Crossbites Flashcards
What type of discrepancy is a crossbite?
Transverse discrepancy in tooth relationship
What is a cross bite?
Discrepancy in the buccolingual relationship of the upper and lower teeth
List the types of crossbites
Posterior crossbite
- Buccal
- -> Unilateral buccal xb with displacement
- -> Unilateral buccal xb without displacement
- -> Bilateral buccal xb
- Lingual
- -> Unilateral lingual xb
- -> Bilateral lingual xb (scissorbite)
Anterior cross bite
Describe a buccal crossbite
Buccal cusps of lower teeth occlude buccal to the buccal cusps of upper teeth
Describe lingual crossbites
Buccal cusps of the lower teeth occlude lingual to the lingual (palatal cusps) of the upper teeth
Describe anterior crossbites
One or more upper incisors are in lingua-occlusion relative to the lower arch
What is the general aetiology for bilateral crossbites?
Most likely a skeletal discrepancy
What is the general aetiology for unilateral crossbites?
Most likely due to local factors e.g. crowding, displacement of teeth
Describe the skeletal aetiology of crossbites?
- Discrepancy in the relative widths of dental arch
- Gross anterior posterior discrepancy
- Genuine asymmetry of the dental bases
List the skeletal discrepancy in width of the arches and what cross bite occurs as a result
- Maxilla narrower than mandible = buccal XB
- Mandible narrower than maxilla = lingual XB
What AP discrepancies are associated with crossbites?
- Class III base = bilateral buccal cross bite and anterior cross bite
- Class II = lingual crossbite
What type of cross bite is associated with asymmetry of dental bases?
Unilateral cross bite without displacement
Describe the soft tissue factors in cross bite formation
- Low tongue position results in unbalanced pressure in upper buccal segments causing narrowing of upper arch (buccal cross bite)
Describe digit sucking as an aetiological factor in cross bite formation
- causes low tongue position and increased buccal pressure as the digit is sucked
- Causing narrowing of upper arch forming buccal crossbite
What are some other less common causes of cross bites
- Mouth breathing (lowered tongue position)
- Surgical repair of cleft palate (contraction of scar tissue = unilateral buccal XB)
Which dental factors are highlighted in cross bite formation?
- Displacement of teeth out of the arch
- Cuspal interferences - displacement of mandible
Why is treatment of XB with displacement important?
They may predispose susceptible individuals to TMJ disorders
Which cross bite may be accepted?
Bilateral buccal without displacement
List treatment options for bilateral buccal crossbites
- FA using expanded arch wires +/- cross elastics to expand maxilla
- URA to expand upper maxilla (quad helix most common)
What considerations are required for use of fixed appliances to treat bilateral buccal cross bite?
How can you overcome this?
- If LFH is already increased - this method may increase it further by palatal tipping of upper teeth
- Overcome using high pull headgear or buccal torque
How does rapid maxillary expansion work treat crossbites?
Skeletal expansion rather than tooth movement
Treatment options for a unilateral buccal cross bite
- URA - T spring for premolars or Z spring for canines
- If severely displaced tooth - extraction
Treatment options for lingual crossbite
- May need surgery and FA if there is a severe skeletal discrepancy
- If localised - FA to move tooth palatally or extract
Treatment options for anterior cross bite
- URA - using Z spring if one or two in anterior cross bite
- Extract tooth if severely displaced/crowding
