Why Does My Dentist Say I Cant Get an Implant for My Extracted Molar?

Everyone situation is unique, however, in almost all cases procedures can be preformed to provide sufficient bone for dental implant placement.  It would be in your best interest to schedule an appointment with an oral surgeon to find out what your options really are....

Dental implants can work in many situations. If there has been a lot of bone damage due to an extensive infection, then that can lower the chance that an implant will be highly successful.

Many times an implant can be placed, even in bone that has had problems. There are often regional gurus who are amazing at getting implants to work in difficult places (sometimes an oral surgeon, or a periodontist).

It sounds to me like you ought to ask more questions about your situation. 

One other concern can be that depending upon the condition of the teeth neighboring the extraction area, a bridge can be far less costly, and repair more problems than just the missing tooth. A dentist who knows you and your conditions well can offer you good advice. 

Here's one warning: don't let ANYONE put an implant in until the dentist that will be making the crown says it's OK. In the end, the dentist building the teeth needs to direct the other specialists to create optimal results.