Department of Oral and Maxillofacial Surgery, College of Dentistry, Yonsei University, Seoul, South Korea.
Oral Science Research Center, College of Dentistry, Yonsei University, Seoul, South Korea.
Arch Oral Biol. 2019 May;101:34-42. doi: 10.1016/j.archoralbio.2019.03.003. Epub 2019 Mar 5.
The purpose of this study was to investigate changes in the dentoalveolus and occlusal plane associated with the hypotrophy of unilateral masticatory muscles following botulinum toxin (BTX) treatment in the juvenile period of rats.
We hypothesized that the loss of functional loading of masticatory muscles and occlusal force invites compensatory dentoalveolar supraeruption, accelerating occlusal cant and skeletal asymmetry. In order to confirm this hypothesis, six-week-old male rats (N = 5) were treated with BTX simultaneously at the unilateral masseter, temporalis, and medial pterygoid muscles, with a booster injection after six weeks for the experimental group. The control group (N = 6) had saline injections on both sides at the same sites and on the same schedule.
After 12 weeks, masseter and medial pterygoid muscles on the BTX side showed hypotrophic change. The mandibular structure was asymmetrical, with decreased size and lateral tilting. The maxillary and mandibular molars were supraerupted from the Frankfort plane or mandibular inferior border with lateral tilt. They accompanied downward occlusal plane cant resulting from the supraerupted maxillary and mandibular molars on the BTX side. The dentoalveolar structural changes included diminished alveolar bone density, narrow periodontal ligament space, and disorganized distribution of periodontal collagen fiber.
Unilateral hypotrophy of masticatory muscles affected the growth, symmetry, and structure of the skeletal jaws and dentoalveolus. Our hypothesis about the dentoalveolar compensation, that muscular hypotrophy was closely integrated with dentoalveolar supraeruption and an inclined occlusal plane, was confirmed.
本研究旨在探讨幼年大鼠接受肉毒毒素（BTX）治疗后，单侧咀嚼肌萎缩与牙牙槽和咬合平面变化的关系。
我们假设咀嚼肌功能负荷丧失和咬合力的丧失会导致代偿性牙牙槽过度萌出，加速咬合倾斜和骨骼不对称。为了验证这一假设，我们对 6 周龄雄性大鼠（N=5）同时在单侧咬肌、颞肌和翼内肌进行 BTX 治疗，实验组在 6 周后进行增强注射。对照组（N=6）在相同部位和相同时间进行双侧生理盐水注射。
12 周后，BTX 侧的咬肌和翼内肌出现萎缩性变化。下颌结构不对称，体积减小，向侧方倾斜。上颌和下颌磨牙从法兰克福平面或下颌下缘向外侧超萌出，伴有侧向倾斜。它们伴随着上颌和下颌磨牙在 BTX 侧超萌出导致的咬合平面倾斜。牙牙槽结构变化包括牙槽骨密度降低、牙周韧带间隙变窄以及牙周胶原纤维分布紊乱。
单侧咀嚼肌萎缩影响了骨骼颌骨和牙牙槽的生长、对称性和结构。我们关于牙牙槽代偿的假设，即肌肉萎缩与牙牙槽过度萌出和倾斜的咬合平面密切相关，得到了证实。
