The influence of botulinum toxin type A on masticatory efficiency

Abstract

Botulinum toxin type A, produced by the gram-positive anaerobic bacterium, Clostridium botulinum act on motor nerve endings and induce muscle relaxation. In dental field, it is used in treatment of masticatory and facial muscle spasm, severe bruxism, facial tics, orofacial dyskinesias, dystonias, and idiopathic hypertrophy of the masticatory muscles, temporomandibular disorders, myofascial pain syndrome and a headache such as chronic migraine. As botulinum toxin type A adapted in various orofacial regions, it often injected into masticatory muscle such as masseter muscle and/or temporalis muscle. In case of botulinum toxin type A injected into masticatory muscles, according to the pharmacological property of itself, it causes a temporary muscle paralysis, weakness, atrophy and consequently, the change of masticatory function. However, there’s been some amount of studies on applications and effects of botulinum toxin type A, but not on change of masticatory function which is the one of side-effects of botulinum toxin injection. Also, several previous studies on masticatory function are just concentrated in electromyographic activity of masticatory muscle or masticatory force after botulinum toxin type A injection. So, this study was aimed to evaluate the masticatory efficiency after botulinum toxin type A injection by questionnaire and mixing ability test. Also, we compared the difference of masticatory efficiency between group that injected into the masseter muscle only and group that injected into the masseter and temporalis muscle. It was concluded that masticatory efficiency was significantly lowered after a botulinum toxin type A injection into the masticatory muscle, but it gradually recovered in a predictable pattern by the 12 weeks. The disturbance of subjective masticatory efficiency was lasted longer than objective masticatory efficiency. When botulinum toxin type A was injected into the masseter and temporalis muscle, the masticatory efficiency was lower than when injection was done only into the masseter muscle. It was statistically significant in the VAS and FIA at 4 weeks, but the MAI showed no significancy. After 4weeks, there was rapid recovery of muscle function in masseter and temporalis muscle group, and the difference between two groups was not significant. It could be concluded that there will be no serious disturbance of mastication compared to injection is done only into the masseter muscle, even if injection is done into the masseter and temporalis muscle in dose of this study. According to the food properties, it was confirmed that people feel more discomfort on taking hard and tough foods after botulinum toxin type A injection and not only hard foods, but also intake of soft and runny foods were influenced by botulinum toxin injection.