Eliane H Dutra1, Sumit Yadav2. 1. Division of Orthodontics, University of Connecticut Health Center, Farmington, Conn. 2. Division of Orthodontics, University of Connecticut Health Center, Farmington, Conn. Electronic address: yadav_sumit17@yahoo.com.
Abstract
OBJECTIVES: To evaluate whether the effects on the mandibular condylar cartilage (MCC) and subchondral bone are transient of botulinum neurotoxin (Botox) injection into the masseter muscle. METHODS: Botox (0.3 U) was injected into the right masseter of 6-week-old female mice (C57BL/6; n = 16). In addition, 16 mice were used as control and received no injections. Experimental and matching control mice were killed 4 or 8 weeks after the single Botox injection. Mandibles and mandibular condyles were analyzed by means of microscopic computed tomography (microCT) and histology. Sagittal sections of condyles were stained for tartrate-resistant acid phosphatase (TRAP), toluidine blue, 5-ethynyl-2'-deoxyuridine (EdU), and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling. RESULTS: Bone volume fraction was significantly decreased on the subchondral bone of the Botox-injected side, compared with the control side and control mice, 4 and 8 weeks after injection. Furthermore, histologic analysis revealed decrease in mineralization, cartilage thickness, TRAP activity, and EdU-positive cells in the MCC of the Botox-injected side 4 and 8 weeks after injection. CONCLUSIONS: The effects on the MCC and subchondral bone of Botox injection into the masseter muscle persisted for 8 weeks after injection and were not considered to be transient.
OBJECTIVES: To evaluate whether the effects on the mandibular condylar cartilage (MCC) and subchondral bone are transient of botulinum neurotoxin (Botox) injection into the masseter muscle. METHODS:Botox (0.3 U) was injected into the right masseter of 6-week-old female mice (C57BL/6; n = 16). In addition, 16 mice were used as control and received no injections. Experimental and matching control mice were killed 4 or 8 weeks after the single Botox injection. Mandibles and mandibular condyles were analyzed by means of microscopic computed tomography (microCT) and histology. Sagittal sections of condyles were stained for tartrate-resistant acid phosphatase (TRAP), toluidine blue, 5-ethynyl-2'-deoxyuridine (EdU), and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling. RESULTS: Bone volume fraction was significantly decreased on the subchondral bone of the Botox-injected side, compared with the control side and control mice, 4 and 8 weeks after injection. Furthermore, histologic analysis revealed decrease in mineralization, cartilage thickness, TRAP activity, and EdU-positive cells in the MCC of the Botox-injected side 4 and 8 weeks after injection. CONCLUSIONS: The effects on the MCC and subchondral bone of Botox injection into the masseter muscle persisted for 8 weeks after injection and were not considered to be transient.
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