Posterior Crossbite

Etiology

The etiology of a cross-bite deformity includes:

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

Epidemiology

Bell and Kiebach (2014) observed posterior crossbite as a common condition in deciduous and mixed dentition, with a prevalence of 5% to 8% in the age group of 3 to 12 years. They also noted a high prevalence (90%) of functional crossbite associated with transverse discrepancies. A study conducted in the Turkish population by Gungor et al (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 Crossbites

There are two types of crossbites: anterior and posterior.

• Anterior crossbite: Present when 1 or more of the upper incisors are in linguo-occlusal
• Posterior crossbite: Present when buccal cusps of upper molars and premolars are present, such that the lower teeth surpass the upper teeth buccally 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

Anterior crossbite can occur in primary and mixed dentition due to disharmony between the child's skeletal, functional, and dental components. It is characterized by 1 or more anterosuperior teeth occluding behind the lingual aspect of anteroinferior teeth.

Dental anterior crossbite

In dental anterior crossbite, 1 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.

Functional anterior crossbite

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 a centric relationship. 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

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 a centric relation. The malocclusion's etiology and the affected teeth' inclination should be evaluated. The upper arch expansion is more likely stable if the teeth to be moved are initially tilted palatally. The appliances used for expansion are a Coffin spring, Quad helix appliance, surgically assisted rapid maxillary expansion, and Ni-Ti palatal expander. The patient has a concave profile, a retrusive upper lip, a predominant chin, and a negative ANB angle.

Evaluation

The differences between a skeletal and dental crossbite include: 

• Dental evaluation: Computed Class III malocclusion must be considered when the incisors are in edge-to-edge relation and the lower incisors are reclined. A clinical evaluation of under jet associated with  Class III molar relation should be done, along with functional evaluation.
• Functional evaluation: An assessment of the relation between the mandible and maxilla to determine any discrepancy in centric relation (CR) or centric occlusion (CO)
• Profile evaluation: Examining the facial proportions, chin, and face positions.
• Cephalometric evaluation: Determine the position of the maxilla and the mandible.

Treatment / Management

Management of 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 impacts treatment plans, prognosis, and stability.[6]

Factors to be considered for treatment:

• What type of movement is required
• Overbite at the end of treatment
• Extraction or nonextraction
• If the movement of the 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 and good anterior retention to counteract the displaying effect of the active element. A bite plane or an active component could move the teeth to free the occlusion with the opposing arch. Fixed appliances can be indicated when there is insufficient overbite to retain the corrected incisors. Open coil 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 palatally placed upper incisors. An adequate overbite and a normal inclination of the long axis of the tooth to be treated are important for retention stability.

Correction of Anterior Crossbite

Preadolescents

1. Use of tongue blade: This method can correct the development of crossbite. A tongue blade resembles a flat ice cream stick placed inside the mouth, contacting the erupting tooth in a crossbite on its palatal side. During the slight closure of the 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 attain a 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 to correct a developing Class III skeletal malocclusion.
5. Chin cup appliance: It can be used to redirect the growth of a prognathic mandible.

Adolescents and Adults

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

Management of Posterior Crossbite

1. The coffin spring is an omega-shaped wire appliance that corrects crossbite in young, developing dentition. The expansion produced is slow and bilaterally symmetrical.
2. A Quad Helix is a fixed appliance soldered to molar bands cemented to the first permanent molars. It can produce slow expansion and be used with a fixed appliance. The forces generated by the appliance can be controlled depending on the amount of activation. Reactivation is done using 3-prong pliers.
3. The rapid maxillary expansion involves a hyrax screw type of appliance capable of splitting the mid-palatine suture and bringing 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 nickel-titanium wire shapes can be attached to a lingual sheath welded to molar bands cemented to the maxillary first permanent molars. Various sizes are available and must be selected depending on the amount of expansion desired and the pretreatment width of the palate.
5. Fixed orthodontic appliances can be used to correct posterior crossbites, 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 exerting a force of 2.5 to 4.5 oz can correct individual tooth crossbites in the posterior segment.

Differential Diagnosis

The differential diagnoses for posterior crossbite include the following:

• Atypical swallowing patterns
• Combination of factors
• Digit or pacifier-sucking habits
• Impaired nasal breathing
• Low tongue position