Department of Orthodontics, University of Washington, Seattle, Washington, USA.
J Oral Rehabil. 2023 Sep;50(9):775-781. doi: 10.1111/joor.13495. Epub 2023 May 24.
Clinical use of botulinum neurotoxins (BoNTs) in masticatory muscles is usually bilateral, but most studies on the functional consequences of BoNT treatment have used unilaterally treated animals.
To test the hypothesis that bilateral BoNT treatment of the rabbit masseter hampers mastication and to assess its effects on bone density of the mandibular condyles.
Ten 5-month-old female rabbits received injections of BoNT into both masseter muscles and nine sham animals received saline. Body weight, incisor bite force during masseter tetany, and surface and fine-wire electromyography (EMG) of the masseter and medial pterygoid muscles were assessed at regular intervals. Half the sample was terminated after 4 weeks and the remainder after 12 weeks. Muscles were weighed and mandibular condyles were scanned with microCT to analyse bone density.
BoNT rabbits lost weight and required a soft-food diet. Incisor occlusal force plummeted after BoNT injection and remained lower than the shams. The duration of masticatory cycles was increased in the BoNT rabbits for 5 weeks, with most of the increase due to the adductor burst. Masseteric EMG amplitude began to improve at Week 5, but remained low on the working side throughout the experiment. At the 12-week endpoint, masseter muscles were smaller in the BoNT rabbits. Medial pterygoid muscles did not compensate. Condylar bone density was reduced.
Bilateral treatment of the rabbit masseter by BoNT severely affected chewing performance. Even after a 3-month recovery period, deficits remained in bite force, muscle size and condylar bone density.
肉毒毒素（BoNTs）在咀嚼肌中的临床应用通常是双侧的，但大多数关于 BoNT 治疗功能后果的研究都使用单侧治疗的动物。
检验双侧兔咬肌 BoNT 治疗会妨碍咀嚼的假设，并评估其对下颌髁突骨密度的影响。
10 只 5 月龄雌性兔双侧咬肌注射 BoNT，9 只假手术兔注射生理盐水。每隔一段时间评估体重、咬肌强直时切牙咬合力、咬肌和翼内肌表面和细钢丝肌电图（EMG）。一半的样本在 4 周后终止，其余的在 12 周后终止。称重肌肉，并用 microCT 扫描下颌髁突以分析骨密度。
BoNT 兔体重减轻，需要软食。BoNT 注射后切牙咬合力骤降，且一直低于假手术组。BoNT 兔的咀嚼周期持续时间增加了 5 周，大部分增加归因于咬肌爆发。咬肌 EMG 幅度在第 5 周开始改善，但整个实验中工作侧仍较低。在 12 周的实验终点，BoNT 兔的咬肌较小。翼内肌没有代偿。髁突骨密度降低。
BoNT 双侧治疗兔咬肌严重影响咀嚼性能。即使经过 3 个月的恢复期，切牙咬合力、肌肉大小和髁突骨密度仍存在缺陷。
