Introduction

Oral diseases such as dental caries (DC) and periodontitis are highly prevalent around the world.1,2,3,4 At the biological level, it is natural for DC, periodontitis and tooth loss (TL) to arise widely in our species,5,6,7 making it a statistical norm for the human species to live with these oral 'diseases'. Once established, these conditions are highly associated with systemic diseases and can ultimately lead to TL, which impacts social and psychological wellbeing.8,9,10,11

Conditions such as DC and periodontitis are complex to treat, and as yet no cure has been found for them. Instead, current treatments offered in day-to-day practice aimed at managing DC, periodontitis and its sequelae TL are either generally restorative or aim to halt disease progression. Furthermore, dentists will commonly recommend behavioural strategies (such as flossing and tooth brushing) that aim to prevent the onset of DC and periodontitis. Yet, as we shall explain below, all of these existing interventions have only limited effects.

Technological advances in dentistry are raising the prospect of new strategies for tackling these conditions. Indeed, it is likely that DC and periodontitis will be targets for novel capacity-altering, biologically based interventions that aim to tackle direct biological risk factors beyond individual fronts of oral disease. However, the prospect of these novel interventions raises moral questions about the proper domain of dentistry.

In this article, we shall argue that dentistry should seek the prevention and cure of DC and periodontitis using novel, biological, capacity-altering interventions, in view of considerations of wellbeing and consistency with accepted dental practices.

Existing approaches in dentistry and new frontiers

The destroyed dental and oral structures in DC and periodontitis result in burdens for life, requiring restoration and additional maintenance throughout one's lifetime. Such interventions aim to restore oral health functionality/hygiene, aiding life extension of the dental organ(s), not to cure. Therefore, seeking to prevent/generate immunity for common oral conditions is still of great importance for oral health.

Although behaviour change has been shown to be efficient in significantly decreasing the number of affected teeth over time,12,13 there are three key factors influencing the effectiveness of that approach: first, independently of socioeconomic status, the personal perceptions of a patient or patient's family on the importance of the behavioural change ultimately influences treatment adherence;14,15 second, manual dexterity;16 and third, genetic and epigenetic factors.17,18,19,20 Furthermore, some patients can develop DC and periodontitis even in an optimal (behaviour) oral hygiene regime scenario; for example, they may do so if they suffer from amelogenesis/dentinogenesis imperfecta,21 hereditary gingival fibromatosis, or experience periodontitis as a manifestation of systemic disease.22,23

Therefore, there is a need for novel interventions that prevent and/or cure DC and periodontitis at a more fundamental level, targeting the biological processes underlying these diseases. Gene-editing technologies such as CRISPR-Cas9 offer some promise in this regard.24,25,26 A reliable predictive genetic marker for DC or periodontitis does not currently exist, but many candidate genes have been proposed.17,18,19 Moreover, DC and periodontitis develop as a result of gene-environmental interaction,17,18,19,20,27,28 suggesting that gene editing offers a potential therapeutic avenue in dentistry, in addition to behavioural enhancement approaches. The use of CRISPR-Cas9 for dental conditions has not been widely discussed, in part because the technology is still in its infancy outside of dentistry, and its safety and efficacy has not yet been established for more serious life-threatening conditions. However, should the safety of the technique be established in the future, such an approach could offer a potential avenue for altering host regulatory genes that are an integral part of fighting against the infectious aspect of DC and periodontitis.29

Moreover, somatic gene-editing interventions could also potentially have important preventative effects. First, somatic interventions could be used to modulate the composition of the native oral microbiome,29 or the pathogenicity of the bacteria causative of DC and periodontitis. If successful, such an approach could decrease the damage caused to the dental organ and supportive tissues, preventing early disease stage development.30 Alternatively, gene editing could be used to modulate dental organ tissues and their supportive apparatus.31,32 Such tissues are constantly exposed to pathogens and commensal microorganisms. Therefore, the ability of local cell populations to respond to the environmental factors could be enhanced via gene editing.

Consistency with current practice

As we suggested above, dentists already attempt to prevent DC and periodontitis by advocating behavioural change. Oral hygiene habits have shown to be successful in TL decrease,12,13 even though such measures were initially met with scepticism in the mid-twentieth century.33

Of course, it may be argued that there is a difference between advocating behavioural changes and performing biologically based interventions. For instance, one might appeal to the fact that the latter infringes on a right to bodily integrity that the former does not. However, whether or not there is a morally significant disanalogy between advocating behavioural changes and performing biologically based interventions is something of a moot point, since dentistry has also already fought to universally implement and perform a biological intervention that is still widely used today - universal systemic water fluoridation. This intervention has been shown to be effective in reducing levels of tooth decay among children.34 Moreover, topical fluoride application to teeth in the dental practice and fissure sealants are also used to prevent DC.35 Whether it is via changing behaviour or through the use of biological interventions, we believe that it is (and always has been) within the professional and ethical domain of dentistry to pursue novel biological preventative and curative strategies against DC, periodontitis and TL.

Considerations for using capacity-altering, biologically based approaches in dentistry

Many of the biological interventions we consider would be either performed prenatally or before adulthood. This has significant implications for their potential moral permissibility, as the recipients cannot provide valid consent to the intervention. However, we often rely on parents to make proxy decisions for their children with regards to preventative medicine. For example, we already allow parents to exercise parental autonomy in order to prevent children developing dental disease by ensuring oral hygiene in their children. Notably, there are also some risks with providing children with oral hygiene; if parents are neglectful or lazy, they may risk causing fluoride-associated conditions in children, which in extreme levels can be toxic and fatal.36

The reason that parental autonomy appears justifiable here is that choosing to prevent oral disease in one's children, by ensuring oral hygiene, meets the following criteria of the kinds of biological interventions that parents may permissibly choose for their children. The intervention in question must be:

  1. 1.

    Safe

  2. 2.

    Unlikely to result in harm to others

  3. 3.

    Compatible with the demands of distributive justice

  4. 4.

    Such that the parent's choices are based on a plausible conception of wellbeing and a better life for the child

  5. 5.

    Consistent with development of autonomy in the child and a reasonable range of future life plans.37

As we have already mentioned, one of the main concerns about the use of gene editing in any context is safety.

In the context of dentistry, there is risk of disruption of neural crest commitment to craniofacial formation;38 therefore, there is a very long way to go before we have a safe and reliable gene-editing technique that would be morally permissible to use for even the most serious medical conditions. Accordingly, our discussion of the use of gene editing in dentistry is naturally oriented towards a future time where the safety and reliability of gene-editing techniques has reached a satisfactory level, such that they might be considered for preventing the harms associated with oral disease.

In the interests of brevity, we shall thus set aside issues raised by safety, as well as harm to others and distributive justice. However, we shall argue that novel biological interventions in dentistry could meet conditions 4 and 5.

Wellbeing and future autonomy

DC and periodontitis are detrimental to wellbeing. The greater the number of reported toothaches, decayed teeth, cases of periodontal disease and missing teeth, the poorer is a person's quality of life.9,39,40 Negative judgements are made about people with flawed dentition, affecting their everyday experiences41,42 and raising the chances for bullying in children.43 Safe and effective biological interventions that prevent or cure DC, periodontitis and TL would enhance the child's wellbeing on any plausible conception, and they would be consistent with the development of the child's future autonomy.

There is of course scope for debate about the level and type of wellbeing of which it is the professional responsibility of dentists to achieve. It might be argued that DC, periodontitis and TL are universal diseases, and so it does not fall within the domain of dentistry to cure (rather than simply treat) these conditions. However, this line of objection overlooks a significant body of research suggesting that these conditions also affect systemic health.44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61 Oral diseases are directly linked to systemic health and some life-threatening diseases. Therefore, capacity-altering interventions for prevention and cure of DC and periodontitis may not only result in common oral diseases benefits, but also in systemic health benefits.

Seeking to cure and prevent these conditions can thus be viewed as a form of indirect preventative medicine. As such, we should not assume that novel biological interventions aimed at securing these benefits will only be permissible if they pose no risk. Some low level of risk may be proportionate, although the precise level of risk to which it would be reasonable to expose children for the sake of these benefits is a question that we cannot adequately address here.

Conclusion

The real problem with existing preventive measures for oral diseases is their ineffectiveness, rather than the strategy of prevention per se. DC is still the most common non-communicable disease worldwide, consuming 5-10% of healthcare budgets in industrialised countries, and is among the main reasons for hospitalisation of children in some high-income countries.3 We suggest that DC and periodontitis cure and prevention by means of novel biological capacity-altering interventions is consistent with the historic and current pursuit of preventative measures already adopted in dentistry. Therefore, potential future use of novel biological capacity-altering interventions should fall within the moral domain of dentistry.