Effects of growth hormone and functional appliance on mandibular growth in an adolescent rat model

Objectives: To investigate the individual and synergistic effects of growth hormone (GH) and functional appliance (FA) on mandibular growth in an adolescent rat model. Materials and Methods: Forty adolescent (6-week-old) female Wistar rats were randomly divided into four groups (10 rats in each group). The control group received a sham treatment (intra-abdominal injection of phosphate-buffered saline), the GH group received an intra-abdominal injection of recombinant human growth hormone, the FA group was treated with a mandibular advancement device, and the GH+FA group received both the GH and FA treatments. The amount of mandibular growth in each group was measured quantitatively using cone-bean computed tomography. The growth of condylar cartilage and expression of matrix metalloproteinases-1 and -13 (MMP-1 and MMP-13) and type II and X collagen (Col II and Col X) were assessed using histological staining and immunostaining techniques. Results: After 4 weeks, there was significant mandibular growth in the FA group compared with the control group (P < .05). The GH I FA group had significantly greater mandibular length, thickness of condylar cartilage, and expression of MMP-1, MMP-13, Col II, and Col X in the cartilage than the other groups (P < .05). The GH I FA group and GH group had significantly greater weight than the FA and control groups (P < .05). Conclusions: The FA as well as GH+FA stimulated mandibular growth in adolescent rats