“A part of my tooth that should be in the gums is visibly out. What can be done to treat it?”

You are seeing gum recession that progressively exposes the tooth root. A. You might be doing damage with aggressive horizontal brushing with too firm a brush. B. You might be clenching or grinding your teeth at night which causes a wedge grove where the root joins the crown called an abfraction. C. You might have a frenum attachment pulling the gum away from the tooth. Each cause has a specific remedy that your dentist will explain. Sometimes tissue grafting is required.

Your best solution should first be to consult with your general dentist. They should be able to advise you as to what can be done.

Sounds like you're describing gum recession. A tissue grafting procedure is the most common treatment. We typically see this when patients brush their gums too hard or if the teeth are being over-loaded when chewing. I would recommend visiting an orthodontist to make sure the underlying cause of the recession is identified before making an investment.

Yes there are multiple ways to treat this depending on the exact situation. In some cases an orthodontist can move that tooth back into the gums to increase the gum tissue on the tooth. In other cases, a periodontist (gum and bone dentist) may be able to cover that tooth with gum tissue taken from elsewhere in the mouth.

I would find a Board Certified Orthodontist in your area and call to see if you can schedule a complimentary consultation. This website has a Board Certified Orthodontist Locator.

https://www.americanboardortho.com/general-public/orthodontist-locator/

I would need either a picture of the tooth or more information in order to answer that question properly. It could be anything from gum recession to periodontal issues, to a bite issue.
If it's a gum (or periodontal) issue, it can likely be treated with a grafting procedure. If it's a problem with the bite, or the tooth has moved out of position, then it can likely be treated orthodontically.

Hope this helps!!