Diagnosis
Dental vs. skeletal open bites
Dental open bites:
- No abnormal extra-oral features.
- The dental features will normally relate to the anterior open bite aetiology. For example, a thumb-sucker will have proclined upper incisors, depressed or retroclined mandibular incisors.
- The open bite should be limited to the incisor region.
- These types of open bites are usually self-corrective if the cause is removed (e.g. cessation of thumb sucking or tongue thrusting). (Cangialosi 1984)
Skeletal open bites:
- Abnormal extra-oral features such as a long face, lip incompetence, steep mandibular plane/border and hyperdivergent jaws.
- Signs of dental compensation is usually present. Increased eruption of the incisors, upright/retroclined incisors
- A narrow palate and forward tongue posture (often adaptive) may be present. (Cangialosi 1984)
Aetiology of the open bite
Dental open bites:
- Environmental causes (i.e. habits like thumb sucking, abnormal tongue function)
- Supernumeraries, odontomas or impacted teeth causing abnormal eruption of incisors
Skeletal open bites:
- Genetics (i.e. downward backward mandibular growth pattern)
- Airway disturbance (i.e. chronic nasal obstruction causing obligatory mouth-breathing)
- Trauma or pathology to the condyle (e.g. condyle fracture, condylar resorption)
- Muscular dystrophy
- Neurological disturbances
Clinical Considerations
Treat the aetiology
- Attempting to correct the anterior open bite without treating the aetiology will be futile as relapse will almost certainly occur.
- Treatment should be directed to the part of the jaws affected by the aetiology. For example, a skeletal open bite with over-eruption of posterior teeth and a gummy smile should be treated with maxilla impaction surgery or molar intrusion mechanics rather than incisor extrusion to close the anterior open bite. Extruding incisors for such a patient will worsen their gummy smile and facial appearance.
High relapse risk
- There are cases when the aetiology cannot be corrected fully or has relapsed that the anterior open bite has a high relapse risk.
- One example is a vertical grower who can continue to grow their mandible downwards a few decades into life causing an open bite to redevelop
- Another example is a partial airway obstruction and mouth-breathing issue which relapses causing a relapse of an anterior open bite as well.
