Clinical periodontal therapy includes initial therapy, surgical therapy and maintenance therapy. Liability on the part of the dentist can be summarized as treatment-related, information-related and documentation-related malpractice. The essential aspects of periodontal malpractice include duty of care, breach the duty of care, causation and damages. Periodontists must provide the patient with enough accurate information in order allow them to make an informed decision. The obligation to take due care before, during and after surgery is mandatory for all clinicians. Nevertheless, there are some differences in the standard of care required, the relevance of expert witness, and the burden of proof between the U.S. and Taiwan.