Management of the Posterior Maxilla
in the Compromised Patient:
Historical, Current, and Future Perspectives
CONTINUED (Page 4)
Thomas J. Balshi & Glenn J. Wolfinger
Periodontology 2000, Vol 33, 2003, 67-81.
Tuberosity and Pterygoid Implants
There has been a longstanding feeling among clinicians that the pterygomaxillary region of the maxilla was unsuitable for implants because of large fatty marrow spaces, limited trabecular bone, and the rare presence of cortical bone covering the alveolus. However, subsequent clinical trials showed that titanium fixtures could successfully osseointegrate in this area26-27. Indeed, the density of some of the pterygomaxillary structures may provide stability that exceeds that offered by the anchorage in any other part of the maxilla28.
Reiser’s anatomic investigations using cadaver dissection have shown that the specific structures that may support implants are the tuberosity of the maxillary bone, the pyramidal process of the palatine, and the pterygoid process of the sphenoid bone29. At times it is possible to place an implant completely within the first of these (and avoid angling the implant apex more distally), depending on the tuberosity’s dimensions and quality. If the height, length, and/or width of the tuberosity are not adequate, however, the implant can be angled and the apex made to engage either the pterygoid process, the pyramidal plate of the palatine bone, or both. Recent observations and measurement of the height, anteroposterior distance, and mediolateral distance of the pyramidal process indicate that placement of implants in the lower half of the pyramidal process is advantageous30.
Such fixtures have provided successful support for a variety of tissue-integrated prosthesis forms, including multi-fixture complete-arch fixed prostheses (Figure 4), complete removable overdentures with fixed retention bars (Figure 1c), multiple fixture-supported restorations independent of the natural dentition (Figure 2 c), and terminal abutments for partial fixed prostheses connected to the natural dentition (Figure 5).