PTH and dental fluorosis: Bone turnover imbalance is often reflected in the abnormality of bone metabolism index [9]; this study shows that the fluorosis group had higher BALP, MMP-2, and MMP-9 than the fluoride-free group and lower OC and PTH than the fluoride-free group, indicating that compared with children without fluorosis, there are obvious bone metabolic index abnormalities in children with fluorosis.