Do we have a case of dental negligence/malpractice?

You need to see an attorney and secure, through that attorney, an expert to evaluate the medical records. The attorney would request medical records both from the hospital and dentist.

No. infection is a risk with any surgical procedure. I doubt if you can prove where the bacteria came from and went to, and I doubt if you could prove that one caused the other. Infection being common there is no guarantee about it.

These are difficult cases. Please ask for a free conference with a med mal lawyer.

It takes the opinion of the medical expert to answer your question. Medical malpractice lawyers typically have such experts available. Consider consulting one.

There are guidelines for pre-medication with antibiotics to prevent bacteremia's that occur during dental work from causing harm to the vulnerable locations in the body and even pre-medication is known not to prevent those problems. Did your father have a known and disclosed medical condition that required pre-medication with antibiotics or would make him susceptible to infection? If not, it doesn't sound like there is a claim though with the severity of the harm, it could be justified in getting records to resolve the question from everyone's mind. It would require the expense of obtaining records and having them reviewed to determine if there is a viable claim. If you do some research you will see that the bacteremias that are caused by dental work can also be caused by daily function such as eating or brushing your teeth so the discovery of bacteria found in the mouth would be difficult to pinpoint to only the dental treatment.

It depends on a number of issues. First it will be necessary to know whether your father had any medical conditions that required antibiotic treatment prior to dental care. Next, it will be important to know what tests were run at the time he went to the urgent care center and what exactly was the bacteria that was cultured when he was ultimately diagnosed with the disc infection. Your father should consult with an experienced medical negligence attorney to see if this infection was preventable and whether it should have been treated sooner so as to avoid the injury that he sustained.

Why ask a lawyer? Ask a dentist. If the dentist says yes, then sue.

Dental infections are more often associated with extractions and root canals than "standard work". You would have to show that the dentist did something to cause the infection (such as failure to sterilize instruments) rather than that your father just happened to pick up the infection at the dentist.