Exploring botulinum toxin's impact on masseter hypertrophy: a randomized, triple-blinded clinical trial.

The present study aimed to assess the effectiveness and functional adverse effects of a single and multiple injections of botulinum toxin A (BoNT-A) for masseter hypertrophy (MH). Twenty-six women complaining about lower third facial enlargement due to MH, received 75 U of BoNT-A (abobotulinum toxin) in each masseter muscles. After 3 months, patients were randomly assigned to receive a second treatment session of Saline Solution: (G1; n = 11) or BoNT-A: (G2; n = 12). Muscle thickness (ultrasound), electrical activity (electromyography; EMG), masticatory performance, and subjective perception of MH were evaluated. Follow-up was performed at 1, 3 and 6 months. Muscle thickness, EMG activity, and masticatory performance were analyzed using ANOVA two-way and Sidak test as post-hoc. Masticatory performance was analyzed by the Friedman's test and Mann-Whitney test. Regarding inter-groups comparisons, there was a significant decrease in the left masseter muscle thickness in the G2 group at the 6 month follow-up (p < 0.02). For EMG, significant differences were evident at the 6 month assessment, with higher masseter activity for G1 (p < 0.05). For masticatory performance, no significant differences were observed throughout the study (p > 0.05) and a higher improvement in subjective perception of MH was observed in the 1 month follow-up for G2 (p < 0.05). In conclusion, BoNT-A is effective for MH, however multiple injections cause functional adverse effects in masseter muscle.

Masticatory function and oral sensorimotor ability in Parkinson's disease: Levodopa on versus off periods.

AIMS: To evaluate masticatory function and oral sensorimotor ability (OSA) in elders with Parkinson's disease (PD) during the levodopa on and off-periods. METHODS AND RESULTS: Participants were 11 partially and completely edentulous elders with PD. Masticatory function was evaluated by mandibular movements, maximum bite force (MBF), and masticatory performance (MP). Mandibular movements reflecting jaw range of motion (ROM) and jaw movements while chewing silicone test material (Optocal), were evaluated using a kinesiograph. MBF was assessed by strain sensors, and MP was determined using the median Optocal particle size (X50 ) after 40 masticatory cycles. OSA was evaluated using oral stereognosis test scores and response time. Evaluations were carried out 30 min before levodopa intake (off-period) and within a 3-day interval 1 h after levodopa intake (on-period). Data were analyzed by Student's t-test, considering a significance level of 5%. During the levodopa off-period, elders showed decreased ROM during protrusion and lateral movements, while no difference was found in maximum opening and mandibular movements during chewing. MBF was lower and X50 was higher during the off-period, indicating worse mastication. However, OSA did not differ between the evaluated times. CONCLUSION: Elders with PD had impaired mastication during the levodopa off-period, although OSA was not altered.