Numbness or tingling ("pins and needles") sensations in the tongue, medically known as paresthesia of the tongue, most commonly occur due to damage to the nervous system. The medical term for the absence of sensation is anesthesia. Damage to the lingual nerve that supplies the tongue has been reported as a complication of dental procedures or surgery such as wisdom tooth extraction, implants, or root canal procedures. Other conditions that damage the nerves, as well as brain conditions such as stroke, can also cause numbness and tingling of the tongue. Sometimes, these sensations extend to involve the lips and/or jaws. Tingling of the tongue associated with nerve damage can occur both before and after eating.

Source: http://www.rxlist.com