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What is Chronic fluoride toxicity results in: and explain in detail?
Chronic fluoride toxicity results from long-term ingestion of small amounts of fluoride. 
Severe pain in the backbones, joints, hip, stiffness in joints and spine. 
Outward bending of legs and hands is seen in advanced stages and these parts lose their shape and contours. This is called knock-knee syndrome.
Pregnant lactating mothers and children are the most vulnerable group. 
Fluoride can also damage a fetus, if the mother consumes excess fluoride during pregnancy. 
Calcium fluoride seemed to be more toxic to the foetus than sodium fluoride. 
Fluoride may lead to blocking and calcification of blood vessels causing cardiac problems. 
In its severest form, ‘crippling fluorosis', the spine becomes rigid and the joints stiffen, virtually immobilizing the patient.

 
Ref : Soben peter 5th edition pg no:281