Measurement of the maxilla and zygoma as an aid in installing zygomatic implants.

PURPOSE This study used maxillary and zygomatic measurements to obtain information for installing zygomatic implants. PATIENTS AND METHODS Angular and linear distances between the maxilla and the zygoma were measured in 12 cadavers (n = 22 sides) classified into short and tall groups by height (140 to 159 cm and 160 to 180 cm, respectively). RESULTS Based on mean and standard deviation values, the installation angle of zygomatic implants was between 43.8 degrees and 50.6 degrees. The distance between the crest of the maxillary alveolar process near the palate and the jugale (Ju) point of the zygoma was between 44.3 and 54.3 mm. The minimum distance between the most lateral corner of the maxillary sinus and the Ju point was 6.41 mm, and the minimum anteroposterior length of the zygoma was 5.68 mm in the shorter group. CONCLUSIONS When the installation angle of zygomatic implants is 43.8 degrees or less, perforation of the maxilla and the zygoma or the infratemporal fossa must be avoided. When the angle is 50.6 degrees or more, perforation of the orbital floor must be avoided. Special attention is needed to ensure osseointegration in shorter patients, because the distance between the most lateral corner of the antrum supporting the zygomatic implant and the Ju point is 10 mm or less. The apex of the implant is 3.75 mm in diameter, and the thickness of the zygoma must be 5.75 mm or more. The threads of the implant must not be exposed from the zygoma in shorter patients.