A discrepancy in the buccolingual relationship of the upper and lower teeth.By convention the transverse relationship of the arches is described in terms of the position of the lower teeth relative to the upper teeth.
The buccal cusps of the lower teeth occludebuccal to the buccal cusps of the upper teeth
the buccal cusps of the lower teeth occludelingual to the lingual cusps of the upper teeth
Local causes Skeletal causes
The most common local cause is crowding where one or two teeth are displaced from the arch early loss of a second deciduous molar causing a second premolar to erupt palatally/lingually retention of a primary tooth can deflect the eruption of the permanent successor leading to a cross bite.
mismatch in the relative width of the arches e.g in thumb sucking, CLAP
an anteroposterior discrepancy, which results in a wider part of one arch occluding with a narrower part of the opposing jaw e.g sk.cl II, sk cl III
Cross bites can also be associated with true skeletal asymmetry e.g trauma to TMJ, Hemifacial microsomia, Hemimandibular hypertrophy
Anterior cross bite Posterior cross bite
An anterior crossbite is present when one or more of the upper incisors is in linguo- occlusion (i .e. in reverse overjet) relative to the lower arch Anterior crossbites are frequently associated with displacement on closure
Cross bites of the premolar and molar region involving one or two teeth or an entire buccal segment. can be subdivided as follows.1) Unilateral buccal crossbite with displacement2) Unilateral buccal crossbite with no displacement3) Bilateral buccal crossbite4) Unilateral lingual crossbite5) Bilateral lingual crossbite (scissors bite)
deflecting contact on closure into the cross bite. can affect only one or two teeth (dental) maxillary arch is of ”similar width” to the mandibular arch (i.e. it is too narrow) with the result that on closure the buccal segment teeth meet cusp to cusp. In order to achieve a more comfortable and efficient intercuspation, the patient displaces their mandible to the left or right
less common Can be dental/ skeletal
more likely to be associated with a skeletal discrepancy, either in the anteroposterior or transverse dimension, or in both.
This type of crossbite is most commonly due to displacement of an individual tooth as a result of crowding or retention of the deciduous predecessor
This crossbite is typically associated with an underlying skeletal discrepancy. often a Class II malocclusion with the upper arch furtherforward relative to the lower so that the lower buccal teeth occlude with a wider segment of the upper arch
A developing cross bite can be managed by:1) Tongue blade therapy2) Lower Inclined plane therapy3) Posterior bite block
A.C.B which ha s already developed can be treated by:1)Double cantilever spring with posterior bite plane2)Fixed appliance(2 x4)
Maxillary expansion Proclination of upper and retoclination of lower anterior teeth by fixed appliance (class III camouflage) Facemask therapy Orthognathic suregry to correct the jaw at fault
Cross elastics fixed appliance
Eliminate sucking habits Remove any tooth interferences Maxillary expansion (rapid/slow) Orthognathic surgery
Done in adolescents and adults where strong interdigitation of suture is present This creates 10 to 20 pounds of pressure across the suture-enough to create microfractures of interdigitating bone spicules rate of 0.5 to I mm/day 2 to 3 week The expansion device is left in place for 3 to 4 months new bone forms in the space at the suture, and the skeletal expansion is stable
Done in preadolescent children esp with cleft 2 pounds of pressure 0.5 mm-1mm per week damage and hemorrhage at the suture are minimized expansion is completed in 2 to 3 months