Broken Root Canal File? (photo)

I would suggest a consultation with an oral and maxillofacial surgeon, and possibly a cone beam CT. This can help determine exactly where the root and sinus are in relation to each other. Doing this first can give you an idea of what your options really are regarding an implant.

It appears that you have a failing root canal with a sinus infection causing continual pain.  This tooth is hopeless and needs to be extracted because it is fractured.  I was able to magnify the radiograph and did not see a severed root canal file but did detect a fractured root.  For the final restoration I would highly recommend a single implant supported crown. Both adjacent teeth do not appear to have a restoration and it would be a shame to prepare them for a 3 unit bridge when only 1 tooth is affected.  Since the sinus cavity is low, an option would be a Transcrestal Sinus Floor Elevation instead of an extensive sinus augmentation.  It is not the end of the world but I highly recommend you see an oral surgeon for the surgical procedure as it is rather simple for a surgeon that does these procedures routinely. 

It is very difficult to remove a broken file, especially in this location. Many  people in this situation choose to have the tooth extracted and an implant placed based on a cost/benefit analysis. The retreatment success rate with a chronic infection is very low. Based on your x-ray, it should not be a problem placing an implant in that area. Andrew Rudnick, DMD, FICOI