Morphological Changes in the Mandibular Condyle Following Botulinum Toxin Injection into the Human Masseter Muscle

Abstract

Purpose: To determine the effects of botulinum toxin (BoNT) injection into the human masseter muscle on the morphology of the mandibular condyle bone using cone-beam computed tomography (CBCT).

Methods: Twenty volunteers were randomly assigned to one of two groups. Group I received a single BoNT injection; Group II received two injections, with the second being administered 4 months after the first. CBCT scans of both temporomandibular joints (TMJs) were performed before and 6 months after the first injection. Bony changes in the cortical layers of the condyle heads were evaluated and the long and short axes of both mandibular condyles were measured. The thickness at the thinnest part of glenoid fossa was also quantitatively measured.

Results: There was no significant difference between pre- and post-injection CBCT images.

Furthermore, no changes in the cortical layers of the condyle heads were observed among the subjects who exhibited mild degenerative TMJ changes. The quantitative measurements (long axis, short axis, and the thickness of thinnest part of glenoid fossa roof) did not differ significantly between pre- and post-injection except for the long axis in Group I.

Conclusions: Within the limitations of this study, it appears that BoNT injections into human masseter muscles do not alter the morphology of the mandibular condyle bone in healthy adults.