RADIOGRAPHIC STENT

5mm metal beads

A radiographic stent will enable the surgeon to visualize anatomic landmarks and their dimensional relationship to each other in two dimensions. X-rays taken with a radiographic stent can then be used in conjunction with a implant transparency overlay to determine implant diameter and length. First a vacuum form with 5mm metal beads (Attachments International, catalog # 40-000050) in the edentulous area of the proposed implant site is produced by the laboratory (Tutorial) and a x-ray or panograph is taken by the surgeon or dentist with the radiographic guide seated in the patients mouth.

6.25mm measurement

Each x-ray machine and panograph produces some dimensional distortion (magnification) on its own in addition to producing varying degrees of distortion with each periapical or pano taken, depending on the focal length of the x-ray beam and the subject areas physical relation to the x-ray beam. To compensate for the distortion, implant manufacturers offer implant transparency overlays printed with outlines of their implants in different levels of magnification.

Transparency overlay

To determine the rate of distortion the metal bead in the x-ray or pano is measured with a boley gauge. The value of the measurement is then used to calculate the rate of distortion against the known dimension (5mm) of the actual metal bead, expressed as a percentage value. For example, if the actual titanium bead dimension is 5mm and the measured dimension of the bead from the x-ray is 6.25mm, then the rate of magnification is 25%. Now the appropriate rate magnification implant transparency overlay can be used to determine pertinent implant dimensions.