Tsai Chi-Yang, Huang Rouh-Yi, Lee Chi-Ming, Hsiao Wen-Tien, Yang Liang-Yo
Department of Orthodontics, Graduate Institute of Dentistry, College of Oral Medicine, Taipei Medical University and Hospital, Taipei, Taiwan.
J Oral Maxillofac Surg. 2010 May;68(5):1081-7. doi: 10.1016/j.joms.2009.12.009. Epub 2010 Mar 2.
Previous animal experiments showed how reduced masticatory function plays an important role in the craniofacial and mandibular regions in the growing period. However, articles focusing on the effects of reduced masticatory function in adult animals are quite scarce. The purpose of this study was to evaluate the effects of reduced masticatory muscle activity on the jaw bones of adult rats.
Botulinum neurotoxin type A (BTX-A) was injected into the left masseter muscle to reduce masticatory muscle function, and sequential changes in the jaw bones were investigated. Ten male 60-day-old Sprague-Dawley rats with a mean body weight of about 300 g were used. The following procedures were performed on each sample: 25 U/mL (0.3 mL) of BTX-A was injected into the left masseter muscle, whereas the right masseter muscle received an equal amount of sterilized saline solution. Ninety days after the procedure, the rats were sacrificed, and the weights of the masseter muscles were recorded. Meanwhile, direct anthropometric measurements were taken, and the cortical thickness, trabecular thickness, and bone mineral content of the skull and mandible were measured. All measurements were evaluated with statistical software.
There were significant differences in all measurements on the BTX-A side compared with those on the control side. The differences included a decreased ramus height, increased gonial angle, and increased crown height of the posterior teeth on the injection side. Significant decreases in the muscle weight, bone mineral content, cortical thickness, and trabecular thickness were also seen on the paralyzed side compared with the non-injection side.
We found that reduced masticatory function in adult rats affected the weight of the masseter muscle and the bony structure and dentition.
以往的动物实验表明，咀嚼功能降低在生长期对颅面和下颌区域起着重要作用。然而，关注成年动物咀嚼功能降低影响的文章相当稀少。本研究的目的是评估咀嚼肌活动减少对成年大鼠颌骨的影响。
将A型肉毒杆菌神经毒素（BTX-A）注射到左侧咬肌以降低咀嚼肌功能，并研究颌骨的连续变化。使用10只60日龄的雄性Sprague-Dawley大鼠，平均体重约300克。对每个样本进行以下操作：将25 U/mL（0.3 mL）的BTX-A注射到左侧咬肌，而右侧咬肌注射等量的灭菌盐溶液。手术后90天，处死大鼠并记录咬肌重量。同时，进行直接人体测量，并测量颅骨和下颌骨的皮质厚度、小梁厚度和骨矿物质含量。所有测量结果均使用统计软件进行评估。
与对照侧相比，BTX-A侧的所有测量结果均存在显著差异。差异包括注射侧下颌支高度降低、下颌角增大和后牙冠高度增加。与未注射侧相比，麻痹侧的肌肉重量、骨矿物质含量、皮质厚度和小梁厚度也显著降低。
我们发现成年大鼠咀嚼功能降低会影响咬肌重量以及骨结构和牙列。
