Dental caries, as the main subject of CWF for public oral health, is a public health problem . Before starting a discussion about public health interventions, it should be warranted first whether the health issue is classified as such. According to the criteria for a public health problem suggested by Sheiham et al. , dental caries satisfies all four conditions: high prevalence of the disease, significant impact on an individual level, considerable impact on wider society, and availability of prevention and effective treatment. From a more general definition suggested by Acheson and endorsed by the World Health Organization , dental caries should also be dealt with “through organized efforts of society” considering its explicit social gradients . Henceforth, the coping strategy against dental caries in public oral health should be different from that in clinical dentistry. The banality of this common knowledge sometimes causes confusion in ethical considerations on health issues.
If dental caries is considered a public health problem, at least for the discussion of CWF, it is reasonable to apply public health ethics to the topic, not clinical ethics. Hitherto, it has not been uncommon to view public health problems with the values of clinical ethics . That is because bioethics emerged from protecting patients in medical practice and participants in clinical research. The recognition of applying ethical values to public health and its importance for policymaking has arisen only as of late compared to clinical ethics.
Most distinctively, the “public” in public health has two prescriptive meanings: “the health of the public” and “collective interventions” . In other words, despite being under the same superordinate concept of bioethics, public health ethics should differ from clinical ethics, which focuses on individual patients’ needs and concerns from healthcare practitioners and systems . The details of the matter lie beyond the scope of this paper, but the contrast of core principles in each discipline can representatively exhibit the difference: autonomy, beneficence, non-maleficence, and justice as four principles for clinical/medical ethics ; and utility, liberty, and equality as three for public health ethics . Liberty corresponds to autonomy as in public health policy for the general public and population group, and likewise equality to justice. However, what is the meaning and weight that “consent” in public health policy carries in contrast to clinical practice for individuals? For example, if a resident agrees on the health education project for the local community, to what extent and until when does the consent remain valid? Can the consent be expanded or assumed to a modified yet consistent policy with the same rationale? The core value of securing an individual’s informed consent in clinical ethics may need to be revisited for public health ethics.
For that matter, ethical frameworks have been suggested to resolve conflicts between values in public health interventions . To produce benefits, prevent harms, and maximise utility, five justificatory conditions are demonstrated as follows: effectiveness, proportionality, necessity, least infringement, and public justification. An ethical evaluation of CWF by means of the framework was also attempted (Table 1). The table is a modified version of the framework suggested by Childress et al.  to clarify the ambiguous interpretation (necessity and least infringement are hard to distinguish)  for CWF. Among the proposed five conditions, the first three (effectiveness, proportionality, and necessity) have been sufficiently applied from the early stages of CWF (Table 1). However, scientific findings still remain contentious regarding the level of evidence from the standpoints of pro- and anti-CWF . Instead of dealing with all conditions, the two latter conditions of least infringement and public justification are discussed for ethical considerations, as we expect the issue of infringement to be the point from which both parties share and start a debate. In the latter part of this paper, this point will lead to public justification, which is to be focused on in the section of “three caveats”.
Table 1. Justificatory conditions  and their application to community water fluoridation (CWF).