Lecture 7

Question 1

what type of orthodontic wire is strong, stiff, formable, and has been used routinely for many years?

Answer 1

stainless steel

Question 2

what type of orthodontic wire is softer than stainless steel, making it more formable, and then the wire can be heat treated to make it harder before it is inserted into the orthodontic appliance?

Answer 2

chromium alloys (elgiloy)

Question 3

what type of orthodontic wire is very useful during the initial stages of orthodontic alignment due to its exceptional ability to apply light force over a large range of activations, and its shape memory and superelasticity?

Answer 3

nickel-titanium alloys

Question 4

which type of NiTi alloy wires regain their original shape after being exposed to heat?

Answer 4

heat activated NiTi wires

Question 5

which type of NiTi alloy wires can be deformed and will rebound back to their original shape?

Answer 5

superelastic NiTi wires

Question 6

what is a weakness of NiTi alloy wires?

Answer 6

they have poor formability

Question 7

what type of orthodontic wire offers a highly desirable combination of strength and springiness as well as good formability, whose properties fall in between stainless steel and NiTi alloys

Answer 7

beta-titanium (TMA)

Question 8

orthodontic appliances should not be reactivated more frequently than ___

Answer 8

3-week intervals

Question 9

why shouldn’t orthodontic appliances be reactivated any sooner than at 3 week intervals?

Answer 9

undermining resorption typically requires 7-14 days and tooth movement is essentially complete in this length of time, but there is an equal or longer period for PDL regeneration and repair that should be observed before force is applied again

Question 10

what might happen if an orthodontic appliance is activated too frequently?

Answer 10

it can short circuit the repair process and can produce damage to the teeth and/or bone that a longer appointment interval would have prevented or would have at least minimized

Question 11

since the presence of orthodontic appliances increases the amount of gingival inflammation, even with good oral hygiene, loss of alveolar bone height might seem likely. however, it is almost never a complication of ortho treatment. why?

Answer 11

• the position of the teeth determines the position of the alveolar bone
• when teeth erupt or are moved, they bring bone with them, so crestal bone loss from ortho treatment is rarely seen

Question 12

usually, as a result of ortho treatment, bone loss averages ___ with the greatest incidences at ___

Answer 12

• less than 0.5mm and rarely exceeds 1mm

- extraction sites

Question 13

bone loss is almost never a complication of ortho treatment, except in what case?

Answer 13

• tooth movement in the presence of active periodontal disease
• however, once the periodontal disease is under control, these teeth can be moved and can have a good bony response

Question 14

with respect to alveolar bone, in the absence of pathologic factors, what happens when a tooth erupts to much?

Answer 14

• the tooth carries the bone with it
• the tooth does not erupt out of the bone
• when a tooth is intruded, it doesn’t move into the bone

Question 15

when teeth are intruded or extruded, the alveolar bone moves with the tooth, thus maintaining the distance between the alveolar crest and the ___

Answer 15

• CEJ

- in other words, the patients biologic width stays about the same when the tooth is intruded or extruded

Question 16

T or F:

intruding a tooth will create new attachment

Answer 16

false; there is little evidence to support this theory

Question 17

T or F:

unless a tooth erupts into an area of the dental arch, the alveolar bone will not form there

Answer 17

• true (“no teeth, no alveolar bone”)

- this is seen when a patient is congenitally missing a tooth

Question 18

what happens to the alveolar bone when a patient has all their teeth extracted for dentures?

Answer 18

• alveolar bone appears to be dependent upon the presence of the teeth
• dentures must be relined every few years as the alveolar bone resorbs

Question 19

___ functions as the teeth’s supporting structure

Answer 19

alveolar bone

Question 20

what happens to the PDL space during orthodontic tooth movement?

Answer 20

it widens

Question 21

during orthodontic tooth movement, the combination of a wider ligament space and a somewhat disorganized ligament means that some increase in ___ will be observed in every patient

Answer 21

mobility

Question 22

the heavier the force, the greater the ___ and the greater the ___ that will develop

Answer 22

• undermining resorption

- mobility

Question 23

excessive mobility could be an indication that excessive forces are being encountered on the tooth. what are two possibilities for the excessive force?

Answer 23

• heavy orthodontic forces
• more likely due to a patient who is clenching or grinding against the opposing tooth, causing traumatic interference
• once the traumatic occlusion is corrected and the forces have dissipated, excessive mobility will usually correct itself without permanent damage

Question 24

what type of pain is typical when orthodontic force is placed on a tooth?

Answer 24

mild aching sensation that varies from patient to patient

Question 25

what can patients use for pain and discomfort that results from orthodontic treatment?

Answer 25

acetaminophen and ibuprofen is usually sufficient

Question 26

orthodontic pain typically lasts how long?

Answer 26

2-4 days and then goes away until the orthodontic appliance is reactivated, or for some patients the pain can cycle throughout the month

Question 27

what is orthodontic pain associated with?

Answer 27

inflammation and mild pulpitis that appears after the orthodontic force is applied (the mild pulpitis has no long-term significance on the pulp of the tooth)

Question 28

to help control pain and discomfort, some orthodontists have their patients chew sugarless gum or chew on a plastic wafer during the first 8 hours after the orthodontic activation. what is the theory behind this strategy?

Answer 28

the teeth are temporarily displaced enough to allow some blood flow through the compressed area, thereby preventing the buildup of metabolic products that stimulate the pain receptors

Question 29

what happens to root structure during tooth movement?

Answer 29

- osteoclast cells attack cementum and bone - defects are created in the surface of the roots - during the repair phase, these defects will typically fill back in with cementum

Question 30

explain how orthodontics utilizes the body's natural body mechanisms to move teeth

Answer 30

- root remodeling and bone remodeling is a constant feature of orthodontic movement - both of these processes are the body's natural mechanism for moving teeth to equalize the pressure in the oral environment

Question 31

under normal circumstances, permanent loss of root structure would only occur if ___

Answer 31

the repair phase was not able to replace the initially resorbed cementum

Question 32

how does shortening of the roots or root resorption occur during orthodontic tooth movement?

Answer 32

- cavities coalesce at the apex of the root so that peninsulas of root structure are cut off as islands - these islands resorb and although the repair process places new cementum over the residual root surface, a net loss of root length occurs

Question 33

T or F: | during orthodontic tooth movement, roots tend to becoming both shorter and thinner

Answer 33

- false - although both the sides and the apex of the root experience resorption, roots become shorter but not thinner as a result of orthodontic tooth movement - this is due to the fact that peninsulas of root structure on the sides are not cut off as islands, allowing the root the opportunity to repair itself in width

Question 34

what are the 4 categories for root resorption accompanying orthodontic treatment?

Answer 34

- category 1: no change in root length - category 2: slight blunting - category 3: moderate resorption, up to 1/4 of root length - category 4: severe resorption, greater than 1/4 of root length

Question 35

over ___% of maxillary incisors and over ___% of all teeth show some loss of root length during orthodontic treatment

Answer 35

90% of maxillary incisors and over 50% of all teeth

Question 36

T or F: for the great majority of patients, the modest shortening in root length is almost imperceptible and is clinically insignificant

Answer 36

true

Question 37

in patients with severe resorption, it is important to distinguish between ___ and ___ resorption

Answer 37

localized and generalized

Question 38

describe generalized root resorption

Answer 38

- all the teeth are affected and these individuals are prone to root resorption even without orthodontic treatment - these individuals are at high risk of further resorption if they undergo orthodontic treatment and orthodontics should be done very carefully, if done at all

Question 39

describe severe root resorption of a localized area

Answer 39

- only a few teeth are involved (typically maxillary incisors) - can be caused by orthodontic treatment in susceptible patients

Question 40

what are some causes of severe localized root resorption during orthodontic treatment?

Answer 40

- too heavy of orthodontic forces, which move teeth too quickly - can also be caused by the roots of maxillary incisors being pushed against the cortical plate during camouflage orthodontic treatment

Question 41

what is camouflage orthodontic treatment?

Answer 41

moving the teeth into less than ideal positions to compensate for skeletal abnormalities

Question 42

what are some causes of severe localized root resorption in cases not related to orthodontic tooth movement?

Answer 42

- parafunctional habits that place continuous abnormal forces on the teeth over time (tongue thrust, clenching, and grinding) - abnormal occlusal relationships which place the patient in a traumatic occlusion (class II, III, and crossbites)

Question 43

T or F: some individuals are more prone to root resorption than others, and there is currently a good way to screen for susceptible patients

Answer 43

- false - there is NOT a good way to screen for susceptible patients - therefore the presence of root resorption is not an indication that the patient has had incorrect or poor orthodontic treatment

Question 44

practitioners need to carefully examine pretreatment radiographs for signs of root resorption, and if a patient shows signs of risk, the patient should be following up with ___ throughout treatment

Answer 44

x-rays

Question 45

T or F: patients who show significant resorption in the initial stages of orthodontic treatment are more likely to have greater resorption at the end of the treatment if the ortho treatment is continued

Answer 45

true

Question 46

what are some important factors to consider in determining the prognosis of teeth that have had significant root resorption?

Answer 46

-it's important that the general dentist understand the incidence, cause, and outcome of root resorption in order to provide the best follow-up treatment

Question 47

T or F: | just because a tooth has moderate to severe root resorption, the tooth is not automatically condemned to extraction

Answer 47

true

Question 48

studies have shown that the incidence of moderate to severe root resorption is about ___% in adolescents and ___% in adults

Answer 48

- 3% in adolescents and 4% in adults - this means that if you treat orthodontic patients for long enough in your career, you will run into this problem eventually

Question 49

some studies show that the presence of hyalinization and sterile necrosis can affect the incidence of root resorption. what are 4 important considerations regarding root resorption in orthodontics?

Answer 49

- light forces - well controlled biomechanics - proper healing periods - length of treatment

Question 50

if a patient were susceptible to root resorption or already has root resorption, then what two things (orthodontically speaking) can contribute to an increase in resorption?

Answer 50

- the farther the tooth is moved | - the longer the duration of treatment

Question 51

with respect to root resorption, does it make a difference if the orthodontic force is continuous or interrupted force?

Answer 51

- research has clearly shown that although considerable variation typically exists, continuous forces tend to produce more extensive root resorption than intermittent forces - this is thought to have to do with the body not being given an appropriate healing period before the next round of tooth activation occurs

Question 52

what type of wire places a continuous force on a tooth?

Answer 52

NiTi archwires

Question 53

NiTi archwires are safe and effective because their initial forces are light enough so that only ___ resorption occurs, but if heavy forces are used with NiTi heat activated or superelastic wires, tooth movement could override the ___ phase and could cause damage to the roots of the teeth

Answer 53

- frontal | - healing

Question 54

is the tendency or susceptibility for root resorption an inherited trait?

Answer 54

recent studies have suggested that external apical root resorption can be traced to a specific locus on a specific gene (IL-1beta gene) but more research studies evaluating a genetic determination of root resorption susceptibility are needed

Question 55

do specific types of orthodontic movement lead to greater root resorption in susceptible patients?

Answer 55

orthodontic intrusion has been thought to cause greater root resorption in susceptible patients but the results have not been conclusive

Question 56

what are the effects of root resorption on tooth vitality?

Answer 56

- typically a tooth with moderate to severe root resorption, the tooth will retain its vitality - unless there is some bacterial or traumatic insult to the tooth, pulp vitality does not seem to be related to the amount of root resorption

Question 57

what happens over the long term to tooth roots that have undergone moderate to severe root resorption due to orthodontic treatment? will the root resorption continue to worsen?

Answer 57

- researchers have reevaluated patients with moderate to severe root resorption many years after orthodontics, and have found that root resorption typically stops after the completion of the orthodontic treatment - although there have been some remodeling of the irregular resorbed edges of the root (this type of remodeling produces a smoother surface on the apex of the root, and the root does not continue to shorten after orthodontic appliances have been removed)

Question 58

do teeth with moderate to severe root resorption require splinting?

Answer 58

- there are no studies that provide us with the answer to this question - splinting may be a good idea in certain situations (patients with parafunctional habits and crown mobility)

Question 59

can teeth with severe root resorption be safely restored?

Answer 59

- depends on the case - fundamental restorative techniques need to be employed for teeth with root resorption the same way they are applied for regular teeth - it's important to remember that if the tooth requires a crown, the crown to root ratio for the tooth may be compromised

Question 60

if a patient requires further orthodontic treatment, will the roots continue to resorb?

Answer 60

-most orthodontists have had to retreat patients who have had root resorption during an earlier phase of ortho treatment

Question 61

if a patient has experienced root resorption and requires further orthodontic treatment, what are some considerations for the orthodontist?

Answer 61

- limit the length of treatment - use light forces - limit the amount of tooth movement - avoid intrusive movements if possible - usually if these rules are followed, root resorption does not tend to increase significantly in these patients, but there is a high degree of variability, and practitioners should always use caution

Question 62

does the amount of force used during orthodontic treatment affect the amount of root resorption?

Answer 62

the greater amount of research has shown that heavy continuous forces can increase root resorption (prolonged duration of treatment can also increase the amount of root resorption)

Question 63

what are the four variables that have been shown to have an increased risk of a patient experiencing root resorption?

Answer 63

1. pre-treatment resorption is visible 2. duration of orthodontic treatment 3. premolar extraction cases (amount of apical tooth movement required) 4. family history of root resorption

Question 64

in addition to the four variables that have been shown to have an increased risk of a patient experiencing root resorption, what is a 5th possibility in the near future that may help identify these patients?

Answer 64

genetic screening

Question 65

like many other craniofacial abnormalities, root resorption seems to be ___, and will therefore require a ___ approach for the treatment of these patients

Answer 65

multifactorial, multifactorial