In a series of 100 cases of oro-antral fistula, twenty fistulas were associated with fracture of the maxillary tuberosity and have been dealt with separately. The remaining eighty fistulas resulted from an attempt at the extraction of a single tooth; of these, one or more roots dislocated into the maxillary antrum in thirty-three cases. Other less common causes of oro-antral fistula were not encountered in this series (Fig. 1). © 1971.
de B. Norman, J. E., & Craig, G. (1971). Oro-antral fistula. An analysis of 100 cases. Oral Surgery, Oral Medicine, Oral Pathology, 31(6), 734–744. https://doi.org/10.1016/0030-4220(71)90126-5