Abstract: Objective To explore the concentration and roles of serum alkaline phosphatases （ALP） in patients with skeleton class II malocclusion. Methods 45 adult patients with skeleton class II malocclusion and 47 ageand sexmatched healthy controls were selected in this study， and the concentrations of serum ALP were collected. The difference between experimental and control groups was assessed by independent Students ttest with SPSS 18.0 software. Results The serum ALP level in patients and that in healthy controls were （41.62±1.97）U/L and （65.83±2.70）U/L， respectively. The serum ALP level in male patients and that in healthy controls were （52.07±4.63）U/L and （68.25±2.65）U/L， whereas that in female patients and that in healthy controls were （36.40±0.92）U/L and （64.04±4.28）U/L， respectively. The serum ALP level in patients＜25 years old and that in healthy controls were （42.15±3.28）U/L and （65.43±4.64）U/L， among which， male patients vs. healthy controls was （52.75±18.55）U/L vs. （69.67±10.67）U/L， and female patients vs. healthy controls was （34.40±3.92）U/L vs. （62.10±18.50）U/L. Further， the serum ALP level in patients＞25 years old vs. that in healthy controls was （41.20±2.45）U/L vs. （66.00±3.35）U/L， and （51.29±18.68）U/L vs. （66.88±11.76）U/L for males， while （37.28±5.56）U/L vs （65.18±24.68）U/L for females. The significant statistical difference was observed （P＜0.05）. Conclusion The serum ALP level in adult patients with skeleton class II malocclusion is lower than that in healthy controls， suggesting weaker bone metabolism in the patients， which may be resulted from mandibular hypodevelopment.

Key words: skeleton, class II malocclusion, serum alkaline phosphatase