Effects of tongue volume reduction on craniofacial growth: A longitudinal study on orofacial skeletons and dental arches.

The interaction between tongue size/volume and craniofacial skeletal growth is essential for understanding the mechanism of specific types of malocclusion and objectively measuring outcomes of various surgical and/or orthodontic treatments. Currently available information on this interaction is limited. This study was designed to examine how tongue body volume reduction affects craniofacial skeleton and dental arch formation during the rapid growth period in five 12-week-old Yucatan minipig sibling pairs. One of each pair received a standardized reduction glossectomy to reduce tongue volume by 15-17% (reduction group), and the other had the reduction glossectomy incisions without tissue removal (sham group). Before surgery, five stainless steel screws were implanted into standardized craniofacial skeletal locations. A series of cephalograms, lateral and axial, were obtained longitudinally at 1 week preoperative, and 2 and 4 weeks postoperative. These images were traced using superimposition, and linear and angular variables were measured digitally. Upon euthanasia, direct osteometric measurements were obtained from harvested skulls. Five en-bloc bone pieces were further cut for bone mineral examination by dual photon/energy X-ray absorptiometry (DEXA). The results indicate that: (1) while daily food consumption and weekly body weight were not significantly affected, tongue volume reduction showed an overall negative effect on the linear expansion of craniofacial skeletons; (2) premaxilla and mandibular symphysis lengths, and anterior dental arch width were significantly less in reduction than sham animals at 2 and/or 4 weeks after the surgery; (3) both premaxilla/maxilla and mandible bone mineral density and content were lower in reduction than sham animals, significantly lower in anterior mandible; (4) craniofacial skeletal and dental arch size were significantly smaller in reduction than sham animals, being most significant in the mandibular anterior length and ramus height, the anterior dental arch and midface width. These results suggest that reducing tongue body volume in young animals slows craniofacial skeletal growth and anterior dental arch expansion during rapid growth. The mandible, in particular its symphysis portion, and the anterior dental arch width are most affected. These effects may in part contribute to the decrease of functional loads in the anterior mouth by a volume-reduced tongue.