Posterior Open Bite: Causes and Orthodontic Treatment

What is a posterior open bite?

A posterior open bite exists when the posterior teeth — premolars and molars — do not contact each other when the jaws are brought together, even though the anterior (front) teeth are meeting. In a normally occluding dentition, closing the jaws produces simultaneous contact across both anterior and posterior teeth. In a posterior open bite, the anterior teeth contact but there is a gap — or series of gaps — in the premolar and molar regions. This can affect one side (unilateral posterior open bite) or both sides (bilateral). It is distinct from anterior open bite, where front teeth fail to contact while posterior teeth meet. Posterior open bite impairs the ability to chew food on the affected side and concentrates all bite forces on the front teeth.

Causes of posterior open bite

Several distinct mechanisms can produce a posterior open bite. Over-eruption of the anterior teeth — where the upper or lower incisors erupt excessively downward or upward respectively — effectively lifts the posterior teeth out of contact by raising the anterior point of occlusal closure. Tongue interposition between the posterior teeth is another mechanism: in patients with a lateral tongue posture (tongue habitually resting or pushing between the upper and lower posterior teeth during swallowing), the tongue prevents full eruption of the posterior segments. Bite turbos — the small blocks of composite bonded to the upper incisors or lower molars by orthodontists to prevent posterior occlusion during treatment of deep bites — can create a temporary posterior open bite by design; this should resolve as anterior intrusion or posterior extrusion proceeds, but in some patients the posterior teeth fail to re-erupt fully after turbos are removed. CPAP (continuous positive airway pressure) devices used for sleep apnoea, and certain mandibular advancement devices, can alter jaw posture during prolonged overnight use and in some cases contribute to posterior open bite development over years of use.

Distinction from anterior open bite

Anterior open bite — where the front teeth do not contact while the back teeth meet — is more commonly discussed and has a well-established aetiology including vertical skeletal excess, tongue thrust, and thumb sucking. Posterior open bite is sometimes confused with anterior open bite in lay descriptions but requires a different diagnostic approach and different treatment mechanics. A key distinguishing feature is which teeth are meeting: in anterior open bite the posterior teeth provide all occlusal contact; in posterior open bite the anterior teeth are the sole or primary contact. Both types can coexist in complex cases.

Diagnosis

Diagnosis involves clinical examination of the occlusion with the teeth brought gently into maximum intercuspation (full closure). Study models or a digital scan taken in accurate occlusion reveal the extent and location of the open bite. Bite registration materials may be used to record the occlusal relationship precisely for articulator mounting. OPG and lateral cephalometric radiographs assess vertical jaw relationships and eruption levels of individual teeth. Video fluoroscopy or clinical observation during swallowing can reveal tongue interposition behaviour if a myofunctional cause is suspected. A thorough history should include questions about tongue habits, CPAP use, previous orthodontic treatment, and any history of bite turbos.

Treatment approaches

Treatment depends on the cause and severity. Posterior intrusion using TADs (temporary anchorage devices — miniature titanium screws placed in the jaw bone) is a highly effective approach: elastic traction from TADs to the posterior teeth creates intrusive forces that depress the molars or premolars, allowing anterior teeth to drift apart and creating space for the posterior teeth to erupt. This is most applicable when posterior teeth have over-erupted. Posterior bite planes — removable or fixed appliances that prop the posterior teeth slightly open while preventing anterior over-closure — can allow passive posterior eruption in selected cases. When bite turbos are the cause, removing them and allowing the posterior teeth adequate time to re-erupt naturally is often sufficient, though this may take several months. Myofunctional therapy targeting tongue posture and swallowing pattern is indicated when tongue interposition is a contributing factor and is particularly important for preventing relapse. Anterior extrusion mechanics (applying forces to bring anterior teeth further into occlusion) are less commonly used for posterior open bite than for anterior open bite.

Aligner limitations for posterior open bite

Clear aligners have known limitations for managing open bite problems, particularly when the treatment objective requires intrusion of posterior teeth. Aligner material itself creates a small increase in vertical dimension (a posterior bite-raising effect), and achieving reliable posterior intrusion without TADs through aligners alone is clinically challenging. Most aligner systems have design features to attempt posterior tooth movement, but independent clinical evidence for their effectiveness in posterior open bite correction is limited compared with fixed appliance mechanics combined with TADs. Patients with posterior open bite being treated with aligners should have realistic expectations about the extent of correction achievable and should discuss whether TADs would enhance the outcome.

Relapse risk

Posterior open bite has a notable relapse tendency, particularly when the underlying cause is not addressed. If tongue interposition persists after orthodontic closure of the bite, the tongue will gradually reopen the posterior spaces over months to years. If CPAP use continues without modification of the device or jaw positioning, the forces on the jaw posture will persist. Long-term retention — including the use of fixed retainers and possible modification of tongue habits through myofunctional therapy — is essential. Patients should be counselled that without addressing the aetiology, retention alone may not prevent relapse.

When surgical intervention is needed

In cases where the posterior open bite is associated with significant vertical skeletal discrepancy — particularly excessive lower face height or a steep mandibular plane angle — orthognathic surgery may be the most appropriate definitive treatment, particularly for adults in whom growth is complete. Surgical options include posterior impaction of the upper jaw (Le Fort I osteotomy with posterior impaction), which physically closes the posterior open bite by moving the entire upper jaw upward. This is a major surgical procedure requiring combined orthodontic and surgical planning. Surgery is generally reserved for cases where the degree of discrepancy exceeds what can be achieved through tooth movement alone, and where the functional and aesthetic impact justifies the intervention.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.