The saliva collection will be performed before the surgical procedure, at least one hour after the patient has fed. It will be collected stimulated saliva through the chewing of parafilm. In the first minute the patient only will normally chew and swallow saliva, in the next five minutes all saliva produced will be deposited in a graduated Falcon tube. Salivary flow is going to be measured and expressed in mililiters per minute. The collected saliva will centrifuged at 14000 rpm for 15 minutes. The supernatant will be collected and freeze at -80oC and the sediment content will be discarded.