Final answer:
A Periapical film is used to diagnose pathologic conditions of the tooth root, including decay, infections, or bone-related issues.
Step-by-step explanation:
To diagnose pathologic conditions of the tooth root, the Periapical film is necessary. This type of radiograph includes the entire tooth from the crown to the root where the tooth anchors into the jaw. The Periapical film is essential for detecting problems below the gum line or in the jaw such as decay, infections, or cysts and can indicate the presence of periodontal disease by showing the bone levels surrounding the tooth.