CASE REPORT
Orthodontic treatment and masticatory muscle
exercises to correct a Class I open bite in an
adult patient
Carrie A. Lindsey, DDS, MS,a and Jeryl D. English, DDS, MSb
Dallas, Tex
iagnosing and treating an open bite malocclusion in an adult is a challenge for the clinical
orthodontist. Patients with skeletal vertical
growth patterns, typical of open bite malocclusions,
exhibit common morphological and functional characteristics, including long anterior face height,1-3 short
posterior face height,1,2 large mandibular plane and
gonial angles,1,2,4 increased dentoalveolar height,4
marked antegonial notching,5 downward tipping to the
posterior maxilla,5,6 and anterior open bite. Functionally, hyperdivergent patients typically have weak bite
forces,7,8 and smaller,9-11 less efficient12 muscles.
Control of the vertical dimension by intruding both
maxillary and mandibular molars and facilitating counterclockwise rotation of the mandible is key to managing open bite malocclusion. Some studies have shown
morphological improvements in children with open
bites who do chewing exercises,12,13 and others have
demonstrated significant forward mandibular autorotation.8,14
In this case report, we discuss open bite treatment
that included a combination of anterior vertical elastics
to extrude the maxillary and mandibular incisors and
clenching exercises to intrude the maxillary and mandibular molars.
D
HISTORY AND ETIOLOGY
The patient was a healthy, 40-year-old woman
referred to the Department of Orthodontics clinic by the
From the Department of Orthodontics, Baylor College of Dentistry, Dallas,
Tex.
a
Graduate student.
b
Formerly Clinic Director; Graduate Program Director.
Presented at the May 2001 meeting of the American Association of Orthodontists, Toronto, Ontario, Canada.
Am J Orthod Dentofacial Orthop 2003;124:91-8
Reprint requested to: Dr Jeryl D. English, Department of Orthodontics,
Chairman and Graduate Program Director, University of Texas Health Science
Center at Houston, Dental Branch, 6516 M. D. Anderson Blvd, #370, Houston,
TX 77030; e-mail, jeryl.d.english@uth.tmc.edu.
Submitted, May 2002; revised and accepted, November 2002
Copyright © 2003 by the American Association of Orthodontists.
0889-5406/2003/$30.00 ⫹ 0
doi:10.1016/S0889-5406(03)00308-1
Department of Oral Surgery at Baylor College of
Dentistry for combined surgical-orthodontic treatment
to correct her open bite. Her medical history included a
rhinoplasty in 1986, a past history of bulimia, and a
penicillin allergy. Her daily medications included birth
control pills, melatonin (as a sleep aid), and Excedrin
(for daily sinus headaches and temporomandibular joint
[TMJ] pain). The patient reported undergoing previous
comprehensive orthodontic therapy in 1972 and said
that her bite had been opening over the last 10 years.
She reported wearing numerous occlusal splints in
attempt to control TMJ pain. Radiographs of her
mandibular condyles did not indicate that a resorptive
process was responsible for the bite opening. It was
speculated that the bite splints did not extend to the
second molars, and this resulted in supereruption and
progressive bite opening. The patient reported severe
TMJ pain on the right side when biting, but her range of
motion during a clinical examination was normal. The
right maxillary and mandibular second molars were the
only teeth in occlusion, and the forces of mastication
concentrated on these teeth probably contributed to the
reported TMJ pain.
DIAGNOSIS
A Class I open bite was diagnosed. Facial analysis
showed a leptoprosopic facial form, a mild deviation of
the nose to the right, a long lower face height, a
deficient gingival display, a convex overall profile, and
a prominent chin (Fig 1). Dentally, the open bite was 8
mm, and the overjet was 2 to 3 mm (Figs 2 and 3).
There was no crowding in the maxillary arch and only
about 1 mm of crowding in the mandibular arch. The
mandibular arch had a reverse curve of Spee of approximately 4 mm. Because of the mildly small maxillary
lateral incisors, a Bolton discrepancy of 1.6 mm anterior mandibular excess existed. Mild gingival recession
and multiple cervical enamel lesions were present.
Probing depths around the molars were 5 mm, and
horizontal bone loss was evident on the radiographs
(Fig 4), although oral hygiene was excellent, with no
signs of active inflammation. Cephalometric analysis
91
92 Lindsey and English
American Journal of Orthodontics and Dentofacial Orthopedics
July 2003
Fig 1. Pretreatment facial photographs.
Fig 2. Pretreatment intraoral photographs.
showed a Class II skeletal tendency with an ANB angle of
4° due mostly to clockwise mandibular rotation resulting
from second molar supereruption (Fig 5, Table). Both
maxillary and mandibular incisors were mildly upright.
TREATMENT PLAN
The initial plan consisted of combined orthodontic
treatment and orthognathic surgery to correct the open
bite malocclusion. Both arches were to be banded or
bonded from second molar to second molar with 0.022
⫻ 0.028-in appliances. With continuous archwires,
leveling and alignment would be accomplished in
preparation for orthognathic surgery. A segmental Le
Fort I maxillary surgery and a bilateral sagittal split
osteotomy mandibular advancement (as needed) were
planned to close the open bite. After surgery, the
occlusion would be detailed and finished. A bonded
retainer from canine to canine would be used for
retention in the mandible, with a Hawley wrap-around
retainer in the maxilla.
TREATMENT OBJECTIVES
Treatment objectives for the maxilla included maintaining the anteroposterior and transverse dimensions,
Lindsey and English 93
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 124, Number 1
Fig 3. Pretreatment study models.
Fig 4. Pretreatment panoramic radiograph.
altering the vertical position through posterior impaction, and repositioning the anterior teeth downward to
close the bite and increase incisor show at rest and
during smiling. The arch would be leveled by intruding
the second molars. Because the patient did not want to
restore the narrow lateral incisors, the anteroposterior
incisor angulation would be maintained in the mildly
upright pretreatment positions.
Objectives for the mandible included maintaining
the transverse dimension, decreasing the mandibular
plane angle, and reducing the lower vertical excess
through autorotation during segmental maxillary surgery. The anteroposterior position of the mandible
would be coordinated with that of the maxilla during
surgery. The anteroposterior and transverse dimensions
Fig 5. Pretreatment cephalometric tracing.
of the mandibular dentition would be maintained and
the reverse curve of Spee leveled through a combination of second molar intrusion and incisor extrusion.
Overall goals for the occlusion were to establish a
Class I molar and canine relationship with ideal overjet
94 Lindsey and English
Table.
American Journal of Orthodontics and Dentofacial Orthopedics
July 2003
Cephalometric summary
Area of study
Measurement
Norms
A
B
Cranial base
N-S-Ba angle
S-N
SNA angle
Maxillary depth
SNB angle
Facial angle
ANB angle
N-ANS
ANS-Me
N-Me
FMA angle
Interincisal angle
U1/SN
L1/Go-Me
L1/N-B
Nasolabial angle
130°
69 mm
82°
90°
79°
86°
3°
50 mm
62 mm
118 mm
23°
134°
103°
95°
4 mm
112°
122°
66 mm
80°
90°
76°
87°
4°
51 mm
75 mm
125 mm
27°
134°
99°
88°
4 mm
111°
123°
66 mm
81°
92°
77°
88°
4°
51 mm
69 mm
119 mm
23°
142°
93°
86°
4 mm
117°
Maxilla to cranial base
Mandible to cranial base
Maxillomandibular relationships
Vertical height
Maxillary and mandibular
incisor position
Soft tissue
and over bite, and to establish centric occlusion coincident
with centric relation and a mutually protected occlusion.
Decreasing the long lower face height would improve facial balance for this patient and result in some
esthetic improvement.
TREATMENT PROGRESS
The maxillary and mandibular arches were banded
and bonded with .022 ⫻ .028-in MBT (3M Unitek,
Monrovia, Calif) appliances, and continuous .016-in
nickel-titanium archwires were placed. After initial
alignment was obtained, continuous .018 ⫻ .025-in
BioForce nickel-titanium (GAC, Bohemia, NY) wires
were placed for 4 months to continue alignment and
begin leveling. As the initial period of leveling began,
the patient was instructed to squeeze her teeth together
to aid in intruding the second molars. She was extremely compliant with this exercise because she was
motivated to speed the treatment process along. Six
months into treatment, continuous .019 ⫻ .025-in
stainless steel archwires were placed, and the leveling
of the arches continued.
By about 10 months into treatment, the leveling
process had significantly reduced the open bite to
approximately 2 mm. Because good progress had been
made in closing the bite through orthodontic leveling
alone, it was decided to attempt to complete the
treatment nonsurgically. A reverse curve of Spee was
added to the maxillary archwire and an accentuated
curve of Spee was added to the mandibular archwire to
continue closing the bite. At the same time, bilateral
trapezoid elastics from the maxillary laterals and canines to the mandibular first premolars, canines, and
A to B
difference
1°
0 mm
1°
2°
1°
1°
0°
0 mm
⫺6 mm
⫺6 mm
⫺4°
⫺8°
⫺6°
⫺2°
0 mm
⫺6°
laterals were initiated (3⁄16-in, 6 oz, Ormco, Orange,
Calif). Throughout treatment, the patient continued
with the squeezing exercise. After 1 month of elastic
wear with the curved archwires in place, the open bite
was reduced to 0 mm. An .018 ⫻ .025-in D-Rect
(Ormco) stainless steel archwire was placed in the
maxillary arch to facilitate extrusion of the maxillary
anterior teeth to improve incisor show on smiling. Fulltime elastic wear continued for 4 months, tapered to night
only for 1 month, and then stopped. The upper archwire
was sectioned, and finishing elastics (3⁄4-in, 2 oz) were
used for approximately 5 weeks. Appliances were
removed, and retainers were delivered. Cooperation
was excellent, and the patient reported no TMJ problems during treatment.
TREATMENT RESULTS
Facial esthetics and balance were improved by
decreasing lower face height through mandibular autorotation (Figs 6-11). The maxillary incisors were retroclined and retruded as the anterior open bite was closed.
The maxillary second molar was intruded approximately 2 mm. The transverse was maintained, and,
other than the mild incisor retrusion, the anteroposterior
dental positions were maintained. The anteroposterior
position of the mandibular molars was maintained
while the incisors were retroclined 2°. The transverse
dimension was maintained. In the vertical dimension,
the second molar was intruded about 1 mm and the
incisors extruded about 2.5 mm as the reverse curve of
Spee was leveled. Class I molar and canine relationships with ideal overjet and overbite were established.
Centric occlusion was established to be coincident with
Lindsey and English 95
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 124, Number 1
Fig 6. Posttreatment facial photographs.
Fig 7. Posttreatment intraoral photographs.
centric relation, and a mutually protected occlusion was
designed. Transverse and vertical dimensions were
maintained in the maxilla. A-point came forward about
1° as the maxillary incisors were uprighted. The transverse dimension was maintained in the mandible, and
the mandibular plane angle decreased 4° as the mandible rotated counterclockwise after intrusion of the
maxillary and mandibular second molars. Lower face
height decreased 6 mm to a more balanced relationship.
The anteroposterior positions of B-point and pogonion
advanced about 1° as the mandible autorotated forward.
FINAL EVALUATION
The final outcome of the treatment is a great
improvement in function and esthetics, but stability of
the open bite closure is questionable. If the etiology of
the open bite was molar supereruption during years of
wearing poorly constructed splints, the result might
remain fairly stable. The main reason this patient could
be treated nonsurgically was her excellent compliance.
She wore the elastics full time, and she performed the
squeezing exercises daily, enabling the orthodontic
intrusion of the second molars.
96 Lindsey and English
American Journal of Orthodontics and Dentofacial Orthopedics
July 2003
Fig 8. Posttreatment study models.
Fig 9. Posttreatment panoramic radiograph.
DISCUSSION
The difficulty of managing anterior open bite malocclusions is not only in obtaining the correct diagnosis, but also in treating the case to a successful facial
and dental result. The orthodontist’s challenge is to
minimize molar extrusion during treatment to prevent
downward and backward mandibular rotation.
Faced with the limitations that routine orthodontic
treatment modalities present, most orthodontists would
agree that a skeletal hyperdivergent open bite malocclusion in an adult is ideally corrected with combined
orthodontic treatment and orthognathic surgery. The
most common surgical procedure is a LeFort I osteotomy, which allows impaction of the posterior maxilla
and autorotation of the mandible.15 This patient was
Fig 10. Posttreatment cephalometric tracing.
hesitant to consent to the orthognathic surgical plan
because of the additional expense and risks of surgery.
The advantages of the orthognathic surgical option are
that the overbite can be overcorrected and relapse is
less than with a nonsurgical approach.16
Lindsey and English 97
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 124, Number 1
Fig 11. Superimposed cephalometric tracings.
Nonsurgical options for correcting open bite malocclusions include anterior vertical elastics, posterior
bite blocks (active and passive), high-pull headgear,
vertical pull chincups, and microimplants. Nonsurgical
options usually require longer treatment time and more
patient compliance.
A common nonsurgical treatment option would be
to use anterior vertical elastics to extrude the maxillary
and mandibular incisors and close the anterior open
bite. This procedure would be appropriate if the open
bite was due to vertical underdevelopment of the
anterior dentoalveolar processes. However, studies
have indicated that skeletal open bites often show
maxillary incisor supereruption.1,2,17,18 Further eruption of the incisors by using vertical elastics elongates
the anterior teeth beyond the limits of stability, resulting in relapse. Rather than closing the anterior open bite
by extruding the anterior dentoalveolar complex, Subtelny and Sakuda17 indicated that these cases would
benefit more from intrusion of the maxillary and
mandibular molars.
Posterior bite blocks containing repelling magnets
have been proposed as a treatment modality for anterior
open bites.19,20 Dellinger19 described the active vertical
corrector as a removable or fixed orthodontic appliance
designed to reciprocally intrude the posterior teeth. By
intruding the posterior teeth, the mandible autorotates
in an upward and forward direction. This form of
treatment is advantageous because it corrects the anterior open bite and simultaneously reduces the total
anterior facial height. However, an adverse side effect
is the creation of a buccal crossbite due to the repelling
forces of the magnets during lateral excursions. Kuster
and Ingervall21 used spring-loaded bite-blocks to avoid
the undesirable lateral effects of repelling magnets.
They found no evidence of posterior teeth intrusion.
Kiliaridis22 compared the treatment effects of plain
posterior bite blocks with posterior repelling magnet
splints. He demonstrated significant intrusion of posterior teeth and no transverse problems with the plain
posterior bite blocks.
A vertical-pull chincup has been successfully used
with conventional orthodontic appliances for correcting
open bite malocclusion.23-25 The chincup controls the
excessive lower anterior facial height and helps to
prevent extrusion of the posterior teeth. Sankey et al26
also showed positive treatment results using a chincup
in conjunction with a bonded palatal expander. They
demonstrated relative intrusion of the maxillary molars,
vertical control of the mandibular molars, and increased
eruption of the maxillary incisors that contributed to
improvements in overbite.
The high-pull headgear appliance is another extraoral
device used to intrude the maxilla. 27-31 Its use is limited
because its forces are applied to the maxilla, with no direct
treatment effects on the mandible’s shape or growth.
Microimplants have recently been used to intrude
molars32,33 with conventional orthodontic appliances.
According to initial reports, microimplants are much
less expensive than traditional osseointegrated implants
and will simplify treatment mechanics. The obvious
disadvantages are that they require a surgical procedure
for placement and removal after treatment.
Finally, all of the previous treatment modalities for
correcting anterior open bite malocclusion have focused on intruding posterior teeth and facilitating autorotation of the mandible. However, if one considers
that craniofacial morphology can be influenced by the
size, shape, and function of the masticatory muscles,
then perhaps strengthening the muscles would produce
an adjunctive treatment modality to correct open bite
malocclusions. It has been a common finding that the
elevator muscles of the mandible influence the transverse and vertical dimensions of the face.34-36 Numerous studies demonstrate that strength training of masticatory muscles can influence morphology.37-40 In a
prospective study of early open bite treatment, English41 demonstrated that light masticatory exercise
combined with high-pull headgear produced significant
reductions in the ANB and gonial angles and reduced
mandibular autorotation by 2.2°.
CONCLUSIONS
Masticatory exercise was an important adjunctive
treatment in correcting an open bite malocclusion in an
extremely compliant adult patient. Additionally, the
patient had infraeruption of the maxillary incisors, and
thus we were able to extrude them to provide a more
98 Lindsey and English
American Journal of Orthodontics and Dentofacial Orthopedics
July 2003
esthetic incisor display. At a retention check 14 months
after removing the appliances, the occlusion appeared
stable. However, long-term verification will be needed
because open bite malocclusions tend to relapse more
than most other types of malocclusions. Perhaps strengthening of the masticatory musculature through clenching
exercises will also help to prevent open bite relapse.
appliance on the dentofacial complex. Am J Orthod 1989;95:
467-78.
Kuster R, Ingervall B. The effect of treatment of skeletal open
bite with two types of bite-blocks. Eur J Othod 1992;14:489-99.
Kiliaridis S, Egermark I, Thilander B. Anterior open bite
treatment with magnets. Eur Orthod Soc 1990;12:447-57.
Pearson L. Vertical control in treatment of patients having backward-rotational growth tendencies. Angle Orthod 1978;48:132-40.
Pearson L. Vertical control in fully banded orthodontic treatment. Angle Orthod 1986;56:205-24.
Pearson L. Case report KP. Treatment of a severe openbite
excessive vertical pattern with an eclectic non-surgical approach.
Angle Orthod 1991;61:71-6.
Sankey W, Buschang P, English J, Owen A. Early treatment of
vertical skeletal dysplasia: the hyperdivergent phenotype. Am J
Orthod Dentofacial Orthop 2000;118:317-27.
Watson W. A computerized appraisal of the high-pull face-bow.
Am J Orthod 1972;62:561-78.
Baumrind S, Molthen R, West E. Mandibular plane changes
during maxillary retraction. Am J Orthod 1978;74:32-40.
Droschl H. The effect of heavy orthopedic forces on the maxilla
of the growing Siamire sciureus (squirrel monkey). Am J Orthod
1973;66:599-617.
Meldrum RJ. Alterations in the upper facial growth of Macaca
mulatta resulting from high-pull headgear. Am J Orthod 1975;
67:393-411.
Firouz M, Zernik J, Nanda R. Dental and orthopedic effects of
high-pull headgear in treatment of Class II, Division I malocclusion. Am J Orthod Dentofacial Orthop 1992;102:197-205.
Park HS, Bae SM, Kyung HM, Sung JH. Micro-implant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin
Orthod 2001;35:417-22.
Bae SM, Park HS, Kyung HM, Kwon OW, Sung JH. Clinical
application of micro-implant anchorage. J Clin Orthod 2002;36:
298-302.
Lowe A, Takada K. Associations between anterior temporal,
masseter, and orbicularis oris muscle activity and craniofacial
morphology in children. Am J Orthod 1984;86:319-30.
Proffit W, Gamble J, Christiansen R. Generalized muscular
weakness with severe anterior open bite: a case report. Am J
Orthod 1968;54:104-10.
Ingervall B. Facial morphology and activity of temporal and lip
muscles during swallowing and chewing. Angle Orthod 1976;
46:372-80.
Lowe A. Correlations between muscle activity and craniofacial
morphology in a sample of control and anterior open-bite
subjects. Am J Orthod 1980;78:89-98.
Kiliaridis S, Johansson A, Haraldson T, Omar R, Carlsson G.
Craniofacial morphology, occlusal traits, and bite force in persons with advanced occlusal tooth wear. Am J Orthod Dentofacial Orthop 1995;107:286-92.
Thompson D, Throckmorton G, Buschang P. The effects of
isometric exercise on maximum voluntary bite forces and jaw
muscle strength and endurance. J Oral Rehabil 2001;28:1-9.
Insoft M, Hocevar R, Gibbs C. The non-surgical treatment of a
Class II open bite malocclusion. Am J Orthod Dentofacial
Orthop 1996;110:598-605.
English J. Early treatment of skeletal open bite malocclusion.
Am J Orthod Dentofacial Orthop 2002;121:563-5.
REFERENCES
1. Cangialosi T. Skeletal morphologic features of anterior open
bite. Am J Orthod 1984;85:28-36.
2. Nahoum HI. Anterior open-bite: a cephalometric analysis and
suggested treatment procedures. Am J Orthod 1975;67:513-21.
3. Nanda S. Patterns of vertical growth in the face. Am J Orthod
Dentofacial Orthop 1988;93:103-16.
4. Fields H, Proffit W, Nixon W, Phillips C, Stanek E. Facial
pattern differences in long-faced children and adults. Am J
Orthod 1984;85:217-23.
5. Bell WH. Correction of skeletal type of anterior open bite. J Oral
Surg 1971;29:706-14.
6. Sassouni V. A classification of skeletal types. Am J Orthod
1969;55:109-23.
7. Proffit W, Fields H, Nixon W. Occlusal forces in normal and
long-face adults. J Dent Res 1983;62:566-71.
8. Ingervall B, Helkimo E. Masticatory muscle force and facial
morphology in man. Arch Oral Biol 1978;23:203-6.
9. Hannam AG, Wood WW. Relationships between the size and
spatial morphology of human masseter and medial pterygoid
muscles, the craniofacial skeleton, and jaw biomechanics. Am J
Phys Anthrop 1989;80:429-45.
10. Weijs WA, Hillen B. Relationships between muscle crosssection and skull shape. J Dent Res 1984;63:1154.
11. Ingervall B, Bitsanis E. A pilot study of the effect of masticatory
muscle training on facial growth in long-face children. Eur
J Orthod 1987;9:15-23.
12. Morales P, Buschang P, Throckmorton G, English J. Maximum
bite force, muscle efficiency, and mechanical advantage in
children with vertical growth patterns. Eur J Orthod 2003 (in
press).
13. Spyropoulos M. An early approach for the interception of
skeletal open bites: a preliminary report. J Pedod 1985;9:200-9.
14. Bakke M, Siersbaek-Nielsen S. Training of mandibular elevator
muscles in subjects with anterior open bite [abstract]. Eur
J Orthod 1990;12:502.
15. Bell WH. LeFort I osteotomy for correction of maxillary deformities. J Oral Surg 1975;33:412-26.
16. Denison TF, Kokich VG, Shapiro PA. Stability of maxillary
surgery in open bite versus non-open bite malocclusions. Angle
Orthod 1989;59:5-10.
17. Subtelny J, Sakuda M. Open bite diagnosis and treatment. Am J
Orthod 1964;50:337-58.
18. Pearson L. Vertical control through use of mandibular posterior
intrusive forces. Angle Orthod 1973;43:194-200.
19. Dellinger E. A clinical assessment of the Active Vertical Corrector—non-surgical alternative for skeletal open bite treatment.
Am J Orthod 1986;89:428-36.
20. Kalra V, Burstone C, Nanda R. Effects of a fixed magnetic
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.