What could cause dark spots on an exposed dental film after processing?

Dark spots on an exposed dental film after processing typically result from premature contact with the developer. This exposure can create areas that are overdeveloped before the film has been properly processed through the entire developing cycle. When the film is placed in the developer too early, it may not have been sufficiently protected from unwanted development, leading to the manifestation of these dark spots.

In the context of film processing, it's crucial to ensure that the film is fully developed in a controlled manner to prevent defects like dark spots. Understanding the developing process and the environment in which the film is handled helps maintain the quality and consistency of the radiographic images produced.

The other options, while they can lead to various types of processing errors or artifact formations, do not directly explain the occurrence of dark spots in the same way as premature contact with the developer does. For example, overexposure to developer generally results in an overall darkening of the film rather than localized dark spots. Insufficient rinsing could lead to retaining chemicals that affect the film in other ways, and exposure to light before processing typically leads to general fogging or a hazy appearance across the film rather than distinct dark spots.