20 May 2020

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Rapid maxillary expansion: the effect on the temporomandibular joints

Davide Elsido

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In the latest issue (May 2020) of The Angle Orthodontist a systematic review was published about the effects of Rapid Maxillary Expansion (RME) on temporomandibular joints.
RME has been used as a routine clinical procedure, with the main objective of mechanically separating the palatine suture in young patients with maxillary transverse constriction, deep palatal vault, and or posterior crossbite. It has also been used in cases of crowding by increasing the perimeter of the arch and other situations where a transverse increase is necessary. After opening the median palatal suture, not only transverse but also vertical and anteroposterior changes occur. Clockwise rotation of the mandibular plane, resulting from a lower and posterior position of the mandible after RME, has been one of the most reported effects. These changes may directly or indirectly affect other structures of the craniofacial complex to which the maxilla is interconnected, including the temporomandibular joint (TMJ).
The current systematic review evaluated the impact of RME on condylar position, disc joint, joint space, and interarticular relationship in growing patients by means of CT or MRI. The studies included were those in which subjects underwent RME only. Based on this review, it was observed that RME did not promote intercondylar impairment in patients with functional unilateral posterior crossbite (FUPC) or maxillary constriction with bimaxillary posterior crossbite. Intercondylar asymmetry was improved to a symmetric position in patients with FUPC. Kasimoglu et al. (2007) investigated the relationship between vertical asymmetries of the mandibular condyle with different occlusion types and concluded that growing patients with FUPC might be at risk for developing skeletal mandibular asymmetries in the future and the early correction of posterior crossbite can help practitioners to prevent skeletal asymmetries. During the analysis of the results of the two studies that evaluated the articular disc, it was concluded that RME was not able to change the articular disc even in patients who had pretreatment disc displacement. There were no studies regarding the effects of RME on the TMJ  after the retention period.
All studies evaluated the immediate effects, with the post-treatment evaluation being performed shortly after the active period or in the retention period (12 to 24 weeks after activation). In conclusion, according to this review RME in growing patients is able, in the short term, to modify the condyle-fossa relationship, not modifying the position or shape of the articular disc, but able to maintain or improve the intercondylar symmetry relationship.

For additional information:  Effects of rapid maxillary expansion on temporomandibular joints: A systematic review