The defining characteristic of a profession—and especially a health-care profession —is that the behaviour of its members is proscribed by a formal code of ethics. The main purpose of such codes is to guide practitioners’ interactions with patients, assuring that patient interests are protected. In other words, the ethical code requires practitioners to place their patients’ needs for proper diagnosis and appropriate treatment ahead of their own needs for income and advancement. The dental profession has a code of ethics that was developed by the American Dental Association many years ago; in most clinical situations, determination of proper behaviour is self-evident. However, the field of temporomandibular disorders (TMDs) has been the subject of considerable controversy for over half a century, and many people have argued that this makes it impossible to evaluate various approaches to treatment of TMDs within an ethical framework. In this article, the authors argue that the large volume of scientific evidence in the contemporary TMD literature provides an ethical framework for the diagnosis and treatment of patients with TMDs within a biopsychosocial medical model. They present a summary of the research with contemporary scientific integrity, which has produced that information over a period of many years. Based on that research, they conclude that dentists may provide conservative and reversible treatments that will be successful for most TMDs and in doing so will comply with the profession’s code of ethics. Conversely, the authors claim that those dentists who continue to follow the older mechanistic models of TMD aetiology and treatment are not only out of step scientifically, but are placing their patients’ welfare at risk by providing unnecessary irreversible bite-changing and jaw-repositioning interventions. Therefore, debate of these issues should not be solely focused on scientific merit, but also upon the compelling ethical obligations that dentists have as a result of the contemporary scientific literature regarding TMDs.