Intrusion of an incisor tooth into the contralateral frontal sinus following trauma. 
Although intrusions of glass fragments into the frontal sinuses are not uncommon in traffic accidents, a case with a tooth in the frontal sinus has never been reported.  We report a patient with traumatic inclusion of an incisor tooth in the contralateral frontal sinus.  Radiographic investigations demonstrated the tooth in the frontal sinus though no skin damage was recognized on the upper face.  The usefulness of CT scan in localizing the missing tooth after facial trauma and its route of entry into the contralateral frontal sinus is discussed.