There is not enough info here to answer the question. I think you're asking for a legal opinion. I also don't know what a temporary tooth is.
I've had temporary caps and they were just that temporary and not intended to last longer than a few weeks or months perhaps. I just don't understand what you're describing. When one puts on a cap the tooth is ground down and a root canal is done. The cap can come off but doesn't break off. A temporary tooth? I don't know what that is.
My mother had to have a couple of teeth in the front pulled many years ago, long before implants. The dentist put in a bridge, which is artificial teeth attached to the healthy teeth on either side of the space from which the teeth were pulled. Doing this would be much less expensive than having an implant but yet would preserve the space so that an implant could be done later as well as be cosmetically appealing.
I can think of at least one reason other than an incorrect dental procedure why a bridge or a cap on the front tooth would fail. We are used to biting into foods, such as fruit or cookies. Doing so may break off a bridged tooth or remove a temporary cap.
I just don't know what it is that your husband has. A temporary tooth which would be a bridge, but yet the decayed one is still there? A cap that's failed twice because the decayed tooth is still there? I don't understand.
I had a decayed molar that the specialist was preparing for a crown when he discovered that the part of the tooth below the gum line was cracked. He advised pulling the tooth which I had done by a regular dentist. He said that a crown would not work well. If this is what you're talking about, did your husband have a choice and chose to have a cap instead of pulling the tooth? IF so then it's not malpractice because your husband was given a choice in hopes that it would work but in the end did not.