Denervation and beta2-adrenoceptor-agonist administration on craniofacial bone density

Beta2-agonist medications are thought to have adverse effects on bone density. Surgical denervation and intramuscular beta2-agonist injections appear to have opposing effects on skeletal muscles. The present study has been designed to assess the effects of denervation of the masseter, intramuscular injection of a beta2-agonist and the combination of both procedures, on bone density in the craniofacial skeleton in rats.

Sprague-Dawley rats were prepared as four groups: 1. surgical sham + saline injection into the masseter (sham); 2. surgical denervation of the masseter (den.); 3. surgical denervation of the masseter + intramuscular formoterol injection into the affected muscle (den.+form.); 4. intramuscular formoterol injection into the masseter (form.). All specimens were submitted for CT examination and volumetric calculations of the mineralised bone tissue were performed.

The sham and form. groups had a greater volume of mineralised bone in the zygoma on the experimental side compared with the control side. The maxilla on the experimental side had a higher volume of mineralised bone in the den.+form. and form. groups compared with the sham and den. groups. The control side of the maxilla had a higher volume of mineralised bone in the den.+form. and form. groups compared with the den. group only.

Intramuscular administration of formoterol appears to induce a bilateral increase in bone mineral density in the maxilla and the zygoma, likely explained as a secondary effect of the well-described increase in muscle mass and strength associated with beta2-agonist administration.