ORTHO pt 2 Flashcards
(147 cards)
1
Q
what are the two bracket slot sizes most commonly used?
A
0.018x0.025 inch and 0.022x0.028 inch
2
Q
the magnitude of the forces generated in the ___ and ___ direction is partly depend on the bracket slot size
A
faciolingual and occlusogingival
3
Q
how can the mechanical behavior of a ductile orthodontic wires in tensile loading be analyzed?
A
in a force-deflection or stress-strain plot
4
Q
___ is the internal response of a wire to the application of external forces defied as force (load) (F) per cross-sectional area (A)
A
stress
5
Q
___ is the deformation or deflection of the archwire as a consequence of the stress and is defined as the dimensional change divided by the original dimension
A
strain
6
Q
what are the characteristics of an ideal orthodontic wire?
A
- high strength
- low stiffness
- high working range
- high fomability
- these characteristics depend on the alloy composition, the crystal structure of the metal, and the manufacturing process
7
Q
each of the major elastic properties of wires (strength, stiffness, and range) is affected by a change in the ___ and ___ of a wire
A
-length and cross section
8
Q
doubling the length of a wire does what to its strength, stiffness, and range?
A
- decreases strength by half
- makes it 8x less stiff (8x springier)
- gives it 4x the range
9
Q
doubling the diameter of a wire does what to its strength, stiffness, and range?
A
- 8x stronger
- 16x stiffer
- working range is decreased by half
10
Q
for large orthodontic movements (usually during initial stages of orthodontic treatment), wires with a ___ load/deflection rate are desirable because they are able to provide constant low forces as the tooth moves and the appliance is deactivated
A
low
11
Q
for minimal tooth movements, such as in maximum anchorage extraction cases or during finishing, a ___ load/deflection rate is desirable
A
high
12
Q
the load/deflection rate of a wire is proportional to the ___ of the material
A
modulus of elasticity
13
Q
the most flexible wire (with the lowest load/deflection rate) is made of what material?
A
nickel titanium alloy
14
Q
the load/deflection rate varies directly with the ___ power of the diameter of a round wire and with the ___ power of the width of a rectangular wire
A
- fourth
- third
15
Q
the load deflection rate varies inversely with the ___ power of the length of a wire segment
A
- third
- increasing the interbracket distance by incorporating loops or helices into the archwire decreases the load/deflection rate
16
Q
nickel titanium orthodontic archwires offer what two very important characteristics?
A
- a very low modulus of elasticity
- extremely wide working range
17
Q
beta titanium wires are frequently known as ___ wires
A
TMA (titanium-molybnenum alloy)
18
Q
describe beta titanium wires
A
- intermediate modulus of elasticity (half that of stainless steel and twice that of nickel titanium)
- excellent resilience, which provides wide working range
- drawback is a high coefficient of friction
- high formability, which allows the clinician to bend the wires and incorporate stops or loops into them if desired
- can be spot-welded
19
Q
describe the characteristics of stainless steel archwires
A
- good mechanical properties, excellent corrosion resistance, and low cost
- when compared with NiTi and beta titanium wires, stainless steel wires exhibit the highest elastic modulus (stiffness) and lowest springback
- can be soldered and welded
20
Q
what is the typical composition of stainless steel wires?
A
- 18% chromium
- 8% nickel
- (“18-8”)
21
Q
what component of stainless steel wires give it corrosion resistance?
A
chromium
22
Q
preadjusted edgewise appliances (brackets with prescriptions) allow what?
A
- rotational control
- horizontal control
- mesiodistal tip control
- torque
23
Q
what is the disadvantage of metal brackets? what are they made of?
A
- unesthetic appearance of the metal color
- stainless steel
24
Q
what are ceramic brackets made of?
A
monocrystalline or polycrystalline ceramics
25
describe the characteristics of ceramic brackets
- highly esthetic
- prone to fracture during torsional and tipping activations
- increased frictional resistance to sliding mechanics
- may cause abrasion of opposing teeth
26
___ brackets have a locking mechanism incorporated into the bracket system to hold the archwire in the slot
self-ligating brackets
27
what is the purported advantage of self-ligating brackets?
- supposedly these systems shorten treatment time by reducing friction and because the wire is efficiently kept engaged in the bracket slot
- these claims are controversial
28
is banding molar teeth preferred by many clinicians?
yes, although contemporary orthodontic treatment can include bonding of all teeth (including molars)
29
what are the 3 reasons headgear is used?
- to modify growth of the maxilla
- to distalize (retract) or protract maxillary teeth
- to reinforce anchorage
30
headgear should preferably be worn how many hours per day?
12-14
31
with headgear, what force level per side is recommended for orthopedic changes? what about for dental movements?
- 250-500g per side for orthopedic changes
| - 100-200g per side for dental movements
32
what are 5 types of headgear?
- high-pull
- cervical-pull
- j-hook
- protraction (reverse-pull, facemask)
- chin cup
33
which type of headgear has the objectives of restriction of anterior and downward axillary growth and molar distal movement, intrusion, and control of maxillary molar eruption?
high pull headgear
34
which type of headgear is used to correct class II malocclusions with deep bite and has the objectives of restricting anterior growth of the maxilla and to distalize and erupt maxillary molars?
cervical pull headgear
35
which type of headgear is generally used to retract canines and incisors, rather than for orthopedic purposes?
j-hook headgear
36
which type of headgear is used in patients with class III malocclusions where there is a maxillary deficiency?
protraction headgear (reverse pull, facemask)
37
which type of headgear is used to correct class III malocclusions resulting from excessive mandibular growth?
chin cup (chin cap)
38
___ appliances hold the mandible in a protrusive position and transmit the forces created by the resulting stretch of the muscles and soft tissues to the dental and skeletal components to produce movement of teeth and modification of growth
functional
39
functional appliances are used most commonly to achieve correction of a class ___ malocclusion
II
40
what is important in the success of functional appliances?
patient compliances (most functional appliances are removable)
41
a ___ is a fixed (or sometimes removable) functional appliance that consists of a piston and tube device that places the mandible in a forward position as the patient closes the mouth; it is usually cemented or bonded to the maxillary and mandibular arches.
herbst appliance
42
with the herbst appliance, there is a tendency for the mandibular incisors to ___
procline (flare)
43
what was the first removable functional appliance developed?
activator
44
which functional appliance consists of the following: an acrylic body that covers part of the palate and the lingual aspect of the mandibular alveolar ridge with a labial bow that fits anterior the maxillary incisors, and on the acrylic adjacent to the maxillary posterior teeth, facets are cut to allow occlusal, distal, and buccal movement of these teeth. on the lingual aspect of the mandibular posterior teeth, facets allow occlusal and mesial movement
activator appliance
45
in addition to the effects of activator appliances on the growth of the mandible, these appliances can ___ and control ___
tip anterior teeth and control eruption of teeth in the vertical dimension
46
which functional appliance has the following characteristics: less bulky than the activator, consists of lingual, horseshoe-shaped acrylic with a wire in the palatal area; facets are introduced into the acrylic to guide the maxillary and mandibular posterior teeth and hold the mandible forward in a postured relationship; a labial bow is present anterior to the maxillary incisors, extending distally, to eliminate the pressure from the buccal musculature
bionator
47
which functional appliance has the following characteristics: removable or cemented two-part design; interaction between the maxillary and mandibular parts controls how much the mandible is postured forward and how much the maxilla and mandible are separated in the vertical dimension
twin block appliance
48
which functional appliance is supposedly more easily tolerated by patients because of its two-part design?
twin block appliance
49
which functional appliance is characterized by the following: consists of oversized stainless steel crowns on the maxillary and mandibular molars, elbows that insert into the tubes on the maxillary crowns, and arms that protrude from the mandibular crowns
mandibular anterior repositioning appliance (MARA, allesee orthodontic appliances, sturtevant, wisconsin)
50
how does the design of the mandibular anterior repositioning appliance result in anterior force to the mandibular arch and posterior force to the maxillary arch?
the lower arms interfere when the patient attempts to bite down, forcing the mandible to reposition forward into a class I relationship
51
noncompliant appliances to correct class II malocclusions are indicated in which situations?
- full or cusp-to-cusp molar/canine relationships
- mild to moderate crowding (0-6mm)
- a profile or other characteristics that do not support an extraction treatment plan
52
what are the two noncompliant appliances?
pendulum appliance and forsus fatigue resistant device (3M unitek orthodontic products, monrovia, california)
53
which noncompliant appliance is characterized by the following: cemented appliance that consists of an acrylic body to use the palate as anchorage with wire extensions to the maxillary premolars; two springs extending from the posterior portion of the appliance are inserted into lingual molar attachments and are activated to distalize the molar teeth
pendulum appliance
54
when using the pendulum appliance, what can you do if expansion of the maxilla is also needed?
an expansion screw may be incorporated into the acrylic body in the midpalatal region (appliance is then called a pandex)
55
which noncompliant appliance consists of a bypass rod, push rod, ball pin, and stainless steel spring module (force module) for each side, with the interarch force deliver system that is efficient in treating class II malocclusions with minimal compliance and breakage problems
forsus fatigue resistant device
56
describe the force generated by the forsus fatigue resistant device
delivers forward, downward force to the anterior mandibular arch and backward, upward force to the posterior maxillary arch
57
appliances to correct posterior crossbites:
___ or ___ appliances are used to correct transverse discrepancies by skeletal expansion of the maxilla or by dental expansion; if expansion is carried out at a rate of ___mm/day, it is called rapid palatal expansion/rapid maxillary expansion. slow expansion is carried out at a much slower rate of ___mm/week
- maxillary or palatal expansion
- 0.5mm/day
- 1.0mm/week
58
what are the types of appliances to correct posterior crossbites?
- hyrax appliance (banded type)
- haas appliance
- hawley-type removable appliance with a jackscrew
- quad-helix and w-arch
- transpalatal arch
59
what is the most commonly used type of rapid palatal expansion/rapid maxillary expansion appliance used for skeletal expansion?
hyrax
60
how does the hyrax appliance create expansion?
- metal framework has an expansion screw that is activated by at least 0.25mm (one quarter turn) per day to produce force levels of 100N
- opens midpalatal suture, which increases maxillary arch width
61
with the hyrax appliance, expansion is usually continued until the lingual cusps of the maxillary posterior teeth come into contact with the ___ of the mandibular posterior teeth
lingual inclines of the buccal cusps
62
when creating expansion using a hyrax appliance, a diastema usually appears between the central incisors as the midpalatal suture separates, but closes spontaneously in a few weeks as a result of ___
the pull of the supracrestal fibers
63
when active expansion using a hyrax appliance is completed, retention for ___ months is recommended with the appliance in place
3-6 months
64
the ___ appliance is used for skeletal expansion and consists of bands that are cemented on maxillary first premolars and first molars. two acrylic pads with a midline jackscrew are connected to the rest of the appliance and the acrylic pads are in contact with the palatal mucosa. it is believed that contact with the palate allows forces from the appliance to be applied directly to the underlying hard and soft tissues, minimizing the amount of dental tipping and maximizing the skeletal effect
haas appliance
65
the ___ is a removable appliance used for skeletal or dental expansion, and may be used to correct mild posterior crossbites in children and young adolescents
hawley-type removable appliance with jackscrew
66
what is the disadvantage of a hawley-type removable appliance with a jackscrew?
compliance and difficulty retaining the appliance in the mouth
67
which appliances are generally for dental expansion and consist of heavy stainless steel wire with 4 or 3 helices that are incorporated to increase the range and flexibility, may be fixed or removable, may be used for symmetrical or asymmetrical expansion of the maxillary dental arch and for correcting rotated molars
quad helix (4-helices) and w-arch (3-helices)
68
because of the tendency for quad-helix and w-arch appliances to cause buccal tipping of teeth, they are suggested for use in cases where ___
only a small amount of expansion is needed or in young children for skeletal expansion before the sutures are well developed
69
the ___ appliance is for dental movement, consists of heavy wire that extends from one maxillary first molar along the contour of the palate to the maxillary first molar on the opposite side
transpalatal arch
70
with transpalatal arch appliances, the arch is adapted to the contour of the palate approximately ___mm away from the tissue
2-3mm
71
why are transpalatal arch appliances versatile?
may be used for expansion or constriction of the intermolar width, for producing root movement of the first molars, for derotation of these teeth, and for anchorage reinforcement
72
what are the 3 appliances used in the mixed dentition?
nance appliance, lower lingual arch, and lip bumper
73
which appliance is used as a space maintainer or for anchorage purposes, has a heavy wire soldered to the palatal aspect of the maxillary first permanent molars and connected to an acrylic button located in the most superior and anterior part of the palatal vault?
nance appliance
74
which appliance is made of heavy orthodontic wire adapted to the lingual aspect of the mandibular incisors, may be fixed or removable, with two U loops in the wire mesial to the first molars that make is possible to adjust this appliance?
lower lingual arch
75
what can the lower lingual arch be used for?
- anchorage reinforcement
- holding arch for space maintenance
- expansion
- increasing dental arch length
76
which appliance consists of a heavy wire inserted into the buccal tubes on the mandibular first permanent molars with the anterior portion that lies 2-3mm away from the alveolar process and the mandibular incisors and usually carries a plastic or acrylic pad?
lip bumper
77
what is the lip bumper appliance used for?
- control or increase the mandibular dental arch length
- upright mesially or lingually tipped mandibular molars
- prevent the interposition of the lower lip between the maxillary and mandibular incisors
- allows lateral and anterior dentoalveolar development
- causes distal movement and tipping of the mandibular first molars
78
what are the two appliances used to control vertical incisor position?
intrusion arch and extrusion arch
79
which appliance is an archwire used for deep bite correction in which extrusion at the molars and intrusion at the incisors takes place. the archwire is activated for incisor intrusion by placing tip-back bends mesial to the molar tubes
intrusion arch
80
which appliance is an archwire used for open bite correction in which intrusion at the molars and extrusion at the incisors takes place
extrusion arch
81
which elastics are used for traction between teeth and groups of teeth within the same arch?
class I elastics (intramaxillary elastics)
82
during canine retraction, class I elastics may be used to facilitate ___
sliding mechanics
83
which elastics are worm from a tooth located in the anterior part of the maxilla (usually from the maxillary permanent canine) to a tooth located in the posterior part of the mandible (usually to the mandibular permanent first molar)?
class II elastics (intermaxillary elastics)
84
what are class II elastics used for?
- correct class II malocclusions
- reduce overbite by extruding the molar
- retract anterior maxillary teeth
- minimize anchorage loss in the maxilla during maxillary incisor retraction
85
which elastics are worn from a tooth located in the posterior part of the maxilla (usually from the maxillary permanent first molar) to a tooth located in the anterior part of the mandible (usually to the mandibular permanent canine)?
class III elastics (intermaxillary elastics)
86
what are class III elastics used for?
- aid in protraction of the maxillary posterior teeth
- improve the overjet in an edge-to-edge or anterior crossbite relationship
- make use of intermaxillary anchorage during mandibular incisor retraction
87
which elastics are worn from the palatal of one or more maxillary teeth to the buccal of one or more teeth in the mandible to help correct crossbites?
crossbite elastics
88
in addition to the desired forces produced by crossbite elastics, they cause ___ and should be used with caution in patients with ___
extrusion of the teeth and should be used with caution in patients with an open bite tendency and a long lower anterior facial height
89
which elastics are run from one side of the maxillary teeth to the other side of the mandibular teeth crossing the midline?
anterior diagonal elastics (midline elastics)
90
what are anterior diagonal elastics (midline elastics) used for?
the correction of noncoinciding maxillary and mandibular dental midlines
91
what are the 4 appliances used for space maintenance?
- band and loop
- distal shoe (before eruption of a permanent molar)
- lingual arch
- nance appliance (maxillary arch)
92
what are the appliances used for space regaining (localized space loss)?
- removable appliance with finger springs to tip teeth distally
- headgear (for the maxillary arch)
- activated lingual arch (for the mandibular arch)
- lip bumper (for the mandibular arch)
- limited fixed appliances (followed by placement of a space maintainer after space is regained)
93
when are space regaining appliances indicated?
when space loss is minor (<3mm)
94
what are the options used for moderate crowding (<4mm)?
- arch expansion (controversial)
- extraction of primary canines (borrows space until permanent teeth erupt, lingual arch necessary if mandibular primary canines are extracted because the permanent incisors will upright lingually and space will be lost)
- flaring of incisors (fixed appliances, removable appliances)
95
what are the options for severe crowding (>4mm)?
- arch expansion (controversial)
| - serial extraction (increased overbite usually results as the incisors tip lingually into any excess space)
96
what are the options to correct a maxillary midline diastema less than 2mm?
- commonly present and self-correcting
- ugly duckling stage
- large space may indicate supernumerary tooth or mesiodens or missing lateral incisors
- treatment may be indicated if there is an esthetic concern or central incisors are inhibiting eruption of lateral incisors or canines
97
what are the options to correct large maxillary midline diastema greater than 2mm?
- not likely to close spontaneously
- fixed appliances may be indicated
- frenectomy after treatment if space reopens persistently or bunching of tissue is unresolved after space is clsoed
98
what are the options to correct generalized spacing?
- postpone treatment unless there is an esthetic complaint
- if spacing of anterior teeth is accompanied by protrusion, fixed appliances are usually required to achieve bodily movement
99
what is the option for overretained primary teeth?
remove primary tooth to encourage eruption of permanent tooth
100
what is the option for ankylosed primary teeth?
- usually resorb on their own
- remove if they cause a delay in permanent tooth eruption or if permanent tooth eruption path is deflected
- if the successor is missing, an ankylosed primary tooth should be removed to decrease chances of a vertical alveolar defect
101
___ is the eruption of a tooth into an unexpected location or into an adjacent tooth
ectopic eruption
102
what are the issues and treatment options for ectopic eruption of lateral incisors?
- may cause loss of adjacent primary canine
- usually indicates lack of sufficient space
- if unilateral, may cause midline shift
- treat by extracting primary canines or space regaining
103
what are the issues and treatment options for ectopic eruption of maxillary first molars?
- may erupt into second primary molar
| - upright erupting molar
104
what are the issues and treatment options for ectopic eruption of maxillary canines?
- may lead to canine impaction
- may resorb adjacent lateral incisor
- extraction of primary canine is indicated
105
other than third molars, what are the most commonly missing permanent teeth?
- mandibular second premolars
| - maxillary lateral incisors
106
what are the treatment options for missing mandibular second premolars?
- maintaining primary second molars may be an option
- some reduction in width of the primary second molars may be necessary to attain good posterior interdigitation
- early extraction of primary second molars (age 7-9 years) may be attempted to encourage closure of the space, but this is unpredictable, and later orthodontic treatment is likely to be needed
107
what are the treatment options for missing maxillary lateral incisors?
- substituting canine in lateral position is an option
- retaining space for later replacement is an option
- the best choice may depend on occlusion and esthetic demands
108
describe posterior crossbites
- unilateral crossbites are usually due to a mandibular shift
- if causing a shift, treatment should be initiated (equilibration to eliminate shift, maxillary expansion using fixed or removable appliance)
109
describe anterior crossbites
- differentiate skeletal from dental causes
- skeletal may be due to deficient maxillary or excessive mandibular growth
- dental is usually due to inadequate space; after space is created, the teeth can be moved forward with fixed or removable appliances with or without extraction of adjacent primary teeth
110
describe maxillary dental protrusion with spacing
- may be due to skeletal discrepancy
- may be due to finger or thumb sucking
- treatment is indicated if esthetically objectionable or in danger or trauma
- a removable appliance can be used to upright teeth
111
describe deep bites
- biteplates can be used to open the bite posteriorly and allow eruption of posterior teeth in patients with short lower face heights
- in patients requiring overbite correction by intrusion, this should be deferred until later comprehensive treatment because of inability to retain in the mixed dentition
112
describe oral habits and open bites
- pacifiers and finger sucking may cause increased overjet, decreased overbite, and posterior crossbite
- if the habit stops before eruption of permanent incisors, most of the negative changes resolve spontaneously
- most important is convincing a child that he or she wants to stop; otherwise, any treatment is likely to fail
- if an appliance is used, it should remain in place for about 6 months after the habit appears to have ceased
- open bites that persist after the habit has ceased are likely to have a skeletal component and may need more complex treatment
113
describe treatment of vertical deficiency (short face)
- cervical headgear has an extrusive force on the maxillary moar, which erupts
- functional appliances allow eruption of upper and lower posterior teeth
114
describe treatment of vertical excess (long face)
- high-pull headgear to the molars inhibits eruption of maxillary posterior teeth
- functional appliance with bite blocks to block posterior eruption
115
how is mandibular deficiency (class II) treated?
headgear restrains maxillary growth forward, whereas functional appliances stimulate mandibular growth
116
how is maxillary deficiency treated?
- transverse deficiency can be treated with expansion
| - anterior-posterior (class III) can be treated with a facemask (reverse-pull headgear, protraction headgear)
117
describe using reverse pull headgear (protraction headgear, facemask) to treat class III maxillary deficiency
- anterior force is placed on the maxilla
- encourages growth at the maxillary sutures
- often used after rapid expansion to disrupt the sutures
- ideal timing is earlier (8-9 years) to encourage maxillary growth
118
what is the treatment for mandibular excess?
- chin cup (chin cap) therapy to restrain mandibular growth
- generally redirects mandibular growth downward rather than deterring growth
- contraindicated in long-face individuals
119
what is the treatment for facial asymmetry?
- facial asymmetry may be due to a congenital anomaly or an early condylar fracture
- asymmetrical functional appliances may be helpful
- early surgery may be indicated when asymmetry is progressively worsening
120
which teeth (other than third molars) are most commonly extracted for orthodontic cases?
first premolars
121
when extracting premolars to camouflage a class II or class III malocclusion, upper premolars can be extracted to camouflage a class ___, and lower premolars can be extracted to camouflage a class ___
II, III
122
when considering extractions for orthodontic cases, removing premolars and uprighting incisors generally increases ___, whereas aligning moderately crowded teeth without extractions flares incisors and decreases ___
overbite, overbite
123
what are the indications for extraction for orthodontics?
- large amount of dental crowding (arch length deficiency)
- minimal overbite or open bite present
- flared incisors
- full lips
- acute nasolabial angle
- anterior recession or minimal or thin attached gingiva
- camouflage of class II or class III relationship
- other missing or severely compromised teeth
- asymmetrical occlusion (unilateral class II or III)
124
what are the indications to avoid extraction in orthodontic cases?
- minimal crowding or spacing present
- deep overbite
- upright incisors
- flat lips
- obtuse nasolabial line
125
describe the stages of comprehensive orthodontic treatment
1. alignment
2. overbite correction
3. correction of molar relationship
4. space closure
5. root correction
6. detailing and finishing
126
why is overbite correction necessary to complete before molar correction and space closure?
because deep overbite would prevent retraction (posterior movement) of the incisors to a normal overjet
127
what is a supracrestal fiberotomy?
cutting of supracrestal gingival fibers to reduce the tendency for the fibers to exert elastic force that may move teeth after treatment, especially rotations
128
one of the purposes of retention after orthodontics is to allow time for reorganization of the gingival and periodontal fibers. how long does it take for significant reorganization of the PDL to occur? what about more complete reorganization?
- significant reorganization occurs in 3-4 months, and full time retention is recommended for that time
- part time retention from 4-12 months allows more complete reorganization of the PDL
- long term retention is often recommended
129
T or F:
| orthodontic treatment is not considered a primary method for treating TMJ problems
true
130
T or F:
| steel ligatures retain less plaque than elastomeric ligatures
true
131
what is the proper sequence of interdisciplinary treatment for adults?
- disease control
- orthodontic tooth movement
- definitive treatment
132
because adults do not have the benefit of ___ during treatment, all interarch corrections must be accomplished dentally or with surgery
- mandibular growth
| - without growth to supplement dental changes, overall treatment may proceed more slowly
133
how is a class III malocclusion corrected in terms of maxillary surgery?
- advancement
| - le fort I downfracture of the maxilla mobilizes it so that it may be advanced
134
how is a class II malocclusion corrected in terms of maxillary surgery?
- setback
- it is difficult or impossible to move the entire maxilla posteriorly
- if desired, a premolar is usually extracted and the anterior segment is moved posteriorly (segmental osteotomy)
135
how is a class II malocclusion corrected in terms of mandibular surgery?
- advancement
- bilateral sagittal split osteotomy (BSSO) of the ramus is the most preferred procedure
- paresthesia is a common side effect, usually disappearing in 2-6 months, but 20-25% continue to have long term alterations in sensation
136
how is a class III malocclusion corrected in terms of mandibular surgery?
- setback
- BSSO can also be used to move the mandible posteriorly
- airway reduction leading to possible sleep apnea may limit use of mandibular setback procedures, so class III correction is often done by advancing the maxilla instead
137
how is an open bite corrected in terms of maxillary surgery?
- superior repositioning
- le fort I is used to move the maxilla superiorly, allowing the mandible to autorotate closed to correct an open bite and shorten the face
138
how is a deep bite corrected in terms of maxillary surgery?
- inferior repositioning
- positioning the maxilla downward would rotate the mandible open to reduce overbite and lengthen the face
- this is one of the least stable surgical procedures
139
how is an open bite corrected in terms of mandibular surgery?
-surgical procedures in the mandible to rotate it closed (correct an open bite) are not recommended because they cause downward rotation at the gonial angle and stretch the muscles of the pterygomandibular sling, causing instability
140
how is a deep bite corrected in terms of mandibular surgery?
- anterior and downward rotation of the mandible
| - accomplished with BSSO for patients with a deep bite and short lower face (tripoding)
141
generally speaking, how can correction of crossbites (transverse corrections) be accomplished?
- maxilla can be expanded or constricted during a le fort 1 procedure
- changes in mandibular width are more difficult
142
describe genioplasty
- the chin can be augmented to improve esthetic outcome using an osteotomy or by adding implant material
- the sliding osteotomy is the preferred method and can be used to move the chin in all three dimensions
- reduction is generally the least predictable for esthetic changes
143
T or F:
| surgery to correct malocclusion is often performed before the adolescent growth spurt
- false
- it is rarely performed before the adolescent growth spurt except in cases with significant psychological impact of facial deformity
- class III cases should wait until growth is complete, but class II surgery can be considered earlier
144
what are some exceptions where early surgery is indicated?
- congenital growth deficiencies
- growth is restricted because of mandibular ankylosis
- these cases require surgery because progressive worsening of the growth deficiency occurs without it
145
after surgery, a soft diet is required for ___ weeks, and the patient returns to continue orthodontics usually for about ___ months to detail the occlusion and finish
- 6-8 weeks
| - 6 months
146
to maximize skeletal movements in a class II occlusion, what can be done to the mandible?
remove mandibular premolars and close that space, increasing the overjet presurgically and allowing a greater surgical movement of the jaws to correct the class II
147
to maximize skeletal movements in a class III occlusion, what can be done presurgically?
extract maxillary premolars, making the anterior crossbite more severe presurgically, allowing more room for surgical movement to correct the class III
