AI} opening may be made into the maxillary sinus when .. teeth are removed and, occasionally, as a result of trauma. This Si:1US perforation happens particularly when a max- ,. iJIri molar with widely divergent roots that is adjacent to edentulous spaces requires ‘extraction. In this instance.he sinus is likely to have become pneumatized into the ,edentulous alveolar process surrounding the tooth, which weakens the entire alveolus and brings the tooth erupts into a closer relationship with the ‘sinus cavity. Other causes of perforation into the sinus include < destruction of a portion of the sinus floor by periapical -Lesions, perforation of the floor and sinus membrane with Injudicious use of instruments, forcing a root or tooth into the sinus during attempted removal, and removal of large cystic lesions that encroach on the sinus cavity. The treatment of oroantral communications is accomplished eicher immediately, when the opening is created, or later, as in the instance of a long-standing fistula or failure of an attempted primary closure.