Clinical Assessment & Presentations
Extra-oral Features
Start your assessment by looking at the patient’s extra-oral features.
Thumb or digit sucking
These are often present in dental open bite patients. It is relatively common in children but should be actively discouraged. There is usually a normal facial appearance appearance apart from the open bite or proclined incisors.
Thumb or digit sucking can cause proclination of the upper incisors and a dental open bite malocclusion. Other habits such as pacifier or foreign objects sucking can cause a similar malocclusion.
Adenoid facies / Long face syndrome
These are often present in skeletal open bite patients. There is a long face appearance due to nasal obstruction and obligatory mouth-breathing. The typical appearance can be seen below.
Skeletal open bites with Adenoid facies are obligatory mouth-breathers with a long face and incompetent lips appearance.
Obligatory mouth-breathers have underdeveloped nostrils (alar base), a short upper lip, narrow maxilla and an open bite.
Lateral cephalogram with a skeletal open bite shows a downward rotated mandible and over-erupted molars. Hypertrophied adenoids can be seen with this patient.
Intra-oral Features
No contact of anterior teeth
In an anterior open bite malocclusion, no contact of the anterior teeth can extend not just within the incisor region but also include canines, premolars and at times, the first molars.
Tongue position and thumb sucking
Anterior open bites are often associated with a forward tongue posture. For many years this forward tongue posture or “tongue thrust” was thought to be the primarily aetiological factor of dental open bites however it is now recognised as only an adaptive behaviour in the majority of cases (CoBourne and DiBiase 2010). For example, a thumb sucking habit causes the anterior open bite and the patient then develops an adaptive forward tongue posture to create a seal for function and speech.
Indeed it is often difficult to tell if the tongue posture is causative or adaptive. A true tongue-thruster will need their tongue behaviour altered for the anterior open bite to close. If unsure, a specialist orthodontic assessment is warranted.
Is the tongue posture adaptive or causative?
Transverse constricted maxilla
Anterior open bites which have a soft tissue aetiology due to mouth-breathing and a lowered tongue posture are often associated with a narrow palate. Typical characteristics are a narrow and high palatal vault, narrow inter-molar distance, posterior crossbites and crowding and/or proclined incisors. Addressing the cause of the open bite such as any nasal obstruction and providing maxilla orthopaedic expansion will often correct both the constricted maxilla and anterior open bite.
A narrow palate associated with soft-tissue changes due to mouth-breathing.
