Protocol For Determining Radiopacity of Posts

 

I.        Research Question:  What is radiopacity of glass fiber posts?

 

II.     Test Method

 

A.     Prepare master tooth used to determine radiopacity of each post

1-     Locate a freshly extracted human maxillary cuspid.

2-     Cut crown off tooth at CEJ using Slow Speed Saw (Isomet).

3-     Prepare root canal using Hedstrom endo files following traditional Step Back technique.

4-     Place master gutta percha cone in tooth and laterally condense.

5-     Drill 9 mm deep into tooth using Gates Glidden Drills # 2, 3, & 4.

6-     Using 1.4 mm reamer, drill 9 mm deep in tooth.

7-     Place a matrix band around tooth and inject core materials (Core Paste LC).

8-     Light cure core material for 40 seconds using Optilux 500 (11mm tip, 725 mW/cm2)

9-     Cut hole in core material to allow insertion of post using high speed handpiece and Midwest #56 bur.

 

B.     Take Radiograph

1-     Seat test post in tooth.

2-     Place test tooth (facial side up) along with aluminum step wedge (1-7mm) on Kodak E speed #2 film.

3-     Place X-Ray head 1.5” above tooth.  X-Ray setting are: 60 Kvp 7 ma .25 seconds.

4-     Expose X-ray film.

5-     Develop film.

 

C.  Determine Gray Scale Measurement

1-     Scan radiographs with consistent scanning settings using 500 dpi resolution.

2-     Load image into software “Image Pro Plus”.

3-     Calculate the gray scale value using line profile function. Use a line with at least 200 points of data and place center of post at the same location on every post.

4-     Average the 200 points.

5-     Calculate and average gray scale values of each of the 7 mm increments of the aluminum step wedge.

6-     Using aluminum step wedge values assign mm of aluminum value to the post. 

7-     Divide the mm aluminum value by the diameter of the post at the location is was measured to get the % aluminum.