The effect of botulinum toxin injected into masseter muscle on condyle and masseter muscle of young beagle dogs

Abstract

This study was based on the previous studies that muscular function can affect craniofacial and mandibular growth during growth period. There had been numerous attempts to regulate mandibular growth by controlling mandiblar function. Botulinum toxin (BoNT) had been studied as a treatment medicine for muscle hypertrophy. The purpose of this study is to analysis the histological effect of BoNT injected into the masseter muscle on the condylar cartilage and the masseter muscle in young beagle dog. Samples were divided into three groups, such as the saline injection, 10U BoNT injection and 20U BoNT injection. BoNT injection was carried-out twice every 4 weeks. After 10 weeks from the first injection, the histological differences in the condylar cartilage and masseter muscle were evaluated. In condylar cartilage the differences of the thickness in P zones were statistically significant between the two groups (group 10U & Control) and group 20U. H zones were significantly different among three groups. Especially in group 20U thinner P zone and H zone were shown. And Histological differences of masseter muscle between experimental groups (group 20U and group 10U) and control group (group Control) were observed. The shape of masseter muscle fibers in group 10U and group 20U was different from that of group Control. And endomysium was seen clearly with the separated cell connections in group 10U and 20U. The area of cross sectioned muscle fiber among three groups showed a significant difference statistically (p<0.05) each other. Each muscle fiber per unit area of group 20U was the smallest. As a result of this, it was confirmed that BoNT injected into the masseter muscle could affect cell differentiation of condylar cartilage, which could ensure that consistent with the results of the previous studies made in lower animals, such as rat. If the further study that BoNT could affect the morphological changes in the mandible is carried out, this study could be a basis for the growth modification treatment of human mandible by using BoNT.