Abstract
Application of implants in dental and oral surgery has increased．However，complications have been occasionally found to result from implant operation．Since implants are buried in bone tissue at one end and exposed to the intraoral environment at the other，there is a high risk of infection．Perforation of the maxillary sinus often results in maxillary sinusitis．Therefore when implants are indicated，more careful consideration is required for application to the maxilla than to the mandible．
Two cases which developed maxillary sinusitis following implant operation in the maxilla visited our clinic．This paper describes problems associated with implant operation in the maxilla．
In one case，maxillary sinusitis was attributed to：（1）inadequate distance between the molar alveolar ridge and the maxillary sinus floor following implant insertion，（2）inadequate initial fixation，and（3）attachment of the denture to the upper end of the lower structure，which had been inserted incorrectly but could not be removed．In the other case，it seemed to have been caused by an error in selecting a suitable lower structure．
