Written by Dr. Tanya Prasad Medically Reviewed by Dr. Shaista Salam | BDS
Table of Contents:
A crossbite is a malocclusion in which the top teeth do not occlude or bite with the lower teeth in the correct position. It is an inadequate transverse relationship between the maxillary and mandibular teeth and can be clinically identified when the lower teeth are in a labial position to the upper teeth. Literature review states that cross-bite is not a self-correcting anomaly and needs early intervention as soon as possible (1).
According to a systematic review, the prevalence of anterior crossbite, posterior crossbite, and crossbite with functional shift were 7.8%, 9.0%, and 12.2%, respectively in children (2). An uncorrected crossbite can lead to adverse effects on the growth potential of the maxillary jaw and result in true asymmetry of the face. An accurate diagnosis and treatment planning should be accomplished at an early stage to ensure a better tooth/skeletal relationship (3). There are various orthodontic appliances that can increase the transverse dimension of the maxilla and effectively treat this malocclusion.
Anterior crossbite is a malocclusion in which one or more upper incisors or canines are in a linguo-occlusal relationship with lower anterior teeth. Anterior crossbite can occur due to a disharmony between the skeletal, functional, and dental components (4,7).
In the case of dental anterior crossbite, there is involvement of one or more teeth. The alignment is straight in both centric occlusion and centric relation, with a visible Class I molar and canine relation. The SNA, SNB, and ANB angles fall within the normal range. This condition may arise due to abnormal axial dental inclination.
A pseudo Class III or functional anterior crossbite can be attributed to mandibular hyperpropulsion. This leads to a lower tongue position and premature canine contact, trapping the upper maxilla. Occasionally, the mandible is advanced mesially to achieve maximum intercuspation. In centric relation, the patient may exhibit an edge-to-edge incisal relation. Centric occlusion shows a Class III molar relation, while centric relation displays a Class I relation. The facial profile is straight in centric relation but becomes concave in maximum intercuspation.
Skeletal anterior crossbite is characterized by a Class III relation of molars and canines in both centric occlusion and centric relation. Achieving an edge-to-edge incisor relation in a centric relation is not possible. It is essential to evaluate the malocclusion's etiology and the affected teeth's inclination. Upper arch expansion is more likely to be stable if the initially tilted palatal teeth are considered. Appliances such as Coffin spring, Quad helix appliance, surgically assisted rapid maxillary expansion, and Ni-Ti palatal expander are used for expansion. The patient typically has a concave profile, a retrusive upper lip, a predominant chin, and a negative ANB angle.
Posterior crossbite occurs when the buccal cusps of the lower posterior teeth surpass the buccal cusps of the upper posterior teeth during occlusion. According to the literature a patient can present with various types of posterior crossbites (4)
Lingual crossbite, also known as scissor bite, is a condition where the buccal cusp of the lower teeth occludes lingual to the lingual cusp of lower teeth. There are two types of lingual crossbites:
The etiology of crossbite can include a multitude of factors such as hereditary influence, inadequate dental arch length, over-retained deciduous teeth, supernumerary teeth, deleterious habits such as thumb sucking, a skeletal-anteroposterior discrepancy of arches, cleft lip, and palate. The diagnosis of crossbite includes various examinations (4):
A dental examination of the patient can reveal whether the incisors are in edge-to-edge relation or a negative overjet is present. A negative overjet with the retroclination of upper anteriors can indicate the presence of a compensated class III malocclusion.
An assessment of the patient's maxilla and mandible should be carried out to determine the presence of discrepancy between centric relation and centric occlusion.
The correction of crossbite is highly effective when using clear aligners. This is because the plastic material has the ability to disocclude the jaws, meaning it helps to prevent the opposing teeth from making contact. The plastic acts as a shield, protecting the tooth from interocclusal forces that could cause a relapse (6).
As the tooth gradually moves towards its corrected position, the opposing tooth also shifts in an equal and opposite direction. This movement increases the force of collision as the teeth approach an edge-to-edge position. It is crucial to consistently shield the teeth in crossbite to prevent relapse during times when they are not covered by the aligner. Facial profile evaluation: A patient with a crossbite can present with skeletal facial asymmetry. An anterior crossbite with class III maloclusion will lead to a concave profile whereas unilateral posterior crossbite can lead to facial asymmetry.
A lateral cephalogram helps in determining the position of the maxilla and mandible and helps in determining the cause behind the crossbite.
A correct diagnosis between true class III and pseudo-class III malocclusion greatly impacts the treatment plan, prognosis, and stability of the treatment plan.
In children, various removable appliances can be given to correct the malocclusion such as tongue blade, Catalan’s appliance, face masks, rapid maxillary expansion, Frankel III appliance, and chin cup appliance (5).
Adults presenting with anterior crossbite can be treated with brackets or aligners. A posterior crossbite can be treated with coffin spring, Quad helix, Hyrax, Niti expanders, fixed orthodontic treatment, and clear aligner therapy.
Once the tooth has successfully reached the edge-to-edge relationship, the interocclusal forces on the crossbite tooth will support the direction of correction. This emphasizes the importance of ongoing protection and careful management during the entire alignment process.
Demonstrating the same, a successful case of anterior crossbite was treated using the Eon aligner system by Dr. Mohammad Al Alawi.
This case report describes the case of a 24-year-old adult male patient with skeletal and dental malocclusion and anterior crossbite associated with a functional mandibular shift. The patient opted for treatment of anterior crossbite with clear aligners. The total treatment time was 26 months which resulted in a stable outcome. At the end of the treatment, the patient reached a Class I molar and canine relation with positive overjet and overbite. The inclination of upper and lower anteriors was improved which resulted in aesthetic and functional enhancement.
A 24-year-old male patient reported with a chief complaint of an anterior crossbite. The patient sought orthodontic consultation to resolve the presence of anterior crossbite and a protrusive mandible that resulted in an unaesthetic profile. General clinical examination revealed the presence of a concave facial profile, negative lip step, and protrusive mandible. The patient had an unremarkable medical history with no relevant previous dental history.
Clinical examination did not reveal the presence of temporomandibular joint dysfunction. The maxillary midline was shifted towards the left while the lower midline was coincident with the facial midline. The patient did not present with any gross facial asymmetry and intra-oral examination revealed a bilateral class III molar and canine relationship. A reverse overjet of 3 mm was present with a 30% underbite. The patient also presented with a midline diastema of 3 mm.
The patient's lateral cephalogram revealed an increased lower third facial height with a downward growth of the mandible and increased gonial angle. The OPG displayed the presence of erupted third molars in all quadrants and the presence of paramolars in the upper right and left quadrants.
The treatment objectives for the patient were:
Recommended treatment plan
An ideal treatment plan consisting of orthognathic surgery with orthodontic decompensation of the dental arches and fixed mechanotherapy was suggested to the patient. However, the patient declined the treatment and opted for dentoalveolar correction of anterior crossbite with clear aligners.
An alternative treatment plan was suggested to the patient involving correction of the dental malocclusion using camouflage treatment. Extraction of all wisdom teeth and expansion and distalisation of lower teeth were advised.
The patient was advised to wear the provided aligner trays for maximum duration throughout the day. Each aligner was to be worn for a duration of 2 weeks after which a new set would be provided. The patient was instructed on how to insert and remove aligner trays correctly.
All third molars were extracted at the preliminary stage of the treatment. After the required healing time, the treatment was commenced and vertical attachments were planned and bonded on upper and lower canines, premolars, and molars.
The first stage of the treatment showed expansion of the upper arch which resulted in an improved arch form. Segmental distalisation of lower posterior teeth was carried out while simultaneously mesialising the upper anterior teeth. Prior to the closure of midline diastema the posterior anterior teeth were mesialised in a segmental fashion.
The upper anteriors were proclined while intruding and retracting the lower anteriors. A total of 56 trays were used for the upper arch and 48 trays were used for the correction of the lower arch. The entire treatment was carried out within 26 months without the need for any IPR.
The treatment plan successfully addressed the patient's chief complaint of an anterior crossbite. A class I molar and canine relation was established at the end of the treatment along with a positive overjet and overbite. The patient's facial profile showed a positive improvement along with the establishment of a functional and stable occlusion. The patient's smile aesthetic improved greatly with the presence of a positive overjet and coincident midlines. Permanent lingual retainers were bonded in the upper and lower anteriors.
Adults with Class III malocclusion often hesitate from uptaking orthodontic treatment due to the fear of orthognathic surgery. However, clear aligners present an aesthetic option to adult patients for the correction of an anterior crossbite. Class III correction can be carried out with the retraction of lower anteriors and mesialisation of upper anteriors, also referred to as camouflage treatment. This not only addresses the patient's chief complaint of an unaesthetic smile but also helps in the establishment of a functional occlusion.
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