250 Theories and techniques of oral implantology

To simplify the approach for diagnosing candidates by radiographic interpretation, the various sites to be evaluated can be divided into five categories:

1. The edentulous maxilla

2. The edentulous mandible

3. The posteriorly edentulous maxilla

(unilateral or bilateral)

4. The posteriorly edentulous mandible

(unilateral or bilateral)

5. Long edentulous spans (maxillary or mandibular) between existing teeth

The edentulous maxilla

When little alveolar bone exists below the floor of the nasal vestibulum and the floor of the maxillary sinus (Fig. 6-57), implants of any design must be contraindicated. There is simply not enough bone for an endosseous implant, and a subperiosteal implant might sink into the maxillary sinus. Rarely, if ever, according to most American implantologists, should a subperiosteal implant be used in the maxilla. After the alveolar bone resorbs, there are very few areas dense enough to support the broad frame-work necessary for the success of a subperiosteal implant.

When a good deal of alveolar bone exists below the antral and nasal vestibular floors, the density of this bone is important. If the bone is extremely po-

Fig. 6-57. Because of lack of bone, both endosseous and subperiosteal implants are contraindicated for this maxilla.

Fig. 6-58. The maxillary bone may be deep enough, but it is too porous for an implant.

interpretation. The radiographic techniques to be used depend upon the intended site.

An intraoral periapical film is excellent for determining the proximity of the maxillary sinus to the alveolar crest. However, many times a periapical intraoral radiograph of the mandible is not adequate to clearly demonstrate the mandibular canal or mental foramen. Therefore the clinician must resort to lateral plate or lateral head extraoral radiographs. Profile views, cephalometrics, cross sectionals, three-quarter clich6s, and topographic x-rays are also important for a complete evaluation in some cases. Many of these various radiographic techniques, how-ever, can be eliminated if the dentist has a Panorex machine. The mandibular canal, mental foramen, and nasal vestibulum all show up clearly in a Panorex. The maxillary sinus, although clear enough, can sometimes be distorted by a slight movement of the patient's head while the radiograph is being taken. Therefore, if implants are intended in the area, a Panorex should always be followed by a periapical intraoral film.

Radiographs, although excellent for determining the bone's height, do not indicate its width. This is an important determinant in selecting the most appropriate type of implant. After the candidate has been accepted and is ready for implantation, Linkow routinely incises the site to confirm his choice of implant.

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