What can cause a blurry image on a dental radiograph?

A blurry image on a dental radiograph is primarily caused by movement during exposure. When a patient moves or there is any shift in position while the radiograph is being taken, it can result in the image being out of focus, leading to blurriness. This movement can occur from the patient unintentionally shifting, or if the x-ray unit is not stable, causing the captured image to lack the sharpness necessary for proper diagnostic evaluation.

The other factors listed, such as overdevelopment, underdevelopment, and insufficient exposure time, typically would not directly lead to a blurry image. Instead, overdevelopment can cause images to appear darker and more contrasted, while underdevelopment usually results in lighter or faint images that lack detail. Insufficient exposure time could also lead to images that are too light, but these aspects are more related to the density and contrast of the radiograph rather than the clarity or sharpness itself, which is primarily influenced by movement. Therefore, movement during exposure is the specific factor that leads to the blurriness observed in dental radiographs.