In a patient with adequate vertical bone height in the anterior maxilla, and who has been treatment planned for an implant-supported overdenture, at least 4 implants are recommended. In the maxilla, fewer than 4 implants will not predictably resist the forces that will be placed on them. Two implants are contraindicated in such cases. Implants in the anterior maxilla that will support overdentures are typically placed with the centers of the implants slightly palatal to the crest in order to avoid dehiscence and thin bone over the facial aspect of the implants. Care should be taken to avoid the incisive canal as an implant placement site, and to avoid dehiscence of the implant within the incisive canal. In the event of a dehiscence of bone in the midportion of the implant due to ridge concavity, particles of bone or dense, nonresorbable hydroxyapatite are placed to obliterate the defect. A membrane may be necessary, but is not necessary for small dehiscences. The patient's current prosthesis should be left out of the mouth for 7 to 10 days following implant surgery, but if the patient cannot comply, the labial flange of the prosthesis can be removed to the gingival margin of the denture teeth, and the crest region can be relieved. Denture adhesive can be used to adhere this relieved prosthesis to the palate, avoiding adhesive on the incision sites. A liquid, pureed diet must be consumed for 2 weeks in such cases.
(Source: AAOMS Surgical Update, American Association of Oral and Maxillofacial Surgeons, Vol. 19, Issue 2, 2004)