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Updated: Apr 25, 2026

Single-stage Dynamic Reanimation of the Smile in Irreversible Facial Paralysis by Free Functional Muscle Transfer
Published on: March 1, 2015
Jaw-stretch reflex is weaker in patients after orthognathic surgery
Yi Luo1, Peter Svensson2, Janek Dalsgaard Jensen3
1Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Fredrik Bajers Vej 7 D2, 9220 Aalborg, Denmark.
Objectives:
The jaw-stretch reflex (JSR) was studied in both patients and healthy participants in order to investigate the possible long-term impact of orthognathic surgery on the motor function of the masticatory system.
Design:
JSR was measured in patients before surgery (PC), 1year after surgery (PS) and in healthy controls (HC) (N=31 in each group). JSR was evoked by a standardized stretch device and recorded bilaterally from masseter and anterior temporalis muscles using surface electromyography (EMG).
Results:
The peak-to-peak amplitude (which was normalized to pre-stimulus EMG activity) of JSRs in PC and PS were significantly smaller than in HC (P<0.001; P<0.001). The onset latency in PS was significantly longer compared with HC (P<0.05). The duration of JSR in PS was significantly longer than in HC and PC (P<0.001; P<0.05).
Conclusion:
Patients with dentofacial deformities are characterized by reduced JSR amplitude. The delayed onset and elongated duration of JSR might be potential indicators of a long-term surgical impact on the motor function of the masticatory system.
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