An investigation of maxillary superimposition techniques using metallic implants

The purpose of this study was to determine if there are discernable, stable, anatomic landmarks in the maxilla that may reliably be used for maxillary superimposition. It was hypothesized that, through the evaluation of cephalometric radiographs of patients with metallic implants, such anatomic landmarks could be identified. The material for this study consisted of pairs of cephalometric radiographs from 50 subjects, 23 males and 27 females ages 8.7 to 20.3 years. All films were taken at least 3 years apart. The mean age at the time of the first film was 11.9 ± 1.4 years, and the mean age at the time of the second film was 16.0 ± 1.7 years. The two serial tracings from each subject were superimposed on the implants and evaluated for best fit of anatomic structures. The maximum distance that the structures varied from perfect superimposition was measured. Rotational changes of the maxilla relative to the cranial base and of the palatal plane relative to the maxilla were evaluated. In the vertical plane, the floor of the orbit raised more than the palatal plane lowered by an average ratio of 1.5 to 1 mm. The maxilla demonstrated varying degrees and directions of rotation relative to the cranial base. The palatal plane demonstrated varying degrees and directions of rotation within the maxilla. Internal structure of the palate was of limited value as a stable area of registration. Infraorbital foramen, PTM, ANS, PNS, A point, and superior and inferior borders of the palate were not found to be stable landmarks for maxillary superimposition. The posterior and anterior portions of the zygomatic process of the maxilla were found to be the most reliable anatomic landmarks for cephalometric superimposition.