Introduction

A crossbite is a discrepancy in the buccolingual relationship of the upper and lower teeth. Crossbite can be seen commonly in orthodontic practice. It can be clinically identified, when the lower teeth are in a buccal or labial position regarding the upper teeth, in a unilateral, bilateral, anterior and/or posterior manner.[1][2][3]

In the transverse dimension, normal occlusion is when the palatine cusps of the upper molars and premolars occlude in the fossa of lower molars and premolars. In the anteroposterior plane, the upper incisors occlude on the labial aspects of lower incisors.

The term buccal crossbite refers to the buccal cusps of the lower teeth occlude buccal to the buccal cusps of the upper teeth. Scissor bite refers to the condition when the buccal cusps of the lower teeth occlude lingual to the lingual cusps of the upper teeth.

Crossbite malocclusion can have a skeletal or dental component or combination of both.

Etiology

The etiology of a cross-bite deformity includes:

• Hereditary influence
• Inadequate dental arch length
• Over retained deciduous teeth
• Supernumerary teeth
• Habits like digit sucking
• Skeletal-anteroposterior discrepancy of arches
• Cleft lip and palate

Epidemiology

Bell and Kiebach in 2014 observed posterior crossbite as a common condition in deciduous and mixed dentition, with a prevalence of 5% to 8% in age group of 3 to 12 years. They also noted a high prevalence of 90% of functional crossbite associated with transverse discrepancies.

A study conducted in Turkish population by Gungor et al. in 2016 evaluated a  high prevalence of bilateral crossbite (51%) and unilateral crossbite on the right side (47.3%) and left side (53.6%) in permanent dentition.[4][5]

History and Physical

Types of Crossbite

Anterior crossbite: Anterior crossbite is present when one or more of the upper incisors are in linguo-occlusal

Posterior crossbite: Posterior crossbite is present when buccal cusps of upper molars and premolars, such that the lower teeth surpass buccally the upper teeth during occlusion.

• Unilateral buccal crossbite with displacement
• Unilateral buccal crossbite with no displacement
• Bilateral buccal crossbite
• Unilateral lingual crossbite
• Bilateral lingual crossbite-scissor bite

Anterior crossbite can occur in primary, and mixed dentition due to a disharmony between the skeletal, functional and dental components of the child. This is characterized by one or more anterosuperior teeth occlude behind the lingual aspect of anteroinferior teeth.

In dental anterior crossbite, one or more teeth are involved. The profile is straight in centric occlusion and centric relation. Class I molar and canine relation can be seen. SNA, SNB, and ANB angles are within normal limits. It can be due to abnormal axial dental inclination.

Pseudo Class III or functional anterior crossbite can be caused by mandibular hyper propulsion, which provokes a lower tongue position and a premature canine contact that entraps the upper maxilla. The mandible is advanced mesially occasionally to obtain maximum intercuspation. The patient can reach an edge to edge incisal relation in centric relation. There is a Class III molar relation in centric occlusion and a Class I relation in centric relation. The facial profile is straight in centric relation and concave in maximum intercuspation.

Skeletal anterior crossbite is characterized by molar and canine Class III relation in centric occlusion and centric relation. An edge to edge incisor relation cannot be obtained in centric relation. The etiology of the malocclusion and the inclination of the affected teeth should be evaluated. The upper arch expansion is more likely to be stable if teeth to be moved are initially tilted palatally. The appliances used for expansion are Coffin spring, Quad helix appliance, surgically assisted rapid maxillary expansion, Ni Ti palatal expander.on. The patient has a concave profile and a retrusive upper lip, predominant chin and ANB angle is negative.

Evaluation

The difference between a skeletal and dental crossbite includes: 

1. Dental Evaluation: When the incisors are in edge to edge relation, and the lower incisors are retroclined, compensated Class III malocclusion must be considered. A clinical evaluation of under jet in association with  Class III molar relation should be done, along with functional evaluation.
2. Functional Evaluation: An assessment of the relation between the mandible and maxilla to determine any discrepancy in centric relation (CR) or centric occlusion (CO)
3. Profile evaluation: An examination of the facial proportions, chin and face positions.
4. Cephalometric evaluation:  Determine the position of the maxilla and the mandible.

Treatment / Management

 Management if Anterior Crossbite

The presence or absence of anterior displacement from centric relation to centric occlusion during mandibular closure must be established as a part of the diagnosis. The distinction between true class III and pseudo class III malocclusions have an impact on treatment plan, prognosis, and stability.[6]

Factors to be considered for treatment:

• What type of movement is required
• Overbite at the end of treatment
• Extraction/non-extraction
• If the movement of opposing tooth required

The type of movement required for correction is assessed. Removable appliances can be considered for tipping movement; the fixed appliance is indicated for bodily tooth movement.  The appliance should incorporate these features, good anterior retention to counteract the displaying effect of the active element. To free the occlusion with the opposing arch, a bite plane could be used or an active component to move the teeth. Fixed appliances can be indicated when there is insufficient overbite to retain the corrected incisors. Open coils springs can be used in straight wire mechanics, to create enough arch length to position the teeth. A negative root torque is sometimes required for a palatally placed upper incisors. An adequate overbite and a normal inclination of the long axis of the tooth to be treated is important for the stability of retention.

Correction of Anterior Crossbite in Preadolescent Age Group

1. Use of tongue blade: This method can be used to correct a developing crossbite. A tongue blade resembles a flat ice cream stick, which is placed inside the mouth contacting the erupting tooth in crossbite on its palatal side. During the slight closure of jaws, the opposing side of the tooth comes in contact with the labial aspect of the opposing mandibular tooth. Light forces generated during this period might help the tooth to attain the better position.
2. Catalan’s appliance or lower inclined plane: The lower inclined plane is constructed at an angle of 45 to the maxillary occlusal plane and can be cemented on lower incisors.
3. Face masks and Rapid maxillary expansion: This method can be used when a skeletal-transverse deficiency occurs in the maxilla
4. Frankel III appliance: Can be used for correction of a developing Class III skeletal malocclusion.
5. Chin cup appliance: It can be used to redirect the growth of a prognathic mandible.

Correction of Anterior Crossbite in Adolescents and Adults

1. Fixed appliances can be used to correct single or multiple tooth crossbite.
2. Use of TADs

Management if Posterior Crossbite

1. Coffin spring is an omega-shaped wire appliance used in correcting crossbite in young developing dentition. The expansion produced is slow and bilaterally symmetrical.
2. Quad helix is a fixed appliance, soldered to molar bands cemented to first permanent molars. It can produce slow expansion and can be used along with fixed appliance. Forces generated by appliance can be controlled depending on the amount of activation. Reactivation is done using the three-prong pliers.
3. The rapid maxillary expansion involves a hyrax screw type of appliance capable of splitting the mid-palatine suture and bring about skeletal changes in a short interval. The RME screw can be incorporated into 2 types of appliances, the banded RME and bonded RME.
4. NiTi Expanders: These are nickel-titanium wire shapes which can be attached to lingual sheath that is welded to molar bands cemented to the maxillary first permanent molars.  Various sizes are available and need to be selected depending upon the amount of expansion desired and the pretreatment width of the palate.
5. Fixed orthodontic appliances can be used for correction of posterior crossbite, as they provide 3-dimensional control over the tooth. The arches can be kept slightly expanded or constricted depending upon the movement required. Cross-elastics of 3/16-inch diameter is exerting a force of 2.5 to 4.5 oz can be used to bring about correction of individual tooth crossbites in the posterior segment.

Differential Diagnosis

• Atypical swallowing patterns

• Combination of factors

• Digit or pacifier sucking habits

• Impaired nasal breathing

• Low tongue position