User:Globalorthodontist/Functional Mandibular Shift
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Functional shift of mandible occurs in patients with unilateral posterior crossbite. The shift has been reported to occur in 80-90% of unilateral posterior crossbite cases. [1][2] This shift occurs in primary dentition about 8.4% and 7.2% in mixed dentition. [2]
Etiology
[edit]Posterior crossbite is know as where the lower molar teeth are more outwards than the upper molar teeth. Small width of maxillary arch, is known to cause either unilateral or bilateral crossbite, leading to a functional shift of mandible. When a person bites down in their Centric relation bite, their midlines are matching and they have a cusp-to-fossa relationship. However, their centric relation bite is not coincident with the Centric occlusion bite. When they bite further from their CR position, their jaw tends to move to either side and thus causing a shift in the mandible. This manifests itself with following characteristics:
- Mandibular dental midline deviation
- Mandibular chin deviation
- Posterior unilateral crossbite
- CO not coincident with CR position
Treatment
[edit]It's been recommended to correct functional crossbites as early as possible. Usually, the treatment is not started until the 1st molar permanent tooth has been erupted.[3]
Self-Correction
[edit]Self-correction of a shift of mandible leading to a posterior unilateral crossbite has been reported to be 0-9% successful.[2][1]
Expansion
[edit]Main Article: Rapid palatal expansion
Rapid Palatal expansion has been known to correct functional crossbite in mixed dentition 84-100% of the time.[4][5] Expansion through other devices such as W arch, quad helix, Haas expander, Hyrax expander or superscrew have also been described in the literature. The crossbite is expected to be corrected within 6-12 weeks after a quarter-turn is done on the screw every third day. Other methods and protocols of expansion have been described in the literature in the past.
Temporomandibular Disorders
[edit]Early correction of the functional crossbite may prevent temporomandibular disorders. Studies have been published which favor this relationship[6] but others do not[7], so the causal relationship is still not properly understood.
See Also
[edit]- [[
References
[edit]- ^ a b Thilander, B.; Wahlund, S.; Lennartsson, B. (February 1984). "The effect of early interceptive treatment in children with posterior cross-bite". European Journal of Orthodontics. 6 (1): 25–34. ISSN 0141-5387. PMID 6583062.
- ^ a b c Kutin, G.; Hawes, R. R. (November 1969). "Posterior cross-bites in the deciduous and mixed dentitions". American Journal of Orthodontics. 56 (5): 491–504. ISSN 0002-9416. PMID 5261162.
- ^ Hesse, K. L.; Artun, J.; Joondeph, D. R.; Kennedy, D. B. (April 1997). "Changes in condylar postition and occlusion associated with maxillary expansion for correction of functional unilateral posterior crossbite". American Journal of Orthodontics and Dentofacial Orthopedics. 111 (4): 410–418. ISSN 0889-5406. PMID 9109586.
- ^ Erdinç, A. E.; Ugur, T.; Erbay, E. (September 1999). "A comparison of different treatment techniques for posterior crossbite in the mixed dentition". American Journal of Orthodontics and Dentofacial Orthopedics. 116 (3): 287–300. ISSN 0889-5406. PMID 10474101.
- ^ Ranta, R. (March 1988). "Treatment of unilateral posterior crossbite: comparison of the quad-helix and removable plate". ASDC journal of dentistry for children. 55 (2): 102–104. ISSN 1945-1954. PMID 3280631.
- ^ Alamoudi, N. (2000). "The correlation between occlusal characteristics and temporomandibular dysfunction in Saudi Arabian children". The Journal of Clinical Pediatric Dentistry. 24 (3): 229–236. ISSN 1053-4628. PMID 11314148.
- ^ Sari, S.; Sonmez, H.; Oray, G. O.; Camdeviren, H. (1999). "Temporomandibular joint dysfunction and occlusion in the mixed and permanent dentition". The Journal of Clinical Pediatric Dentistry. 24 (1): 59–62. ISSN 1053-4628. PMID 10709545.