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I am sorry to hear about this situation.
It sounds like they are using legal discovery. See HERE. Discovery must be narrowly tailored to get specific information pertinent to the case. However if one's medical information is pertinent to the case, then they can request it and use it. While HIPAA applies to dental records, HIPAA gives an exception to a subpoena or discovery.
However, the third party (i.e. you) whose medical records are used CAN file a motion asking the Court to not have those records produced in discovery, and then the Court will determine if there is information in those records pertinent as evidence, in a hearing. 45 C.F.R. § 164.512(e).
Even if the Court allows it, if any of that discovery/subpoenaed medical information is ever filed with the Court, one can file a motion asking the Court to redact information such as names and other identifiers, out of privacy. Then the Court can do so at its discretion.
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