If a tooth is salvageable, the best way to treat an abscessed tooth is to do a root canal. Otherwise, the only other way to get the abscess out is to extract the entire tooth.

Treatment depends on diagnosing the cause. Is it an endodontic (root canal) infection or a periodontal (gum) infection? You cannot provide definitive treatment without knowing the source. If it is endodontic, then a trip to the endodontist is needed. Likewise, visit to the periodontist would be in order. The only other definitive treatment would be extraction.