Changes in masticatory function after injection of botulinum toxin type A to masticatory muscles

Abstract

This study examined changes in masticatory function after botulinum toxin type A (BTX-A) injection using objective and subjective tests during 12 weeks. Also, we compared differences in masticatory function between group in which only masseter muscle (M group) was injected and group in which masseter and temporal muscle (M-T group) were injected. Forty subjects were assigned into two groups; M group (n = 20) and the M-T group (n = 20). The Meditoxin(®) was used as BTX-A injection. The mixing ability index (MAI) was used as the objective indicator, and visual analogue scale (VAS) and food intake ability (FIA) index were used as subjective indicators. Overall, the masticatory function drastically declined after 4 weeks and gradually recovered with time. Compared with the pre-injection state, the masticatory function decreased by 89·2% (MAI), 12·2% (FIA) and 32·2% (VAS) 4 weeks after the injection (P < 0·05). When the results between M group and M-T group were compared, scores of VAS and FIA were significantly different 4 weeks after the injection (P < 0·05), but the MAI score showed no significant difference between two groups. In conclusion, this study showed that masticatory function was significantly decreased after BTX-A injection into the masticatory muscle after 4 and 8 weeks from injection. However, masticatory efficiency measured using MAI could completely recover after 12 weeks. Furthermore, after 8 weeks from the injection, the masticatory function measured after injection into only the masseter muscle was similar to that measured after injection into both masseter and temporal muscle.

Efficacy and Safety of Botulinum Toxin Type A on Persistent Myofascial Pain: A Randomized Clinical Trial

“…These results support a dose-duration effect for the toxin [ 25 ]. In addition, MP which is partially related to muscle activity was reduced after 7 to 28 days of BoNT-A injections, corroborating another study [ 26 ] reporting the improvement of MP following BoNT-A applications after 28 days and a completed returned to baseline values after 90 days. Conversely BoNTA-L compared to SS showed no significant differences at any evaluation point.…”

Literature review of the adverse events associated with botulinum toxin injection for the masseter muscle hypertrophy

“…According to Ahn et al and Kim et al, patients experienced a 20‐40 percent decrease in mean bite force 2 weeks after treatment compared to pre‐injection values. According to Park et al, when compared to pre‐injection values at 4 weeks post‐injection, masticatory function decreased by 89.2% (mixing ability index), 12.2% (food intake ability), and 32.2% (visual analog scale), respectively. The bite force will gradually be restored in 3‐8 weeks and usually returns to pre‐injection levels in around 12 weeks .…”

“…According to Park et al, when compared to pre‐injection values at 4 weeks post‐injection, masticatory function decreased by 89.2% (mixing ability index), 12.2% (food intake ability), and 32.2% (visual analog scale), respectively. The bite force will gradually be restored in 3‐8 weeks and usually returns to pre‐injection levels in around 12 weeks . In a MRI evaluation study, muscular atrophy persisted for 4 months after a single treatment and full recovery took sixth months …”

“…The bite force will gradually be restored in 3-8 weeks and usually returns to pre-injection levels in around 12 weeks. 18,[34][35][36][37][38][39]42,43 In a MRI evaluation study, muscular atrophy persisted for 4 months after a single treatment and full recovery took sixth months. 8,33…”

Short-term improvement of masticatory function after implant restoration

“…Among these, Sato et al [ 2 ] proposed the use of artificial food composed of two-color utility wax cubes and formulated a mixing ability index (MAI), scores of which are determined by the degree of color-mixing and the shape of the wax after chewing. Several previous studies have reported that the FIA and MAI scores can successfully evaluate masticatory function in patients with temporomandibular disorders or botulinum toxin injections and in orthodontic patients [ 3 4 5 ].…”