Putting bridges on implants?

The simple answer is the bridge won't last long term. Has it been done? Sure. I don't. You risk losing the implant and the tooth because an implant is immobile in bone while the tooth moves up to a millimeter. The allowed movement of your tooth will create movement on your implant, ultimately creating bone loss and loss of the implant.

Excellent question.  The reason implants and teeth are not splinted is because natural teeth have some give.  They are surrounded by a soft ligament that acts as a shock absorber.  Therefore when you bite the teeth move a little.  Implants don't move they are rigid in bone.  Connecting something that moves with something that does not move is risky as it places too much stress on the implant.  In cases where the natural tooth has little mobility we can use super rigid cement, protect the bite and hope for long term success. 

It is not recommended to splint (attach) natural teeth to implants. Generally speaking, the rule is one tooth for one implant.  On very rare occasions we use one implant for two teeth. We do not recommend bridges with spaces with implants. The stresses are usually too much and might cause failure or possible fracture of the implants or abutments.

There are
some cases, depending on each patient’s case, where it could be done. The
regular way to perform it is implant on implant, but there is also that option.
If you could post your X-ray it would be easier to answer for your specific
case.