Knife-edge residual ridges: A clinical report

Abstract

A, fter tooth extraction, residual alveolar ridges undergo a series of remodeling processes including immediate repair of the wounds and long-term residual ridge resorption (RRR). RRR can occur in all patients at a substantially different rate.’ This unique phenomenon is caused by the continuous activity of localized osteoclasts at the surface of the residual alveolar bone,2x” which results in a morphologic variety of edentulous residual ridges. For example, if bone resorption is emphasized at the crest of the residual alveolar bone, it becomes flattened. When bone resorption is more active at the buccal and/or lingual areas, the residual alveolar bone may become a knife-edge shape. The pathophysiologic mechanism of RRR is not well undrrstood; however, it has been reported that postmenopausal women have a tendency to develop knife-edge residual ridges in the mandible4 and flat residual ridges in the maxilla.:’ The shape of the residual ridge is an important factor in determining the diagnosis and prognosis of removable, fixed, and implant prosthodontic treatments. Sometimes the residual ridge appears well rounded clinically, whereas further examination reveals a knife-edge bony ridge covered by soft tissue. Because evaluation of the three-dimensional morphology of the residual alveolar bone is essential for the placement of dental implant fixtures, a number of sophisticated but expensive diagnostic techniques have been introduced.“-” Once the residual alveolar bone is tliagnosed as knife-edge, the treatment plan may include removal of the thin bone structure for a better adaptation of the implant fixture at the shoulder level. It is also necessary to be prepared with several sizes of implant fixtures because the accurate ridge width cannot be determined before the osteotomy. For the purpose of understanding the morphologic fc,atures of the residual ridge, this clinical report presents the distinct oral appearances associated with knife-edge or flat