Naturally, any surgical intervention that might impinge upon these organs or threaten their functions should be undertaken with great care by an operator thoroughly familiar with all structural and functional, dental and nondental aspects that might be interrupted or impaired by an implant intervention.

The Dental Arch

Classic descriptions of oral anatomy typically depict the dental arch either as having a full complement of healthy, natural teeth or as being totally edentulous. Although the structure and form of the teeth themselves are often beautifully presented, their supporting tissues tend to be treated more generally. Indeed, the use of the term "supporting" implies secondary importance. Yet the diseased or debilitated state of these tissues is the major cause of tooth loss, and these tissues provide the basis for the masticatory replacements of millions of patients. It therefore seems important to re-examine these "supporting" tissues in depth.

More research is needed on the changes in mass, volume, shape, and biochemistry of the tissues directly or indirectly involved with teeth — or their artificial replacements. Granted, we recognize how these tissues appear when the tooth is healthy or when they reach a diseased state that will contribute to tooth loss. However, few pages are given to the progressive deterioration of these tissues in a "non-disease" state until they re-appear in dental literature to serve as a base for a conventional denture.

The upper dental arch is formed by a bony process extending from each maxilla and covered by mucoperiosteal tissues. The arch itself is a good example of how reorientating information about morphology can lead to a fresh approach in dental restoration or — at the very least — stimulate more productive questions about dental implants.

The Bony Ridge

The bulk of a healthy ridge's volume is composed of alveolar bone, a type of bone that is highly responsive to both internal and external chemical and physical stimuli. An internal stimulus, such as a systemic disorder, can cause alveolar bone to lose mass and volume. External stimuli, often mechanical in origin, can trauma-

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