Orthodontic Diagnosis - Scissor Bite

Scissor bite is a type of bite which involves the outward positioning of the upper posterior teeth and inward positioning of the lower posterior teeth. This occurs with the presence of an expanded upper arch and constricted lower arch.

A scissor bite does not significantly impact the facial profile. However, the ability to chew is impacted because there is no contact between the molars. The treatment of a scissor bite can involve the use of an expansion device of the lower arch and the use of cross-elastics in an orthodontic treatment. The use of Temporary Anchorage Devices (TADs) has recently been found to correct a scissor bite.

According to the American Journal of Orthodontics & Dentofacial Orthopedics, scissor bite can also be accompanied by various degrees of facial asymmetry.

It is important to correct a scissor bite, because it interferes with the ability to properly chew food. The inability to chew food occurs because the molars don’t line up or have contact with each other. When left untreated, scissor bite can also result in gum recession. This occurs because the overlapping molars can rub against the gum line and apply pressure. Gum recession can lead to a variety of other issues, including periodontal disease.

Fortunately, scissor bite can be corrected in patients, both young and old. The treatment approaches can differ drastically based on the severity of the case. The treatment plan also varies based on the age of the patient.

Interceptive treatment is recommended because it is uncommon for scissor bite to correct itself. In addition, if a scissor bite exists in a child with baby teeth, it often remains even once the permanent teeth have erupted. Delaying treatment can require more extensive, complex treatment in order to correct the problem in the future.

Treatment

Patients who have a scissor bite malocclusion where only a few teeth are out of alignment can usually be treated using orthodontics, assuming the patient has a normal overbite.

Every orthodontic case is unique, and scissor bite cases vary for each patient. As a result, below are some popular appliances that are used in treating scissor bite.

1. Intermaxillary Cross-elastics: Elastics are applied to the upper teeth and connected to the lower teeth in a cross pattern. For example, the elastic may connect from the tongue side of your upper arch to the cheek side of your lower arch.
2. Trans-palatal Arch Appliance: This appliance is used in order to maintain the upper jaw’s arch width and move the molars into positions which can’t be accomplished only using wires. The appliance is bound around the first molars on each side of the mouth and a thin wire spans the roof of the mouth.
3. Lingual Arch Appliance: This appliance works by keeping the molars from drifting forward. It also prevents the molars from blocking the space where the permanent teeth will eventually erupt.
4. Temporary Anchorage Devices: Use of these devices can decrease the width of the arch and upright the molars in order to correct scissor bite without the use of surgery.

The surgical approach

In cases where numerous teeth are involved in the scissor bite and the overbite is deep, surgery may be required. The surgical correction of scissor bite can include a procedure called dentofacial osteotomy. In dentofacial osteotomy, the jaw bone is cut, moved, modified and realigned to correct the relationship between the molars in the upper and lower jaws.