What is anterior crossbite?

February 28, 2022

  

In a growing child, there is a phase of development when the permanent teeth begin to replace the milk teeth. The shift in the dentition is such, that there comes a stage when a child houses some permanent and some milk teeth at the same time. This period is extremely critical as the positioning of the teeth during this age group decides the future alignment of the teeth and the relation of the upper teeth with their power counterparts.

A proper bite needs to be established in a growing child. A child falling in the age group of 7-10 years should be closely monitored every 6 months by a dentist. During this stage the upper and lower front teeth (permanent central incisors) and the upper and lower back teeth (first permanent molars) find their way inside the oral cavity. When one or both upper central incisors erupt in an abnormal pattern, it often results in an abnormal closure of the anterior (front) teeth bite. This results in one or both of the upper front teeth being placed behind the lower incisors. Thus, the upper tooth or teeth get locked inside the lower front teeth and the patient is said to exhibit an anterior crossbite.

An anterior crossbite is ideally corrected between the age of 7 to 10 years. This anomaly needs to be corrected at the earliest as an untreated crossbite of the anterior teeth can result in long-term orofacial complications. Firstly, the backward position of the upper front teeth flattens the upper lip. It thus hinders the relation between the lips. Next, the improper bite does not allow the patient to make sideways movement while chewing food. Parents might complain that their child "chews or chops his or her food like a rabbit."

The abnormal positioning of the upper teeth exerts a greater than normal force on the lower front teeth. This leads to damage of the ligament and the bone surrounding the lower front teeth. This is can also force the erupting lower teeth out of the arch. Moreover, since the upper incisors are locked, the lower incisors frequently brush the front surface of the upper front teeth, resulting in wearing of the upper incisors. The bite surface of both upper and lower front teeth get abraded. An anterior bite that persists for a longer time can cause severe complications of the temporomandibular joint (TMJ). This is the joint that attaches the lower jaw to the skull through which we can make various functional movement for speech and chewing.

In order to correct an anterior crossbite, based on the patient's compliance and severity of the crossbite, a dentist has a range of treatment modalities available. The most basic approach is called a tongue blade exercise which can be also performed at home by the patient once he or she is trained by the dentist. In this, the patient is asked to place a tongue blade at an angle of 45° to the incisor that is in crossbite. The idea is to push the incisor in front in order to bring it at the desired position. One session of this exercise should last 30 minutes. Results can be observed within 2 hours to 2 weeks. Parental supervision plays a crucial role in this treatment aspect.

Another approach is to make the patient wear an appliance called the lower lingual inclined plane. In this, the lower front teeth are covered by an acrylic appliance that has a slope. When the patient bites, the upper tooth or teeth in crossbite is pushed against the slope such that it gets a force to be pushed forward. Initially, the patient might not be able to close his back teeth when this appliance is wore. However, as the teeth in crossbite move to their desired position, the posterior teeth meet each other and the treatment is deemed successful. This approach resolves the anterior crossbite in 2 to 4 weeks.

There are certain appliances that rectify the anterior crossbite in 2 to 16 weeks. These appliances might take more time than the methods mentioned above but ensure a proper alignment of teeth through even application of forces every 2 weeks. The appliance that the patient wears can have a spring in it which pushes the tooth in crossbite forward. The appliance also has a bow-like component that runs through the middle of the front surface of the front teeth. This bow ensures that the teeth that is being pushed limits itself within the arch. Finally, there are wire components that help the appliance to fit snugly in the mouth.

An anterior crossbite is corrected and treated based on how the patient closes the mouth, how many teeth are involved in crossbite and if at all there is adequate space in the upper arch to move the teeth in crossbite. Thus, anterior crossbite should be checked as soon as possible by the parents and an intervention by the dentist can help in guiding the teeth in proper bite and alignment.

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