The orthodontic biomechanics of different skeletal deformities are explained

1. Biomechanics and treatment
of dentofacial deformity
Part 2
dr Maher FOUDA
Faculty of Dentistry
Mansoura Egypt
Professor of orthodontics

2. Decompensation of the dentition is an essential component
of the orthodontics in combined surgicalorthodontic
treatment. Historically, the goal of presurgical
orthodontics was to completely remove any
compensations in the dentition that had occurred
secondary to the skeletal discrepancy in all three
dimensions.
Decompensation

3. Philosophically, this meant that the
discrepancy at the dental level represented the underlying
skeletal discrepancy. Unfortunately, however,
the limited space acquired from extractions and
auxiliary force-delivery systems such as headgears
and elastics resulted in less than ideal decompensations
in a significant number of patients.

4. This often resulted in the need for adjunctive procedures
such as genioplasty or onlay grafting in the paranasal
and midfacial regions in circumstances of inadequate
decompensation in the mandibular and maxillary
arches, respectively.
Dental relationship
before orthodontic
treatment
Dental relationship after
orthodontic
decompensation.
(Exaggerated
reverse overjet visible)
Dental
relationship after
surgery
Unilateral cross-bite

5. Skeletal Class II malocclusions usually have compensations
of either maxillary incisor retroclination
or mandibular incisor proclination (or both). However,
it is possible that patients present with significant
deviations from the anticipated compensations.
Class II Pre-surgical
orthodontic decompensation. In this
Class II patient, the lower incisors
were
proclined and the upper incisors
were
upright initially. Pre-surgical
orthodontics
has corrected the incisor
inclinations,
resulting in an increased overjet.
This
in turn facilitates maximum skeletal
correction.

6. Decompensation
of retroclined maxillary incisors usually
requires a force to advance the incisor crowns,
which will undoubtedly change the vertical position
of the incisal edge as the tooth rotates close to the
center of resistance. If further intrusive movements
are required, additional intrusion arch mechanics
may be instituted.
Patient with a Class II division 1
malocclusion. Prior to surgery

7. Decompensation of proclined
mandibular incisors in skeletal Class II patients is often
challenging because of added complexities of
leveling the mandibular curve of Spee. Mandibular
first premolars are often removed to create space to
decompensate the mandibular incisors to a relatively
normal position within the mandibular skeletal base.
Class ll, division 1 patient. (a) The lower incisors are proclined
and mildy crowded, with no space for retraction. (b) Pre-
molar extractions have allowed lower incisor decompensation

8. (a to c) A patient with a skeletal Class II malocclusion who requested an
improvement in chin definition. The mandibular teeth
have clearly compensated for the mandibular retrognathism by proclining.
Unfortunately, when the mandible is ultimately
advanced, the maxillary second molars remain unopposed
and will most likely require extraction

9. (d and e) Decompensation was performed by extracting two
mandibular first premolars and tipping the mandibular incisors
backward.

10. (f and g) The mandible and chin were then advanced. The postsurgical
occlusion required minor detailing to finish in a Class III molar relationship.

11. (h to j) After treatment, an excellent occlusal outcome
was observed, although the maxillary second molars would be extracted
because they were no longer nonfunctional. Decompensation of
the mandibular teeth enabled a pleasing change in the facial profile with
the addition of an advancement genioplasty.

12. Bone plates for decompensation of Class II
malocclusions
The introduction of temporary anchors to the orthodontic
armamentarium has extended the range
of tooth movement that can be considered in combined
surgical-orthodontic treatment. Dr Junji Sugawara
from Sendai, Japan, has popularized this technique
with the Sendai skeletal anchorage system.

13. Because many patients require extraction of the
third molars prior to orthognathic surgery, there is
an opportunity to place bilateral bone anchors simultaneously,
immediately lateral to the mandibular
first molars .
Bone plates are
placed buccal to the first molar.
The design of the plates
enables
the force from an elastic chain
to be placed from an extension
arm attached to the archwire to
the bone plate at a point that
approximates the center of
resistance
of the mandibular arch
(A). This will enable the entire
mandibular arch to be
translated
distally (B).

14. The bone plates may be
used as anchors to retract the entire mandibular
arch and level the curve of Spee simultaneously .
(a and b) This teenage boy
presented with a Class II,
division 2 malocclusion with
mild maxillary retrognathism
and moderate
mandibular retrognathism. (c
to e) The mandibular teeth
were slightly proclined and
crowded with an increased
curve of Spee. (f to h) Usually
the mandibular premolars
would be extracted to create
space to upright and level the
mandibular arch, but bone
plates were placed at
the time of third molar
removal to be used as
anchors to upright the
mandibular arch.

15. (i) The presurgical cephalometric radiograph reveals
good control of the mandibular incisor inclinations and the bone plates in position. The maxillary incisors
have also been decompensated.
( j) The maxilla and mandible were both advanced, and a simultaneous advancement genioplasty was
performed. (k to n) After treatment,
the facial and dental outcomes were excellent.

16. Fixed appliances are placed prior to placement of
the bone plates to ensure that the surgeon is able to
place the plates lateral to the mandibular first molars.

17. It is important to ensure that the bone plates
are readily accessible for cleaning and that the sulcus
depth is adequate so that there is enough extension
of the plate from the soft tissue. If the plate
is placed too far posteriorly, cleaning is difficult,
and access to the plate may be uncomfortable and problematic.
.

18. This failure to maintain excellent oral
hygiene around the bone plates facilitates propagation
of bacterial products below the soft tissue
along the bone plates. This may lead to pain, tooth
mobility, and ultimate failure of the bone plate. Patients
are therefore encouraged to use small interdental
brushes around the bone plates with topical
chlorhexidine gel.

19. Bone plates can also be used in patients who have
previously undergone mandibular extraction. Moreover,
treatment times appear to be shorter because
treatment does not require the closure of extraction
sites and the alignment of roots, and the maxillary
second molars do not need to be considered for
extraction.

20. This technique progresses toward the limitations
of routine orthodontics in achieving ideal
inclinations of teeth prior to orthodontics.

21. Bone plates for decompensation of Class III
malocclusions
It is also possible to consider bone plates to simultaneously
create space for alignment and retraction of
irregular maxillary teeth in patients who would historically
be treated with extraction of maxillary premolars
only.

22. As with the Class II patients, extraction
of third molars in Class III patients offers an opportunity
to place bone plates lateral to the maxillary
first molars. The bone plate will extend into the zygomatic
buttress region, and similar considerations
related to hygiene access and sulcus depth must be
addressed.

23. Buccal segments with extension arms are placed
on the posterior teeth. It is important to extend
arms above the occlusal plane to direct the force as
close as possible to the center of resistance of the
posterior tooth segments. This will minimize tipping
and facilitate translatory tooth movements. The
bone plates offer a quick solution to creating space
for alignment and retraction and are only removed
at the time of definitive surgery .

24. (a to g) This young adult presented
with a Class III malocclusion with
significant crowding in the maxillary arch
and a Class III skeletal relationship
characterized
by maxillary retrognathism. Historically
this problem may have been treated
with extraction of the maxillary first
premolars
to create space for both decompensation
and alignment of the maxillary
arch. The need for extraction of the third
molars provided an opportunity to place
bone plates in the maxilla to facilitate
space creation.

25. the true skeletal maxillary
retrognathism after the bone plates were
placed buccal to the maxillary first molars.
(i) A 0.019 × 0.025–inch TMA segment
was placed in the maxillary posterior teeth
with an extension arm to deliver a force as
close to the center of resistance as
possible
to move the posterior teeth backward
with possible translatory tooth movement.
(j and k) The mandibular arch was bonded,
but no attempt was made to engage the
h i canines until space was created.

26. (l to o) The maxilla
was
advanced after space
was gained. Alignment
and detailing were
then performed.

27. (p to v) After
treatment, the facial
and
occlusal outcomes
reveal an improved
midface projection
and a normal
occlusal
relationship.

28. Bone plates can also be utilized to assist in decompensating
mandibular teeth by facilitating mandibular
arch protraction. Again, placement of extension
arms is necessary to direct the forces on the
posterior teeth as close to the center of resistance
as possible. This enables the mandibular spaces to
be closed while protraction of the mandibular arch
occurs. The mandibular incisors may be placed in the
ideal position prior to definitive surgical planning.

29. Surgical Correction of Skeletal
Discrepancy Followed by
Dental Compensation
The development of sophisticated imaging and surgical
planning software has opened the door for new
approaches to managing dentofacial deformities. In
some specific types of malocclusions such as Class III
and open bites, it may be possible to carefully analyze
and determine the ideal position of the skeletal bases.

30. The bony maxilla or mandible may be placed
in an ideal position in three planes without any attempt
to decompensate the respective teeth. Bone
plates are placed at the same time as the definitive
orthognathic surgery and are used to compensate
the teeth after a period of initial healing.
Panoramic radiograph obtained immediately after
surgery. Orthodontic mini-plates were implanted at
the zygomatic buttress and the mandibular body
during surgery
A and B, Facial photos and (C) cephalometric radiograph obtained 9 days after jaw
surgery. Patient showed a Class II profile and Class II denture with open bite. D–F, Her
mandible was maintained in the proper position using a surgical split and up-and-down
elastics at the canine regions. Facial swelling takes a little bit longer to resolve.

31. Complex tooth movements can also be considered,
which may include intrusive changes in the
posterior dentition as well as retraction and protraction
of targeted arches. Maxillomandibular elastics
can also be incorporated into the mechanical plan.
The principle of regional acceleratory phenomena
(RAP), by which metabolic activity in bone is significantly
enhanced, contributes to acceleration of
the compensatory tooth movements, significantly
reducing treatment time.
Seventeen days after surgery, when orthodontic treatment
started. Leveling of upper and lower dentition began using
0.016-inch nickel-titanium (Ni-Ti) archwires. The surgical splint
was placed at the mandibular posteriors and modified to an
occlusal splint by flattening the occlusal surface.

32. Moreover, patients can
undergo surgery at the beginning of treatment or
early in the orthodontics phase and do not have to
suffer through the progressively worsening esthetic
issues related to fully decompensating the dentition
Two months after surgery (lateral view). A, Rectangular nickel-titanium (Ni-Ti) archwires were engaged and
intrusion and distalization of maxillary molars and protraction of mandibular dentition were carried out. The
occlusal splint was discontinued at that time. B, Skeletal anchorage system (SAS) biomechanics are also
applied at this stage. The photo shows SAS biomechanics that were applied to the patient. In combination
with intrusion and distalization of maxillary dentition and protraction of mandibular dentition, the patient’s
Class II denture will be improved quickly.

33. (a and b) This patient presented with a Class III malocclusion on a Class III skeletal base characterized by moderate
maxillary retrognathism
and mandibular prognathism. (c to e) The maxillary and mandibular teeth had compensated by maxillary incisor
proclination and
mandibular incisor retroclination. Surgical maxillary advancement was considered in isolation because of the issues
related to mandibular
surgery, and surgery was planned to reposition the maxilla into an ideal position without decompensating the teeth,
instead using bone
plates to compensate the teeth after surgery. The goals of treatment were primarily related to positioning the skeletal
maxilla and mandible
ideally relative to one another. Bone plates would be placed simultaneously and would be used to move the maxillary
and mandibular teeth
to their ideal inclinations.

34. (f to h) Prior to surgery, no attempt was made to align the maxillary canines because this would further procline the
maxillary teeth. While Ni-Ti wires avoided these teeth, the mandibular curve of Spee was leveled by mandibular incisor
proclination, as this
was part of the treatment goal.
(i to k) Because there was still time before the surgery was scheduled, a passive, rectangular stainless
steel
wire was placed in the maxillary arch, and a 0.019 × 0.025–inch stainless steel wire was placed in the
mandibular arch.

35. Whereas the
pretreatment cephalometric radiograph (l) shows the compensations in the dentition with
proclined maxillary and retroclined mandibular
incisors, the immediate postsurgical cephalometric radiograph (m) shows the maxillary
dentition related in a Class II relationship and bone
plates placed in both arches. (n) The maxillary arch has been retracted to reduce the projection
of the maxillary dentition with bone plate
anchorage.

36. (o) The presurgical facial profile reveals the significant midface deficiency. (p)
The immediate postsurgical photograph shows a
significantly protrusive upper lip because the teeth have been set into a
significant Class II relationship (q to s).

37. (t to v) Initial traction commenced with an elastic chain from the bone plates to the canines with
simultaneous Class II
elastics. The occlusion corrected rapidly, and slight seating elastics then attempted to improve the
intercuspation.
(w to y) As the occlusion
settled, an intrusive spring attached to the bone plate on the maxillary right side was used to level a
slight occlusal plane cant.

38. (z to dd)
After treatment, the facial outcome included a significantly
improved midface projection, and the occlusal relationships
at debanding were
excellent.

39. Class III malocclusions with significant open bites
may now be treated by placement of appliances and
surgical repositioning of the jaw(s) to an ideal geometry.
Careful consideration must be given to the
impact of closure of the vertical dimension when
any intrusive movements have been calculated. The
observed speed of treatment with fixed appliances
following the surgery has made this an appealing
process to consider .

40. (a to e) This patient presented with a Class III malocclusion on a
Class III skeletal base characterized by moderate maxillary
retrognathism
and mandibular prognathism but the additional complication of
increased lower facial height with an anterior open bite.

41. (f)
The maxillary teeth were significantly crowded, and the maxilla was skeletally
narrow.

42. (g) The sequence of treatment and goals included
initially placing appliances on the teeth in a passive relationship (A). The maxilla would then be placed in a significant Class II relationship.
The advancement of the maxilla would consider the anticipated autorotation following intrusion and retraction of the maxillary posterior
teeth. Bone plates would be placed lateral to the maxillary molars, and vertically directed forces would be applied to the posterior teeth
from the bone plates. Simultaneously, elastics would be applied to retract the maxillary arch (B). When the open bite had resolved, retraction
of the maxillary arch would be refocused by applying a force through the center of resistance by attaching an extension arm to a rigid
rectangular wire (C).

43. (h to j) Fixed appliances and rectangular 0.018 × 0.025–inch stainless
steel wires were placed just before surgery, and
during surgery the maxilla was repositioned into a significant Class II
relationship. The patient functioned in the surgical splint for at least
2 to 3 weeks before active orthodontic tooth movement was initiated.
After 2 to 3 weeks, retraction of the maxillary canines began with
the use of bone plates as anchors.

44. k to m) Intrusive forces were added to the posterior teeth via
vertically directed forces applied to the posterior teeth.
(n to p) When the open bite had closed, extension arms were added to 0.019 × 0.025–inch
rectangular archwires to facilitate bodily retraction of
both arches.

45. (q and r) Pretreatment (q) and immediately presurgical (r) cephalometric
radiographs reveal the Class III open bite relationship.
(s) Immediate postsurgical cephalometric radiograph shows a Class II open
bite relationship with the increased vertical dimension. (t) Closure
of the open bite and reduction in facial height as well as Class II correction
are achieved rapidly by using the bone plates in the maxillary
and mandibular arches.

46. (u to z) After treatment. Significant improvement in facial
form and occlusion have been achieved in less than 12
months of treatment.

47. In some patients, third molar extractions must be
performed at least 6 months prior to definitive jaw
surgery, and these extractions provide an opportunity
for placement of bone plates to commence decompensation
of the dentition. Following definitive
surgery, if decompensation is incomplete, the bone
plates may remain and be utilized for the postsurgical
period, taking advantage of the RAP.
A, A preoperative
radiograph showing
full bony impaction on
the right. B,
Postoperative
radiograph of the
same patient, with an
outline of the third
molar visible.

48. Special Considerations in
Managing Class III Problems
Class III problems can present with either maxillary
retrognathism or mandibular prognathism (or
both), with over half of the white population presenting
with some degree of maxillary retrognathism.
Face profile
view and
occlusion
relationship
s
characterizi
ng a
skeletal
Class III
case
Skeletal Class ΙΙΙ may
be caused Α) either by
the maxilla; Β) or
by the mandible; C) or
by both jaws

49. It is important to appreciate that there has
been a historical trend to treat the majority of Class
III patients with maxillary surgery either in isolation
or combined with mandibular setback, even in the
presence of mandibular retrognathism. There are
some very important issues to consider when planning
surgical treatment for Class III patients .
A skeletal Class ΙΙΙ patient, whose face
improved following the
placement of a cotton swab behind the
upper lip; however, no balance
was achieved, and therefore, it was
inferred that the retrusion of the
maxilla and the protrusion of the
mandible are to blame

50. Issues to consider when planning surgery for Class III
patients

51. Growth and the Class III patient
The cephalocaudal gradient of growth describes the
fact that mandibular growth will probably continue
for longer periods even when maxillary growth
has diminished. This is particularly significant in
male patients.
Skeletal Class III with narrow alveolar housings unsuitable for
non-surgical camouflage

52. During this growth, it is important
for the orthodontist to monitor the magnitude and
direction of growth, because significant deleterious
dental compensations may occur.
The mandible grows less than the amount of overcorrection;
thus the mandibular incisors are proclined for the residual
overjet correction

53. This is particularly
relevant for mandibular incisor retroclination,
which in severe cases can influence the dimension
of the alveolar process above the chin, making future
decompensation problematic because the AP
bony dimension of the chin may be too thin.

54. Serial
superimpositions are recommended to determine if
unfavorable inclinations occur; if so, a fixed lingual
arch is recommended to maintain the mandibular
incisor position and arch length (Fig 17-20).
(a) In growing Class III patients,
often the mandibular incisors
compensate by retroclining significantly,
which affects the way that the chin
and alveoli remodel. (b) A lingual arch
is indicated in patients who exhibit
this growth change to maintain arch
length.

55. Annual
serial cephalometric superimpositions should be
evaluated to determine when growth has ceased;
only then should definitive surgery be
considered.
(A and B) Male subject with untreated Class
III malocclusion. Observation
interval: 6 years, 2 months.

56. It is also important to recognize that many Class
III patients’ mandibles grow asymmetrically, and the
chin is often deviated to the left. This is important
to appreciate because if clinicians do not want to
operate on the mandible for some of the aforementioned
reasons, it may be necessary to compensate
the dentition in the mandibular or maxillary arch to
achieve a satisfactory occlusion.

57. It is possible to modify
the maxillary midline by 1 to 2 mm without appreciable
deviations, but temporary anchors should
be considered to address mandibular midlines if the
midline deviation is greater than 2 mm and the clinician
wishes to avoid operating on the mandible.

58. It has been reported that early surgery on the
mandible can be considered if significant psychologic
impact is a concern. The likelihood of repeat surgery
is high, but supplementation of a minor condylectomy
or condylar shave has been suggested to
prevent further overgrowth if required.

59. Orthodontic mechanotherapy
It is important to take a set of progress models just
prior to surgery to assess the anticipated occlusalrelationships.

60. At initial banding, the mandibular
brackets must be sufficiently low on the labial of
the teeth to enable adequate vertical overlap to be
achieved at the time of surgery. In addition, it is a
significant advantage to proceed to surgery with a
mild mandibular Bolton discrepancy.

61. This will ensure that incisor overlap is encouraged, particularly in the
event of any minor postsurgical occlusal changes.
The combination of bracket positions and mandibular
Bolton discrepancy will act as a type of escape
valve in the event of unexpected changes.
Segmental orthognathic surgery for Bolton discrepancy
correction
Oral and Maxillofacial Surgery Cases 4
(2018) 108e114

62. Slight interproximal
enamel reduction may be considered in
the mandibular arch to achieve the desired Bolton
discrepancy. Some clinicians like to open spaces distal
to the maxillary lateral incisors to achieve the desired
outcome, but these spaces may be difficult to
close in some circumstances.

63. Biomechanics of Class III surgical
correction
There are reported significant changes in muscular
force after correction of the Class III relationship.
These changes have been compared to changes observed
in long-faced patients when facial heights
are adjusted toward normal dimensions.

64. When the
maxilla and mandible are repositioned, even to effect
reduction in mechanical advantage according
to lever principles, it appears that the relatively
larger mandibles are accompanied by larger muscle
masses; therefore, geometry alone does not explain
changes in possible masticatory efficiency.

65. Stability of mandibular setback
The stability of mandibular surgical setback is generally
unpredictable, and special caution must be taken
by the surgeon to ensure that the proximal segment
is not rotated back during fixation, although
this is difficult to achieve on a routine basis.

66. Special Considerations in
Managing Open Bites and
Long-Face Problems
Growth and long-face problems
Young children with long faces are often identified
early in their preadolescent years. These children
continue to develop in unique ways, often expressing
significant vertical growth changes in the maxilla
and mandible.

67. The etiology of these problems
has been the subject of controversy, with theories of
form and function interactions such as diminished
muscle force, aberrant obstructive respiration, and
nonnutritive oral habits.

68. Unlike children with normal
facial height, growing children with long faces
do not exhibit the increased ability to deliver
larger forces through their teeth as they progress
through puberty. However, facial height changes
appear to be well established before the magnitude
of muscle forces diverge.
normal
facial height

69. Increased nasal airway resistance
has been shown to be associated with long faced
children, and changes in airway dimensions by
maxillary expansion or adenoidectomy have been
shown to have short-term effects on facial growth
direction. Very little high-level evidence suggests
a significant role of aberrant function on facial growth changes.
hypertrophied tonsils and/or adenoids (Fig. 6), open-bite, crossbite, excessive anterior faced height (Fig. 7),
incompetent lip posture, excessive appearance of the maxillary anterior teeth and gums (Fig. 8)

70. The role of genetics in determining orofacial
form is complex, and efforts are being focused on
attempting to comprehend facial growth changes
from the underlying genome. No definitive conclusions
have been forthcoming, and the clinician is
still confronted with the patient who presents with
minimal vertical overlap and a slightly long face in
preadolescence.
(Fig. 9), V-shaped palate (Fig. 10), and venous pooling under the eyes (Fig. 11).

71. The treatment usually progresses to
a satisfactory conclusion, yet in the postadolescent
period, significant vertical growth continues until
late adulthood, often resulting in maxillary vertical
excess and anterior open bite. These growth changes
do not seem to be consistent, and various components
of the face may contribute in a range of
magnitudes to the final outcome.
Early treatment maximizes the success of corrective
orthodontics and orthopedics (Fig. 12).

72. The implications for the orthodontist are significant
in that treatment, which may include maxillary
and mandibular surgery, should be delayed until
growth has ceased. Similar to the strategy presented
for Class III patients, annual serial cephalometric
superimpositions should be evaluated for stability
before definitive surgical planning is undertaken.
A woman in her early 20s shown before and after orthognathic surgery for a long face growth
pattern . Reconstruction also included segmental maxillary osteotomies with arch expansion.
This approach also widens the nasal cavity to decrease intranasal airway resistance and
improve breathing.

73. The reduced occlusal
forces dictate that postsurgical orthodontics should
be minimized in both magnitude of tooth movements
and treatment time to minimize any extrusive
side effects, which inevitably accompany most
orthodontic tooth movement.
A teenage girl with a long face growth pattern is treated with a comprehensive orthodontic and surgical approach. After orthodontic (dental) decompensation,
her surgical procedures included a maxillary Le Fort I osteotomy in segments (vertical intrusion, horizontal advancement, and arch expansion) bilateral sagittal
split osteotomies of the mandible (horizontal advancement and counterclockwise rotation); oblique osteotomy of the chin (vertical shortening and horizontal
advancement); and septoplasty, inferior turbinate reduction, and recontouring of the nasal floor. A, Frontal views in repose before and after treatment. B, Frontal
views with smile before and after treatment. C, Oblique facial views before and after treatment. D, Profile views before and after treatment. E, Occlusal views
with orthodontics in progress and then after surgery. F, Articulated dental casts that indicate analytic model planning. G, Lateral cephalometric views before and
after treatment

74. Orthodontic mechanotherapy and
sequencing
Patients must be prepared carefully for surgery, and
all alignment and leveling should be complete before
proceeding to surgery. The only exception is
open bite patients who exhibit multileveled occlusal
planes, when surgical leveling of the occlusal plane
is planned .

75. (a to e) This adult patient presented with an anterior open bite with normal
tooth display on smiling. A surgical correction was
planned to segment the maxilla and intrude the posterior teeth. The maxilla
would be advanced slightly to address the issues associated
with the mandible rotating forward.

76. (f to i) The maxillary arch was aligned in two levels, with care taken to open
spaces distal to the lateral
incisors and prepare sufficient space between the roots for the osteotomy,
minimizing the likelihood of root damage. The Bolton discrepancy
was carefully checked, and the mandibular anterior brackets provided
adequate room for the teeth to overlap and establish a positive
vertical overlap at the time of surgery.

77. (j to n) After treatment, the final occlusion and
esthetic outcome were pleasing.

78. From the orthodontist's perspective,
all third-order corrections, marginal ridge
discrepancies, and root second-order corrections
must be achieved before surgery. Clinicians should
progress through to large-dimension rectangular
wires such as 0.021 × 0.025–inch TMA wires in both
arches to achieve full expression of the preadjustedappliance

79. It is also important to ensure that when progress
models are articulated, either in one piece or segmented
as required, that the models “snap” together
at the time of surgery (Box 17-2).
Progress check for presurgical models
in open bite patients

80. It is possible that
the surgeon and orthodontist will prescribe spot
grinding to achieve this goal. Placement of the mandibular
brackets must provide sufficient clearance
for the maxillary incisors so they are not locked into
a complete vertical overlap.
It is critical to take progress records before scheduling surgery. (a to c) In this case,
progress models reveal that a Class I canine
relationship cannot be achieved without an edge-to-edge occlusion. A decision has to be
made to open up space for larger lateral incisors
or to perform interproximal reduction on the mandibular anterior teeth. It is important for
the arches of open bite patients to fit precisely
at the time of surgery to minimize postsurgical orthodontics.

81. Moreover, it is important
to create a mild mandibular Bolton deficiency
by either interproximal reduction or opening spaces
distal to the maxillary lateral incisors (Fig 17-22).

82. Stability of surgical management
in long-faced patients
It is extremely difficult to guarantee stability of
open bite treatment in children because of the uncertainties
associated with postadolescent growth.
Children with a history of nonnutritive sucking habits
appear to enjoy success if the habit is ceased in a
timely manner.

83. Surgical correction of long-faced patients has resulted
in a demonstrable increase in bite force magnitude.
The theory for this outcome has been
attributed to biomechanical changes in the mechanical
advantage afforded by the reoriented muscles
of mastication.
The mathematic modeling
components
considered by Throckmorton et al,
who attempted to
predict changes in muscle force.

84. The changes in bite force for other types of skeletal
corrections are not so predictable from biomechanical
models with patients demonstrating similar,
increased, and decreased bite force following mandibular
advancements and setbacks and maxillary
inferior repositioning.
mandibular advancement using sagittal split
osteotomy and restoration of correct occlusion
The bilateral sagittal split ramus
osteotomy for mandibular setback

85. It appears that
generally it is difficult to determine the outcome of
orthognathic surgery on bite force. Moreover, there
is some weak evidence that an increase in the number
of occlusal contacts and bite force magnitude
may contribute to enhanced stability of orthodontic
treatment.

86. Stability of open bite treatment in adolescents
or adults with surgical and nonsurgical treatment
modes has been the subject of systematic reviews.
It appears that both modes of treatment are equally
effective (or ineffective) if success is measured by
attainment of a complete vertical overlap.

87. Significant
changes in the vertical overlap are observed in
both groups, and caution must be taken in offering
patients a guarantee of success unless other factors
such as change in gingival display during smiling, lip
incompetency, and improvement in the soft tissue
facial profile are added into the equation.

88. Special Considerations in
Managing Skeletal Asymmetry
The management of skeletal asymmetry is complex.

89. Skeletal asymmetry is present, to some extent, in
all individuals. There appears to be a trend toward
a significant directional asymmetry in the craniofacial
region, with most adults exhibiting right-sided
dominance or chin deviation to the left.

90. These
findings have been reported to be age and sex specific,
with the average younger child exhibiting left sided
dominance in prepubertal years, equivalence
at or around puberty, and right-sided dominance
in adulthood.

91. Janson et al have suggested that
variation in size of the right and left hemimandibles
of more than 3 to 4 mm may be considered to be of
significance and may require further follow-up.

92. The etiology of facial asymmetry is complex and
may include:
• Functional shifts of the mandible associated with
occlusal interferences
• Craniofacial anomalies such as hemifacial microsomia
and plagiocephaly
• Trauma to the condyle and altered function
• Condylar hyperplasia
• Hemimandibular hyperplasia
• Degenerative conditions of the joints such as rheumatoid
arthritis and other autoimmune diseases
• Ankylosis of the temporomandibular joint secondary
to infection
• Hemifacial atrophy disorders

93. Contemporary imaging techniques are now available
to add significant value to the diagnosis and
management of facial asymmetry. The important
issues to comprehend are consistent with other dentofacial
deformities except that the interactions between
hard and soft tissues are even more complex
in three dimensions.

94. The goals of presurgical orthodontics
are to remove dental compensations in all
three dimensions followed by surgical treatment to
idealize the relationships of the skeletal structures
Asymmetries present
complexities
in compensations that are best
envisioned
by 3D imaging techniques.
Correction
of these complex
compensations
is essential to maximize the
impact of the
skeletal correction.

95. Significant effort has been directed to
development of software to assist with planning
and facilitating surgical procedures .
The surgical movement of leveling
and advancing the maxilla and rotating
and advancing the mandible can be
planned out on the computer, and splints
can be constructed to assist in positioning
during surgery. (a) Asymmetry before surgery.
(b) After surgery.

96. Maxillary expansion
Maxillary arch expansion has been performed in
children for more than a century. Although doubt
was originally cast over the suggestion that Dr E.
H. Angell had succeeded in separating the maxilla
along the midpalatal suture, it has become a routine
procedure to manage crowding and posterior
reverse articulation (also known as crossbite)
relationships.

97. It is important to recognize that like AP skeletal
problems, transverse maxillary deficiency is also accompanied
by transverse dental compensations. The
mandibular teeth tend to tip lingually and the maxillary
teeth buccally to a variable degree.
Clinical
manifestationoftransverseproblems.(A)Idealbuccalocclusion,(B)insufficient
buccaloverjet, (C) transversecompensation,and(D)openlingualocclusion.

98. Skeletal expansion is usually achieved in the child
by separating the midpalatal suture, and expansion
progresses until slight overexpansion has been
achieved. This is to account for the anticipated relapse
demonstrated in many studies and the need
to address the transverse compensations in the dentition.
A) Frontal, severe upper anterior crowding
with lack of space for the left and right upper
lateral incisors and the right upper canine
tooth; B) frontal with opening of the
diastema between the upper central
incisors;
C) upper occlusal showing the reduction of
the upper arch transverse distance due to
maxillary atresia and upper
lateral incisors with lingual inclination; and
D) upper occlusal after the opening of the

99. As the child progresses beyond puberty, the
circummaxillary sutures become more interdigitated
and continue to increase in complexity throughout
adulthood. These changes make it more difficult,
if not impossible, to achieve skeletal transverse
changes in the adult.
Maxillary transverse deficiency with excessive
curve of Spee and open bite deformity, which require
segmental Le Fort leveling surgery to correct.

100. Many adult patients present with dentofacial deformity
that may be characterized by maxillary skeletal
narrowing independently or in combination
with other skeletal problems.

101. The clinician has the
choice of surgically assisted maxillary expansion or
a segmental Le Fort I procedure.
The surgically assisted rapid palatal expansion (SARPE) is a procedure
designed for skeletal transverse widening of the basal maxilla, the
palate, and the dental arch.
The widening itself is done with either a tooth born or bone born
distraction device in the days following the osteotomy.
A tooth borne expansion device is fixed to at
least two teeth on either side of the palatal
osteotomy
A bone borne device is fixed to the palate on
either side of the palatal osteotomy with screws
or pins.
The expansion device is activated to assure that
bilateral symmetric expansion occurs. The
device is then deactivated (returned to starting
position) prior to wound closure.
Various types of osteotomies have been described to facilitate
maxillary and palatal expansion. Today, usually a subtotal Le Fort-I
osteotomy (without downfracture) and a sagittal osteotomy of the
maxilla and palate either on one or both sides of the septum is
performed

102. Expansion and retention
After a suitable latency period, the palate is distracted at a rate of 0.5 -1.0 mm per day.
During the distraction phase, a diastema will form between the two incisors (at the
osteotomy site). Movement of the teeth into the regenerate will occur spontaneously
unless the teeth are prevented from doing so by orthodontic appliances.
After reaching the desired expansion the device is left in place to retain the expansion
and to allow for bone consolidation for at least 3 – 6 months before removal. Even after
removal of the distraction device, it may be necessary to stabilize the expansion with an
orthodontic appliance or an acrylic splint for an extended period of time

103. Upper view illustrative of segmental maxillary osteotomy:
A) osteotomies between canines and premolars; B)
osteotomies between laterals and canines; C) osteotomy
between central incisors.
Segmental Le Fort I osteotomy is a surgical technique that is commonly
used to correct maxillary transverse discrepancies up to 6 - 7 mm in adults

104. of the maxilla in four mobile segments. Vertical interdental
osteotomies were implemented between the maxillary lateral
incisors and the canines. Two horizontal osteotomies,
parallel with the septum were performed to expand the maxilla
transversally. Following the osteotomy, the maxillary
segments were anteriorly repositioned and connected to
the mandible in the correct occlusal relationship. The
mandibular and maxillary arches were wired together and
acted as a unit, rotating around the condylar heads.
A LeFort I osteotomy was performed with segmentation
Case report
SEGMENTAL LEFORT I OSTEOTOMY FOR TREATMENT
OF A CLASS III MALOCCLUSION WITH
TEMPOROMANDIBULAR DISORDER

105. SARME for planned for the
correction of posterior crossbite. HYRAX expansion
device was inserted and surgical expansion of upper
maxillary arch was performed [Figure 4]. The patient was
called after 1 week for suture removal [Figure 5]. The
protocol for HYRAX activation was three-fourth-turn on
the first postoperative day, followed by one-fourth-turn in
the morning and another one-fourth-turn in the evening.
Overcorrection of posterior cross bite was achieved in
about 3 weeks. The HYRAX screw was kept passive as a
retainer for about 5 months.
(a-b) One week after surgery(a-b) Surgically assisted rapid
maxillary expansionCorrection of transverse maxillary deficiency
and anterior open bite in an adult Class III
skeletal patient

106. Differences between surgically assisted maxillary expansion and
segmental Le Fort I maxillary expansion

107. The surgically assisted expansion requires an additional
procedure with a large maxillary expansion device
fitted to the maxillary arch prior to placement of
edgewise appliances. Segmental Le Fort I surgery
may be performed at the same time as other definitive procedures.
Clinical situation before treatment After insertion of four mini-
implants and bonding of
lingual brackets
After surgigally assisted rapid
maxillary Expansion 14 NiTi
archwire is inserted
Clinical situation before (left) and after (right) SARME:
basal maxillary expansion and palatal tipping of
Clinical situation before treatment

108. The choice of surgical procedure
may be based on the surgical preference of the surgeon
or orthodontist, the goals of treatment, the
need for presurgical extractions (eg, third molars),
and cost. It appears that both procedures are equally
stable (or unstable), being at the lower end of the
hierarchy of stability as outlined by Proffit et al.

109. Surgically assisted maxillary expansion
Surgically assisted maxillary expansion can be considered
in adult patients with transverse skeletal
narrowing in isolation or those with more complex
skeletal problems who require other general anesthesia
procedures prior to placement of fixed orthodontic appliances.

110. The appliance is either cemented
to bands on the posterior teeth or attached to
the lateral palatal walls using temporary anchorage
devices. Early studies do not demonstrate any significant
advantage in the outcome of the skeletally
anchored expander, although it could be placed at
the time of the osteotomy.
The surgically assisted rapid palatal
expansion is a 2-segment
LeFort I without the downfracture to
correct the transverse width
discrepancy by a transpalatal distraction.
Note that the osteotomy at the
lateral buttress must be well designed
so as to interference. A small
wedge may be resected to allow
expansion

111. An osteotomy is performed in the maxilla with
variations in clinical protocols ranging from complete
lateral corticotomy of the maxilla toward the
piriform aperture to separation of the midpalatal
suture to disarticulation at the pterygoid plateS .
The type of osteotomy that is
performed to assist in
surgically assisted
rapid maxillary expansion
varies depending
on the clinician.

112. It is recommended that the surgeon activate
the jackscrew at least 5 mm at the time of surgery
to ensure that the maxilla is truly disarticulated
so that symmetric expansion can take place.
(I) Paramedial osteotomies from
posterior nasal spine to a point
posteriorly to the incisive canal.
(II) Osteotomies from the piriform
rim to the
pterygomaxillary junction. (III)
Osteotomies and separation of
the pterygoid
fissure.
Clinical intra- and extra-
oral manifestations of
maxillary transverse
deficiency (MTD).

113. The expansion procedure progresses along the
protocols of distraction osteogenesis for 4 to 5 days
after surgery, with two activations per day, until the
desired expansion is achieved.
Before surgically assisted rapid palatal expansion(SARPE):Patient with agenesis of the
upper lateral incisors and unilat-eral posterior crossbite(A);narrow arch and Hyrax appliance
cemented(B);immediately after expansion protocol: frontal view(C)and occlusal view(D)

114. Similar to expansion
in children, expansion is ceased when the maxillary
arch is overexpanded to account for relapse and removal
of transverse compensations. It is important
to observe a large diastema developing between the
central incisors and inform the patient about the necessity
for excellent oral hygiene immediately adjacent
to the central incisors.
Intra-
oralviewsoftheclosureofthe
diastema:6monthsaftersurg
icallyassistedrapidpalatalex
pansion(SARPE)(AandB);cl
osureofthediastema:8mont
hsafterbonegrafting(CandD)

115. The sulcular epithelium
will be exposed as the teeth separate (Atherton’s
patch), and if symmetric expansion is occurring, the
sulci will be equally exposed .
It is important to observe
equal amounts of sulcular
epithelium
being exposed on both
central incisors during
expansion
(arrows). This exposure is
known as Atherton’s patch
and indicates
that the expansion is
proceeding symmetrically.

116. A complication may occur during activation that
is not encountered as frequently in children. As a
consequence of the significant mobility in the palatal
segments combined with the goal of placing the
screw deep in the palate to direct forces closer to
the center of resistance of the maxilla, the appliance
may experience significant flexing, which may result
in binding of the screw .
“Bone
Anchored”
Surgically
Assisted Rapid
Maxillary
Expansion: A
scientific and
clinical
evaluation.

117. This is a difficult
problem to overcome because it will probably
require removal and redesign to a more superficial
depth. Although less than ideal biomechanically,
this may be required to ensure that the screw functions
adequately.
Placement of the expansion screw in surgical expansion
patients may be problematic if placed too high in the palatal
vault.
The extreme flexibility of the osteotomized segments may
result in
significant flexure not seen in pediatric patients, and this
may bend
the appliance, causing the screw to bind. This is extremely
disappointing
for the clinician and the patient because often the appliance
will have to be removed and remade with the screw placed
more superficially.

118. The biomechanics of maxillary expansion have
been studied in finite element models with and
without surgery, and the variations in osteotomy design
add confounders to the predictive modeling.
Naturally, there are greater translatory movements
of the palatal halves.
Pre-treatment intraoral photographs showing
transverse maxillary deficiency and posterior
crossbite. A. Frontal view B.
Occlusal view C. Cephalogram(lateral) D.
Cephalogram(PA).
Tent screws for expansion. A. Four tent screws were
inserted prior to the osteotomy surgery under local
anesthesia. B. Impression of
the upper maxillary arch was taken for the appliance.
Tent screw(Tent screw, Neobiotech, Seoul, Korea).
A. Lateral view. B. Occlusal View. Tent screw has a
hole for the cover screw.
Adaptation of the customized palatal expander. A. The
patient underwent a bilateral osteotomy and splitting of
the midpalatal
suture and the appliance was placed on the palatal
vault under general anesthesia. B. panoramic view
after surgery.
Surgically assisted rapid palatal expansion with
tent screws and a custom-made palatal expander:
a case report

119. The appliance is usually left in
place for at least 3 to 4 months to provide time for
consolidation of the osteoidlike tissue. The expander
is then removed and replaced with bands and a
0.032 × 0.032–inch hinge cap palatal attachment
with a horseshoe palatal arch to retain the expansion
while alignment procedures are performed.
the tooth-borne expansion device.
Intraoperative view of the Le Fort
I osteotomy line.
Intraoperative view of the interdental separation.

120. (a) Following active expansion,
the screw can be tied off with a segment
of brass wire (arrow) to prevent it from
turning back. (b) The expander is left in
place for 4 to 6 months before removal
and placement of a hinge cap palatal arch,
an essential retention mechanism.

121. A round 0.032-inch stainless steel palatal arch
provides enough rigidity yet enables pure crown
tipping palatally to remove the previously compensated
maxillary molars .

122. An adult patient presents with
a primary complaint of irregular teeth. (a
to e) The maxilla is observed to be narrow,
and the dental relationships exhibit a
posterior reverse articulation and lingually
compensated posterior teeth in the mandibular
arch.

123. (f) Surgery is performed and
the appliance activated. (g to k) The maxillary
arch has been expanded and the teeth
aligned to a pleasing esthetic and functional
outcome. The mandibular arch compensations
have also been addressed.

124. A similarly
fabricated mandibular lingual arch may also be used to
tip the lingually compensated mandibular posterior
teeth to their correct positions.
A 12-year-old female patient: a) with end on molar
relation on right side; b) lingually tipped mandibular
first molars bilaterally; c,d) posterior scissor bite on
left side and deep bite.
: Insertion of the 3D Lingual arch immediately after the
extraction of the second premolars. [Table/Fig-3]: Holding
arch with anterior bite plane in the upper arch.
a) Lower arch was bonded along with the 3D lingual
b) removed the 3D lingual arch after the correction of molar uprighting.
Three-Dimensional Control
on Lingually Rolled in Molars
using a 3D Lingual Arch
Journal of Clinical and Diagnostic Research. 2017 Aug, Vol-11(8): ZR01-ZR03

125. A repositioning osteotomy
of the maxilla is required. Usually in these
circumstances, open bite patients are leveled with
fixed appliances, avoiding the need for segmental
osteotomies and the associated periodontal and
root transection risks.

126. Moreover, surgically assisted
expansion can provide additional space for irregular
teeth that may have necessitated tooth extraction
or possible periodontal compromise if the crowding
was treated with dentoalveolar expansion.

127. Segmental maxillary expansion
Segmental surgery of the maxilla may be required
to address transverse discrepancies of the maxilla
or to ensure that stepped occlusal planes are maintained.
The design of the osteotomy depends on the
specific requirements of the patient. The magnitude
of relative expansion of the canines, premolars, and
molars will influence the type of osteotomy, ranging
from a two- to four-piece maxillary osteotomy .
Transverse stability in two- and three-piece segmental
Le Fort I osteotomy.

128. The design of the
segmental
osteotomy depends
to a
large extent on the
desired expansion
needs. If more
posterior expansion
is required than
anterior expansion,
then a two-piece
osteotomy
may be required. If
there are steps in the
occlusal plane, it is
possible that this will
influence where the
osteotomy is
performed.

129. In addition, the leveling of the stepped occlusal
planes may be simultaneously achieved during
expansion. Significant increase in intercanine width
may not be possible with segmental expansion, so
when it is required, surgically assisted expansion
should be considered; there is a fundamental difference
in the response to expansion between these
two approaches .

130. The nature of
expansion varies
between surgically
assisted
rapid maxillary
expansion (more
anterior) (a) and
two-piece
Le Fort I expansion
(b), as indicated
diagrammatically.

131. It is important to ensure that the patient is prepared
adequately with proper coordination of the
arch forms prior to surgery. It is necessary to coordinate
the maxillary arch form from the ideal
dimension of the mandibular archwire.

132. The necessary
V-bends or steps should be placed between
the brackets associated with the osteotomy site so
that the segments of the arch are aligned to the
complete mandibular arch.

133. Furthermore, adequate
space must be developed between the roots to facilitate
the osteotomy. This may be achieved by diverging
the roots or opening space with compressed
coils. Divergence of the roots may be achieved by
either placing adjustment bands in the wires or
bonding the brackets .

134. Creating space for
segmental
osteotomies is
essential to minimize
the risk to tooth
roots during surgery.
This may be
achieved with either
push coils (a and
b) or placement of
artistic bends (c) or
bracket angulations
(d) to diverge the
roots. Brackets will
then have to
be rebonded after
surgery.

135. Brackets will then
have to be rebonded after surgery. Extended postsurgical
orthodontics in open bite patients may be
problematic because of the associated extrusive side
effects (as discussed earlier), so in these patients minor
tooth inclination corrections should be planned
along with minimal root divergence.

136. The model surgery must overexpand the maxillary
arch in segments by at least 10% to 15% to compensate
for the significant relapse that is to be anticipated.
.
Segmental surgery design (a) To expand the intercanine
width osteotomy is performed between canines and lateral
incisors. Note the four incisor teeth in the anterior
segment are almost in a straight line (black arrows). (b) If
the intercanine width is
appropriate the interdental osteotomy can be positioned
between the canine and first premolar. (c) Amidline
osteotomy is an option
if the transverse deficiency is due top a ‘V’ shaped arch
(d) A unilateral cross bite can be corrected with a
unilateral osteotomy.

137. Following segmental surgery, the patient
will require an occlusal wafer wired to the maxillary
teeth for at least 4 to 6 weeks to minimize relapse
Surgical splint in maxillary arch. Mouth opening exercise should be taught for oral
function rehabilitation using some elastics. Mouth opening enough for functional
recovery and forthcoming orthodontic treatment should be obtained.

138. The wafer can then be removed and a low–load
deflection continuous maxillary archwire placed
together with a palatal arch. It is possible to activate
the palatal arch to narrow or broaden for fine
adjustments. Minor irregularities in levels and arch
form can then be re-evaluated before proceeding to
finishing procedures.
(a–e) Intra-oral views demonstrating the
extent of the AOB. An increased overjet is
also evident, with spacing in the upper arch
as a result of previous loss of premolars
(a–e) Segmental mechanics used to
create separate leveling in the upper
arch prior to impaction of the segments
(a–e) Post-operative intra-oral occlusal
views. An acceptable Class I buccal and
incisal relationship was achieved. Full
space
closure was accomplished
Three-part bi-maxillary osteotomy: a
case report involving resorbable plates
ournal of Orthodontics, Vol. 32, 2005, 75–84

139. Reference: