• If there is pain or burning, or there is bleeding in the mouth and lips. However it has to be noted that the pain is not an absolute criterion, as for example in the case of oral cancer the initial stages are painless the main lesion is escaped the attention
  
  
• When there are changes in mucosal palpation, like irregular surface, or stiffness, or swelling of the oral mucosa, the jaws or the skin area around the mouth
  
  
• When changes of color of the oral mucosa as white, red or pigmented (dark) spots are observed
  
  
• In cases of swellings or tumorous lesions are formed
  
  
• In cases of erosions and ulcerations of oral mucosa (usually painful)
  
  
• Combination of the above
  
  
• When there is difficulty in chewing and swallowing
  
  
• In case of complaints against the placement of total or partial dentures or mucous problems beside fixed prosthetic restorations

Although, the majority of problems observed in the mouth are harmless and easily treated, there should be increased suspicion for any change one sees in the oral cavity or lips, especially when there is a history of smoking, a known systemic disease, and making drugs for any reason because a more dangerous disease could also be observed in the mouth including cancer.