Figure 3-1. Dental film dispenser.
a. Film Construction.
(1) An x-ray film has two parts, the cellulose acetate base and the emulsion
covering it. The base is made of cellulose and is a transparent plastic that is clear or
with a slightly bluish tint. The emulsion is a thin coating of a special gelatin with minute
particles of a silver compound. When x-rays penetrate through soft tissue, such as the
cheek or the gingiva, they also penetrate the emulsion easily, which causes the silver
compound to stick to the cellulose base during processing. Therefore, the film is darker
(this is known as radioluscence). When x-rays are directed to hard tissue (which is
dense), such as bone, tooth enamel, and metal restorations, fewer x-rays reach the film.
So, more of the silver compound is removed by processing. This results in lighter
shades on the film (which is known as radiopaque).
(2) All dental x-ray films (intraoral films) have an embossed dot (a raised
spot) to identify right and left. This raised dot is on the side of the film facing the x-ray
tube. The purpose of the embossed dot is to assist in mounting radiographs in correct