Sewerin I
Københavns Tandlaegehøjskoles Afdeling for Radiologi.
Tandlaegebladet. 1991 Aug;95(11):473-6.
The tangential projection represents an extraoral projection which with success can be performed with the dental X-ray set. The film is placed lateral to the angle of the mouth in a vertical position level with either the maxilla or the mandible. If a view of the midline is wanted the film is placed parallel with the sagittal plane; if e.g. the canine region is of interest the film is angulated. The central X-ray is directed horizontally and perpendicularly to the film passing (as a tangent) the anterior surface of either the maxilla or mandible. The beam area used for periapical projections is ideal also for this projection. The tangential projection is indicated as a supplemental projection for three-dimensional localization of e.g. supernumerary teeth in the maxillary anterior region and for the buccolingual position of an impacted canine. It is also very useful in combination with frontal projections in the planning of insertion of dental implants. According to the Danish legislation it is not allowed to use the dental X-ray set for extraoral projections unless intensifying screens are used. However, the Danish Institute of Radiation Hygiene has accepted tangential projections using dental X-ray films and omitting intensifying screens in edentulous patients due to their better resolution, which is of particular importance in the planning of implant insertion.
切线投影是一种口外投影，使用牙科X射线机即可成功进行。胶片垂直放置于口角外侧，与上颌或下颌处于同一水平。若需要观察中线视图，则将胶片与矢状面平行放置；例如，若关注尖牙区域，则将胶片成角放置。中心X射线水平且垂直于胶片，（以切线方式）穿过上颌或下颌的前表面。用于根尖周投影的射线束区域对于这种投影也很理想。切线投影适用于对上颌前部区域多生牙等进行三维定位，以及确定阻生尖牙的颊舌向位置等补充投影。在牙科种植体植入规划中，它与额部投影结合使用也非常有用。根据丹麦法律，除非使用增感屏，否则不允许使用牙科X射线机进行口外投影。然而，丹麦辐射卫生研究所已认可在无牙患者中使用牙科X射线胶片并省略增感屏进行切线投影，因为其分辨率更高，这在种植体植入规划中尤为重要。
