Objective The purpose of this study was to evaluate the maximum binding（Bmax） and affinity Kd value changes of acetylcholine receptor（n- AchR）on rat′s superficial masseter muscles after functional mandibular advancement. Methods Forty 5- week- old male SD rats were randomly divided into experimental and control groups. The mimic functional appliances were only used in experimental groups, and the rats of two groups were killed after 1, 3, 7, 14 days. Radio- ligand binding assay（RBA）was applied to determine the Bmax and Kd value of n- AchR on the superficial masseter muscles. Results The Bmax of n- AchR in experimental groups was higher than that in the control groups at all time points, and the differences had statistical significance. The Kd value of n- AchR was higher in experimental group than that in control groups in 1, 3, 7 days, while Kd value in experimental group of n- AchR was lower than that in control groups in 14 days. The differences had statistical significance in 7 and 14 days, but the differences had no statistical significance in 1 and 3 days. Conclusion The functional orthopedics can increase the Bmax and affinity of n- AchR on rapid growing rat′s superficial masseter muscles.
