Journal of Dental Sciences 19 (2024) 1328e1337

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Review article

Strategic treatment planning for anterior

open bite: A comprehensive approach
Jo-Yun Hsu a, Johnson Hsin-Chung Cheng a,b,
Sheng-Wei Feng a,c, Pin-Chuang Lai d, Noriaki Yoshida e,
Pao-Chang Chiang a,f*

a
School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
b
Division of Orthodontics, Department of Dentistry, Taipei Medical University Hospital, Taipei, Taiwan
c
Division of Prosthodontics, Department of Dentistry, Taipei Medical University Hospital, Taipei,
Taiwan
d
Department of Periodontics, School of Dentistry, University of Missouri, Kansas City, Missouri, USA
e
Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of
Biomedical Sciences, Nagasaki, Japan
f
Department of Dentistry, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan

Received 11 March 2024; Final revision received 1 April 2024

Available online 16 April 2024

KEYWORDS Abstract Anterior open bite (AOB), characterized by the lack of vertical overlap between
Anterior open bite upper and lower anterior teeth, poses a considerable challenge in orthodontics. The condi-
(AOB); tion depends on many factors that combine to render it difficult to achieve post treatment
Extractions; stability. AOB is commonly classified as dental, skeletal, or functional on the basis of the clin-
Habit correction; ical presentation and causative factors. Traditionally, skeletal AOB necessitates surgical
Mini-screws; intervention, whereas nonsurgical approaches such as extrusion arches and the Multiloop
Oral myofunctional Edgewise Archwire Technique (MEAW) can be employed in more straightforward cases. Func-
therapy (OMT); tional appliances are reserved for situations in which a patient’s growth potential offers the
Stability possibility of effectively addressing AOB. This review presents a strategic treatment
approach for addressing AOB, taking into account the classification and severity of the con-
dition. The proposed SHE framework describes the use of mini-screws (S) for anchorage and
vertical control, encouragement to correct habits (H), and the utilization of extractions and
elastics (E). By incorporating extra-radicular mini-screws, AOB closure is achieved through
anterior retraction in extraction cases or whole arch distalization of dentition with elastics
in non-extraction cases. This framework emphasizes habit correction through a regimen of
oral myofunctional therapy (OMT) and habit-correcting appliances to enhance posttreatment
stability. This review suggests that nonsurgical correction is viable in the majority of cases,

* Corresponding author. School of Dentistry, College of Oral Medicine, Taipei Medical University, No. 250, Wuxing St., Taipei 11031,
Taiwan.
E-mail address: m204095009@tmu.edu.tw (P.-C. Chiang).

https://doi.org/10.1016/j.jds.2024.04.001
1991-7902/ª 2024 Association for Dental Sciences of the Republic of China. Publishing services by Elsevier B.V. This is an open access article under
the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
 Journal of Dental Sciences 19 (2024) 1328e1337

whereas surgical intervention should be reserved for severe cases of skeletal vertical over-
growth or horizontal discrepancies.
ª 2024 Association for Dental Sciences of the Republic of China. Publishing services by Else-
vier B.V. This is an open access article under the CC BY-NC-ND license (http://
creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction Etiology

Anterior open bite (AOB) is identified by the lack of vertical AOB is a multifactorial condition involving a combination of
overlap or contact between the upper and lower anterior genetic, developmental, and environmental factors.1,2 In
teeth. AOB is commonly classified into three distinct types: the past, developmental factors including thumb-sucking,
dental AOB, skeletal AOB, and functional AOB.1 However, in tongue-thrusting, and mouth-breathing habits were the
clinical practice, categorizing a case exclusively into one of primary concerns in the development of AOB. Correction of
these types can be challenging or even impossible because these habits during early childhood helps in decreasing the
of the intricate nature of the condition.2,3 difficulty in treating AOB thereafter. Recently, genetic and
Dental AOB is characterized by a normal craniofacial epigenetic contributions to the etiology of AOB have been
pattern with proclined and under-erupted anterior teeth.1 gaining attention. Further exploration of their role in AOB
Individuals may have this condition due to experiencing development and their interaction with environmental
ankylosis of the anterior teeth following traumatic tooth factors holds promise for extending the treatment strategy
replantation,4e6 having systemic or localized factors that of AOB to the molecular level in the near future.
cause delayed teeth eruption,7 or having a persistent
thumb-sucking habit that hinders complete eruption of the (1) Genetic factors
incisors.8,9
Skeletal AOB is marked by specific anatomical charac- Genes involved in the development of craniofacial dis-
teristics, including an overlarge mandibular plane angle, orders play a role in the etiology of AOB. Specifically, the
gonial angle, anterior facial height, and total facial height FGFR2 gene is linked to Crouzon syndrome and Apert syn-
as well as an anteriorly upward-tilting palatal plane and a drome, which cause midface hypoplasia, a high-arched
retrognathic mandible.10,11 Skeletal AOB can be caused by palate, and malocclusions, including AOB.31,32 Another
several factors that disrupt the growth patterns of the gene that may cause AOB is the TCOF1 gene associated with
maxillae, mandible, and dentoalveolar complex, such as a TreachereCollins syndrome, a genetic disorder character-
hereditary predisposition, developmental disorder, and ized by micrognathia, cleft palate, and other craniofacial
history of trauma.12,13 These disruptions contribute to the anomalies.33 Additionally, in certain rare hereditary dis-
hyperdivergence of inter-base angles, resulting in an eases, such as trichorhinophalangeal syndrome linked to
augmented posterior vertical dimension.1,14 Such vertical the TRPS1 gene, AOB malocclusion is a common clinical
posterior excess impedes the establishment of a normal manifestation.34
overbite even when the anterior teeth are overerupted. Numerous studies have revealed the potential involve-
Functional AOB is closely associated with the behavior of ment of genetic and epigenetic pathways in AOB. Exploring
the head and neck muscles during speaking, breathing, these mechanisms may offer valuable insights into pro-
chewing, and swallowing. The equilibrium of the dentition spective therapeutic targets for preventing or correcting
can be affected by imbalances in the orofacial muscular AOB. An illustrative example is the matrix metal-
system, particularly by abnormalities in the tongue, lips, loproteinase family member MMP-9, which modulates
and cheeks.15e18 The resting position of the mandible is extracellular matrix metabolism within periodontal liga-
influenced by the temporomandibular joint.19 Maintaining ments. This specific protein plays a critical role in tooth
occlusal stability is challenging in individuals with a eruption, craniofacial development, and the establishment
temporomandibular disorder (TMD). AOB is a predisposing of a proper occlusal relationship. In the study conducted by
factor for TMDs, and TMDs can also lead to AOB.20e22 The Küchler et al.,35 the authors hypothesized that the GG ge-
AOBeTMD connection arises from internal disc de- notype of the MMP-9 rs17576 variant, involving a glutamine-
rangements with compression of retro-discal tissues,23 to-arginine substitution, may serve as a protective factor
hemifacial dystrophy in the lower face due to joint dis- against AOB.
eases,24 or neuromuscular deficiency of the masticatory Gene polymorphismsdincluding TNF-⍺, FAM83H, ENAM,
muscles.25 Additionally, macroglossia resulting from AMGX, PAX5, PTPN11, SOS1, and IGF-1dare currently being
amyloidosis, acromegaly, or BeckwitheWiedemann syn- investigated as potential causes of AOB because of their
drome can induce a tongue-thrusting habit. This habit roles in inflammation and dentoalveolar embryology.36e42
pushes the incisors outward, causing a V-shaped maxillary Until now, the existing knowledge in genetics and epige-
arch and disrupting the balance of the orofacial muscula- netics has not been sufficient to bridge the gap between
ture, leading to AOB.26e28 Finally, retrognathia, adenoid/ genetics and orthodontic practice. However, numerous ef-
tonsil hypertrophy, and nasal obstruction may contribute to forts have been made to leverage these findings to facili-
a mouth-breathing habit,29,30 which exacerbates AOB. tate accurate diagnosis and provide more precise

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prognoses. In a farsighted view, individualized gene therapy (2) Index for evaluating severity
may be applicable by eliminating phenotypical expressions
of dentofacial dysmorphologies, including AOB. By Some case reports propose the use of nonsurgical ap-
addressing genetic factors early, interventions during proaches for effectively managing AOB cases under the
mixed dentition stage may help prevent the development dental or dentaleskeletal combined category. By contrast,
of AOB, or reduce the difficulty of orthodontic and severe skeletal AOB may necessitate orthognathic surgery
orthognathic treatments in adulthood for individuals pre- to correct large deviations. Despite the clarity in classifi-
disposed to malocclusion. cation and definition, standardized criteria for clinically
evaluating the severity of AOB are lacking. The lack of a
(2) Developmental and environmental factors universally accepted standard makes it challenging to
consistently and objectively assess the degree of AOB
Developmental factors such as prolonged thumb- severity in a clinical setting. However, the Photographic
sucking, pacifier use, and tongue-thrusting during early Open Bite Severity Index (POSI), a novel measurement tool
childhood can exert mechanical forces on the teeth, dis- proposed by Huang et al., can score the severity of AOB on
rupting their alignment and contributing to the develop- the basis of intraoral photographs and may serve as a
ment of AOB. Additionally, chronic mouth breathing, standard for evaluating AOB.49
often associated with nasal congestion or airway issues, The six classifications of the POSI are based on the type
can affect the facial growth pattern and increase the risk and quantity of teeth with insufficient vertical overlap, as
of developing AOB. Environmental factorsdincluding diet, depicted in Fig. 2. As the POSI increases, the extent of
stress, infections,43 and medications44 dmay also pre- teeth without vertical overlap increases; these teeth range
dispose individuals to AOB. Finally, the tongue’s resting from specific incisors (POSI I, II, and III) to all incisors (POSI
position plays a crucial role in the development of AOB IV), to all anterior teeth (POSI V), to anterior teeth
and is influenced by both developmental and environ- extending into the premolar region (POSI VI).
mental factors, affecting the teeth from childhood to Huang’s student, Sherry X. Wan, conducted additional
adulthood. experiments to validate the effectiveness and reliability
of the POSI as an indicator for anticipating the severity
and treatment difficulty of AOB.50 A lower POSI value
Diagnostic index suggests a simple condition with contributing factors such
as a tongue-thrusting habit, local interference with tooth
(1) Index for assessing skeletal pattern and determining eruption, and transitional developmental disharmony. By
potential surgical requirements contrast, increased involvement of posterior teeth is
associated with risks of long-face syndrome, mesially in-
Various indicators from cephalometric analysesdsuch as clined mandibular molars, and temporomandibular joint
the Downs mandibular plane angle, the Steiner mandibular disorders. The POSI thus provides valuable insights into
plane angle, and lower anterior face heightdare commonly the complexity and severity of AOB and its possible
employed to assess the dentoalveolar and skeletal re- contributing factors, making it simple for dentists to
lationships associated with AOB. However, these assess- determine appropriate treatment options for the
ments can be influenced by reference lines such as the SeN condition.
and Frankfort planes, potentially leading to overestimation
or underestimation of hyperdivergency between the jaw
bones. Recognizing this limitation, Kim and Vietas proposed Strategic treatment planning
two novel indices for AOB evaluation: the overbite depth
indicator (ODI) and anteroposterior dysplasia indicator (1) Conventional treatment approach for anterior open
(APDI).45 Additionally, the KIX index, defined as APDI/ODI, bite
has been employed to assess the potential need for
orthognathic surgery.46 The parameters used in lateral Conventional nonsurgical approaches offer potent means of
cephalometric analysis are illustrated in Fig. 1. correcting AOB. The extrusion arch and the Multiloop
The ODI is determined by the sum of the ABeMP and Edgewise Archwire (MEAW) techniques are instrumental in
PPeFH angle measurements. According to Kim, the mean treating AOB.
ODI value is 74.5 for a normal mouth and 74.0 for a One of the first treatments developed for correcting AOB
maloccluded mouth, with standard deviations of 6.07 and was extrusion arches, which extrude incisors to close the
7.31 , respectively.47 An ODI value below the norm suggests open bite. Extrusion arches are bent from a 0.016  0.022-
a greater tendency for vertical growth. The ODI offers an inch stainless steel wire and are designed with the posterior
accurate assessment of AOB, overcoming the challenges end seamlessly inserted into the molar tubes; the anterior
associated with traditional cephalometric parameters. By segment of the arch is meticulously secured incisal to the
contrast, the APDI serves as an index for evaluating sagittal anterior teeth that require extrusion, facilitating
skeletal relationships. This index is computed by summing controlled and targeted movement of the teeth along the
three angles: FHeNPg, PPeFH, and ABeNPg. Finally, a KIX main wire.51 Extrusion arches can treat POSI VI cases and
index exceeding 1.5 signifies a high APDI value and a low achieve a reported 5-year stability of 75%.52 Nevertheless,
ODI value, suggesting a higher-than-average risk of skeletal extrusion arches are only suitable for patients exhibiting
class III malocclusion and skeletal AOB and thus indicating inadequate incisor exposure during rest and smiling. If an
that surgical intervention may be required.48 individual has compensatory supererupted incisors,

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Figure 1 Illustration of ODI, APDI, and KIX in lateral cephalometric analysis. The Overbite depth indicator (ODI) is determined by
adding the angle between AB and MP (denoted as q1) and the angle between PP and FH (denoted as q2). The anteroposterior
dysplasia indicator (APDI) is determined by summing the angle between PP and FH (denoted as q2), the angle between FH and NPg
(denoted as q3), and the angle between AB and NPg (denoted as q4). KIX is an acronym for an index without a full name, calculated
by dividing APDI by ODI (Note: AB represents the line connecting point A and point B, MP signifies the mandibular plane, PP denotes
the palatal plane, FH refers to the Frankfort horizontal plane, and NPg refers to the line connecting nasion and pogonion.) Modified
from Fatima et al.45

Figure 2 Illustration of the six types of photographic open bite severity index (POSI). Modified from Huang et al.49 Six types of
anterior open bite (POSI I to XI) are depicted through drawings derived from photographs displaying the coronal view of patients’
dentition, with posterior teeth in maximum intercuspation. POSI I is defined as the absence of vertical overlapping involving 1 or 2
lateral incisors. POSI II is defined as the absence of vertical overlapping involving only 1 central incisor. POSI III is defined as the
absence of vertical overlapping involving both central incisors. POSI IV is defined as the absence of vertical overlapping involving all
incisors. POSI V is defined as the absence of vertical overlapping involving all anterior teeth, and POSI VI is defined as the absence of
vertical overlapping extending to at least 1 premolar.

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extrusion arches are not recommended because they may approaches intrude molars by curbing the natural vertical
adversely affect esthetic outcomes. growth tendency of the posterior dentoalveolar complex,60
The MEAW technique utilizes 0.016  0.022-inch stain- influencing masticatory muscle function,61 or using magnets
less steel wires and double edgewise brackets with 0.018- incorporated into removable appliances.62 However, the
inch slots for delicate extrusion of incisors. The configura- advent of temporary anchorage devices (TADs) has revolu-
tion of the archwires is five pairs of L-shaped loops on each tionized the field because these devices offer more effec-
side; the 2e3 mm vertical segment of the loop serves as a tive vertical control during the correction of AOB. TADs
break between the teeth, and the horizontal loop length provide a reliable means of achieving satisfactory
varies from 5 to 6 mm mesial to the canine to 7e8 mm anchorage, whether for retraction in extraction cases or for
between the premolars and 8e9 mm between the molars. whole arch distalization of dentition in non-extraction
Two symmetric 3/16 heavy anterior vertical elastics are cases.63,64
placed between the first loop, and a force of approximately TADs encompass mini-screws and mini-plates strategi-
150 g is exerted to close the AOB.53 The MEAW technique cally placed in the dentoalveolar region to provide
utilizes loops to preserve wire elasticity and maintain mo- anchorage, facilitating predictable tooth movement. Mini-
lars in a distally upright position.54,55 This approach results screws differ from mini-plates in their cost-effectiveness,
in higher overall efficiency of the incisor extrusion lack of requirement for open-flap surgery, and versatile
compared with that achieved with extrusion arches. More- application.65 Titanium, titanium alloys, and stainless steel
over, maintaining the molars in a distally upright position is are the primary materials used to manufacture mini-
advantageous to the whole arch distalization of dentition in screws. Intra-alveolar mini-screws are inserted in the
non-extraction cases. However, evidence supporting the inter-radicular areas of both jaws, whereas extra-alveolar
efficacy of the MEAW technique in modifying skeletal pat- mini-screws are inserted in the infra-zygomatic crest re-
terns56 is lacking. Additionally, no consensus exists on gion of the maxilla and the buccal shelf of the mandible.66
whether the MEAW technique can be used in cases with The use of extra-alveolar mini-screws minimizes the risk of
molar intrusion. root damage. Because they can be inserted into the dense
Addressing AOB by predominantly relying on the extru- cortical bone, these screws can be long and have large di-
sion of anterior teeth raises concerns about posttreatment ameters, rendering them less likely to fail.67
relapse. Extruded anterior teeth are prone to relapse The biomechanical process employed to close AOB by
because periodontal fibers have elastic recoil, unlike the using extra-alveolar mini-screws is as follows: Elastics such
fibers in intruded posterior teeth, which maintain their as power chains or coiled springs are employed to introduce
position due to occlusal forces. Posttreatment AOB relapse a clockwise rotation in the maxillary dentition and a
following the use of extrusion arches may be associated counterclockwise rotation in the mandible and its denti-
with the pullback of extruded anterior teeth and an tion. The anchorage is secured by two infra-zygomatic
imbalanced tongue-thrusting habit.52,57,58 screws alone or reinforced with an additional two buccal
shelf screws. The closure of AOB is a direct consequence of
(2) Contemporary perspective on non-surgical anterior the resultant force being occlusal to the center of resis-
open bite treatment: The “SHE” framework tance of the dentition, leading to a modification of the
occlusal plane. The use of infra-zygomatic screws induces
Orthodontists must be cognizant of skeletal deviations simultaneous incisor extrusion and molar intrusion. For
and dentition crowding during AOB correction. Additionally, more precise torque control, an additional mini-screw can
they must precisely control the torque of anterior teeth and be strategically placed in the anterior region.67
judiciously apply posterior anchorages. Achieving post- In a study by Xun et al., the ability of screws to correct
treatment dentition stability often involves additional skeletal AOB through intrusion of the posterior dentoal-
considerations, such as implementing counterclockwise veolar region was evaluated. The results indicated that the
rotation of the mandible through molar intrusion, using average duration of molar intrusion during AOB correction
fixed or removable retainers for dentition maintenance, was 6.8  1.1 months. Overbite increased by an average of
and rehabilitating a stable tongue posture through myo- 4.2 mm, with maxillary molars intruding by a mean distance
functional therapy or tongue cribs.59 Moreover, AOB cases of 1.8 mm and mandibular molars intruding by a mean
combined with bimaxillary protrusion or class II or class III distance of 1.2 mm. Additionally, the mandibular plane
malocclusion require tailored strategies to address the angle (SNeMP) was reduced by 2.3 , leading to a favorable
specific complexities of these scenarios. counterclockwise rotation of the mandible and closure of
Contemporary nonsurgical treatment approaches for the AOB.68
AOB can be conveniently referred to by the acronym SHE,
where the “S” refers to the utilization of mini-screws, the H d habit correction
“H” refers to habit correction, and the “E” refers to Thumb sucking, tongue thrusting, and mouth breathing are
extraction or the application of elastics. Fig. 3 illustrates habits that are associated with the development of AOB and
and summarizes this conceptual framework. play a pivotal role in posttreatment relapse of AOB.
Whether these habits contribute to the development of
S d mini-screws AOB or the growth pattern of AOB influences the formation
Traditional methods for addressing vertical problems in of these habits43 remains controversial. Hong et al. con-
orthodontics include vertical pull chin caps, passive pos- ducted a study on the electromyographic characteristics of
terior bite blocks, and active vertical correctors. These muscles associated with mastication (the masseter,

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Figure 3 The SHE framework in nonsurgical treatments of AOB. This diagram illustrates the biomechanical process involved in
nonsurgical AOB treatment. Four extra-radicular mini-screws (S) are inserted to act as anchorages for anterior retraction in
extraction cases (E) or whole arch distalization of dentition in non-extraction cases. This corrective process involves clockwise
rotation of the maxillary dentition, counterclockwise rotation of the mandible and its dentition, extrusion of anterior teeth, and
intrusion of molars. These actions contribute to the closure of the open bite (CR Z center of resistance. M Z moment. F Z force.
S Z mini-screw. H Z habit correction. E Z extraction or elastics. Ex. Z extrusion. In. Z intrusion.) When addressing habit
correction in AOB treatment, the tongue and lips are pivotal components influencing the etiology and risk of relapse of AOB. In
particular, training must focus on placing the tip of the tongue at a specified spot just posterior to the incisive papilla, with the
entire body of the tongue attaching to the palatal vault. The proper resting position of the tongue is illustrated in pink in the
diagram.

temporalis, and anterior digastric) and muscles associated masticatory muscles when at rest, coupled with diminished
with mouth closure (the orbicularis oris and mentalis). biochemical advantages during chewing function.70 The
Their findings demonstrated considerably higher activity of concomitant lip weakness may lead to forceful mouth
the anterior temporalis and mentalis muscles during the closure and mentalis strain,71 as depicted in Fig. 4.
rest position in individuals with skeletal AOB than in those The characteristics of a hyperdivergent jaw relationship
without. Additionally, higher activity in both the orbicularis include a large gonial angle and severe vertical maxillary
oris and mentalis muscles was observed during the lip- excess, potentially causing a posterior shift in load appli-
sealed swallowing process in these individuals. However, cation position and an increase in the moment arm,72
in the interdental centric position, the electromyographic leading to masticatory muscle weakness during occlusal
signals of the masseter and temporalis revealed weakness, function. Such muscle weakness suggests that the balance
indicating a smaller muscle contraction force during func- of the orofacial musculature is substantially disturbed in
tional activities.69 patients with AOB. Rehabilitation combined with ortho-
The hyperdivergent jaw relationship in patients with dontic treatment may be necessary to stabilize the treat-
AOB is believed to result in greater muscular tension in ment outcome or to expedite the treatment progress in

Figure 4 A hyperdivergent jaw relationship results in excessive tension of the muscles involved in mouth closure when in the
resting position.

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individuals with skeletal AOB. Finally, tongue cribs effec- jelly reinforce the sensation of correctly swallowing and
tively enhance posttreatment stability in patients with are used to gradually increase the training difficulty. Small
AOB.73 Tongue cribs serve as a tactile habit corrector, foods like raisins and peanuts are suitable for molar-
discouraging tongue thrusting due to the discomfort asso- chewing practice. Moist foods, including apples, pears,
ciated with touching them. and cucumbers, are recommended for “quiet sucking”
Oral myofunctional therapy (OMT) consists of individual practice. Quiet sucking trains patients to collect the juice
muscle training, chewing, swallowing, and pronunciation squeezed out during mastication and quietly swallow it
exercises and training to position the lips and tongue in a without tongue thrusting or engaging other facial muscles.
relaxed posture.74 The goal of OMT is to encourage relax- Finally, body posture is closely linked to the development
ation of muscles around the oral cavity, ease the burden of orofacial myofunctional disorders. Keeping the back
imposed on the dental arch by overly tense jaw muscles, upright and extending the muscles to align the head, neck,
and establish a routine for long-term maintenance. The and shoulders are crucial steps in establishing proper
rationale behind OMT is that an imbalance in the orofacial posture for subsequent orofacial balance.81
muscular system could cause both the onset and recurrence
of AOB.69 We propose that OMT can prevent deformities in E L extractions and elastics
children with AOB. Additionally, orthodontic treatments in Malocclusionsdincluding bimaxillary protrusion, class II
conjunction with OMT are effective in adults, resulting in malocclusion with excessive horizontal open bite, and class
relatively short treatment times and establishing long-term III malocclusion with a compensatory dentition pat-
orofacial muscular stability.75 terndcan be effectively addressed using an extraction
An increasing number of case reports and review articles strategy to create space for sagittal relationship modifica-
endorse the utilization of OMT to treat AOB. However, only tions. When managing AOB combined with malocclusion,
a few papers provide comprehensive details on its applying the “drawbridge effect” or the “de-wedging ef-
constructive implementation. The concept of OMT can be fect” during anterior retraction increases overbite. The
traced back to Dr. Rogers’ notion (1929) of the “living or- “drawbridge effect” refers to anterior retraction following
thodontic appliance,” which posits that oral musculature extractions as the space-closing force pulls the anterior
alone has the potential to correct malocclusion without teeth downward like a drawbridge being lowered. The “de-
retention or appliances being needed.76 The foundations of wedging effect” refers to the idea that following the
OMT are rooted in the five stages of ingestion reported by extraction of posterior teeth, particularly the second pre-
Leopold and Kagel in 1983. In order, these stages are the molars, the mesial movement of the remaining posterior
cognitive, preparatory, oral, pharyngeal, and esophageal teeth promotes a mesial shift in the masticatory fulcrum.82
phases.77 The muscles targeted for training are the tongue, This shift is believed to be advantageous for the closure of
lips, facial expression muscles, masticatory muscle groups, AOB by reducing the vertical skeletal height or the
and soft palate. The objective is to establish a harmonious mandibular plane angle.83 Extraction can also assist in
oral environment that facilitates efficient chewing,78 cor- alleviating mentalis strain in individuals with lip incompe-
rects atypical swallowing, and maintains a proper tongue tence, helping to establish a balanced oral environment
resting posture.74 A harmonious oral environment is ach- that promotes the closure of AOB.
ieved by training overly tense muscles to relax and Elastics are widely employed for correcting AOB. When
strengthening underactive muscles, enhancing masticatory securely anchored by TADs, these elastics can be employed
function and improving the stability of the dental arch. to rotate the occlusal plane and achieve anterior retraction
The clinical methodology of OMT, as described by O. and in extraction cases or to the whole arch distalization of
M. Takahashi,79 outlines specific steps to train distinct dentition in non-extraction cases. According to Al-Thomali
muscle functions. OMT training typically involves pointing et al., no significant differences in AOB posttreatment
the tongue at a specific spot, correctly producing sounds, stability were observed between extraction and non-
and trapping substances on the dorsum of the tongue, often extraction cases.84 However, the study by Janson et al.
facilitated by assistive devices such as sticks, straws, cot- revealed that individuals undergoing extraction exhibited a
ton rolls, or water sprayers, and incorporating foods such as significantly greater level of stability (74.2%) than that
yogurt, a raisin, an apple, or a biscuit. In OMT, the “spot” is observed in individuals not undergoing extraction (61.9%).85
the region slightly behind the incisive papilla. Several
methodologies in OMT involve training the tip of the tongue (3) Surgical approaches for severe anterior open bite
to rest and swallow while pointing at the spot to exert
negative pressure around the oropharyngeal tract,80 which In cases where adult patients display excessive vertical
aids in correcting atypical swallowing in adults. An addi- skeletal growth, surgical intervention may be necessary to
tional technique is the “lip exerciser” created by Zick- correct AOB. Surgical treatments for skeletal AOB typically
efoose, designed to enhance the closing strength of the include maxillary impaction and bilateral sagittal split
orbicularis oris through bucket-bearing and resistance osteotomy (BSSO) of the mandible followed by its coun-
against a pulling hand. Increased lip-closure strength also terclockwise rotation.
plays a role in stabilizing the dentition and countering the The impaction of the maxillae can be categorized as
outward force exerted by the tongue. either differential posterior impaction or segmental
In addition to water, foods of various consistencies play impaction. In differential posterior impaction, a Le Fort I
a role in OMT.79 Soft foods such as pudding, yogurt, and down-fracture of the maxillae is executed, and the entire

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block of the dentoalveolar complex is rotated and strategies involve the use of retainers, tongue cribs, and
impacted, with the posterior maxilla being raised more OMT. Because genetic factors may be significant contribu-
than the anterior maxilla. Consequently, presurgical or- tors to the etiology of AOB, they may also be worthy sub-
thodontic treatment often involves proclination of incisor jects of future therapeutic research. However, a thorough
teeth to compensate for the differential impaction of the understanding of the genetic factors behind AOB remains
maxilla. In the case of segmental impaction of the maxilla, elusive, and these factors have yet to be incorporated into
a vertical cutting line is established either distal to the therapies for treating AOB. Exploring the intricate genetic
lateral incisors or distal to the canines. Subsequently, the and epigenetic pathways governing the development of the
two segments created by this line are separately impacted. teeth, craniofacial bones, and head and neck muscles holds
Typically, the two segments are separately aligned preop- great promise for the early correction and prevention of
eratively,86 as in the approach reported by Naini et al., AOB. Future studies are warranted to explore genetic
which involves assessing the facial profile, evaluating the therapies as adjuncts to individualized treatments for AOB.
skeletal pattern, and preoperatively establishing the ob-
jectives of orthodontic treatment.86 These preoperative
factors depend on incisor inclination, appropriate incisal Declaration of competing interest
display, and the design of the smile line in relation to the
lips. The authors have no conflicts of interest relevant to this
One study discovered a nonsignificant difference in post- article.
AOB-treatment stability between surgical and nonsurgical
cases.87 Moreover, according to a systemic review con-
ducted in 2013, vertical relapse is a characteristic of Acknowledgments
combined treatment involving both surgical and nonsurgical
approaches. An increase in anterior facial height of This work has not received any funding.
1.2e1.4 mm was observed after Le Fort I surgery.88
Furthermore, BSSO of the mandible is susceptible to post-
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