I have a patient (limited finances) with a failed 4-unit bridge from his maxillary second molar to his first premolar. The second molar is intact and stable and a suitable abutment but the first premolar must be extracted due to non-restorable caries. I have treatment planned this for a new 4-unit bridge from the second molar (natural tooth) to an implant in the first premolar site. For those of you who have experience with cases like this, what would you recommend? What is the long-term prognosis?