The etiology and treatment of posterior crossbite in children

HEALTH AND WELLNESS 1/2015

WELLNESS AND HEALTH

CHAPTER XXVIII

Department of Maxillofacial Orthopaedics and Orthodontics,

Wroclaw Medical University

Katedra Ortopedii Szczękowej i Ortodoncji,

Uniwersytet Medyczny im. Piastów Śląskich we Wrocławiu

TOMASZ ŻYŁA, BEATA KAWALA, MAGDALENA DUBOWIK

The etiology and treatment of posterior crossbite in children

Etiologia i metody leczenia zgryzu krzyżowego

u pacjentów w wieku rozwojowym

Key words: crossbite, maxillary constriction, early treatment

Słowa kluczowe: zgryz krzyżowy, zwężenie szczęki, leczenie wczesne

INTRODUCTION

Posterior crossbite is a type of malocclusion characterized by a discrepancy be-

tween the maxillary and the mandibular arch in the transverse dimension [16]. It usu-

ally results from the decreased upper arch width. The reported prevalence ranges from

7% to 23% [2,12,21,26,31]. According to the presence on either one or both sides of

dental arch, posterior crossbite can be classified as unilateral or bilateral. Unilateral

posterior crossbite is predominant and occurs in 80% of patients with transverse di-

screpancies [21]. Constriction of the maxillary arch makes contact in centric relation

unstable and leads to a functional shift of the mandible upon closure. This refers to a

functional unilateral crossbite, whereas in a true unilateral posterior crossbite there is

no mandibular shift and crossbite is observed in both centric relation and maximum

intercuspation [2]. In growing patients most cases of unilateral crossbite are functional

in nature. Narrowing of the upper arch is usually symmetrical and the facial asymme-

try is related to the lateral deviation of the mandible, which may promote remodeling

of the temporomandibular joint and impairment of normal mandibular growth [21,33].


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Classification of posterior crossbite is based on the position of the maxillary teeth.

The most common form, posterior lingual crossbite is diagnosed when the buccal

cusps of the maxillary teeth are palatal to the buccal cusps of the mandibular teeth.

Posterior buccal crossbite occurs when the palatal cusps of the maxillary teeth occlude

buccally to the buccal cusps of the mandibular teeth [33]. Posterior crossbite can be a

result of dental or skeletal abnormalities or a combination of the two. Dental crossbite

is caused by improperly inclined or malpositioned teeth. Posterior crossbite of skeletal

origin is defined as a discrepancy between the width of the maxilla and the mandible.

In general, the more teeth occlude in crossbite, the greater skeletal component

involved. Bilateral crossbite is mostly a consequence of maxillary skeletal deficiency.

If it is associated with severe skeletal class III malocclusion, it should be left untreated

or corrected as a part of combined orthodontic-surgical treatment [16].

The etiology of posterior crossbite is complex and involves hereditary and envi-

ronmental factors [21,27]. The well-known causes are nonnutritive sucking habits,

airway obstruction leading to mouth breathing, lowered tongue posture and short du-

ration of breastfeeding [4,8,11,12,19,20,24,27,36,39,40]. It has been observed that po-

sterior crossbite develops more often in children with early extractions of primary

teeth [28].

Early correction of posterior crossbite with a functional shift of the lower jaw is

indicated. If left untreated, this type of malocclusion may cause several changes in

hard and soft tissues including development of skeletal asymmetries, alteration of soft

tissue growth, adaptive changes in the temporomandibular joints and attrition of pri-

mary and permanent teeth [3]. Spontaneous correction of posterior crossbite is unli-

kely. The reported frequencies of self-correction range from 17% to 45% [6]. Poste-

rior crossbite with a functional shift of the mandible is usually corrected by a symme-

trical expansion of the maxillary arch. Cases of true unilateral posterior crossbite

require unilateral expansion. Overexpansion of the unaffected side should be avoided

[2].

NON-NUTRITIVE SUCKING HABITS

Sucking behaviors in infants and young children arise mainly from the physiologic

need for nutrients but also from psychological necessities [4]. Most children up to 24

months of age engage in sucking of a digit or pacifier [8]. It is well-established that

prolonged sucking habits are associated with development of various malocclusions

such as anterior open bite, class II malocclusion and posterior crossbite [6,8,11,32].

The increased prevalence of posterior crossbite in children with sucking habits results

from a widening of the mandibular arch and narrowing of the maxillary arch [40].

Studies have shown that pacifier and digit habits have different impact on the dental

arch and occlusion. Bishara et al. found a significantly greater incidence of posterior

crossbite in children with pacifier habits (41.7%) than those with digit habits (15.2%).

On the other hand, the incidence of increased overjet was significantly greater in chil-

dren with digit habits than in children with pacifier habits. Both habits resulted in

similar incidence of anterior open bite and class II canine relationships. Moreover, the

Tomasz Żyła, Beata Kawala, Magdalena Dubowik


375

authors demonstrated no significant differences in occlusal characteristics between

children breast-fed for 6 to 12 months and with no habits compared to children who

were not breast-fed and had habits lasting less than 12 months [4]. This may indicate

that short duration of non-nutritive habits (less than 12 months) has little or no effect

on occlusion. However, finger or pacifier habits lasting more than 48 months have

deleterious impact on dental arch morphology [4]. Children who used pacifiers for

longer than 3 years have 5-fold increased risk of posterior crossbite development [5].

BREASTFEEDING

The literature suggests that exclusive bottle-feeding in the first 6 months of life is

a risk factor for non-nutritive sucking habits after 12 months of age. On the contrary,

children who are exclusively breastfed show lower risk of non-nutritive habits deve-

lopment [24]. Breastfeeding has many beneficial effects on growth and development

of craniofacial region. It affects the movement of masticatory muscles and promotes

correct swallowing pattern and breathing [5]. There are differences in the activity of

the oral and facial muscles in breastfed and bottle-fed infants. Early introduction of

bottle-feeding may impede normal development of the maxillary arch and result in

posterior crossbite. Children diagnosed with posterior crossbite were breastfed for

shorter period of time compared to patients with no posterior crossbite [12]. Another

study showed that children who were breastfed for more than 12 months had a 20-fold

lower risk for posterior crossbite development compared with children who were

never breastfed and a 5-fold lower risk compared with those breastfed between 6 and

12 months. [14].

UPPER AIRWAY OBSTRUCTION

The hyperplasia of adenoids and tonsils causes many health problems including

Eustachian tube dysfunction, rhinosinusitis, obstructive sleep apnea, swallowing di-

sturbances, reduced ability to smell and taste, halitosis, speech disorders and abnormal

facial growth. The nasal airway obstruction forces a patient to breathe through the

mouth. This in turn alters the soft tissue pressure on the jaws and teeth and affects

facial growth pattern. Postural changes such as lip incompetence, lowered tongue po-

sition, proclination of the upper incisors, posterior rotation of the mandible and head

tilted backwards appear as a consequence of mouth breathing [20,35,39]. Giuca et al.

found higher prevalence of posterior crossbite in children with otitis media compared

to healthy controls. Moreover, the authors showed that hypertrophic adenoids and ton-

sils were more common in otitis media group [9]. Allergic rhinitis is one of the main

causes of airway obstruction and is reported to be a risk factor for increased overjet

and posterior crossbite development [20]. Diouf et al. demonstrated that the grade of

tonsillar hypertrophy correlates negatively with the maxillary intercanine and inter-

molar widths. The authors also found a significant positive correlation between the

palatal vault height and degree of the tonsillar hypertrophy [7]. Snoring and obstruc-

tive sleep apnea in childhood, usually caused by adeno-tonsillar enlargement, may

result in restless sleep, daytime fatigue, aggressiveness, hyperactivity and delayed


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growth. Children with obstructed nocturnal breathing have narrower maxilla, increa-

sed anterior facial height, shorter lower dental arch, posterior mandibular rotation and

higher prevalence of posterior crossbite [19]. Patients with genetically constricted ma-

xilla have an increased risk of snoring and sleep disordered breathing during the pe-

riod of physiological adenoid hypertrophy. The reduction in maxillary width persists

throughout childhood independently of performed adenotonsillectomy. This suggests

that orthodontic widening of the maxilla can be utilized in cases of chronic snoring

and upper arch narrowing [18]. It is reported that maxillary expansion improves sleep

characteristics by increasing sleep efficiency and total sleep time [1].

TEMPOROMANDIBULAR JOINT AND MUSCLE FUNCTION

Occlusal interferences, which usually appear as a result of maxillary constriction,

force the mandible to shift laterally into a position of maximal occlusal contact. This

causes improper stress and growth disturbances in temporomandibular joints. Untre-

ated functional unilateral posterior crossbite may lead to mandibular and facial asym-

metry [15,17]. Several studies found association between the presence of unilateral

posterior crossbite and temporomandibular joint signs and symptoms such as muscle

tenderness, muscle pain, headache and clicking [34,37,38]. Sonnesen et al. reported

that the level of maximum bite force was significantly lower in unilateral posterior

crossbite group compared to controls. The authors suggest that this is a result of the

altered muscle function in children with this type of malocclusion [34]. The kinesio-

graphic assessment of masticatory cycles in children with functional unilateral poste-

rior crossbite revealed asymmetries and irregularities. Unilateral masticatory cycles

were predominant. Orthodontic treatment with selective grinding and direct resin pla-

cement resulted in significant increase of total maximum lateral movements and im-

provement of the symmetry of cycles. Lateral excursions on non-crossbite side resto-

red the normal masticatory jaw movement [25]. Ultrasound evaluation of swallowing

pattern in children with unilateral posterior crossbite and children with normal occlu-

sion showed that duration of a phase IIb and the entire act of swallowing were longer

in the crossbite group. In the phase IIb the tongue moves in a posterior direction to-

wards the pharynx. The increased duration of phase IIb and the whole swallowing act

might be explained by the fact that the tongue in children with crossbite has to travel

a longer distance since it usually rests in the anterior part of the oral cavity. The study

also demonstrated higher prevalence of infantile swallowing pattern in children with

unilateral posterior crossbite [27]. Another study showed statistically significant diffe-

rence in the length of the lingual frenulum between the children with and those wi-

thout posterior crossbite. The crossbite group had shorter frenulum and thus lowered

tongue position. This changes the equilibrium of soft tissue pressure on the upper arch

and might cause maxillary constriction [23].

TREATMENT

The orthopedic expansion of the maxilla is achieved by the separation of the mid-

palatal suture. The sutural opening can be usually performed up to age of 16 in females



377

and up to age of 18 in males; however, this is highly individual and depends on the

cessation of the skeletal growth [3,13]. Persson and Thailander studied the degree of

obliteration in the midpalatal suture on histological sections of autopsy material. The

earliest suture closure was observed in a 15-year old female, while the oldest person

without ossification was 27 years old. This study confirms that the total obliteration

of the midpalatal suture is very variable [29]. As was mentioned above, early correc-

tion of posterior crossbite with a mandibular shift is required because it prevents from

the development of skeletal asymmetries in the adulthood. The treatment in the deci-

duous dentition should be limited to the correction of the premature occlusal contacts

in primary teeth, most often the canines. The success rate of this method is only 30%

to 50%. However, other techniques can be employed; it is recommended to postpone

the treatment to the phase of early mixed dentition when the first permanent molars

erupt. If the posterior crossbite is of dental origin, tipping and/or translation are used

to move individual teeth to correct position. If the posterior crossbite is caused by

skeletal transverse discrepancies maxillary base expansion is the treatment of choice

[21]. Correction of dental crossbites can be accomplished with various appliances

such as removable expansion plate, transpalatal arch, quad helix, W arch and 2 x 4

appliance [3,21]. The acrylic-based removable appliance usually has a single expan-

sion screw located at the midline between the premolars or primary molars. The re-

tention is provided by Adams or ball clasps. Turning the screw once or twice a week

applies pressure to the palatal surfaces of the teeth and the alveolar processes and

produces movement. Removable appliances usually expand the maxillary arch by tip-

ping the teeth and the alveolar processes buccally, although the separation of midpa-

latal suture is possible in primary and early mixed dentition. Skeletal expansion can

be achieved with jackscrew appliances which are fixed to the teeth by bands or bon-

dable acrylic pads. Haas and Hyrax appliances incorporate an expansion screw mostly

attached to orthodontic bands on the first permanent molars and first premolars. Haas

appliance includes an acrylic button molded to the palate, in which the jackscrew is

embedded and to which the bands are attached. In the Hyrax appliance the heavy ro-

und wires are soldered to the screw and connected with the bands [3,41]. Maxillary

base expansion can be produced by rapid maxillary expansion (RME) or slow maxil-

lary expansion (SME). RME modality is usually defined as two turns of the expansion

screw daily (0.5 mm) [10]. The initial force tips the maxillary molars buccally until

the speed of screw activation exceeds the speed of root movement. After that, the

midpalatal suture separates and skeletal expansion begins [21]. Reported side effects

of RME include external root resorption, higher levels of pain and discomfort espe-

cially during initial activation compared with SME, microtrauma of the midpalatal

suture and relapse [10,22]. Slow maxillary expansion is defined as one turn of the

jackscrew (0.25 mm) every other day. SME is thought to provide the maximum rate

at which the sutures can adapt, with minimum tearing and hemorrhaging compared

with RME [10]. RME treatment produces both orthodontic (tipping and translation of

the teeth) and orthopedic (sutural expansion) effects [13]. SME is as effective as RME

in determining skeletal expansion [22]. Generally, skeletal changes are approximately

30% to 50% of the amount of dental changes. It is advised to overcorrect the posterior

crossbite so that the buccal incline of the maxillary molars’ palatal cusps contacts with


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the lingual inclines of the buccal cusps of the mandibular molars. This allows for phy-

siologic rebound that will occur in the upper arch and for compensatory buccal uprigh-

ting of the lower teeth as a result of the changes in the soft tissue pressure [3]. The

appliance should be left intraorally in a passive state for retention of 4 to 6 months

[3,10]. A significant side effect of orthopedic maxillary expansion is downward di-

splacement of the maxilla and bite opening caused by the tipping of the posterior teeth.

Some authors suggest that use of bonded jackscrew appliance prevents bite opening.

More rigid appliance is thought to reduce dental tipping and additionally by biting on

the acrylic pads, muscles stop the maxilla from being displaced downward [41]. A

comparison of the effectiveness of quad helix, expansion plate, and composite onlay

in correction of the unilateral posterior crossbite in mixed dentition showed that tre-

atment with quad helix is the most effective. Expansion plate was unsuccessful in one

third of the cases because of lack of patient’s cooperation [30].

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ABSTRACT

Posterior crossbite is caused by a transverse discrepancy between the maxillary

and mandibular arches. The etiology is multifactorial with both genetic and environ-

mental factors. Nonnutritive sucking habits, upper airway obstruction leading to mo-

uth breathing and short duration of breastfeeding are well-established causes of ma-

xillary constriction. Temporomandibular signs and symptoms such as muscle tender-

ness, headache and clicking are more common in patients with unilateral crossbite and

a lower jaw deviation. The early treatment of unilateral posterior crossbite with a

functional shift of the mandible is required due to possible development of facial ske-

letal asymmetries.

STRESZCZENIE

Zgryz krzyżowy w odcinku bocznym spowodowany jest niezgodnością w wymia-

rze poprzecznym między łukami zębowymi szczęki i żuchwy. Etiologa jest wielo-

czynnikowa, o podłożu zarówno genetycznym, jak i środowiskowym. Dobrze pozna-

nymi przyczynami zwężenia szczęki są nawyk ssania, niedrożność górnych dróg od-

dechowych skutkująca ustnym torem oddychania oraz krótki okres karmienia natural-

nego. Dolegliwości ze strony stawu skroniowo-żuchwowego takie jak tkliwość mię-

śni, bóle głowy oraz objawy akustyczne są spotykane częściej u pacjentów z jedno-

stronnym bocznym zgryzem krzyżowym ze zbaczaniem żuchwy. Wskazane jest

wczesne leczenie jednostronnego bocznego zgryzu krzyżowego ze zbaczaniem żu-

chwy ze względu na prawdopodobieństwo rozwoju szkieletowej asymetrii twarzy.

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The etiology and treatment of posterior crossbite in children

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