Posterior crossbite – detailed

Associated functional shift

• A functional displacement of the mandible can occur as a result of a posterior crossbite. Such a shift can cause masticatory dysfunction and a facial asymmetry which may be significant concerns to the patient. (Mohlin and Thailander 1984)

Unilateral posterior crossbite

• Asymmetric muscular activity associated with a unilateral crossbite and shift can lead to asymmetric skeletal and dental development, and it hence should be corrected as early as possible (Harrison and Ashby 2001)
• Early treatment of a posterior crossbite associated with displacement can prevent perpetuation into the permanent dentition (Harrison and Ashby, 2001)

Bilateral posterior crossbite

• Bilateral posterior crossbites can involve a dental or skeletal transverse deficiency.
• A skeletal transverse deficiency should be corrected during early treatment as the inter-maxillary sutures have more predictable orthopaedic expansion during this younger age group (Baccetti et al. 2000).

Airway or associated problems requiring treatment

• Other associated problems are upper airways resistance from hypertrophied adenoids, tonsils or chronic rhinitis.
• These patients become obligatory mouth-breathers and often have transverse deficient maxilla with posterior crossbites. These conditions need referral to an orthodontist and ENT.

Dental wear

• A posterior crossbite can lead to unfavourable occlusal contacts on the buccal teeth. Dental wear may result and should be treated before irreversible damage to the teeth occurs.

Associated functional shift

• A functional displacement of the mandible can occur as a result of a posterior crossbite. Such a shift can cause masticatory dysfunction and a facial asymmetry which may be significant concerns to the patient. (Mohlin and Thailander 1984)

Unilateral crossbite in a growing child

• Asymmetric muscular activity associated with a unilateral crossbite and shift can lead to asymmetric skeletal and dental development, and it hence should be corrected as early as possible (Harrison and Ashby 2001)
• Early treatment of a posterior crossbite associated with displacement can prevent perpetuation into the permanent dentition (Harrison and Ashby, 2001)

Severity of the crossbite

• There is no strict guideline on the severity of a crossbite to treat/refer.
• IOTN (Brook and Shaw 1989) rates a crossbite with 1-2mm slide as mild, and >2mm slide as moderate need of treatment/referral.

Temporomandibular disorder

• There is only a weak association between posterior crossbites with a functional shift and the later development of temporomandibular disorder (Mohlin and Thilander 1984)

Airway or associated problems requiring treatment

• Other associated problems are upper airways resistance from hypertrophied adenoids, tonsils or chronic rhinitis.
• These patients become obligatory mouth-breathers and often have transverse deficient maxilla with posterior crossbites. These conditions need referral to an orthodontist and ENT.