Sympathetically mediated dental pain and its control

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1. Purpose Mastication needs cooperation of masticatory muscles, but the exact role of the each muscle for mastication is not completely clear. The purpose of this study was to evaluate the change of masticatory muscles under the unilateral masseter muscle dysfunction induced by Botulinum toxin A (BTXA) injection in rabbits. BTXA binds to presynaptic nerve endings and inhibits the release of acetylcholine, leading to temporary partial denervation and reduction of muscle fiber.2. Materials and Methods White Japanese rabbits were injected with 10 units of BTXA into the left masseter muscle. The effect of a neuromuscular blockade of masseteric activity was evaluated with serial computer tomography (CT) scans with 0.63mm slice thickness and 0.1mm slice interval taken after 4 weeks.3. Results The masseter muscle size of BTXA injected was reduced to about 80% against the control side. This indicated the morphologic change caused by the neuromuscular blockade.4. Coclusion To study the exact role of each muscles for mastication, masseter mucle dysfunction was made by BTXA injection into the masseter muscle. The most suitable dose, timing and the degree of dysfunction were established. The elrctro-myography is considered to investigate the functional change. This animal model helps the understanding of the mechanism of tempolo-mandibular dysfunction.