Esthetics also influence whether or not a single-unit restoration is advisable. It is more difficult to fashion a complimentary restoration for a single central incisor than to pleasingly restore both central incisors simultaneously with one crown supported by an implant (7), and the other by the prepared remaining central incisor (8). A lateral incisor, with its bilateral counterpart three teeth away, poses fewer matching problems and would more easily give satisfactory results.

If a large diastema (9) existed before tooth loss, a single-unit restoration filling the gap would be awkward and unnatural looking. If the restoration were small and maintained the diastema, it would be very difficult to stabilize. It would be better to use the implant to anchor a two- or three-unit fixed bridge, with two crowns closing the diastema (10. )

Bone in a state of flux is also an unwise implant site for a single-tooth restoration. Lateral extensions from the single-unit or splinting do not provide as much stability as does inclusion in a multi-unit restoration. Therefore, if a single-unit restoration is contemplated in an extraction site, implantation should be postponed at least three months to allow firm healing of the socket. Space should be maintained with a conventional appliance to prevent drifting or tipping.

Caution: When a single-unit fixed restoration is used on a pre-teenager or a teenager, the parent also should be instructed about implant care. Both patient and parent should learn what promotes loosening and to recognize its symptoms. It would be unwise to rely upon the child to report back to the dentist to restabilize or replace the implant if it should loosen. The bone of a neglected implant site can eventually resorb so much that the substitute pontic would have to be unnaturally long to meet the ridge. This unattractive solution in the incisor region would make the patient and dentist very unhappy.

More commonly, the single-tooth implant is used to minimize the number of teeth to be included in restoration or to provide additional balanced support between natural abutments for a multi-unit fixed prosthesis. For example, when a first bicuspid is missing, a conventional solution is a three-unit fixed bridge with the second bicuspid (11) and cuspid (12) as abutments. However, an implant can be used in the span, and a two-unit restoration fabricated for the second bicuspid (13) and for the implant (14). This is particularly desirable when the canine is esthetically perfect. In this

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