Evaluation of anatomical references for locating the course of the posterior superior alveolar artery for dental implant surgery.

This retrospective cohort study aimed to identify the best anatomical reference for predicting the posterior superior alveolar artery (PSAA) location. Computed tomographic images of 90 maxillary sinuses were evaluated. We studied five references, including the alveolar crest, maxillary sinus floor, zygomatoalveolar crest, hard palate and soft palate, and measured the distances between them and the PSAA. Variations in the distance were evaluated by the standard deviation and coefficient of variation (CV). The zygomatoalveolar crest was an unstable reference, owing to its high standard deviation and CV. The smallest CV was for the distance between the alveolar crest and PSAA, although the distance was smaller in edentulous jaws than dentulous jaws. The distance between the sinus floor and PSAA was larger in male and edentulous patients. The PSAA was detected in 40.0%, 44.4%, 54.4% and 56.7% of the sinus walls at the first and second premolar and the first and second molar positions, respectively. At these tooth positions, the respective heights above the hard palate were 11.2 ± 4.9, 8.2 ± 4.9, 6.2 ± 2.8 and 8.1 ± 2.9 mm. The hard palate was the most stable reference for predicting the location of the PSAA, irrespective of sex, age and dentition.

Measurement of the zygomatic bone and pilot hole technique for safer insertion of zygomaticus implants.

The zygomaticus implant was developed for patients with severe bone resorption of the posterior maxilla. These may eliminate or minimize the need for bone grafting. Although the zygomaticus implant has shown a remarkable success rate in this difficult-to-treat patient population, the method requires an advanced surgical technique and carries an increased risk of complications. There have been few anatomical studies on the zygomatic bone in relation to the insertion of zygomaticus implants. The height and thickness of the zygomatic bone for the insertion were measured in this study. The thickness at the 90° angle point, where the upper margin of the zygomatic arch and the temporal margin of the frontal process of the zygomatic bone intersect and where the apex of the implant penetrates, was found to be 1.8±0.4 mm; this gradually increased inferiorly and anteriorly. Thus, the penetration point of the apex of the zygomaticus implant should be located more inferoanterior to the 90° angle point, as the thickness in this region is thinner than the diameter of the implant. Based on the results of this study, a newer and safer insertion method for the zygomaticus implant using a drill guide is proposed.

[Dependence of scattered Mn K alpha / K beta X-ray intensity ratio on the scatterer materials].

The K alpha / K beta ratio of Mn KX-rays scattered by metallic samples changed remarkably with the geometry between the sample and the (55)Fe source-Si(Li) detector system. On the contrary, this intensity ratio changed little in the cases of non-metallic scatterer samples such as lucite or mylar. This difference is interpreted as due to the occurrence of strong or weak interference in the coherent scattering photons.