Aob correct by le fort i or bsso

Oral Maxillofacial Surg Clin N Am 19 (2007) 321–338

Anterior Open Bite Correction by Le Fort I
or Bilateral Sagittal Split Osteotomy
Johan P. Reyneke, BChD, MChD, FCMFOS (SA), PhDa,b,*,
Carlo Ferretti, BDS, MDent (MFOS), FCD (SA) MFOSa,c
a
Department of Maxillofacial and Oral Surgery, Faculty of Health Sciences,
University of the Witwatersrand, Johannesburg, South Africa
b
Department of Oral and Maxillofacial Surgery, Faculty of Dentistry,
University of Oklahoma, Oklahoma City, OK, USA
c
Department of Maxillofacial and Oral Surgery, Chris Hani Baragwanath Hospital,
Faculty of Health Sciences,
University of the Witwatersrand, Johannesburg, South Africa

Some of the most challenging dentofacial de- causative mechanisms, and the question remains
formities facing surgeons and orthodontists are incompletely answered.
anterior open bite malocclusions. Determining the Nonnutritive sucking is a normal developmen-
cause of an anterior open bite and formulating tal phenomenon whose frequency decreases with
a diagnosis are complicated by the role of age. Persistence of the habit beyond the age of 6
neuromuscular and genetic influences. Long-term years is strongly associated with open bite maloc-
skeletal and dental stability are a concern because clusion [1]. Complicating the issue is the fact that
of the influence that the neuromusculature has on there is a wide racial variation in the incidence of
the repositioned jaws and stability of teeth after anterior open bite, which suggests a modulating ef-
vertical orthodontic mechanics required for clos- fect of genetic control of skeletal proportions [2,3].
ing open bites. Nasopharyngeal and oropharyngeal obstruction as
a result of one of several possible conditions, such
as allergic rhinitis, enlarged adenoids, and enlarged
Etiology
tonsils, has been associated with development of
Mechanistic insights on the development of the anterior open bite deformity [4].
anterior open bite malocclusion remain subject to It is proposed that obstruction to normal nasal
debate and discussion. Patently, two philosophies breathing triggers an adaptive neuromuscular
may concur with research findings: the morpho- response that results in open rotation of the
genetic theory and the adaptive theory. The mandible, inferior and anterior repositioning of
anterior open bite may be the result of aberrant the tongue, and extended head posture giving rise
genetic control of morphology via growth pat- to the classical ‘‘adenoidal facies.’’ There are
terns, or a malformation secondary to functional several implications of these functional adapta-
aberrations of the naso-oropharyngeal apparatus. tions to nasal breathing. First, a change in the
It has proven difficult to separate these two direction of mandibular growth from horizontal
to vertical results in increased lower facial height.
Second, inferior and anterior repositioning of the
tongue has several dental effects, including
* Corresponding author. Centre for Orthognathic
narrowing of the maxillary dental arch caused
Surgery and Implantology, Sunninghill Hospital, PO by the unopposed action of the buccinator muscle,
BOX 5386, Rivonia, South Africa. retroclination of the upper incisors caused by
E-mail address: drjprey@global.co.za (J.P. Reyneke). the unopposed actions of orbicularis oris, and
1042-3699/07/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved.
doi:10.1016/j.coms.2007.04.004 oralmaxsurgery.theclinics.com

322 REYNEKE & FERRETTI

proclination of the lower incisors caused by open bite. Because vertical problems (in particular
increased tongue pressure. The case for this in patients with anterior open bite) can result from
mechanism has been strengthened by the finding habits, environmental influences, or vertical skel-
that early removal of the obstruction and return etal growth problems, the diagnosis has two
to nasal breathing often results in normalization important components: the specific anatomic
of anterior height. Finally, chronic mouth breath- location of the discrepancy (eg, maxilla, mandible,
ing can cause alterations in head posture, most or both) and identification of a cause. In young
commonly extension or upward rotation of the growing individuals, the major cause of anterior
head, in an attempt to improve oropharyngeal open bite is sucking habits and environmental
patency. This altered posture has been associated influences. The open bite as a result of thumb
with several disturbances in craniofacial morphol- sucking is usually limited to the anterior region,
ogy, including increased lower facial height, with a narrow palate, often posterior cross bites,
mandibular and maxillary retrognathism, and and relatively normal facial proportions. The
steep mandibular plane. most important step in the treatment is to stop
Increased vertical development of the maxilla the habit. For this purpose a removable appliance
also has been associated with several muscle with a crib is used. The sucking habit stops
weakness syndromes. Weakness of the mandibu- immediately in approximately 50% of patients
lar elevators and decreased biting force allow the and the open bite starts to close rapidly. In the
posterior teeth to overerupt and the mandible to remaining children the thumb sucking may persist
rotate downward. It has been reported that the for a few weeks; however, the device is usually
biting forces of patients with long faces are below effective in 85% to 90% of cases [1]. At this stage,
normal, although the bite force of preadolescent orthodontic correction of the cross bites solves the
patients with long face characteristics is normal transverse and anterior open bites. The long-term
[5,6]. The role of decreased bite force as an etio- prognosis depends on the growth pattern, how-
logic factor in the development of vertical maxil- ever, and a poor response to treatment suggests
lary excess and anterior open bite is not clear, persistent excessive vertical growth. These patients
however. most probably develop vertical maxillary excess
In the past, tongue thrust or abnormal tongue and an anterior open bite malocclusion.
activity during speech has been blamed for the Not all children who are thumb suckers de-
development of anterior open bite malocclusion velop anterior open bites. In children with chronic
and poor stability after treatment. Various at- mouth breathing, one, or all, of three neuromus-
tempts to change patients’ swallowing patterns, cular responses must be present for an anterior
such as speech therapy and removable appliance open bite malocclusion and altered skeletal re-
with a crib, have been used to control anterior sponse to develop: (1) altered mandibular posture,
open bite problems. Contemporary research has (2) altered tongue posture, (3) extended head
shown, however, that tongue thrust swallow is posture [4]. Several studies have shown that an
a physiologic adaptation to an anterior open bite obstructed upper airwaydassociated with altered
rather than the cause of it. An abnormally large mandibular posturedis related to increased lower
tongue or true macroglossia should first be facial height [8,9]. Removal of the cause of the na-
differentiated from pseudomacroglossia and only sopharyngeal obstruction (eg, enlarged adenoids
then considered as an etiologic factor in the or tonsils, allergic rhinitis) has been reported to
development of an anterior open bite. A large decrease the open bite [4]. Upper airway obstruc-
tongue also may be the cause of poor stability tion may be one factor in the multifactorial etio-
after treatment [7]. logic complex that influences the dentition and
It seems that an anterior open bite is pre- morphogenetic facial pattern.
dominantly the result of alterations in mandibular In young individuals in whom vertical growth
growth patterns, and more attention is required persists and in patients who have reached adoles-
for treatment philosophies that address this fact. cence, environmental causes for anterior open bite
become less important than skeletal factors. Skel-
etal anterior open bite malocclusion in adults is
basically a vertical dentofacial problem caused by
Diagnosis
excessive vertical development of the maxilla,
As with the diagnosis of all malocclusion, it is shortening of the mandibular ramus, or a combina-
important to identify the cause of the anterior tion of both. It is important to distinguish between

ANTERIOR OPEN BITE CORRECTION 323

Fig. 1. An anterior open bite (A) in an 8-year-old patient was treated by orthodontic expansion of the maxillary dental arch
combined with habit control (thumb sucking) (B). The arrow indicates the ‘‘gate’’ incorporated into a removable appliance.
A stable posttreatment result was achieved (C). (Courtesy of T. McCollum, BDS, MDent, Johannesburg, South Africa.)

the two skeletal deformities because it ultimately headgear and class III elastics [12], titanium screw
determines the surgical treatment plan. anchorage [13], a rapid molar intruder appliance
[14], reverse headgear combined with class III

Treatment of growing individuals
Box 1. Clinical, dental, and
Anterior open bites in children with mixed cephalometric findings of patients
dentition and good facial proportions are usually with anterior open bite deformity
caused by prolonged thumb sucking (beyond the
age of 6 years) or other environmental influences, Aesthetic features
and the most important corrective measure in Lower third of the face almost always
these patients is cessation of the habit. Posterior elongated
cross bites are usually the result of narrowing of Excessive incisor exposure under the
the maxilla. Removable and fixed appliances can upper lip
be effective in the correction. Maxillary dental Increased interlabial gap
expansion not only corrects the cross bites but Gummy smile
also assists in closing the anterior open bite and Obtuse nasolabial angle
should be combined with habit control (Fig. 1). Retrusive chin
By the time adolescence is reached, environmental Dental characteristics
causes become less important. Skeletal factors Open bites may be associated with all
should be considered after poor response to habit types of malocclusion; however,
control and maxillary expansion [10]. relative or absolute mandibular
deficiency and class II malocclusion
are most common
Treatment of nongrowing individuals Tendency for the maxillary arch to be
V-shaped and the mandibular arch to
Orthodontic correction of anterior open bite be U-shaped
Posterior cross bites
The treatment of patients with anterior open
Flat or reverse mandibular occlusal plane
bite by means of orthodontic treatment alone
curve
usually focuses on three areas: (1) extrusion of
Stepped maxillary occlusal plane
upper and lower incisor teeth, (2) intrusion of
molar teeth, and (3) expansion of the maxillary Cephalometric features
dental arch. This orthodontic treatment requires Increased anterior facial height
almost exclusively the use of vertical mechanics. Steep mandibular and occlusal plane
Extrusion of incisor teeth can be accomplished in angle
three ways: (1) the use of anterior elastics, (2) Normal mandibular ramus height
using a continuous arch wire from molar to molar Saddle cranial base
to level an excessive occlusal curve in the maxil- Increased distance from tooth apices to
lary arch, and (3) leveling a reverse curve of Spee the nasal floor
in the lower arch in the same manner. The Palatal plane is tipped up anteriorly and
mechanics to intrude the molars include intrusion down posteriorly
of molars with miniplate anchorage [11], high-pull


Fig. 2. This 17-year-old patient developed an anterior open bite as a result of excessive vertical growth of her maxilla.
The mandible rotated clockwise, which resulted in a class II anterior open bite malocclusion (A–F). The maxillary dental
arch was aligned in two segments (11 to 17 and 21 to 27) (G–L). The open bite was surgically corrected by superior
repositioning of the maxilla (more in the posterior area than anterior) and expanded, which allowed the mandible to
autorotate (O). A balanced aesthetic result and functional occlusion were achieved (M–R).

and anterior box elastics [15], zygomatic anchor- Most of the reports in the literature regarding
age [16], and bite blocks with repelling magnets orthodontic correction of skeletal anterior open
[17]. Expansion of the maxillary posterior teeth bite are case reports that discuss speciﬁc ortho-
in adult individuals with skeletal transverse dontic techniques or introduce new orthodontic
deﬁciency usually results in dental tipping and mechanics. There is, however, a paucity of studies
questionable stability [18,19]. regarding results after orthodontic correction of


Fig. 2 (continued)

anterior open bite malocclusions to draw any problems have questionable long-term stability
evidence-based conclusions [20–22]. Few studies and may build relapse into the surgical result. The
have reported on the pretreatment aesthetic con- basic goal of presurgical orthodontic treatment
siderations and facial aesthetic outcomes. Regard- should be to align the maxillary teeth (either in
less of the specific mechanism used to achieve the segments or in one piece) and avoid any mechanics
tooth movements, stability is unpredictable and in that are intended to close the bite. Segmental
many cases results in compromised aesthetics surgery is indicated when the maxillary dental
[23,24]. In cases in which the anterior open bite arch has a tendency to natural segments or to level
is associated with increased incisor angulation the occlusal curves surgically. This does not mean
(as may be found in cases with bimaxillary that individual teeth within a segment should not be
protrusion), correction of the incisor angulation leveled; intrusion of the incisors or maintaining
by tipping the incisors has a relative extrusion their pretreatment height is recommended. Open-
effect, thus closing the bite. ing the bite before surgery improves stability
because relapse of incisor intrusion serves to further
Combined orthodontic and surgical treatment close the bite after surgery. Orthodontic alignment
Anterior open bite secondary to vertical maxillary of the maxilla in segments can be done with or
excess: Le Fort I maxillary osteotomy with or without extractions. The need for extractions in
without mandibular surgery these cases is dictated by the amount of crowding
The common but variable clinical, dental, and and the dental movements necessary to place the
cephalometric findings of patients with skeletal upper and lower incisors in their desired angulation
anterior open bite deformity as a result of vertical and in the central trough of bone. Keep in mind that
maxillary excess are as shown in Box 1 (Fig. 2): the angulation of the incisor and posterior teeth can
be altered with segmental surgery. In cases in which
Presurgical orthodontic treatment segmental surgery is contemplated, care should be
Presurgical orthodontic mechanics should not taken to coordinate the arch form of the maxillary
be directed toward correcting vertical, transverse, segments with the mandibular arch and deviate the
or anteroposterior skeletal problems. Orthodontic roots of the teeth adjacent to the intended in-
tooth movements for the correction of these terdental osteotomy sites.


Although the mandible may require surgical (3) the need for surgical correction of a transverse
advancement or setback, the lower dental arch discrepancy.
serves as the ‘‘template’’ and ultimately dictates
The amount of superior repositioning of the max-
the symmetry and form of the upper arch. The
illa. The amount of superior repositioning of the
presurgical orthodontic treatment goals are to
anterior and posterior maxilla is influenced by two
place the lower dentition symmetrically in the
aspects: (1) The planned ideal maxillary incisor/
ideal anteroposterior, vertical, and transverse
upper lip relationship determines the amount of
positions in relation to its supporting bone. In
vertical and anteroposterior repositioning of the
individuals with a severe reverse curve of Spee in
anterior maxilla. In most cases the incisor teeth
the lower arch, consideration should be given to
require superior repositioning. In some cases,
surgically leveling the mandibular arch by means
however, the incisor height may need to be
of segmental mandibular surgery.
maintained, whereas in other cases the anterior
Orthodontic mechanics expressly intended to
maxilla may have to be inferiorly repositioned.
close the bite should be avoided during the
The final anteroposterior and vertical positions of
presurgical orthodontic phase. Bite blocks with
the maxillary incisor are the key to treatment
repelling magnets, high-pull headgear, miniplate
planning [25,26]. (2) The final occlusal plane is
anchorage for molar intrusion, vertical elastics,
determined by the mandibular occlusal plane after
molar expansion beyond its alveolar bone base, or
autorotation of the mandible. The amount of
any other device used to close the bite are
superior repositioning of the posterior maxilla is
inadvisable. Previous attempts to close a skeletal
determined by the height of the mandibular
anterior open bite orthodontically without con-
posterior teeth after autorotation.
sidering surgical correction will leave the clinician
with a dilemma. After orthodontic attempts to The position of the mandible after autorotation.
close the bite, pretreatment orthodontic records The anteroposterior position of the lower incisor
must be compared with current records to evalu- after autorotation determines whether mandibular
ate the potential for dental relapse. It is recom- surgery is indicated. Individuals with a class I
mended to discontinue all vertical mechanics and molar relation, combined with vertical maxillary
allow vertical relapse by placing light sectional excess and an anterior open bite malocclusion,
arch wires to maintain alignment and rotations. end with a class III dental relationship after
Once no further vertical opening of the bite maxillary superior repositioning. Based on the
occurs, the patient can be re-evaluated for appro- aesthetic requirements of the case, the clinician
priate surgery and orthodontics. must decide whether the class III dental relation-
ship should be corrected by advancement of the
maxilla (Fig. 3) or mandibular setback (Fig. 4).
The mandible of an individual with vertical
Surgery maxillary excess and a class II occlusion rotates
The anterior open bite in this group of patients to a class I relation after superior repositioning
is caused by excessive vertical growth of the of the maxilla and may not require mandibular
maxilla. The vertical deformity often occurs in surgery. Patients with class III anterior open bite
conjunction with either a primary or secondary and vertical maxillary excess end with a class III
sagittal deformity. During treatment planning occlusion of increased severity after vertical
three factors should be considered: (1) the amount correction of the maxilla and anterior rotation
of superior repositioning of the maxilla, (2) the of the mandible. These cases most probably need
position of the mandible after autorotation, and a mandibular setback procedure in conjunction
:

Fig. 3. The typical clinical signs of vertical maxillary excess (ie, increased lower facial height, the appearance of
mandibular deficiency, and convex profile caused by the backward rotation of the mandible). A gummy smile and an
increased interlabial gap are well demonstrated in this 19-year-old patient (A–D). He had a class I open bite malocclusion
and a tendency to bilateral posterior cross bites (E). The upper dental arch was orthodontically aligned in one segment
and the lower arch leveled (F). The surgical treatment plan consisted of a three-piece Le Fort I maxillary osteotomy with
superior repositioning and expansion of the maxilla. The mandible autorotated into a class III dental relation. The facial
aesthetics required maxillary advancement rather than mandibular setback. For optimization of facial aesthetics, the
chin was advanced by means of a genioplasty (G,H). The posttreatment results (I–M).


Fig. 4. This 22-year-old male patient presented with an increased lower facial height, mandibular prognathism and asym-
metry to the left, and a class III anterior open bite malocclusion (A–C). The preoperative orthodontic treatment consisted of
the aligning the maxillary arch in three segments (the anterior segment, including the four incisor teeth), and leveling the
lower dental arch (D–F). The treatment plan consisted of superior repositioning and expanding the posterior maxilla by
means of a three-piece Le Fort I osteotomy, which allowed the mandible to autorotate and close the open bite. The class
III dental and skeletal relation, however, worsened after autorotation of the mandible, which necessitated mandibular set-
back and correction of the mandibular asymmetry at the same time (G, H). The posttreatment results (I–N).

with maxillary advancement (see Fig. 4). This Poor midface esthetics are usually the conse-
decision is based on the aesthetic requirements quence of maxillary setback procedures (>3 mm).
of each case. Individuals who have vertical maxil- A combination of maxillary superior reposition-
lary excess and severe class II malocclusion and ing and setback will compromise the esthetics even
anterior open bites end with a class II occlusal re- more and should be avoided. The mandible
lationship after maxillary superior repositioning. should rather be advanced in these cases, and
To establish a class I occlusion, these cases often the maxilla superiorly repositioned and preferably
require additional mandibular advancement pro- slightly advanced. The slight advancement (2–3
cedures (Fig. 5). mm) has the added technical advantage that the


Fig. 4 (continued)

posterior maxilla is moved away from the bite. The problem often stems from poor preopera-
pterygoid plates, which avoids diﬃculty in re- tive diagnosis, inappropriate presurgical orthodon-
moving bone posteriorly to allow for adequate tics, poor surgical management, and poor
superior repositioning of the posterior maxilla. postsurgical orthodontic control [28]. Initially the
Because of the disproportionate vertical excess clinician should determine whether the discrepancy
of the posterior maxilla in open bite deformities, is skeletal or dental in nature and whether it is rel-
it often requires more bone removal in this area ative or absolute. Only when the dental casts are
than in correction of non–open bite deformities held in their correct sagittal relationship with the
with vertical maxillary excess. In all of these canines in a class I occlusion can an absolute cross
treatment scenarios the chin contour and posi- bite be revealed. When the cross bite is obviously
tion should be evaluated to enhance the aes- skeletal in nature, compensatory dental expansion,
thetic outcome. When considering a genioplasty headgear, arch wires or through-the-bite elastics
procedure, two important aspects should be kept should be avoided. These dental changes have
in mind: (1) genioplasty is not a substitute for a high potential for relapse that may only manifest
mandibular surgery and (2) chin shape or long after treatment [29].
contour is more important than chin position Presurgical orthodontic tipping of molar teeth
(anteroposterior position of pogonion). that leaves the lingual cusps hanging below the
occlusal plane has additional surgical problems.
The need for surgical correction of a transverse Hanging palatal cusps of the molars increase the
discrepancy. An individual with an open bite amount of surgical expansion of the palate that is
malocclusion and skeletal vertical maxillary excess required. Surgical palatal expansion in these cases
often has a transverse skeletal deﬁciency of the would involve expansion of the bony base and an
maxillary arch. These cases require surgical expan- element of uprighting of the molar teeth. The
sion of the maxilla by segmental surgery. Surgical increased amount of expansion leads to increased
expansion of the maxilla has been shown to be one potential for relapse (Fig. 6).
of the most unstable orthognathic procedures, Transverse stability can be enhanced by
however [27]. Transverse relapse is one of the placing a bone graft in the palatal defect.
most common postsurgical complications and in- Stabilization of the bone graft can be facilitated
evitably leads to recurrence of the anterior open by performing the palatal osteotomy in the


Fig. 5. A 16-year-old female patient with a class II anterior open bite malocclusion (A–C). Her maxilla was vertically
excessive and mandible anteroposteriorly deﬁcient. Both dental arches were orthodontically leveled, aligned, and coor-
dinated before surgery (D). After the superior repositioning of her maxilla, the bite was closed and the mandible rotated
into a class II occlusion. Her mandible was advanced by means of a bilateral sagittal split osteotomy and her chin
augmented by means of a sliding genioplasty (E, F). The posttreatment results (G–J).

mid-palate, where the bone is thickest. The loss of the graft. Performing bilateral osteoto-
disadvantage is that the mucosa in this area of mies in the palate facilitates larger expansion;
the palate is at its thinnest. A tear in the palatal however, grafting these areas where the bone is
mucosa exposes the graft and eventually leads to thin is more diﬃcult.


Fig. 6. With the maxillary posterior teeth in good angulation, a 5-mm expansion of the upper dental arch creates a 5-mm
bony defect in the palate (A, B). When the posterior teeth are orthodontically expanded, however, the molar teeth are
tipped buccally and the palatal cusps tend to hang. The expansion of the upper arch also needs to include a rotational
movement to ‘‘tuck’’ the buccal cusps in. A 5-mm dental expansion leads to a 10.5-mm bony defect (C, D).

The use of a splint during surgery and Preoperative orthodontic treatment
maintaining the splint in position for at least 6 In general, avoidance of presurgical bite-closing
weeks after surgery allow stabilization during mechanics also applies in these cases. A transverse
bone healing and may enhance skeletal stability. discrepancy between the upper and lower arch may
Obtaining immediate postsurgical orthodontic exist. The absolute or true transverse discrepancy
control by placing a palatal bar or a strong arch can be measured by holding the models in the
wire or both to support the palatal expansion desired class I relation. The potential cross bites
further enhances stability of the result. In patients should be corrected orthodontically if the discrep-
who have macroglossia, reduction of the tongue ancy falls within the range of stable orthodontic
at the time of orthognathic surgery should be movement. When an absolute cross bite exists
considered. An abnormally large tongue does not because of a transverse maxillary deficiency that
adjust to the decreased oral volume after surgical is not the result of dental tipping, three surgical
correction and plays an important role in relapse. options should be considered: (1) surgically assisted
A normal-sized tongue with forward posturing expansion of the maxillary dental arch [30], (2) nar-
does adjust to the smaller volume after surgery, rowing of the mandibular arch by an osteotomy
however. Pretreatment tongue thrust swallowing through the symphysis [31,32], and (3) two-jaw sur-
disappears after correction of the anterior open gery with surgical expansion of the maxilla by
bite because the physiologic necessity for tongue means of segmental surgery [33].
thrust has been eliminated.
Surgery
Individuals who have anterior open bite as
Open bite secondary to short mandibular ramus a result of short mandibular rami do not have the
with a normal condyle: mandibular surgery typical facial, skeletal, and occlusal features asso-
The clinical features of individuals with ciated with patients with vertical maxillary excess
anterior open bites as a result of deficiency of and open bite. Aesthetic and functional correction
the mandibular ramus height differ from patients in these cases demands a different surgical
with vertical maxillary excess. Although variable, approach, and consideration should be given to
the clinical features are as shown in Box 2 (Fig. 7). correcting this type of dentofacial deformity by


ramus osteotomy, two muscle groups are
Box 2. Features of anterior open bite stretched: the suprahyoid muscles and the medial
caused by deficiency in mandibular pterygoid and masseter muscle. The suprahyoid
ramus height musculature is lengthened when the symphysis of
the mandible is rotated superiorly and is further
Aesthetic features stretched after mandibular advancement and gen-
Normal incisor upper lip relations ioplasty. Although suprahyoid myotomies have
Normal paranasal configurations and been used successfully in animal studies to de-
alar base widths crease postsurgical relapse [34], human studies
Sufficient upper lip support and nasal tip have not supported these results [35]. Epker advo-
projections cated clinical evaluation of the patient and careful
Slightly increased anterior lower facial examination of the cephalometric prediction to
height determine the possible need for suprahyoid myot-
Convex profile and retrusive chin omies [36]. Measurement of the potential length-
Dental characteristics ening of the suprahyoid muscles is made from
Class II occlusion is usually present (the the surgical treatment prediction tracing. If the
dental relation should be seen in the suprahyoid muscles will lengthen more than
context of the horizontal change after 30%, a suprahyoid myotomy is indicated [37].
back and downward rotation of the The amount of suprahyoid muscle stretch would
mandible as a result of the short be influenced directly by the amount of mandibu-
mandibular ramus) lar rotation required to close the open bite. The
Maxillary and mandibular dental arches authors believe, however, that the role of supra-
exhibit normal occlusal curves hyoid muscle stretch in long-term stability needs
although the occlusal planes deviate further research.
Transverse dimensions of the dental When the sagittal split ramus osteotomy is
arches are usually coordinated performed (as described by Trauner and Obwe-
geser [38] and modified by Dal Pont [39]) and the
Cephalometric features distal segment is rotated counterclockwise, the
No posterior vertical maxillary excess posterior mandibular height is increased (Fig. 8).
Short mandibular ramus heights, which Downward rotation of the distal segment at the
may be associated with mandibular mandibular angle and lengthening of the ramus
anteroposterior excess or deficiency stretches the pterygomandibular sling and soft tis-
Mandible of an individual with class III sue envelope. Postoperative muscular force leads
occlusal relation appears excessive to poor proximal segment control and causes skel-
with a concave profile; individuals with etal relapse [40]. Splitting the mandibular ramus
class II occlusions exhibit convex along the lower border followed by counterclock-
profiles and retrusive chins wise rotation also stretches the medial pterygoid
muscle and the stylomandibular ligament on the
means of mandibular surgery. Surgical closure of medial aspect of the mandibular ramus (Fig. 9).
an anterior open bite by mandibular surgery in- When the sagittal split of the mandibular
volves counterclockwise rotation of the mandible ramus is performed according to the modified
at the posterior teeth. Historically this surgical technique suggested by Epker [41], the mandibu-
movement of the mandible has been considered to lar ramus is not lengthened during counterclock-
be unstable [27]. Reports in the literature identify wise rotation of the distal segment, and the
three main factors that may influence the stability pterygomandibular sling is not stretched
after orthognathic surgical procedures: (1) stretch- (Fig. 10) if the mandible is advanced.
ing of soft tissue, (2) neuromuscular adaptation,
and (3) alteration of the muscle orientation [27]. Neuromuscular adaptation. The postoperative
These factors are particularly important when clos- adaptation of the neuromusculature after most
ing an open bite by counterclockwise rotation of orthognathic procedures is good. Backward rota-
the mandible. tion of the ramus (proximal segment) may stretch
the medial pterygoid muscle and stylomandibular
Stretching of soft tissue. If the mandible is rotated ligament attached at the medial side of the ramus,
counterclockwise by means of a bilateral sagittal however (see Figs. 9 and 10). The muscle and


Fig. 7. This 20-year-old patient had a severe class II anterior open bite as a result of a short mandibular ramus. The
typical soft tissue, skeletal, and dental characteristics of patients who have open bite and short mandibular rami are
exhibited (A–D). The presurgical orthodontic treatment consisted of retraction of the upper and lower incisor teeth, level
and alignment, and coordination of both dental arches (E). A functional occlusion was established by mandibular
advancement, and an aesthetic chin contour was achieved by advancement and slight downgraft of the chin by a genio-
plasty (H). The posttreatment results 3 years after debanding (F–I).


Fig. 8. The medial side of the mandible demonstrates the sagittal split osteotomy performed through the lower border of
the body and posterior border of the ramus of the mandible (the so-called ‘‘long split’’) (A). The mandible is advanced by
10 mm and rotated counterclockwise by 3.5 mm at the incisor area, which increases the ramus height by 8 mm (B).

ligament attachment also interfere with posterior changes in the inclination of the mandibular
repositioning the distal segment and lead to ramus alter the orientation of the mandibular
backward and downward rotation of the proximal elevators. The three masseter muscle bundle
segment. Stripping the attachments of the medial groups and temporalis muscle with their respec-
pterygoid muscle and stylomandibular ligament tive attachments and orientations are demon-
from the medial side of the angle of the mandible strated in Fig. 11.
during surgery is recommended. The length of the There is a paucity of studies in the literature
temporalis muscle is also inﬂuenced by backward regarding the long-term postoperative stability
rotation of the ramus, and control of the proximal after surgical closure of anterior open bite dento-
segment is important to facilitate neuromuscular facial deformities by surgical counterclockwise
adaptation (Fig. 11). rotation of the mandible. However, skeletal
stability after counterclockwise rotation of the
Muscle orientation. Muscular adaptation is least
mandible as part of the rotation of the maxillo-
possible when muscle orientation is changed. The
mandibular complex was studied and reported by

Fig. 9. The medial view of the mandible illustrates the attachments of the medial pterygoid muscle and stylomandibular
ligament and their relation to the medial aspect of the sagittal osteotomy design, which includes the lower and posterior
border [37,38]. Counterclockwise rotation of the distal segment increases the height of the ramus and stretches the muscle
and ligament (A). When the osteotomy is performed according to the Epker [40] modiﬁcation, the height of the ramus is
not increased and the muscle and ligament are not stretched (B). The arrow indicates the anterior border of the
pterygomandibular sling.


Fig. 10. The medial side of the mandible illustrates the sagittal osteotomy. The horizontal osteotomy is extended just
posterior to the lingula, whereas the vertical osteotomy is performed through the buccal cortex and extended through
the inferior border to include the medial cortex. This osteotomy design results in the medial osteotomy running
from just posterior to the lingula downward to the lingual side of the vertical osteotomy (the so-called ‘‘short split’’)
(A). The mandible is advanced by 10 mm and rotated counterclockwise by 3.5 mm at the lower incisor tip. Note that
there is no increase in the posterior ramus height (B).

Reyneke [42] and Chemello and colleagues, [43]. to be comparable to other mandibular surgical
With this surgical design, an anterior open bite procedures.
is created by surgical counterclockwise rotation
of the maxillary occlusal plane. The counterclock- Open bite secondary to a combination of vertical
wise rotation of the maxilla is followed by the maxillary excess and short mandibular ramus
surgical rotation of the mandible. Long-term Many individuals with anterior open bite may
postoperative stability in both studies was found display a combination of the clinical, dental, and

Fig. 11. The deep muscle group of the masseter tends to have a vertical orientation, whereas the superﬁcial masseter
muscle groups have a more oblique orientation (A). The orientation of the temporalis muscle is more vertical, and
any posterior rotation of the proximal segment changes the orientation and length of the muscle (B).


cephalometric features of excessive vertical de- cannot be avoided, however, use of rigid fixation
velopment of the maxilla and deficient develop- is not recommended but rather a period of 3 to 4
ment of the mandibular rami. In these cases the weeks of intermaxillary fixation. Any orthodontic
treatment objectives should be aimed at address- treatment, such as class III elastics, that increases
ing the specific skeletal, soft tissue, and dental the loading of the condyles (and could reinitiate
problems as discussed for each of the two the condylar resorption process) should be
groups. avoided.
Degenerative joint disease (osteoarthrosis). Osteo-
Open bite secondary to short mandibular ramus arthrosis of the temporomandibular joint is not an
with condylar resorption acute entity but rather a progressive degenerative
Any process of resorption of the condyle alters disease that alters the position, morphology, and
the morphology of the condyle and its position in physiology of the bony joint structures. It involves
the glenoid fossa. Resorption of the condyles and the progressive uncontrollable degeneration of the
consequent shortening of the mandibular rami mandibular condyle, and unfortunately, the
lead to the development of a class II anterior open diagnosis and treatment selection are complicated
bite malocclusion. When considering correction of by the variability of the rate of progression of
an anterior open bite caused by resorption of the resorption. Patients experience chronic signs of
condyle, the clinician should differentiate between joint pain, crepitus, and hypomobility with pe-
idiopathic condylar resorption, degenerative joint riods of acute exacerbations. It may be possible to
disease, and rheumatic arthritis with destruction obtain short-term relief of the symptoms by
of the condyle. conservative partial reconstruction of the joint
and orthognathic surgery; however, in most
Idiopathic condylar resorption (condylysis). Al-
patients the natural progression of the degenera-
though condylysis may occur in any patient
tive process leads to recurrence of the open bite
population, it often presents in relatively young
and increasing joint symptoms. Total joint re-
caucasian women with high mandibular and
placement combined with orthognathic correction
occlusal plane angles and develops into a class II
of the dentofacial deformity is often the final
anterior open bite malocclusion. The anterior
treatment solution.
open bite usually develops progressively with no
Treatment planning for combined orthog-
pain or hypomobility. The process is usually self-
nathic surgery and total joint replacement does
limiting and may last from 6 months to 2 years. It
not differ from conventional orthognathic treat-
is thought that the resorption may be related to
ment planning. There is, however, a limited
chronic excessive loading of the mandibular
amount of mandibular advancement that can be
condyle, which produces progressive remodeling
obtained by the placement of a joint prosthesis.
of the condyle. There are two important aspects
To maintain satisfactory contact between the
when planning the correction of the existing
implant and the mandibular ramus, the advance-
dentofacial deformity: (1) ensuring that the re-
ment should be limited to 7 to 8 mm.
sorption process is inactive and (2) treating the
deformity in such a way that the loads on the
condyles are not increased. To establish whether
the condition is still active, the patient’s previous
Summary
dental records, cephalometric radiographs, and
occlusal models can be compared with current Development of an anterior open bite is
records. An alternative method, such as a radio- predominantly the result of an altered growth
isotope bone scan of the temporomandibular pattern that involves excessive vertical growth of
joints, may help to detect the presence of any the maxilla, lack of vertical mandibular ramus
resorptive activity in the condyle. Treatment development, or both. Successful correction of
should be delayed until the disease becomes anterior open bite dentofacial deformities requires
quiescent. careful assessment of the specific anatomic
Surgical correction should focus on the max- location of the discrepancy and an understanding
illa, and mandibular advancement should be of all factors that may influence the stability of
avoided if possible. Maxillary setback, which results. The flowchart (Fig. 12) summarizes the
may compromise the aesthetic outcome, may suggested principles of surgical orthodontic treat-
have to be considered. If mandibular surgery ment of anterior open bite dentofacial deformities.


Anterior open bite

Posterior vertical Short mandibular
maxillary excess ramus

Le Fort I Osteotomy Bilateral sagittal Normal condyle or
(superior repositioning) Condylar resorption
split osteotomy fractured condyle

Mandibular closed rotation
If stable Monitor condyle

Correction of AP If resorption
Acceptable
discrepancy with progressive
mandibular AP
maxilla and BSSO
position
(if necessary)

Genioplasty Condylar replacement

Fig. 12. The flowchart summarizes the suggested treatment philosophies that focus on anterior open bite correction, in
which surgical correction is aimed at the specific anatomic location of the discrepancy.

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