mesial and distal to the socket and its length engage healthy bone beneath the socket floor, the implantation procedure may be under-taken immediately (11) .

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 a 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 (12) and cuspid (13) as abutments. However, an implant can be used in the span, and a two-unit restoration fabricated for the second bicuspid (14) and for the implant (15). This is particularly desirable when the canine is esthetically perfect. In this type of situation, the bone must firmly encase the single natural abutment and be clear of the mental foramen.

The methods for inserting a single-tooth implant, whether it be to support a single-unit restoration or for inclusion in a multi-unit restoration, are very much the same.

Because the single-tooth implant is atypically tall, the operator must reflect an unusual amount of tissue to visualize the ridge, particularly the labial surface. Undercuts may occur at any level on the ridge, and labial concavities are typical in anterior situations.

The exceptionally deep groove must be slightly lingual to the labio-lingual cortices at the narrowest diameter of the ridge, wherever it occurs. If the ridge is wide, the bur could also be angled toward the harder bone of the lingual plate.

The most desirable alignment for a single-tooth implant is along the arch line (16) . Because of the extreme narrowness and in-creased length of the blade, its lever arm action is greatly increased (17) while the broader surface of the body of the blade is subject to lateral forces (18) which are the major cause of dislodgement. Sometimes there is insufficient space between the roots of the teeth

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