Effects of masticatory muscle function affected by BTX on maxillofacial bone growth through the sutural modification

Objectives: To evaluate the effect of botulinum toxin type A (BTX)-induced masticatory muscle hypofunction on the maxillofacial suture bone growth of growing rats. Setting and Sample Population: Department of Orthodontics at Taipei Medical University. Forty-eight male 4-week-old Wistar rats were divided into four groups. The N group received injections of normal saline into each of the masseter and temporalis muscles. The M group received injections of normal saline into each of the temporalis muscle and injections of BTX into each of the masseter muscle. The T group received injections of normal saline into each of the masseter muscle and injections of BTX into each of the temporalis muscle. The MT group received injections of BTX into each of the masseter and temporalis muscles. Material & Methods: Rats were sacrificed after 42 days of growth. Changes in body and muscle weight were measured. Anthropometric measurements of the maxillary arch, sutural bone mineral density and sutural bone deposition distances were recorded. Statistical comparisons were performed using analysis of variance. Results: No significant change in body weight was found across groups. However, significant decreases were observed in muscle weight, anthropometric measurements, sutural bone mineral density and bone apposition distance in the BTX-injected group. Conclusions: Reduced masticatory muscle function in growing rats can affect maxillofacial suture bone growth.