The implant was unrelated to the tag, officially called the "upper labial frenulum", and the implant was for one of the two front teeth (Upper Central Incisor).
You'd have to get technical advice from Dentistry SE or something like that, but it is unlikely that this constitutes malpractice, instead was found to be necessary in the course of the implant. You could hire a lawyer to research the question to see if there is a reasonable probability that you could recover damages from a lawsuit, but the main difficulty would be establishing that you've been harmed. You would need an expert dental witness to establish that there is no reasonable connection between the implant and the frenectomy, and it might be an impossible to find a credible witness to that effect given that there is ample evidence that it can be necessary.
If you are really saying that he is denying having performed the procedure, then in addition you would have to prove that he did, maybe with before and after pictures.