A crossbite is a discrepancy in the buccolingual relationship of the upper and lower teeth. Crossbite can be seen commonly in orthodontic practice. It can be clinically identified, when the lower teeth are in a buccal or labial position regarding the upper teeth, in a unilateral, bilateral, anterior and/or posterior manner.
In the transverse dimension, normal occlusion is when the palatine cusps of the upper molars and premolars occlude in the fossa of lower molars and premolars. In the anteroposterior plane, the upper incisors occlude on the labial aspects of lower incisors.
The term buccal crossbite refers to the buccal cusps of the lower teeth occlude buccal to the buccal cusps of the upper teeth. Scissor bite refers to the condition when the buccal cusps of the lower teeth occlude lingual to the lingual cusps of the upper teeth.
Crossbite malocclusion can have a skeletal or dental component or combination of both.
The etiology of a cross-bite deformity includes:
Bell and Kiebach in 2014 observed posterior crossbite as a common condition in deciduous and mixed dentition, with a prevalence of 5% to 8% in age group of 3 to 12 years. They also noted a high prevalence of 90% of functional crossbite associated with transverse discrepancies.
A study conducted in Turkish population by Gungor et al. in 2016 evaluated a high prevalence of bilateral crossbite (51%) and unilateral crossbite on the right side (47.3%) and left side (53.6%) in permanent dentition.
Types of Crossbite
Anterior crossbite: Anterior crossbite is present when one or more of the upper incisors are in linguo-occlusal
Posterior crossbite: Posterior crossbite is present when buccal cusps of upper molars and premolars, such that the lower teeth surpass buccally the upper teeth during occlusion.
Anterior crossbite can occur in primary, and mixed dentition due to a disharmony between the skeletal, functional and dental components of the child. This is characterized by one or more anterosuperior teeth occlude behind the lingual aspect of anteroinferior teeth.
In dental anterior crossbite, one or more teeth are involved. The profile is straight in centric occlusion and centric relation. Class I molar and canine relation can be seen. SNA, SNB, and ANB angles are within normal limits. It can be due to abnormal axial dental inclination.
Pseudo Class III or functional anterior crossbite can be caused by mandibular hyper propulsion, which provokes a lower tongue position and a premature canine contact that entraps the upper maxilla. The mandible is advanced mesially occasionally to obtain maximum intercuspation. The patient can reach an edge to edge incisal relation in centric relation. There is a Class III molar relation in centric occlusion and a Class I relation in centric relation. The facial profile is straight in centric relation and concave in maximum intercuspation.
Skeletal anterior crossbite is characterized by molar and canine Class III relation in centric occlusion and centric relation. An edge to edge incisor relation cannot be obtained in centric relation. The etiology of the malocclusion and the inclination of the affected teeth should be evaluated. The upper arch expansion is more likely to be stable if teeth to be moved are initially tilted palatally. The appliances used for expansion are Coffin spring, Quad helix appliance, surgically assisted rapid maxillary expansion, Ni Ti palatal expander.on. The patient has a concave profile and a retrusive upper lip, predominant chin and ANB angle is negative.
The difference between a skeletal and dental crossbite includes:
Management if Anterior Crossbite
The presence or absence of anterior displacement from centric relation to centric occlusion during mandibular closure must be established as a part of the diagnosis. The distinction between true class III and pseudo class III malocclusions have an impact on treatment plan, prognosis, and stability.
Factors to be considered for treatment:
The type of movement required for correction is assessed. Removable appliances can be considered for tipping movement; the fixed appliance is indicated for bodily tooth movement. The appliance should incorporate these features, good anterior retention to counteract the displaying effect of the active element. To free the occlusion with the opposing arch, a bite plane could be used or an active component to move the teeth. Fixed appliances can be indicated when there is insufficient overbite to retain the corrected incisors. Open coils springs can be used in straight wire mechanics, to create enough arch length to position the teeth. A negative root torque is sometimes required for a palatally placed upper incisors. An adequate overbite and a normal inclination of the long axis of the tooth to be treated is important for the stability of retention.
Correction of Anterior Crossbite in Preadolescent Age Group
Correction of Anterior Crossbite in Adolescents and Adults
Management if Posterior Crossbite
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