SINCE 1971 EMPOWERING DOCTORS AND STAFFS TO ATTAIN GREATER SUCCESS THROUGH EDUCATION AND KNOWLEDGE
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SINCE 1971 EMPOWERING DOCTORS AND STAFFS TO ATTAIN GREATER SUCCESS THROUGH EDUCATION AND KNOWLEDGE |
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Orthodontic
management of long face syndrome. General
Dentistry, 1997 Vol. 45, No 6, pp. 568-572.Dr. Jim Prittinen,DDS Abstract Management
of the vertical dimension of occlusion is one of the most difficult aspects of
orthodontic therapy. Patients with
long face syndrome are prone to develop more severe symptoms during orthodontic
treatment. This article describes a
cephalometric measurement (the MM angle), which is useful in the diagnosis of
long face syndrome. It also gives
treatment options designed to minimize the expression of long face syndrome
characteristics. Long face syndrome is among the most
difficult problems encountered in the practice or orthodontics.
And, unless orthodontic treatments are carefully monitored and
controlled, patients with long face syndrome risk developing even more severe
characteristics of the syndrome.1
Characteristics of long face syndrome include excessive eruption of posterior
teeth, large increases in vertical dimension, dental and skeletal open bite, and
a retrusively positioned mandible – all of which have been major causes of
poor orthodontic results.2
Monitoring for
long face syndrome throughout treatment is an important part of the proper
therapy for patients who are at risk. One
of the best ways to measure whether long face syndrome characteristics exist is
to measure the cephalometric MM angle – the angle between the palatal plane (ANS
– PNS) and the mandibular plane (Go-Gn) (Fig. 1). The average MM angle is 26°. Larger MM angles (more than 32°)
warn the clinician that further increases in this angle may result in an
increase in long face syndrome characteristics.3
Frequent (every six to ten months) cephalometric radiography, to monitor changes
in the MM angle, is necessary for patients who are at risk of developing
characteristics of long face syndrome. Treatment alternativesThere
are various treatment modifications that reduce the likelihood of the expression
of long face syndrome characteristics. Premolar extractions have proved to be effective and should
be carefully considered. Also,
closing space by moving molars forward reduces the vertical dimension of
occlusion. This permits the
mandible to rotate into a more closed position along its arc of closure,
resulting in a more forward positioned chin and a smaller MM angle.4
Conversely, procedures that result in bite opening, such as arch expansion and
advancing teeth, should be avoided.
Long face syndrome also can be controlled by minimizing the extrusion of
posterior teeth, particularly maxillary molars.
They extrude more easily than mandibular molars for two reasons: the
masticatory muscles restrict the posterior mandibular teeth more than their
maxillary counterparts; and the thin cortices and trabecular bone of the maxilla
provide less resistance to movement than the thick cortices and more dense
trabeculae of the mandible.5-7
Use of arch wires – Careful
force application helps to control extrusion of posterior teeth.
Also, using arch wires with a low load-deflection rate greatly reduces
tooth extrusion. (The
load-deflection rate of an arch wire is defined as the force that an arch wire
produces per unit of activation.) Two
characteristics, size and composition of the wire, contribute to the wire’s
load-deflection rate.8
Every wire and bracket system exerts extrusive force upon the teeth, but these
extrusive forces are expressed differently in different patients.9
Figure 2 show the relative load-deflection rates of commonly used arch wires.10
Since patients with long face syndrome have relatively weak masticatory muscles,
high load-deflection rate arch wires (e.g., stainless steel) easily overpower
their masticatory muscles, resulting in posterior tooth extrusion.
Patients who do not have long face syndrome generally have stronger
masticatory muscles, so the same high load-deflection rate arch wires will not
cause as much posterior tooth extrusion in such patients.
As a rule, stainless steel arch wires should be avoided in patients with
long face syndrome. Leveling and
aligning can be done with low load-deflection rate arch wires, such as those
made of nickel-titanium. However,
these arch wires are too flimsy to be used for space closure and other
mechanics. An intermediate
load-deflection rate arch wire is needed for these procedures.
TMA, a titanium-molybdenum alloy arch wire (Ormco, Orange, CA), is firm
enough for these mechanics, and its load-deflection rate is low enough to
prevent unwanted molar extrusion.
Anchorage enhancement is another way that maxillary molar extrusion can
be prevented. The enhancement can be accomplished with transpalatal arches
(TPAs). 11 TPAs are fabricated by
attaching a heavy wire (.036 ss), with a 5 mm diameter loop at the midline, that
has been secured to the mesiolingual surfaces of the maxillary molar bands.
(Fig. 3). When a patient talks or
swallows, the tongue exerts a palatally directed force against the loop.
This, in turn, helps to overcome the extrusive force of most orthodontic
mechanics.11
(Molar crown rotation and root torque can also be accomplished with the
use of TPAs) The more a patient exhibits the characteristics of long face
syndrome, the more critical is the need to use a TPA.
High –pull headgear -
High-pull headgear (HPHg) prevents maxillary molar extrusion even more
effectively than a transpalatal arch. In
patients with long face syndrome, the masticatory muscles do not support the
palate. This lack of muscular
support causes the posterior half of the palate to tip downward and mesially,
carrying the maxillary molars downward and mesially as well (Fig. 4).
12, 13 The direction of force
applied by the HPHg helps prevent this palatal tipping (Fig. 5).
Clinically, it has been demonstrated that 14 hours of HPHg wear per day
eliminates most maxillary molar extrusion.
HPHg is also used for Class II correction.
Fourteen hours of HPHg wear per day helps correct Class II discrepancies
in two ways: the maxillary restriction common to all types of headgear and
repositioning appliances occurs, and probably more important, the restriction of
maxillary molar eruption allows the mandible to rotate into a more forward
position as it grows.14
A number of clinicians, including Terel Root in the 1970s, recognized the
importance of maxillary molar vertical restriction as a method of Class II
correction. According to Root, “A high-pull facebow is used in
individuals in whom increases in vertical dimension are to be avoided.
As a growth guidance appliance, it (HPHg) can decrease vertical
development of the maxilla, thereby allowing for autorotation of the mandible,
and maximizing the horizontal expression of mandibular growth.”15
Twin Block appliance – Using
a twin block appliance is an alternative method of Class II correction.
It consists of repositioning the mandible by using removable maxillary
and mandibular splints with acrylic ramps.
The ramps measure 5 mm to 8 mm in thickness in the premolar region. This impinges on the patient’s freeway space, which, in
turn, results in increased masseter tension.
This tension not only restricts vertical descent of the maxillary
posterior teeth, but also produces a relative intrusion of the posterior aspect
of the maxilla in growing patients.16
This phenomenon, which is called the bite-block effect, provides excellent
vertical control. Although
long-term studies documenting the results of this treatment are not yet
available, the early results are promising.
Figure 6 shows the cephalometric superimposition of a long face syndrome
patient. Her Class II malocclusion was corrected with twin block.
Notice the excellent vertical control, highlighted by a 2°
decrease in the MM angle. The MM
angle was controlled due to the bite-block effect.
No further tipping of the PNS occurred during this treatment phase.
The next phase of treatment involves fixed appliance therapy.
Low load-deflection arch wires and a transpalatal arch will help control
the MM angle. Premolar extractions
will help reduce crowding, dentoalveolar protrusion, and the MM angle. Summary and conclusionsLong
face syndrome has been recognized for many decades as one of the major problems
in orthodontic treatment. A number
of clinicians and lecturers warn against the indiscriminate use of heavy forces
in patients in whom adverse side effects, such as long face syndrome, may be
expressed. One of the most
important duties of the orthodontic clinician is to avoid counterproductive side
effects (excess molar extrusion) even if their probability of expression appears
low.17
Orthodontic clinicians must be aware of the symptoms of long face
syndrome, and, even if a small chance of excess molar eruption exists, must use
a mechanical system that minimizes this side effect. Dr. Prittinen practices general dentistry in Virginia, Minnesota, and is also an orthodontics instructor for the United States Dental Institute. Address correspondence to: James R. Prittinen, DDS, 216 North Fifth Avenue, Virginia, and MN 55792. References: 1. Graber T, Swain B. Orthodontics: current principles and techniques. St. Louis: C.V. Mosby Co.; 1985:81:408. 2. Proffit W. Contemporary orthodontics. St. Louis: C.V. Mosby Co.; 1986:86:161. 3. Bennett JC, McLaughlin RP. Orthodontic treatment mechanics and the pre-adjusted appliance. Aylesbury, England: Wolfe Publishing; 1993:123. 4. Bennett JC, McLaughlin RP. Orthodontic treatment mechanics and the pre-adjusted appliance. Aylesbury, England: Wolfe Publishing; 1993:149. 5. Carriere J, Carriere L. Softlanding treatment through inverse anchorage. J Clin Orthod 1995; 29:479. 6. Graber T, Vanarsdaall R. Orthodontics: current principles and techniques, ed. 2. St. Louis: C.V. Mosby Co.; 1994:224. 7. Graber T, Swain B. Orthodontics: current principles and techniques, p. 214. 8. Burstone C, Nanda, R. Retention and stability in orthodontics. Philadelphia: W. B. Saunders; 1993: 13-14. 9. Graber T, Swain B. orthodontics: current principles and techniques, p. 214. 10. McNew B. Treatment of a patient with a Class II, Division I malocclusion and a dolichocephalic skeletal pattern. Am J Orthod 1995; 108:544. 11. Proffit W. Contemporary orthodontics, p. 86. 12. Nanda S. The development basis of occlusion and malocclusion. Chicago: Quintessence Publishing Co.; 1983: 46. 13. Graber T, Swain B. Orthodontics: current principles and techniques, p. 375. 14. Graber T, Swain B. Orthodontics: current principles and techniques, pp. 81, 609. 15. McNamara J. A practical approach to early orthodontic and orthopedic treatment. Lecture. Ann Arbor, Michigan, November 27, 1995. 16. McNamara J. A practical approach to early orthodontic and orthopedic treatment. Lecture. Ann Arbor, Michigan, November 28, 1995. 17. Graber T, Swain B. Orthodontics: current principles and techniques, pp. 81, 409. |
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