A periapical radiograph shows a space between the end of a post and the gutta-percha in a tooth with an otherwise well-done root canal. What is the most likely cause?

Correct answer: C. The post was too short

• A. INCORRECT — Post-related root resorption appears as progressive widening of the root canal or root outline changes, not as a simple gap.
• B. INCORRECT — The scenario specifies the root canal was well done. A space between the post and gutta-percha specifically indicates a post length issue, not an obturation problem.
• C. CORRECT — When a post is too short, it does not reach the apical end of the prepared post space, leaving a visible gap (space) between the end of the post and the coronal end of the remaining gutta-percha on radiograph. This is a direct result of inadequate post length selection.
• D. INCORRECT — Since the root canal is described as well done, this eliminates incorrect gutta-percha placement as the cause.