Crossbites

1. Crossbites By Catriona Kirkwood, Harvey Sandhu, Claire Saad, Zan Johar, Shano Roshani, Jeffery Bowman, Valentina Khrypta and Nicholas Brown

2. Is an irregularity in the relationship of the upper and lower teeth. Described in terms of the position of the lower teeth to the upper teeth. Can either be a lingual or buccal crossbites.

3. Buccal or Lingual Lingual: This is when the buccal cusps of the lower teeth occlude inside the lingual cusps of the upper teeth. . Buccal: This is when the cusps of the lower teeth occlude buccal to the buccal cusps of the corresponding upper teeth.

4. Anterior and Posterior Crossbites can be further devided into anterior or posterior crossbites and bilateral or unilateral crossbites. Anterior Crossbites - This is when the upper incisors are in reverse overjet and occlude lingual to the lower incisor. An example of this would be an extreme class III incisor relationship Posterior Crossbite - These are crossbites of the molar and premolar regions. One tooth can be in crossbite or a whole sextant can be in crossbite.

5. Aetiology of Crossbites Dental Skeletal Soft tissues

6. Dental • Crowding • Presence of supernumerary • Trauma • Prolonged retention of primary teeth • Premature loss of primary dentition

7. Skeletal components • Smaller maxillary to mandibular intermolar dental width ratio • Increased lower face height • Excessive abnormal mandibular growth laterally

8. Soft tissues • Non-nutritive sucking habbit • Pacifier • Both pacifiers and digit sucking beyond age 4 associated with development of posterior crossbites. Others: • Upper airway obstruction • Neonatal intubation

9. Displacement of the mandible • In order to achieve maximum intercuspation, mandible may displace laterally • Centre line shift in lower arch towards displacement side • Unilateral crossbites with no displacement can be due to a skeletal asymmetry

10. Rapid Maxillary Expansion (RME) • Technique that produces a rapid sutural expansion at the mid-palatal suture • Indicated for patients with transverse maxillary deficiency ≥ 4mm • Commonly used to correct posterior crossbites • Treatment carried out during or before the pubertal growth spurt • An expander is cemented to premolars+molars • The desired expansion obtained by consecutive activation

11. Progress monitored radiographically • Active treatment for 2-3 weeks followed by a retention period of 3-6 months • A study found the mean expansion of 5.5mm in the molar and 3.2 mm in the canine regions obtained immediately after treatment of children with unilateral posterior crossbites • Possible side-effects include formation of midline diastema, changes to nasal morphology, continual relapse

12. Quad Helix Stainless steel appliance used with 4 active springs Causes expansion in maxillary arch Appliances bonded to both maxillary 6’s Use to treat mild malocclusions

13. Advantages and Disadvantages Produces fast results (3-6 months) Cheap in comparison to other similar appliances. Requires few visits to orthodontist for adjustments. Doesn't produce excessive amounts of force like RME. Hard to make adjustments after cementation Cant be used in lower arch Effects patient speech in early stages Inefficient in providing any distalization of posterior arches.

14. Upper Removable Appliances • This example shows how a simple T spring can be used to push incisors over the bite.

16. For treatment of an anterior crossbite with an URA: • There should be adequate space to tip the tooth into. • A positive overbite must be present after treatment. • Preferably the incisors should be slightly retroclined before treatment to prevent excessive proclination. • Similarly the patient should be a class 1 or mild class 111 skeletal pattern.

17. Treating Posterior Crossbites With URAs • A URA with a midline screw can be used to expand the upper arch. • Expansion is primarily by tipping the molars buccally. • Generally this is not recommended, as the palatal cusps of the molar teeth may swing down and prop open the occlusion, leading to reduced overbite.

18. Treatment of crossbites in the deciduous, mixed and permanent dentition Rationale for Treatment • Displacing contacts may cause TMJD • Bilateral buccal crossbites can be as efficient at chewing as teeth with normal bucco-lingual relationship- treat with caution. • Lingual bilateral crossbites (scissors bite)- cusps don’t meet making chewing near impossible • Anterior crossbites may be associated with displacement or move lower incisors labially causing gingival recession- early treatment is advisable

19. Treatment of Anterior XB Deciduous Dentition • Self correction may occur therefore treatment is delayed. Mixed Dentition • Removable appliances-if there is sufficient space available, sufficient overbite + tilting movements required. • Wait until permanent dentition is established if not possible. Permanent Dentition • Treatment is with fixed appliances. • Insufficient overbite to retain central incisors-consider moving lower incisors lingually to increase the overbite. • In a crowded arch- extraction of the displaced tooth may be an option

20. Treatment of Posterior Crossbite Unilateral Buccal Crossbite Deciduous Dentition • Removal of premature contacts may prevent posterior crossbites in the mixed/2° dentition. If not effective-an upper removable expansion plate can expand the upper arch and reduce risk of posterior crossbite occurring in the 2° dentition. Mixed Dentition • Spontaneous correction of crossbites does not occur. • Treatment tends to be delayed till 2° dentition so malocclusion can be corrected in one episode. Permanent Dentition • One tooth displacement- treatment using fixed appliances relieving crowding where/if necessary. Consider extraction of the tooth. • Cross elastics used if correction of the XB requires opposite movement of the opposing tooth. Has potential for relapse-alternative means of retention/more comprehensive treatment considered. • All the teeth in a buccal segment involved(usually with displacement) treatment is to expand the upper arch to fit around the lower arch using a URA with a midline screw/quadhelix appliance (QH). The QH is more successful and treatment is quicker. A little relapse is to be expected therefore slightly over expand but note that stability is aided by good cuspal interdigitation. • Successful treatment of a unilateral buccal crossbite with displacement can potentially prevent TMJD.

21. Bilateral Buccal Crossbite • Often accepted unless the upper buccal segment teeth are tilted palatally. • Treatment requires rapid maxillary expansion (RME). • Relapse may cause a unilateral buccal XB with displacement. • RME expansion takes approximately 19 days and needs retaining. • Common in patients with repaired cleft lip and palate. Treat by expansion using a quadhelix to stretch the scar tissue. Lingual Crossbite (Scissors bite) • Single tooth displacement can be extracted or fixed appliances can align the affected tooth relieving crowding where/if necessary. • Severe cases- treatment involves palatal movements of the upper teeth with buccal movements of the lower teeth with a fixed appliance. • Lingual XB associated with a Class II skeletal pattern is treated using a functional appliance (twin blocks) followed by fixed appliances.

22. Case Study- Before Treatment

23. Rapid Maxillary Expansion

24. Quadhelix

25. End Result

26. References Harrison J.E, Ashby D. Orthodontic treatment for posterior crossbites. Cochrane Database of Systematic Reviews 2001 D. Gill, F. Naini, M. McNally, A. Jones. The managment of transverse Maxillary deficiency. Dental Update 2004; 31: 516-523