High resolution is obtained with:

Intraoral dental X-ray film is made as a double-emulsion film—that is, both sides of the base are coated with an emulsion. With a double layer of emulsion, less radiation is required to produce an image.  Direct exposure film is used for intraoral examinations, because it provides higher resolution images than screen-film combinations. Some diagnostic tasks, such as detection of incipient caries or early periapical disease, require this higher resolution. Reference: White and Pharoah's Oral Radiology Principles and Interpretation 7th edition page no 64