What is a common cause of a dark Panoramic X-ray (PAN)?

A dark Panoramic X-ray (PAN) typically results from an overdevelopment of the film, which is why having too much developer is the correct answer. When the film is exposed to the developer for a longer duration than appropriate or if the developer solution is overly concentrated, it leads to excessive darkening of the image.

In this case, the film reacts more intensely than intended, resulting in a darkened PAN, which can obscure important diagnostic details. Proper film processing is crucial to achieving accurate results, and any disruption in this balance can lead to faults like a dark image.

The other options pertain to different issues that can affect X-ray quality but do not specifically relate to excessive darkness. For instance, incorrect exposure time may lead to underexposure and a lighter image, inadequate film processing could lead to a washed-out appearance, and using expired film generally results in fogging or unclear images rather than merely a dark PAN.