The causes of frequent clenching of teeth in nine-month-old children include the following: First, the symptoms caused by teething. At nine months of age, children will have teeth eruption, when the teeth erupt will appear gum swelling, there will be involuntary often clenching teeth, you can give children appropriate application of teething stick to relieve the symptoms. Secondly, there are symptoms caused by children suffering from vitamin D deficiency rickets. Children suffering from vitamin D deficiency rickets will also cause frequent clenching of teeth, will be accompanied by occipital baldness, sweating and other symptoms, you can give children timely supplementation of vitamin D and calcium carbonate granules and other drugs to relieve. Children’s frequent teeth clenching as they get older, most of the symptoms will slowly ease.