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Botulinum toxin in masticatory muscles: short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits.

ABSTRACT: Paralysis of the masticatory muscles using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters as well as for conditions involving muscle spasm and pain. The effects of this treatment on mastication have not been evaluated, and claims that the treatment unloads the jaw joint and mandible have not been validated. If BTX treatment does decrease mandibular loading, osteopenia might ensue as an adverse result. Rabbits received a single dose of BTX or saline into one randomly chosen masseter muscle and were followed for 4 or 12 weeks. Masticatory muscle activity was assessed weekly, and incisor bite force elicited by stimulation of each masseter was measured periodically. At the endpoint, strain gages were installed on the neck of the mandibular condyle and on the molar area of the mandible for in vivo bone strain recording during mastication and muscle stimulation. After termination, muscles were weighed and mandibular segments were scanned with micro CT. BTX paralysis of one masseter did not alter chewing side or rate, in part because of compensation by the medial pterygoid muscle. Masseter-induced bite force was dramatically decreased. Analysis of bone strain data suggested that at 4 weeks, the mandibular condyle of the BTX-injected side was underloaded, as were both sides of the molar area. Bone quantity and quality were severely decreased specifically at these underloaded locations, especially the injection-side condylar head. At 12 weeks, most functional parameters were near their pre-injection levels, but the injected masseter still exhibited atrophy and percent bone area was still low in the condylar head. In conclusion, although the performance of mastication was only minimally harmed by BTX paralysis of the masseter, the resulting underloading was sufficient to cause notable and persistent bone loss, particularly at the temporomandibular joint.

SUBMITTER: Rafferty KL

PROVIDER: S-EPMC3278508 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Botulinum toxin in masticatory muscles: short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits.

Rafferty Katherine L KL Liu Zi Jun ZJ Ye Wenmin W Navarrete Alfonso L AL Nguyen Thao Tuong TT Salamati Atriya A Herring Susan W SW

Bone 20111202 3

Paralysis of the masticatory muscles using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters as well as for conditions involving muscle spasm and pain. The effects of this treatment on mastication have not been evaluated, and claims that the treatment unloads the jaw joint and mandible have not been validated. If BTX treatment does decrease mandibular loading, osteopenia might ensue as an adverse result. Rabbits received a single dose of BTX or saline into one r ...[more]

PMID: 22155510

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Project description:Masticatory muscle activity during teeth clenching is associated with changes in many physiological parameters throughout the body. Clenching can improve muscle activity, force production, rate of force development, and joint fixation. Hence, teeth clenching and masticatory muscle activity can be important in competitive sports activities. Sport climbing is becoming increasingly popular and will be included for the first time in the Summer Olympic Games, Tokyo, 2020. However, masticatory muscle activity in sport climbers has not yet been studied. The aim of the presented study is to compare the bioelectrical activity of the masticatory muscles in sport climbers and non-climbers in order to determine the relationship between these muscles and climbing activity. 44 subjects without masticatory system disorders (16 women and 28 men, average age 26.3) were divided into two groups of 22 sport climbers (8 women, 14 men, climbing experience >4 years), while 22 people (8 women, 14 men, with no regular sports activity) were assigned to the control group. Electromyographic examination of temporalis anterior (TA) and masseter muscle (MM) was evaluated in three conditions: during resting mandibular position, during maximum intercuspation clenching, and during maximum voluntary clenching with cotton rolls between teeth. For statistical analysis, the W Shapiro-Wilk test and the Mann-Whitney U test were used. Sport climbers showed significantly higher bioelectrical activities of MM during maximum intercuspation clenching (238.45 ?V vs. 83.87 ?V, p = 0.002), and during maximum voluntary clenching with cotton rolls between teeth (300.01 ?V vs. 101.38 ?V, p = 0.001) compared to controls. The differences between groups in relation to the resting bioelectrical activity of the MM muscles, and TA muscles in all conditions were not statistically significant (p > 0.05). Higher bioelectrical activity of masseter muscles during clenching in climbers can be associated with this sports activity. However, the mechanism remains unknown and requires future research.

Dataset Information

Botulinum toxin in masticatory muscles: short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits.

Publications

Botulinum toxin in masticatory muscles: short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits.

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