets from Dentaurum USA?
use Weingard pliers for debonding
place a blue separating ring around bracket base for protection
These brackets use chemical bonding!
57
According to research (Cochrane NJ 2017), enamel damage is more frequent and severe when debonding __ brackets vs. ___ brackets
ceramic
metal
58
According to research (Cochrane NJ 2017), enamel damage is less severe when ceramic brackets are bonded with ___ compared to ___
RMGI cement
composite resin
59
According to research (Cochrane NJ 2017), where is the most common site of failure when debonding mechanically retained ceramic brackets?
bracket/bonding-material interface
60
According to research (Cochrane NJ 2017), which tooth has the highest risk of enamel damage when debonding ceramic brackets?
maxillary laterals
61
According to the Kitahara-Ceia FMA 2008 article, in a chemically retained ceramic bracket, the difference between the enamel surfaces before and after debonding [was/was not] statistically significant indicating that....
was statistically significant
procedures of bonding and debonding of chemically retained ceramic brackets resulted in enamel damage
62
According to the Kitahara-Ceia FMA 2008 article, in a mechanically retained ceramic bracket, the difference between the enamel surfaces before and after debonding [was/was not] statistically significant indicating that....
was not statistically significant
Mechanically bonded ceramic brackets does not significantly alter the enamel surface when debonding
63
According to the Suliman SN 2015 article, both polycrystalline and mono crystalline ceramic brackets can be debonded successfully with minimal enamel damage. However, Polycrystalline brackets had slightly [less/more] damage than mono crystalline. Why?
more
iit was attributed to a more demanding cleanup
64
What is the major advantage of ceramic brackets?
esthetics
65
Name 6 disadvantages of ceramic brackets
1. higher incidence of fracture during debonding (so don't delegate removal of ceramic brackets)
2. unable to withstand strong torque forces
3. should be avoided in compromised teeth
4. enamel wear can occur on opposing teeth
5. causes nicks in the arch wire and increases friction
6. Don't use in pts who will undergo orthognathic surgery
66
What should you tell patients about ceramic brackets during a consult?
more chance of damage to enamel during debond
if brackets fracture could have more enamel damage
brackets fail more than metal brackets
67
Enamel damage from debonding of metal brackets occurs about __/10 times whereas ceramic occurs __/10 times. if RMGI is used instead of composite, about __/10 result in enamel damage.
1
3-4
2
68
Metal brackets fracture about __/10 times whereas ceramic brackets fracture about __/10 times
0
1-3
69
At present are we likely to encounter drugs that stimulate tooth movement?
No, not yet anyway
1. Vitamin D (may have an effect?)
2. prostaglandins DO accelerate tooth movement but injection of prostaglandins into PDL is very painful
3. Relaxin (pregnancy hormone) reduces collagen synthesis and increases collagen breakdown, but its effect on tooth movement is still inconclusive
70
What are prostaglandins formed from? What are they?
Arachidonic acid, which is derived from phospholipids.
prostaglandins are mediators of inflammation, body temp, blood flow/clotting.
71
When are prostaglandins released and what causes their release?
They are released when COX2 breaks down arachidonic acid
Orthodontically, the release of PGE2 by COX 2 is activated when cells are mechanically deformed during the application of pressure on the PDL
72
What role do prostaglandins play in orthodontics?
prostaglandins (namely PGE2) stimulate osteoclastic and osteoblastic activity
Activates Rank-L from osteoblasts which causes a conversion of macrophages into activated osteoclasts on the compression side
73
True or false... when prostaglandins are inhibited it may slow down tooth movement
true
74
Prostaglandins activate ___ from ___ which causes a conversion of ___ into activated ___ on the ___ side of the PDL
Rank-L
macrophages
osteoclasts
compression
75
How can corticosteroids influence tooth movement? be specific
they reduce prostaglandin synthesis by inhibiting the formation of arachidonic acid (the precursor to prostaglandins)
less prostaglandins = less tooth movement
76
How do NSAIDs work and how could they influence tooth movement?
inhibit COX2 enzyme (responsible for converting arachidonic acid to prostaglandins)
less prostaglandins = less tooth movement
77
Describe how Tylenol works and how it could influence tooth movement.
Tylenol acts CENTRALLY, not peripherally, therefore tooth movement should NOT be affected
78
If orthodontic patients are taking NSAIDs PRN for ortho-related pain, would this likely affect tooth movement?
Nope. in this case, dosages are low and of short duration, thus unlikely to interfere with tooth movement
If pt was taking NSAIDs constantly for other condition such as arthritis, it could affect tooth movement because dosage and duration is increased
79
Since NSAIDs and Tylenol act differently, would a combo of the two provide better pain control than either one separately?
possibly. Current study going on in ortho rn. In other dental treatment though, the answer is yes.
80
What is the mechanism of bisphosphonates and how might they affect tooth movement?
Bisphosphonates are synthetic analogue of pyrophosphate, which bind to hydroxyapatite in bone in order ro prevent osteoporosis. they act as specific inhibitors of osteoclast-mediated bone resorption, so the modeling/remodling of bone during tooth movement is slower
81
Bisphosphonates are synthetic analogues of ___ which bind to ___ in bone in order to prevent ___
pyrophosphate
hydroxyapatite
osteoporosis
82
Why should elective procedures, such as extractions for ortho, be avoided for patients taking bisphosphonates?
elective extractions for orthodontic treatment can cause osteonecrosis of mandibular bone
83
What are some additional drugs that might affect orthodontic force?
tricyclic antidepressants
antiarrhythmic drugs
antimalarial drugs
methylxanthines
anticonvulsants (phenytoin)
tetracyclines
84
When teeth erupt or are moved, what happens to the alveolar bone?
when test erupt or are moved, they bring alveolar bone with them.
the only exception fo this is when the pt has active per dx.
85
What happens to the bone if a tooth is congenitally missing or extracted at an early age?
a permanent defect will occur unless another tooth is moved into that spot rather quickly
86
What can be down when a maxillary lateral incisor is missing and a prosthetic replacement is planned?
erupting teeth to bring bone with it
orthodontic tooth movement can create the alveolar bone needed to support an implant to replace a missing maxillary lateral incisor
have permanent canine erupt mesillay into the empty spot and then move distally to its proper position once the pt has stopped growing (this will stimulate bone formation in an area that would normally not occur)
87
Can bone support around periodontally involved teeth be improved by intruding teeth?
Normally when intruding teeth, the alveolar bone follows so the same amount of root is embedded in bone as before. There are reports of therapeutic intrusion resulting in smaller pockets (but the smaller pocket depths are due to an elongated junctional epithelium, not actual no bony support)
88
Can a tooth with normal periodontist be moved into an area of reduced bone height and maintain its attachment level?
"space closure in areas of major bone loss sometimes leads to an improvement in bone height if at least ONE wall of the periodontal pocket remains"
so, it may happen but cannot be predicted and promised to the pt. Good control of periodontal condition is key to success
89
According to the Bollen article, do we have evidence that ortho treatment has a positive effect on periodontal health?
no
90
What is the rationale for incorporating local injury to the alveolar process to accelerate tooth movement?
bone remodeling is accelerated during wound healing = teeth will move faster after local injury to the alveolar process
91
According to profit, how long after corticotomy would one expect that bone remodeling could be accelerated? corticocotomy is most effective in reduction of __ time.
2-4 months
key result is reduction in alignment time
92
What is the Kole technique associated with corticotomy?
teeth move within minutes/hours using a still arch wire that causes greenstick fractures of the bone at root apex. This causes rapid tipping movements, not bodily movement
93
What modifications to corticotomy have been proposed?
Piezocision - Incisions without flaps
Microperforations (propel)
94
What are some pros and cons to piezocision compared to corticotomy?
less invasive than corticotomy (small facial incisions with addition of bone graft)
can damage root, cause dehiscence, fenestration
95
What are some pros and cons to microperforations compared to corticotomy?
cost-risk ratio is favorable (no perio surgery)
lack of data regarding its effectiveness
96
What are profits conclusions regarding recommending corticotomy/piezocision/microperforations to accelerate tooth movement?
hesitant to recommend until further studies are completed
the benefits of reduction of time is beneficial, but the extent of the risks and its lack of evidence of effectiveness of treatment prevents the recommendation to be used commonly
97
In addition to corticotomy-like procedures, what are some other proposed approaches to accelerate tooth movement? comment on if it is effective or not
vibration (no definitive evidence)
tissue penetrating light (no definitive evidence)
ultrasound (plausible theory but lacking evidence)
low level laser therapy (unable to accelerate tooth movement)
electrical current (lacks evidence)
dentoalveolar periodontal distraction (lacks evidence)
98
What were the conclusions from the Charavet article "piezocision-assisted orthodontic treatment using CAD/CAM customized ortho appliances a RCT in adults"?
piezocision seems to be effective at accelerating tooth movement during a period of 3 months after surgery
greater efficacy in maxilla than mandible
small scars left in 66% of its, so may be contraindicated in cases of high smile line
99
Describe the pain response to normal orthodontic force levels
no immediate pain (develops a few hours later)
pain is "mild aching, pressure sensitivity" (biting into hard objects hurt)
lasts 2-4 days then disappears
100
How long does the pain response to normal orthodontic forces last?
2-4 days
101
What is the response to heavy orthodontic force?
pain is immediate (3-5s after) because the PDL is crushed
Leads to increased mobility of teeth (reversible)
Leads to increased undermining resorption
102
What causes orthodontic tooth pain?
Crushed/ichemic PDL undergoes sterile necrosis
inflammation at apex of the tooth (increased tenderness to pressure suggests this)
mild pulpits
greater force = greater pain
103
What can be done to help alleviate pain associated with tooth movement?
NSAIDs (inhibits prostaglandins)
Acetaminophen (chronic use can cause liver damage)
Increase blood flow (chew gum during first 8 hours to prevent buildup of metabolic products that stimulate pain receptors)
104
What are 2 other possible sources of pain/inflammation for orthodontic patients and how should we address them?
Latex allergy
Nickel allergy (20% pts have nickel allergy, however only about 8% respond in oral mucosa) If truly allergic use Ti brackets and TMA wire
105
Some external root resorption occurs in orthodontics in __% of maxillary incisors. Over __% of teeth have some loss of root.
90%
50%
106
Describe the etiology of external root resorption in orthodontics.
cementum is removed and repaired in much the same way as alveolar bone during orthodontic moment. Even deep crater defects will be repaired eventually, restoring the roots original contours. However, when an "island" of cementum gets cut off (which mostly occurs at the apex), it will be resorbed rather than repaired.
107
What are some reported suggestions relating etiologic agents for somewhat more extensive moderate resorption?
conical roots with pointed apexes
distorted/dilacerated roots
Hx of trauma
Long treatment duration
pre-existing short roots
heavy forces
intrusive forces
ABCD (Already short, Battering (trauma), Conical roots, Dilaceration)
108
True or false.. ortho is the etiologic factor for severe generalized root resorption.
false. etiology is unknown. it is very rare
109
true or false... ortho is the etiologic factor for severe localized resorption
true. maxillary incisors are most prone.
110
What are some recommendations to avoid severe localized root resorption?
take pans every 6-9 months
its who show greater resorption during this initial time frame are more likely to have greater resorption by the end of treatment
111
True or false... roots pressing agains the cortical plate increases chance of resorption by 20x.
true
thus root resorption occurs more frequently in camouflage treatment
112
According to research, what are the biggest culprits of ortho related root resorption?
heavy and intrusive forces
long duration
(treatment pauses can help reduce extent of root restoration)
113
Define center of resistance. where is it located on a single rooted tooth?
where you can apply force and get movement without rotation
on the long axis between 1/3 of the root length apical to alveolar crest (note that if you have perio or long roots, the position will change)
114
Where is the center of resistance located on a multi-rooted tooth?
1-2mm apical to the furcation
115
What is a moment of a force (definition)?
measurement of the tendency for a force to produce rotation
moments are a measure of the turning tendency produced by a force
116
How do you calculate a moment's magnitude?
equal to the magnitude of the force multiplied by the perpendicular distance from the line of action to the point of reference and is measured in units such as gram millimeters
117
How do you determine a moments direction?
follow the line of action around the center of resistance towards the point of origin
118
What is a couple?
a couple consists of two forces of equal magnitude with parallel but noncolinear lines of actions and opposite directions. A couple can allow pure rotation (the center of resistance will not move at all
119
How do you calculate a couple's moment?
the magnitude of each moment about the center is calculated by multiplying the magnitude of one of the force by the perpendicular distance between the forces
120
Does it matter where on a rigid object the couple is applied?
it does not matter where on a rigid object a couple is applied; the external effect is the same.
121
Define center of rotation?
a point about which a body appears to have rotated, determined from its initial and final positions. Its historical only, the final compared to the initial, a point where it appears to have rotated
122
Where is the center of rotation moved in order for translation?
infinity
123
Where is the center of rotation moved in order for controlled tipping?
Apex
124
Where is the center of rotation moved in order for uncontrolled tipping?
slightly apical to the center of resistance
125
Where is the center of rotation moved in order for root movement?
incisal edge
126
What are the three basic types of NiTi wires?
Stabilized martensite
Superelastic (AKA active austenitic)
Thermoelastic (AKA active martensitic)
127
```
Define the following:
Ms
Mf
As
Af
```
Ms = Martensite start (initial temperature at which the martensitic phase is formed)
Mf = Martensite final (Final temperature at which the martensitic phase is formed, full martensite)
As = Austenite start (Initial temperature at which austenitic phase is formed
Af = Austenite final (Final temperature at which the austenitic phase is formed , full change)
(At higher temperatures, beyond Af, the alloy exists exclusively in the austenitic phase)
128
What is the shape memory effect and which type of wire is it usually associated with?
the ability of the material to "remember" its original shape after being plastically deformed while in the MARTENSITIC form. Involves a thermal reaction
The AUSTENITIC phase can memorize a shape if you lower the temperature
CuNiTi is often thermoelastic
129
What is pseudoelasticity? What wire is it usually associated with?
AKA superelasticity
materials displaying superplasticity are austenitic alloys that undergo a transition to martensite in response to stress (Stress-induced martensite).
Elastic response to stress (phase change between austenitic and martensitic phase)
130
What is stress-induced martensite (SIM)?
formed due to deformation. initially the wire is austenitic. enough stress is put on the wire until isolated sections become martensitic (rest is austenitic). Occurs typically over 2mm of deflection, then once the wire moves back within 2mm, it returns to austenitic phase. This gives the wires superelastic/pseudoelastic properties.
131
In order for SIM to form, what should the Af (TTR (temperature transitional range)) be according to Santoro?
35-37C (close to/slighlty below the oral temperature)
132
What is the Af (TTR) for superelastic wires (no SIM)?
22-28C
133
For an ideal thermoelastic wire (active martensitic) at what temperature is Af (TTR)?
35-40 close to intraoral temperatures
134
Define springiness
low change in force per change in deflection. if its stiff its more change in force per deflection.
135
Define springback
amount of deflection that will return toward original shape..
springbuck occurs after permanent deformation occurs; there is a return (or springback) towards the original shape but it doesn't quite get all the way there because of the permanent deformation
136
Define range
the amount of deflection (elastically) BEFORE permanent deformation occurs
if the wire is deflected beyond the range it will NOT return to its original shape.
137
Define stiffness
High change in force per change in deflection
stiffness is proportional to the slope of the elastic portion of the force-deflection curve
138
# Define formability
Which wires have the best formability, which has the worst?
amount of permanent deformation a wire can withstand before failing/breaking
SS = BTi > NiTi
139
Define strength
maximum load the material can resist before permanent deformation
strength = Stiffness x range
140
What three points are representative of strength?
proportional limit
yield strength
ultimate tensile strength
141
Define proportional limit
highest point where stress and strain still have a linear relationship (elastic zone of deformation)
142
define yield strength
the intersection of the stress-strain curve with a parallel line offset at .1% strain
143
define ultimate tensile strength
the maximum load a wire can sustain
144
according to Santoro, how much deflection is required before superelastic behavior is detected?
2mm
145
When does an austenitic SE wire perform optimally?
cases of severe dental crowding; this allows the minimum deflection of 2mm to be reaped, and irregular inter bracket span will accentuate deflection and generate localized areas os SIM, typically in the lower incisor area.
146
What is the best wire (cost/benefit ratio) for mild crowding?
a small diameter work-hardened alloy wire (classic nitinol/stabilized martensite), or a multi stranded round SS wire (gains properties of springiness from each individual wire being so small but then also gets its strength when all of the small wires are combined together)
147
what is the average delivery force (2mm or more deflection at oral temp) of an austenitic SE NiTi (possibly like a 27 degree CuNiTi)?
between 200-300 grams (review: we want 50 for tipping/rotating/extrusion, 100 for bodily movement, 10 for intrusion, 75 root movement)
148
What is the delivery force (2mm or more deflection) of 35C (thermal elastic) and 40C Cu NiTi?
100g
149
How much force is recommended for tipping teeth?
50g
150
How much force is recommended for translation of teeth?
100g
151
How much force is recommended for rotating of teeth?
50g
152
How much force is recommended for intrusion of teeth?
10g
153
how much force is recommended for extrusion of teeth?
50g
154
how much force is recommended for root movement (torque)?
75g
155
What is graded thermodynamic NiTi?
graded thermodynamic NiTi wires are heat treated to certain segments of the arch, allowing them to deliver selective, differential forces to each arch segment (100g in anterior, 300g in posterior for example)
156
According to Santoro, Martensite has a modulus of elasticity of ___ and austenite of ___
2Mpsi
8Mpsi
157
What does Burstone say about the "ideal shape-driven approach" (using a wire that is shaped to the desired occlusion and hoping that the brackets will finally align themselves on the wire) to wire bending?
The "ideal" shape driven approach to bending an orthodontic appliance can lead to undesirable side effects and may not operate in a manner predicted by a superficial reading of the relationship of a wire to the bracket. Furthermore, teeth do not move to the final straight wire position, but undergo extraneous and undesirable movements because of the intervening force systems produced
158
Describe the ideal shape driven approach
the orthodontist forms a wire to the shape in which the desired occlusion would be if all of the brackets were to finally align themselves on the wires. When you get to sitiffer and stiffer wires, they will align themselves.
This can lead to undesirable side effects! So, understand the force systems!
159
If you place a step bend in a wire, how much do the forces and moments change depending on WHERE the bend is placed?
there is no change in the magnitude or the moment
| these bends should be about 1/3mm at a time to not create too large of forfces
160
Which class geometry (ideal arch article) has the same force system as a step bend?
class 1 - moments are in the same direction and of equal magnitude
161
If you place a V-bend , how do the force systems change from a centered bend to a bend that is 1/10 of the distance from one bracket to the other?
A v-bend placed between two brackets radically alters the force system depending upon the MD placement of the apex of the V.
bend 1/10 distance from one bracket to the other, short moments are in the same direction.
162
What forces and moments are produced if the V bend is 0.5L (half of the length)
forces: no vertical force
moments: equal and opposite on each tooth
163
What forces and moments are produced if the V-bend is placed 0.4L
Forces: opposite vertical forces
moments: unequal, moment farthest away from V-bend. opposite directions
164
What forces and moments are produced if the V-bend is placed 1/3L?
forces: opposite vertical forces
moments: no moment on 2nd bracket.
165
What forces and moments are produced if the V-bend is placed .2L?
forces: opposite vertical forces
Moments: both moments in SAME direction
166
At which position of a V-bend would you get equal and opposite moments?
centered
167
At which position of a V-bend do you get NO moment on one of the brackets?
if the bracket is 2/3L away
168
Most problems (80% of mistakes) with bracket positioning occurs on what teeth?
Lateral incisors and second molars
169
Where is the most common mistake in marginal ridge discrepancies? where is the second most common problem area?
how we we achieve good marginal ridge relationships?
maxillary 1st and 2nd molars
mandibular 1st and 2nd molars
good vertical placement. Make sure slot is parallel to marginal ridges
170
According to Burstone, why would you use a TPA for rotation before placing a buccal arch wire?
avoid the medial force side effect of the buccal wires
171
If you were to use a TPA to rotate your patients upper first molars mesial out, and placed equal and opposite coupes, what movements would you predict other than equal and opposite rotations?
none
172
If you were to use a TPA to rotate one upper first molar mesial out by placing a bend on one side only, what movements would you predict other than that rotation?
unilateral couple to rotate mesial out
mesial force on the molar you're rotating, distal force on the opposite side.
173
In order for SIM to form, where should the Af/TTR be according to Santoro?
close to/slightly below oral temperature for the formation of SIM
35-37C
174
27C CuNiTi is an example of a __ wire
superelastic (Austenitic active)
175
35C CuNiTi is an example of a __ wire
Thermoelastic (Martensitic active)
176
When does a superelastic wire (austenitic active) perform optimally?
in cases of severe dental crowding (when the deflection will exceed 2mm to generate SIM in a localized area of the arch
177
What is the average delivery force (2mm or more deflection at oral temp) of a superelastic wire (austenitic active) possible like 27C CuNiTi?
200-300g
| this is often too much force though
178
What is the delivery force (2mm or more deflection) of a 35 or 40 CuNiTi?
100g
179
In a preadolescent child, headgear must be worn for at least ___ hours/day to be effective in controlling growth. ___ is released during the evening, so instruct pts to wear HG accordingly. What is the current recommendation of force per side?
10-12hrs
growth hormone
12-16oz (350-450g)
180
How do you select the inner bow size for HG?
inner bows have an adjustment loop to help it fit.
inner bow should closely fit with the upper arch WITHOUT contacting teeth except at the molar tubes (stay within 3-4mm of other teeth at all points)
181
True or false... the inner bow HG should contact all teeth
false.
it should fit closely around the upper arch but WITHOUT contacting the teeth except at the molar tubes. the inner bow should be within 3-4mm of the teeth at all points
182
How do you fit the width (transverse) of the inner bow of HG?
by adjusting the loops to expand or contract the inner boy and by bending the short portion of th bow that fits into the molar tubes
after the inner bow is fitted to the perimeter the inner bow should be expanded by 1-2mm to keep posterior teeth out oc cross bite as AP changes are made.
183
True or false.... you should expand the inner bow width by 1-2mm to prevent posterior cross bite as AP changes are made
true
184
After you put the inner bow into one side of the head gear tube, how do you adjust the A/P position of the other side?
The extension of the inner bow out of the end of the HG tubes should be evaluated. ideally, the end of the inner bow would be flush with the end of the tube. don't let it extend distal out of the tube more than 1mm
185
How should you position the anterior part of the bow of HG vertically relative to the lips?
should be adjusted so that the junction of the inner and outer bows rests passively and comfortably between the lips
186
In anticipation of differential growth, and the wider part of the lower arch moving mesial relative to the upper, what can be done to the inner bow, which type of headgear is this modification important for and why?
the inner bow must be expanded by 1-2mm to keep the posterior teeth out of cross bite as AP changes are made
most important in CERVICAL pull HG, because this type of HG has a tendency to tip the molars lingually as they extrude.
187
How should the width of the outer bows in HG be positioned relative to the cheeks?
the outerbow should rest several MM from the soft tissue of the cheek
check before and after the straps of the head/neck strap are attached
188
If you do NOT want MD tipping of the molar, and you are using cervical-pull HG, what length of the outer bow (short or long) would allow the LFO to be closest to the CoR to give you bodily movement?
Longer outer bow
this is because this will allow the LFO to be through the CoR
189
If you do NOT want MD tipping of the molar, and you are using High-pull HG, what length of the outer bow (short or long) would allow the LFO to be closest to the CoR to give you bodily movement?
Short outer bow
this is because it will allow the LFO to be through the CoR
190
How can you check clinically whether you are putting a moment from a force-off-center with the outer bow length and position you have selected for your HG?
If the bow does not move during pushing with a finger, the force is through the center or resistance of the maxillary first molar and the molar will move bodily (not tip)
If the bow moves up, the roots of the maxillary first molar will move distally
if the bow moves down on the lower lip, the roots of the maxillary first molar will move medially and the crown distally
191
Regarding protraction facemark, the chance of true skeletal change appears to decline at age ___. the chance of clinical success begins to decline at age ___. what is the recommended force and duration for protraction facemark?
8yo
10-11yo
350-450g per side for 12-14hrs/day
192
Describe which type of headgear and where the outer bow should be positioned if you want distal movement and intrusive force without a moment.
HPHG with outer bow on the line of CoR.
193
Describe which type of headgear and where the outer bow should be positioned if you want distal movement and intrusive force with root distal moment.
HPHG with outer bow ANTERIOR to the CoR to create a counterclockwise moment
194
Describe which type of headgear and where the outer bow should be positioned if you want distal movement and extrusive force with root distal moment.
CPHG with the outer bow SUPERIOR (and distal) to the CoR to create a counterclockwise moment
195
According to the Angelopoulou article, ibuprofen appears to lower orthodontic pain when compared to placebo at ___ hours after separators and AW placement, but NOT at 24 hours
2 and 6 hours
196
According to the Salmassian article, pain due to ortho activation starts at ____, peaks at ___, and returns to baseline at ___
3 hours
19 hours
7 days
197
Ortho treatment is possible after ___ months of discontinuation of bisphophsonates
3 months
198
What is the difference between positive and negative torque?
positive torque = crown facial, root lingual
negative torque = crown lingual, root facial
199
Describe the molar relationship that Andrews found and how did he address it with his bracket prescritpion?
distal surface of DB cusp of U6 made contact with the M surface of the MB cusps of the L7s
put 5 degree tip on upper first molars and no tip on second molars
200
Which teeth do we typically have the most difficulty in achieving proper root angulation?
maxillary laterals
maxillary second pemolars
mandibular first premolars
201
How long should enamel be etched with 37% phosphoric acid for orthodontic purposes?
30 seconds
more time on the molars (30-60s)
202
True or false.. Beta Titanium has the same strength as SS
false. it has the same strength as NiTi. but stiffness is somewhere between NiTi and SS
203
___ consists of TWO forces of EQUAL MAGNITUDE, with parallel but noncolinear lines of actions and opposite senses
A Couple
204
how do you calculate the moment of a couple?
Magnitude of ONE of the forces multiplied by the perpendicular distance between the two forces
205
If protraction facemask was pulled straight from lips, what effect of rotation would it have on the maxilla?
counterclockwise rotation (increasing tendency for open bite)
206
Explain the hysteresis phenomenon
For superelastic wires, the amount of force to deflect the wire into maligned brackets (transitioning from A to M) is more than the force exerted on the teeth by the wire at each amount of deflection
For Thermoelastic wires, the transitions from M to A (due to warming) and back (when wire is cooled) occur with varying stiffness at each temperature. this is also called hysteresis
207
What do you call a teacher who doesn't toot in public?
A private tutor
208
On the second premolars, the tendency is to place the bracket too __ (which causes ___), so err on the ___ side for these teeth
```
distal
causes mesial of tooth to rotate in, giving a class 2 bicuspid appearance
```
mesial
209
True or false... the anatomy of lower 1st and 2nd premolars are so similar that the brackets are interchangeable. Not so on the maxillary arch
false. it is the other way around.
anatomy of the 1st and 2nd upper premolars are so similar that the brackets are interchangeable. lower arch have separate brackets for L4 and L5
210
True or false... the brackets for the lower incisors are all the same
true
211
Visualizing the most prominent portion of the labial/buccal surface serves as a guide for...
finding the long axis of the tooth
finding the correct location for MD placement of bracket on canines and premolars (for flat teeth (incisors) just visualize MD dimension
212
does improper bracket replacement in the vertical dimension most likely increase or decrease vertical dimension?
increase
213
For open bite tendency patients do you want to place anterior brackets more gingival or occlusal?
gingival. posterior teeth should be more occlusal
214
What is the most common bracket placement for upper arch?
```
centrals = 4
laterals = 3.5
canines = 4.5-5
Bicuspids = 4
1st molars = 3.5
2nd molars = 3
```
215
What is the most common bracket placement for lower arch?
```
incisors = 4
canine = 4.5
bicuspids = 4
1st molar = 3.5
2nd molar = 3-3.5
```
216
Name some common mistakes in bracket placement
MD placement of U4s
2s lateral axial inclination
4s and 5s height
3s axial inclination and MD position
different height between R and L
217
which teeth have the highest rate of bonding failure?
1st and 2nd molars
L5s
218
What are some modifications that are included in extraction prescriptions?
anti-tip and anti-rotation in prescription depending on the extraction case
canines have increased distal root tip
molars have M out D in rotation built in
219
What are some disadvantages of extraction prescription bracket systems?
tip on canines create undesirable force vectors in early stages of treatment
increases inventory
overcorrections show
220
[insufficient/excessive] distal root angulation of U1s can create an artificial tooth size discrepancy and increase overjet
excessive
221
Are bracket shapes rounded at the incisal end or gingival end?
gingival
they are flat towards the incisal end
222
how can a bracket not fully seated cause rotation?
excess composite on one side can tilt the bracket, causing rotation
223
Should bracket height be established to line up the cusp tips or contact areas?
contact areas
224
Seating a molar band too far [occlusal/gingival] is a common error and results in ___ and __ errors resulting in ___
height and torque errors
marginal ridge discrepancy
225
Name some indications for banding teeth instead of bonding
teeth that will receive heavy intermittent forces
short clinical crowns
incompatible bonding tooth surface
preferred for molars
226
Errors in horizontal bracket placement causes ___
rotations
227
What is the most difficult and most controversial aspect of bracket positioning?
vertical dimension
228
When using a height gauge in the incisor region, the gauge should be placed ___ degrees to the ___ surface
90 degrees
LABIAL surface
229
when using a height gauge in the canine, premolar, and molar regions the gauge is placed ___ with the ___
parallel
occlusal plane
230
When viewed from the buccal, the molar tube and band should be parallel with the ___
buccal cusps
| be careful to not seat the mesial of the lower molar bands too gingival
231
why are non-convertible tubes preferred for lower first molars instead of convertible?
they are less bulky, stronger, more comfortable, and cause fewer interferences
232
What does DSC stand for and what does it do?
Differential scanning calorimetry
measures heat flow as temperature changes
233
What does DMA stand for and what does it do?
Dynamic mechanical analysis
measures the real component of the complex modulus - the storage modulus- as the temperature changes
234
Storage modulus is directly proportional to the ___
dynamic force applied
235
What is the storage modulus (Gpa = measure of stiffness) for SS at 20C?
183 GPa
236
What is the storage modulus for TMA at 20C?
64 GPa
237
What is the storage modulus for Nitinol classic (stabilized martensite) at 20C?
41 GPa
238
What is the storage modulus for CuNiTi austenitic (higher temp)?
60-70 GPa
239
What is the storage modulus for CuNiTi martensitic (lower temp)?
20-35 GPa
240
Describe, for 35 CuNiTi (assume the wire is being heated, coming from the cooled state) what the stiffness would be when placing the wire (~23C).
relatively pliable (springy)
~30 GPa
241
Describe, for 35 CuNiTi (assume the wire is being heated, coming from the cooled state) what the stiffness would be the wire reaches oral temperature (~37C) for teeth with NO deflection (no SIM).
~60 GPa
242
Describe, for 35 CuNiTi (assume the wire is being heated, coming from the cooled state) what the stiffness would be the wire reaches oral temperature (~37C) for teeth with 6mm of deflection .
Af moves from 33C to 39C (curve moves to the right) because you will express SUPERELASTIC properties in this scenario. Af is reactive to both temp and stress.
~40 GPa
storage modulus would be lower and the part of the wire with 6mm deflection would be MORE flexible than the rest of the wire at oral temp because the deflection induced SIM to form
243
Describe, for 35 CuNiTi (assume the wire is being heated, coming from the cooled state) how stiff the section of wire in which 6mm of deflection has occurred and oral temperature is reached
slightly more stiff than at room temp.
At room temp, the deflection induced SIM to form causing the deflected part to be less stiff than the rest of the wire. then when oral temp is reached the deflected part becomes more stiff than it was initially. It is still less stiff than the rest of the wire at oral temp though
244
Describe, for 35 CuNiTi (assume the wire is being heated, coming from the cooled state) what would happen to the stiffness of the section of wire where 6mm of deflection had occurred when the tooth moves into alignment
stiffness would increase when it becomes within 2mm deflection as it transitions from SIM to austenite
During this transition, Af would return to 33C. at oral temp, Gpa would be 60 (without deflection)
