Can dental x-rays miss detecting a dental abscess?

Yes. When there is an abscess in the bone, then it appears in the x-ray by the pattern of bone destruction. If an abscess is small, or limited to soft tissue, then it will not be evident on an x-ray. Additionally, an x-ray is a 2-dimensional view of a 3-d environment - if the abscess is superimposed by another structure in the image, then the abscess may not be evident in the x-ray.
Yes. An early dental abscess may not show up on dental x-rays until there is enough bony erosion from the infection generally in 1-2 weeks.
Yes. Many dental infections are diagnosed by x-rays due to the changes in the surrounding bone.The soft tissue of a tooth must be diseased prior to a abscess. In early stages there is often no detectable changes in the bone.