You need to retain a professional malpractice attorney to file a lawsuit in the Common Pleas Court where the potential Defendant is located or where the malpractice occurred.
By answering, no attorney-client relationship is established. The answer provided is for information purposes. You should contact an attorney directly to obtain a definitive opinion regarding your question.
The first step is to find a local Ohio attorney that handles this type of work. Then discuss what happened. Either you or the attorney could acquire the medical records and have an expert review them. Then, if justified, a lawsuit can be filed by the attorney. Laws governing malpractice are very complex and regulated to a higher degree than other areas of the law. So a lawyer's assistance is necessary.
Where can you go? Or where do you file the lawsuit? I assume you are asking "What do I do, I want to file a Dental Malpractice Claim against a dentist?" The lawsuit would have to be filed in the County (Common Pleas or Municipal Court, depending on case value) where the malpractice happened or Defendant's principal place of business. Whether or not you will be successful in collecting any money damages agaist the dentist will need to be evaluated by an experienced personal injury or malpractice lawyer. Unfortunately, the potential damages ($) you could collect from the alleged malpractice may not economically justify the time/cost of pursuing your claim. The Statute of Limitations (time to file a lawsuit) for medical/dental malpractice claims in Ohio is one (1) year. So, if you are going to do something about it, pay attention to the time you have to consult/jhire a lawyer to help you. You will need to obtain all the records and films from the offending Dentist's office and have them reviewed by another dentist (i.e. "expert witness"). Experts don't work for free and usually require anywhere from $500 to $1,500 deposit to even look at your case and give you an "expert opinion" of whether or not any "malpractice" occurred. If you are serious, you need to get started right away. Best wishes.