Spring - Midterm

Question 1

Excessive loss of crestal bone height is almost never seen as a complication of orthodontic treatment . True or False?

Answer 1

True. But presence of orthodontic appliances increases the amount of gingival inflammation.

Question 2

What is the typical amount of bone loss associated with ortho treatment, and in what sites is it the greatest?

Answer 2

Usually bone loss averages less than 0.5 mm and rarely exceeds 1mm with the greatest incidences at extraction sites.
– The reason is that 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 orthodontic treatment is rarely seen.
• The only exception is tooth movement in the presence of active periodontal disease, but once the periodontal disease is under control, these teeth can be moved and can have a good bony response.
• In the absence of pathologic factors, a tooth that erupts too much simply carries alveolar bone with it, it does not erupt out of the bone.

Question 3

Unless a tooth erupts into an area of the dental arch, alveolar bone will not form there. True or False?

Answer 3

True. Seen when a patient is missing a tooth. No teeth, no alveolar bone.
- Maybe alveolar bone is a completely different type of bone than regular maxillary and mandibular bone.

Question 4

What happens to the biological width of a tooth when it is intruded or extruded?

Answer 4

• Although some have proposed that intruding a tooth will create new attachment, there is little evidence to support this theory.
• When teeth are intruded or extruded, the alveolar bone moves with the tooth, thus maintaining the distance between the alveolar crest and the cementoenamel junction on the tooth.
• In other words, the patient’s biologic width (3mm = 2mm biologic width + 1mm sulcus depth) stays about the same when the tooth is intruded or extruded.

Question 5

What are the characteristics of stainless steel archwires?

Answer 5

strong, stiff, formable and has been used routinely for many years.

Question 6

What are the characteristics of chromium alloy archwires?

Answer 6

softer than stainless steel making it more formable and then can be heat treated to make it harder.

Question 7

What are the characteristics of nickel-titanium alloy archwires?

Answer 7

very useful during initial stages of orthodontic alignment due to their exceptional ability to apply light force over a large range of activations and due to its shape memory and superelasticity.
– Shape memory refers to the ability of the material to remember its original shape after being plastically deformed.
• Heat activated nickel-titanium alloy wires.
• Superelastic nickel-titanium alloy wires.
– Weakness of nickel-titanium wires is they have poor formability

Question 8

What are the characteristics of beta-titanium (TMA) archwires?

Answer 8

This type of wire offers a highly desirable combination of strength and springiness as well as good formability.

Question 9

What are the main six different types of orthodontic brackets to choose from?

Answer 9

Self-ligating
Ceramic
Metal
Plastic
Single Wing
Twin

Question 10

What are the three properties that each bracket has?

Answer 10

1. Torque
2. Angulation
3. Offset

Question 11

What is osteoid? What is it made of?

Answer 11

Osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue
– Osteoid is comprised of type I collagen (~94%) and non-collagenous proteins.

Question 12

What gives the hardness and rigidity to the bone?

Answer 12

The presence of mineral salt in the osteoid matrix does, which is a crystalline complex of calcium and phosphate (hydroxyapatite)

Question 13

What is the composition of calcified bone?

Answer 13

Calcified bone contains about 25% organic matrix (2-5% of which are cells), 5% water and 70% inorganic mineral (hydroxyapatite).

Question 14

What are the two main types of bone?

Answer 14

Woven bone and lamellar bone.
– Woven bone is characterized by a haphazard organization of collagen fibers and is mechanically weak.
– Lamellar bone is characterized by a regular parallel alignment of collagen into sheets (lamellae) and is mechanically strong.
• Woven bone is produced when osteoblasts produce osteoid rapidly. This occurs initially in all fetal bones, but the resulting woven bone is replaced by remodeling and the deposition of more resilient lamellar bone.
• In adults, woven bone is formed when there is very rapid new bone formation, as occurs in the repair of a fracture. Following a fracture, woven bone is remodeled and lamellar bone is deposited. Virtually all bone in the healthy mature adult is lamellar bone.
• It typically takes 12 weeks for Woven bone to mature to Lamellar bone, creating a 3 month window which is typically used for full time retainer wear after orthodontic treatment.

Question 15

What is anchorage in orthodontics?

Answer 15

• Anchorage – is the resistance to unwanted tooth movement.
• In orthodontics for every desired action there is an equal and opposite reaction.
• Reaction forces can move other teeth as well and cause movements that are unwanted. Anchorage is used to minimize unwanted tooth movement, while maximizing desired effects.

Question 16

In orthodontics, it is difficult, but possible, to consider only the teeth whose movement is desired. True or False?

Answer 16

False, it is simply not possible.
• Reciprocal effects throughout the dental arches must be carefully analyzed, evaluated and controlled.
• A major part of treatment planning is maximizing the tooth movement that is desired while minimizing undesirable side effects

Question 17

What is the anchorage value equivalent to?

Answer 17

The “anchorage value” of any tooth is roughly equivalent to its root surface area.
Other teeth used as anchorage – The goal is to maintain the concentration of force on the tooth that movement is desired, while keeping the pressure in the PDL of the anchor teeth as low as possible, ideally below the threshold that tooth movement occurs.
– This threshold is quite low,so multiple anchorage teeth are often necessary to distribute the force.

Question 18

How can you minimize the displacement of anchor teeth in orthodontics?

Answer 18

By arranging the force system so that the anchor teeth must move bodily (translation 70-120gm) if they move at all, while the anterior teeth are allowed to tip (35-60mg).
An example would be moving the 1st molar and premolar forward with bodily movement, and retracting the incisors by tipping them lingually.
– The approach is called stationary anchorage. In this example, treatment is not complete because the roots of the lingually tipped incisors will have to be uprighted at a later stage,
– But two-stage treatment with tipping followed by uprighting can be used as a means of controlling anchorage by distributing the force over a larger PDL area of the anchor teeth reduces pressure there.

Question 19

What are the different ways to get skeletal anchorage in orthodontics?

Answer 19

Palate (acrylic plate in roof of mouth)
Head or neck - use of a head gear
Cortical anchorage - using the resistance of cortical bone to remodeling as anchorage
Temporary anchorage devices (TADs), implants and ankylosised teeth

Question 20

What is the minimum number of weeks to wait between reactivating orthodontic appliances?

Answer 20

No more frequently than 3 week intervals.
• Undermining resorption requires 7 – 14 days and tooth movement is essentially complete in this length of time.
• There is an equal or longer period for PDL regeneration and repair that should be observed before force is applied again
• Activating an appliance too frequently can short circuit the repair process and can produce damage to the teeth or bone that a longer appointment interval would have prevented or at least minimized

Question 21

Some increase in mobility in teeth will be observed in every patient. True or False?

Answer 21

True
• The combination of a wider ligament space and a somewhat disorganized ligament means that some increase in mobility will be observed in every patient

Question 22

How do you get greater mobility with teeth during orthodontic movement?

Answer 22

• The heavier the force the greater the undermining resorption should be expected an the greater the mobility that will develop. Excessive mobility is an indication that excessive forces are being encountered by the tooth.
– This could be due to the patient clenching or grinding against the tooth that has moved into a position of traumatic occlusion
• Once the traumatic occlusion is corrected and the forces have dissipated, excessive mobility will usually correct itself without permanent damage.

Question 23

All patients experience pain with orthodontic treatment. True or False?

Answer 23

• A patient will feel a mild aching sensation when the orthodontic force is placed on a tooth but there is a great deal of individual variation with some patients reporting little or no pain whereas others experience considerable discomfort

Question 24

How long does orthodontic treatment pain usually last for?

Answer 24

• This pain typically last for 2 to 4 days and then goes away until the orthodontic appliance is reactivated

Question 25

What causes the pain in orthodontic treatment?

Answer 25

• The pain is associated with the inflammation and mild pulpitis that appears after the orthodontic force is applied and the development of ischemic areas in the PDL that will undergo sterile necrosis
• This mild pulpitis has no long-term significance but can aggravate existing conditions due to previous root canal treatment or trauma

Question 26

Why does chewing sugarless gum maybe help with orthodontic treatment pain?

Answer 26

– This presumably works by temporarily displacing the teeth enough to allow some blood flow through the compressed area, thereby preventing the buildup of metabolic products that stimulate the pain receptors.

Question 27

How do we treat teeth that have been non-vitalized by intrusive trauma?

Answer 27

– If a tooth has been non-vitalized by intrusive trauma and required pulp therapy and if the tooth is to be orthodontically extruded, root resorption is less likely if a calcium hydroxide fill is maintained until the tooth movement is complete and then the root canal filling is placed.

Question 28

What do clast cells attack during tooth movement?

Answer 28

They attack cementum, as well as bone. This creates a defect in the surface of roots, and during the repair phase, these defects will fill back in with cementum.

Question 29

When does shortening of the root occur with ortho treatment?

Answer 29

• Shortening of the root occurs when cavities coalesce at the apex, 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 30

Do roots become thinner during ortho treatment?

Answer 30

– 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.

Question 31

What fills in the craters in the dentin during tooth movement and what would cause permanent loss of root structure to occur during ortho treatment?

Answer 31

– Osteoclasts removing bone
– Areas of beginning root resorption that will be
repaired by later deposition of cementum
– If resorption penetrates through the cementum and into the dentin, the result will be cementum repair that fills in craters in the dentin.
– Root remodeling is a constant feature of orthodontic tooth movement the same way that alveolar bone is removed and replaced. But permanent loss of root structure would only occur if the repair phase was not able to replace the initially resorbed cementum.

Question 32

What are the three categories of root resorption from ortho treatment?

Answer 32

Category 1 - slight blunting
Category 2 - moderate resorption, up to 1/4 of root length
Category 3 - severe resorption, greater than 1/4 of root length

Question 33

What percentage of maxillary incisors and all teeth in general show some loss of root length during ortho treatment?

Answer 33

• Over 90% of maxillary incisors and over half of all teeth show some loss of root length during orthodontic treatment.
• For the great majority of patients, this modest shortening is almost imperceptible and is clinically insignificant
• In patients with severe resorption it is important to
distinguish between generalized and localized resorption.

Question 34

What are the characteristics of generalized root resorption?

Answer 34

• generalized resorption - 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.
– At this point the etiology of severe generalized resorption is unknown but genetics is believed to play a major role.

Question 35

What are the characteristics of severe resorption of a localized area?

Answer 35

– This can be caused by orthodontic treatment
– Is believed to be caused, when heavy forces are
used in susceptible patients.
– Or if the roots are pushed against the cortical plate during camouflage treatment.
– Some individuals are more prone to root resorption than others, and the presence of root resorption, is not an indication of incorrect orthodontic treatment.

Question 36

Patients who show significant resorption in the initial stages of orthodontic treatment, are less likely to have greater resorption at the end of treatment. True or False?

Answer 36

False. They are more likely.

Question 37

What is the incidence of moderate to severe root resorption in adolescent patients and adults?

Answer 37

Studies have shown that the incidence of moderate to severe root resorption is about 3 percent in adolescence patients and 4 percent in adults.

Question 38

Why does root resorption occur? What have studies shown?

Answer 38

This is not completely understood, but some studies have shown that the presence of hyalinization and sterile necrosis can affect the incidence of root resorption. Therefore light forces and well controlled biomechanics with proper healing periods are important during orthodontic treatment.
If a patient were susceptible to significant root resorption and already has root resorption, then the farther the tooth is moved and the longer the duration of treatment, the more root resorption will occur.

Question 39

With root resorption, does it make a difference if the ortho force is continuous or intermittent?

Answer 39

Researches have clearly shown that although considerable variation typically exists, continuous forces tend to produce more extensive root resorption than intermittent forces

Question 40

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

Answer 40

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

Question 41

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

Answer 41

Orthodontic intrusion has been thought to cause greater root resorption in susceptible patients but the results have not been conclusive. This is most likely due to the fact that high forces are very easy to obtain while doing intrusive movements and so intrusive forces should be avoided if possible in a patient that is susceptible or showing signs of root resorption.

Question 42

What are the effects on root resorption on tooth vitality?

Answer 42

Typically a tooth with moderate to severe root resorption 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 43

What happens over the long term to tooth roots that have undergone moderate to severe root resorption?

Answer 43

– Researchers have reevaluated patients with moderate to severe root resorption many years after orthodontics and have found that root resorption typically stops after completion of their orthodontic treatment.
– Although there may be some remodeling of the irregular resorbed edges of the root with time due to reparative deposition of cellular cementum, this type of remodeling merely produces a smoother surface long term and the root does not continue to shorten after orthodontic appliances have been removed.

Question 44

Do teeth with moderate to severe root resorption require splinting?

Answer 44

– There are no studies that provide us with the answer to this important clinical question
– I believe that parafunctional habits and crown mobility are key indications that splinting should be used.

Question 45

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

Answer 45

– This question also requires further research but most orthodontists have had to retreat patients who have had root resorption during an earlier phase of orthodontic treatment.
– In these cases the orthodontist should limit the length of treatment, limit the amount of tooth movement and avoid intrusive movements if possible.
– Usually if these rules are followed root resorption does not tend to increase in these patients.

Question 46

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

Answer 46

Kokick doesn’t think so, but Iverson believes that the greater amount of research has shown that heavy continuous forces can increase root resorption.

Question 47

What are three factors very important to avoid root resorption in ortho treatment?

Answer 47

1. Light forces
2. Well controlled biomechanics
3. Proper Healing periods

Question 48

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

Answer 48

1. Pre treatment root resorption is visible
2. Duration of ortho treatment
3. Premolar extraction cases (amount of apical tooth movement required)
4. Family history of root resorption

Question 49

What is Pro-Seal and Opal Seal and what do they do?

Answer 49

• Pro-Seal (Reliance Orthodontics) is a fluoride filled, light cured sealant with a proprietary catalyst that sets the resin without an oxygen inhibited layer
• Its complete polymerization prevents oral fluid absorption and reduces toothbrush abrasion.
• It can inhibit long term decalcification, even in patients with poor oral hygiene.
• Opal seal is another orthodontic sealant, which claims to help eliminate decalcification during orthodontic treatment.

Question 50

According to the study, Prophylactic sealing around the orthodontic bracket pad periphery with an unfilled sealant or a filled flowable composite restorative material did not significantly reduce the incidence of decalcification. True or False?

Answer 50

True

Question 51

What are the characteristics of GC MI Paste?

Answer 51

GC MI Paste is a specially formulated paste that remineralizes the enamel. It replenishes the calcium and phosphate lost during acid production by the plaque. Another product that does not require a prescription is Tooth Mousse GC.

Question 52

What are the characteristics of Colgate’s PreviDent 5000?

Answer 52

Another item that can be prescribed is Colgate’s PreviDent 5000 Plus (Rx only) or Colgate PreviDent 5000 Sensitive (Rx only) tooth paste.
– Both deliver 5000 ppm of fluoride in a professional strength 1.1% Sodium Fluoride paste.
– In three to six months, caries remineralized by 57% in most patients.
– These products are not recommended for children under 6 years old.

Question 53

What are the characteristics of DMG ICON infiltrating resin for white spot lesions?

Answer 53

– After the CG MI paste or fluoride is used for a period of time, and if there are still some white spots, an infiltrating resin like DMG ICON can be applied to reduce the appearance of the white spots.
– The resin infiltrates the enamel and changes the color of the white spot to a more tooth colored enamel.
– ICON may not completely get rid of all the white spots but it does accomplish a better appearance

Question 54

What is crenated, or scalloped, tongue?

Answer 54

Crenated tongue (also called scalloped tongue), is a descriptive term for the appearance of the tongue when there are indentations along the lateral borders as the result of compression of the tongue against the adjacent teeth.
•  This usually results from habits where the tongue is pressed against the lingual surfaces of the dental arches, or from any cause of macroglossia
•  Pressure from the tongue against the teeth can move the teeth into abnormal positions and can prevent the teeth from coming together and can cause and open bite (lateral and anterior).
•  Root resorption and bone and gingival loss can be associated with tongue pressure parafunctional habits, which place the teeth in a situation comparable to an traumatic occlusion

Question 55

What kind of rotation makes maxillary incisors more prominent in the maxilla during normal growth?

Answer 55

Typically during normal growth the maxilla undergoes a small amount of forward rotation, which rotates the maxilla up anteriorly and down posteriorly. This rotation tends to tip the maxillary incisors forward which increases their prominence.
So backward internal rotation of the maxilla would make the anterior portion go down and upright the maxillary incisors and decrease their prominence.
A small amount of forward rotation is the usual pattern, but backward rotation also frequently occurs.

Question 56

What does headgear to the maxilla and mandible?

Answer 56

• Extraoral force applied to the maxillary teeth radiates to the sutures of the maxilla, where it can affect the pattern of skeletal maxillary growth.
• Depending upon the direction of pull, the maxilla can be restricted in its growth in the anterior posterior (AP) and vertical (Vert) dimensions.
• Restriction of growth of the maxilla in a class II patient allows the mandible to “catch up” as it grows normally in the AP and vertical dimensions, which corrects the patients class II relationship.

Question 57

What does occipital pull with head gear do?

Answer 57

Restricts inferior and anterior maxillary growth

Question 58

What does cervical pull with head gear do?

Answer 58

Restricts superior and anterior maxillary growth

Question 59

What does combination pull with head gear do?

Answer 59

Restricts anterior maxillary growth

Question 60

If you use head gear to force the maxilla to move backward and downward, instead of downward and forward, would the lower molars or upper molars erupt more?

Answer 60

Lower molars would erupt more than the upper molars

Question 61

How does the maxilla open at the midpalatal suture with palate expanders?

Answer 61

It opens as if on a hinge, with its apex at the bridge of the nose. The suture also opens on a hinge anteroposteriorly, separating more anteriorly than posteriorly.

Question 62

How many millimeters is the maxilla usually expanded during palatal expansion?

Answer 62

Between 5 mm to 15 mm

Question 63

What happens to the midpalatal suture with age?

Answer 63

Like the other sutures of the facial skeleton, the midpalatal suture becomes increasingly tortuous and interdigitated with increasing age.
• In childhood (early mixed dentition), sutural expansion can be accomplished with almost any type of expansion device.
• By early adolescence interdigitation of spicules in the suture has reached the point that a jackscrew with considerable force is required to create microfractures before the suture can open.
• By the late teens, interdigitation and areas of bony bridging across the suture develop to the point that skeletal maxillary expansion becomes impossible.

Question 64

What are the differences between rapid and slow maxillary expansion?

Answer 64

• Rapid maxillary expansion is considered to be at a rate of 3 – 7mm per week.
• Slow maxillary expansion is considered to be at a rate of 1 – 2 mm per week.
• Rapid expansion was recommended when the technique was reintroduced in the 1960s because it was thought that this produced more skeletal than dental change.
  – Recent research has show this not to be true. But this is true initially:
  – the teeth cannot respond to the quick heavy force produced through rapid expansion, and the suture is opened with 10 mm of expansion in 2 weeks.
  – At this point, there might be 8 mm of skeletal change and only 2 mm of tooth movement at the time the expansion is completed.
• What the research showed, was that during the next 8 weeks, while bone is filling in, orthodontic tooth movement continues and allows skeletal relapse, so that although the total expansion is maintained, the percentage due to tooth movement increases and the skeletal expansion decreases.
• With slow expansion at the rate of 1 mm per week, the total expansion is about half skeletal/half dental from the beginning. The outcome of rapid versus slow expansion looks very different at 2 weeks but quite similar at 10 weeks.

Question 65

What can implant supported expansion techniques help with?

Answer 65

• For a patient that might have a narrow maxillary arch with palatal screws for delivery of expansion force directly to the bone. The expansion device has a wire framework that clips over the exposed head of the bone screws.
• Although the molars are attached to the expansion device, the attachment is to a bar along which the attachment can slide, so the expansion force will be only against the screws.
• This procedure is performed when maximum skeletal expansion, and minimal dental expansion is desired.

Question 66

What did the research study comparing skeletal changes from different types of expanders show?

Answer 66

Both expanders showed similar results. The greatest changes were seen in the transverse dimension; changes in the vertical and anteroposterior dimensions were negligible. Dental expansion was also greater than skeletal expansion. The authors discovered similar tipping of the molars with both appliances.

Question 67

What are the negative effects from using removable expansion appliances?

Answer 67

– The overall apical and crestal stress in the periodontium of anchor teeth is higher in a removable appliance compared to a fixed appliance
– Removable appliances also produce higher stress in both cortical and spongy bone from forces produced against the hard palate and alveolar bone.
– The vertical displacement (Crown tipping) of molar cusps is higher in removable appliances than fixed.
– Patient compliance is worse for removable appliances
• Generally a fixed bonded palatal expansion appliance is superior to a removable appliance

Question 68

What does internal rotation of the mandible mean?

Answer 68

• Internal rotation of the mandible (i.e., rotation of the core relative to the cranial base) has two components:
– Rotation around the condyle, or matrix rotation
– Rotations centered within the body of the mandible, or intra-matrix rotation

Question 69

The body of the mandible in most individuals rotates during growth in a way that would tend to increase the mandibular plane angle (down anteriorly and up posteriorly). True or False?

Answer 69

False, it usually tends to decrease the mandibular plane angle. This can occur either by rotation around the condyle or rotation centered within the body of the mandible.

Question 70

While a mandibular suture is present, it is very constrained. True or False?

Answer 70

False, there is no mandibular suture to expand skeletally.

Question 71

Moving lower incisors forward more than 2 mm is problematic for stability. True or False?

Answer 71

True, because lip pressure seems to increase sharply at about that point.

Question 72

Dental expansion across the canines is not stable. True or False?

Answer 72

True
–  0 mm for canines, not to exceed 1 mm.
–  2 mm for first premolars.
–  2-3 mm for second premolars.
–  3 mm for molars.

Question 73

Dental expansion across the premolars and molars is not stable. True or False?

Answer 73

False.  It can be stable if it is not overdone (this is referring to dental expansion only, not skeletal expansion).
–  0 mm for canines, not to exceed 1 mm.
–  2 mm for first premolars.
–  2-3 mm for second premolars.
–  3 mm for molars.

Question 74

Why is the response of the mandible to force when compared to the maxilla so different?

Answer 74

• Since the mandible like the maxilla grows largely in response to growth of the surrounding soft tissues, it should be possible to alter its growth in somewhat the same way maxillary growth can be altered by pushing back against it or by pulling it forward.
• To some extent this is true but the attachment of the mandible to the rest of the facial skeleton via the temporal mandibular joint is very different from the sutural attachments of the maxilla.
• It should not be surprising that the response of the mandible to force transmitted to the temporomandibular joint is quite different.

Question 75

What were the differences with and characteristics of the soft cup and hard cup chin appliances used to move the mandible?

Answer 75

The soft cup is more comfortable but increases the chance that the lower incisors will be tipped lingually, which is undesirable in skeletal Class III patients.
• Extra-oral force of this type has been shown to remodel the TMJ joint and restrain mandibular growth on experimental animals but the appliance has to be worn on a full time or nearly full time basis, something that children simply wont due.
– Another problem with a chin cup device is that the extraoral force aimed at the condyle of the mandible tends to load only a small portion of the rounded surface
• It is fair to say that controlling excessive mandibular growth is an important unsolved problem in contemporary orthodontics.

Question 76

What is a Delaire-type facemask and what does it do?

Answer 76

Is used for class III patients, deficient maxillary growth
•  Delaire-type facemask (sometimes called reverse pull headgear)
–  Used to place forward traction against the maxilla and a restrictive force against the mandible.
–  In class III patients the maxilla often is deficient vertically, and antero-posteriorly.
–  A downward and forward direction of force usually is needed, which is provided by the Delaire-type facemask.

Question 77

What are the three effects that a reverse pull headgear (Delaire-type facemask) has?

Answer 77

– (1) some forward movement of the maxilla, the amount depending to a large extent on the patient’s age;
– (2) forward movement of the maxillary teeth relative to the maxilla
– (3) downward and backward rotation of the mandible because of the reciprocal force placed against the chin.

Question 78

When fixing class II occlusion, deficient mandibular growth, producing a larger mandible is not a desired result. True or False?

Answer 78

True. MARA/Herbst appliance are used for this.
• If growth stimulation is defined as an acceleration of growth, so that the mandible grows faster while it is being protruded, growth stimulation can be shown to occur for many, but not all, patients.
– If growth stimulation is defined as producing a larger mandible at the end of the total growth period than would have existed without treatment, this is harder to demonstrate a positive effect.
• Many studies have shown that the ultimate size of the mandible in treated and untreated patients is remarkably similar.

Question 79

What is the research on whether growth modification treatment can produce permanent skeletal changes and what is the difference between acceleration and stimulation in growth?

Answer 79

• The difference between growth acceleration in response to a functional appliance and true growth stimulation can be represented using a growth chart.
- If growth occurs at a faster-than- expected rate while a functional appliance is being worn and then continues at the expected rate thereafter so that the ultimate size of the jaw is larger, true stimulation has occurred.
If faster growth occurs while the appliance is being worn, but slower growth thereafter ultimately brings the patient back to the line of expected growth, there has been an acceleration, not a true stimulation.
- Although there is a great deal of individual variation, the response to a functional appliance most often is similar to the solid line in this graph.
- The extent to which growth modification treatment can produce permanent skeletal change remains controversial

Question 80

What is the definite threshold for time of duration of force needed to move a tooth?

Answer 80

At least 6 hours

-Whether a similar duration threshold applies to sutures is unknown

Question 81

When is the best time to wear a growth modification device?

Answer 81

During the evening and sleeping hours when growth hormone is being released.
• It has been shown that addition of new bone at the epiphyseal plates of the long bones occurs mostly, perhaps entirely, at night.
• We do not know if facial growth follows this same pattern but it seems likely.

Question 82

What is orthodontic camouflage?

Answer 82

Moving the teeth to camouflage a skeletal abnormality

Question 83

What does showing probable profile outcomes from different treatment end up doing to the patient?

Answer 83

Heightens their esthetic awareness

Question 84

How long does Phase 1 treatment usually last?

Answer 84

6-12 months, then patient is placed into retainers.
Patients who have undergone phase 1 treatment will typically undergo phase 2 treatment (full orthodontic treatment) later when the primary dentition is lost, which is typically around the age of 11 or 12.

Question 85

Before or at what age should every child receive an ortho evaluation and panoramic X-ray?

Answer 85

Before the age of 8

Question 86

What are the mani reasons to refer your patient for early ortho treatment and intervention (phase I)?

Answer 86

Crowding
abnormal growth and development
ectopic eruption and impactions
traumatic occlusal relationships
possibility for trauma
severe deep bites
cross bites (anterior and posterior)
class III occlusion/anterior crossbites
abnormal habits (mouth breathing, tongue posture)
missing teeth
abnormal dental eruption
supernumerary teeth
fused teeth

Question 87

When is it normal to have a small amount of crowding in the mandibular arch?

Answer 87

In the mandibular arch in both sexes, the amount of space for the mandibular incisors is negative (1-2mm) for about 2 years after their eruption, meaning that a small amount of crowding in the mandibular arch at this time is normal

Question 88

What are the three sources that the additional space to align mandibular incisors, after the period of mild normal crowding, is derived from?

Answer 88

1. A slight increase in arch width across the canines
2. Slight labial positioning of the central and lateral incisors
3. A distal shift of the permanent canines when the primary first molars are exfoliated.
   • The primary molars are significantly larger than the premolars that replace them, and the “leeway space” provided by this difference offers an excellent opportunity for natural or orthodontic adjustment of occlusal relationships at the end of the dental transition.
   • Both arch length (L), the distance from a line perpendicular to the mesial surface of the permanent first molars to the central incisors, and arch circumference (C) tend to decrease during the transition (i.e., some of the leeway space is used by mesial movement of the molars).

Question 89

At what age is the ugly duckling stage most prominent?

Answer 89

At age 9, when the maxillary incisors flare laterally and are widely spaced when they first erupt.
The position of the incisors tends to improve when the permanent canines erupt, but this condition increases the possibility that the canines will become impacted and theses patients should be referred to an orthodontist for evaluation