Despite the changes in concepts and management strategies during recent years, dental caries is still one of the most prevalent diseases worldwide, with 2.3 billion people having untreated caries lesions in the permanent dentition [1]. One of the most controversial issues is the switch on transmissibility of the disease and the current view as a non-communicable disease (NCD), also known as chronic disease. Until not long ago, dental caries was defined as a communicable infectious disease [2], and understood as an infection of the hard-dental tissues, blaming specific bacteria for its causation [3] (i.e., Streptococcus mutans and Streptococcus sobrinus). Under that concept, a successful preventive approach aimed to avoid the acquisition and infection with the putative causative microorganisms, that once acquired during the “window of infectivity”, will remain colonizing the mouth. The therapy, once the person was “infected”, encompassed the eradication of the causing bacteria via the use of a whole range of antimicrobials or, at the lesion level, through tissue removal, up to sound dentin [4]. However, trying to eradicate specific bacteria from the dental biofilm is a lost battle, as putative pathogens are endogenous to the mouth and will remain as members of the bacterial consortium, regardless of the attempts to eliminate them [5]. Surprisingly, the concept of dental caries as caused by acids from food fermentation and strongly associated with habits, as we conceive it today, was presented more than a century ago, in 1877 [6]. In this article we review the foundations to consider dental caries as an ecological and behavioral NCD.

Dental caries is now understood as an NCD. After the 72nd Session of the World Health Organization's (WHO) World Health Assembly in Geneva, Switzerland in May 2019, the World Dental Federation (FDI) and the International Association for Dental Research (IADR) signed a joint statement for dental caries to be included among the NCDs [7]. According to the WHO, NCDs are those with a long duration, also called chronic diseases. NCDs usually have multiple associated factors that can explain their onset, including genetic, physiological, environmental, and behavioral determinants [8]. Cardiovascular diseases, all types of cancer, chronic respiratory and diabetes are amongst the most common NCDs worldwide. However, accepting the non-communicable character of dental caries is not as extended as other paradigmatic changes in dentistry. This concept implies profound changes in the way the dental profession approaches the disease. Despite the great support for the concept of Minimally Invasive Dentistry worldwide and the fact that most dental schools are switching to conservative approaches for caries lesion management, the idea of caries disease as a NCD and its corresponding management strategies based on that idea, are not equally widespread. Based on evidence, this article attempts to synthetize the conceptual construction of dental caries as a NCD and propose ideas for management, rooted on these conceptual views. Although the categorization of caries as a NCD has been mentioned before in several places, the rationale to support this concept is still weak and partially developed. Hence, we aimed to provide a holistic support for the idea of caries as NCD, using a multidimensional conceptual framework, involving biological, medical and sociocultural components and how they can be integrated into an effective disease management. Furthermore, a more accurate understanding of the nature of the disease will allow the inclusion of caries into the public health policy, along with other NCDs and with the interdisciplinary health team.

Technological advancements and scientific evidence allowed the change on the understanding of dental caries, from an infectious to a non-infectious disease. The main foundation for moving away from the infectious pathogenesis is that dental caries does not follow the three canonical Koch's postulates [9]. As presented in Table 1, dental caries hardly qualifies into the category of infectious disease based on multiple facts: [1] the putative pathogen(s) can still be isolated from healthy subjects [2, 10], the mere presence of the putative pathogen(s) does/do not cause the disease. Indeed, pathogenic microorganisms in caries, are also present under healthy conditions, but at lower levels, indicating that they cannot be considered infectious in nature; [3] there is not a single specific bacterium causing the disease. Conversely, dental caries has a polymicrobial nature, induced by commensal bacteria with the potential of causing disease under imbalanced environmental conditions, posed by exposure to frequent and high amounts of sugars. During ecological imbalances, known as dysbiosis, the dental biofilm is stressed by highly acidic conditions, turning commensals into pathobionts, potentially causing the disease [11]. Consequently, the presence of specific bacteria such as S. mutans, which was blamed as the pathogen causing dental caries, does not determine the acquisition of the disease [12]. Since oral environmental changes are responsible for the switch from symbiosis to dysbiosis, the type of bacteria in the dental biofilm becomes less important than the overall metabolic activity of the bacterial consortium under sugars-rich and acidic conditions [13]. Indeed, competition within the species of the biofilm is dependent on the conditions imposed by the presence of sugars [14, 15].

Unlike communicable infectious diseases that have a rapid onset and progression, NCDs are also called chronic diseases, due to their long duration and generally slow progression. No consensus has been reached about the time needed to consider a disease as chronic, but general agreement indicates that any illness that lasts longer than 6 months can be considered chronic. Hence, and since dental caries lesions slowly progress over the years, caries may be considered as a chronic disease. It has been reported that a newly formed caries lesion may compromise the entire enamel, in a range of 6–6.3 years [31, 32].

Most common NCDs include cardiovascular diseases, cancer, respiratory diseases, and diabetes, and are responsible for more than 60% of deaths, constituting the main cause of mortality in the world with more than 40 million deaths per year [33]. NCDs contribute about 80% of the total burden of disease, resulting in exorbitant economic costs and a major public health issue. Although most of the NCDs do not share the same etiological factors, they have similar health risk behaviors, such as high sugars consumption, alcohol drinking, tobacco use, malnutrition and low physical activity or sedentarism. All these factors are deeply related to psychological, social, cultural, and economic factors [34]. Since the main etiological factor in dental caries is sugars consumption, poor dietary habits, and deficient biofilm control, it is plausible to argue that the disease shares common risk factors and/or etiology with other systemic NCDs, for example diabetes and obesity (Table 2). Indeed, a recent WHO report on oral health states the need to address “the common risk factors of oral diseases and other NCDs through an integrated approach, focusing on key risks, such as tobacco and harmful alcohol use, unhealthy diets and poor hygiene” [35].

Another trait of most NCDs is that they are preventable. Prevention of NCDs typically imply a reduction of associated risk factors [36]. For example, preventive strategies for type 2 diabetes and cardiovascular disease involve behavioral change toward a healthy diet and lifestyles [37]. Caries management should follow the same scheme and emphasize prevention by intervening behavioral factors over the restorative treatment of the already created caries lesions. Acting on lesions is too late as a preventive strategy. Regardless of the benefits of using minimally invasive therapeutic approaches to tackle caries lesions, a successful preventive program should aim at correcting health behaviors to avoid the biofilm dysbiosis, before the onset of any detectable clinical sign of the disease.

Recent and ongoing investigations point toward an influence of oral health on systemic conditions and vice versa, with an accepted bi-directional relationship [38]. Caries disease is linked to morbidity and death through tooth loss. Dental caries is the main reason for tooth loss, so adding tooth loss to untreated dental caries increases the burden of oral disease [39] and the impact of caries on systemic health. Dental caries may affect people from early life and usually persists over the years until death. Recent studies have shown that tooth loss, irrespective of the cause, is associated with the incidence of other NCDs, such as myocardial infarction, heart failure, ischemic stroke and death from all causes, becoming a good predictor of cardiovascular outcomes [40]. The association of tooth loss seems stronger with myocardial infarction followed by heart failure stroke and overall mortality. In fact, having ≥5 missing teeth substantially increased the risk for cardiovascular outcomes, and even a small number of missing teeth [1–4] was associated with an increased risk for myocardial infarction, stroke, and death [40].

Though the link between tooth loss, derived from caries, and cardiovascular disease is consistent, causality is not completely elucidated, but it could be attributed to chronic low-grade inflammation of oral tissues, as inflammation contributes to the pathogenesis of atherosclerosis [40]. Likewise, the underlying mechanism in the association of dental caries and coronary heart disease remains unclear. The penetration of oral bacteria through cavitated caries lesions causes chronic infection and inflammation of the dental pulp without treatment and the periapical tissues [41]. Severe dental caries may cause chronic inflammatory response in the endothelial coronary cells through bacterial invasion from decayed teeth [42]. Also, severe dental caries can induce atherosclerosis and exacerbate cardiometabolic risk factors that contribute to the onset of coronary heart disease [43]. These biological mechanisms can be responsible for the association between dental caries and coronary heart disease. Yet, better designed studies with more controlled factors are necessary to confirm such association [42].

Caries has also been associated with cognitive impairment and dementia [44]. It is well-known that people with dementia may lose the capacity to maintain an appropriate oral hygiene, resulting in more dental biofilm stagnation, thus, increasing their risk of developing periodontal disease and dental caries. The inverse directionality of the association, that is, dental caries and tooth loss as an explanation for cognitive impairment and/or dementia is less explored and still insubstantial. Further research to test these associations result of interest and should be considered in future research initiatives. If a causative role of dental caries is demonstrated for cardiovascular and/or neurodegenerative disorders, oral health should be more decidedly incorporated within the group of NCDs, with an interdisciplinary approach (see below).

Dental caries is profoundly rooted in health risk or unhealthy lifestyle behaviors, such as high sugars consumption which is also related with low income [45, 46]. A lifestyle is the way people live and is strongly associated with the behavioral and motivational spheres of human beings [36, 47]. Considering known risk factors, such as low socio-economic [45, 46], high sugars consumption and other unhealthy lifestyles [48, 49], these risk factors are key pieces for preventing and managing NCDs, at a global scale. To achieve a healthy life, several changes in habits have been recommended [50]. While overall healthy behaviors should be applicable too, in dental caries a poor nutrition with excess of sugars and an inadequate biofilm control are the most relevant behavioral and modifiable factors [51, 52]. In fact, compelling evidence has demonstrated that poor health behaviors are correlated with a higher prevalence of dental caries [53–56]. As previously described, there are substantial reasons to worry about controlling dental caries disease. As dental caries is the result of interactions between biological, behavioral, sociocultural and contextual factors [57], approaches to manage dental caries should be at both the individual, and the population level.

A more comprehensive and holistic approach in caries conceptualization will incorporate the disease among other NCDs, such as metabolic disorders, obesity, and type 2 diabetes, all of them having high sugars consumption as one of the etiological factors. Dietary habits and health risk behaviors become common risk factors for this group of NCDs [82]; hence, reducing sugars consumption is a complex task, as it is deeply rooted in social patterns and lifestyles. The high complexity of all NCDs and particularly dental caries, highlights the need for considering theories and multidimensional models that use interdisciplinary and participative approaches to treat, integrating oral health into the interdisciplinary team work [83]. It is already natural to think of an interdisciplinary teamwork for managing type 2 diabetes, with a whole range of professionals participating at different levels. However, it is also common to observe that health care for people with one or more NCDs is provided by multiple professionals, typically without coordination and communication among them [84].

To effectively manage dental caries, a collaboration between dentists, physicians and other members of the health team is required. Having an interdisciplinary approach to one of the most prevalent oral diseases worldwide appears as a potent strategy. Although dentists are not exempt from rising awareness and implementing dietary assessment and counseling as part of their daily work [85], a collaboration with psychologists, nutritionists and other professionals should be part of the complete pool of strategies to implement healthy food choices more effectively. Furthermore, sugars consumption has been associated with additive behaviors and emotions, with a strong neurobiological support [86]. Hence, managing sugars consumption should encompass other health professions to comprehensively approach a complex and multidimensional problem. It is easy to anticipate that isolated dentists working in a dental office and making efforts to reduce sugars intake will be a cumbersome or almost impossible goal, without engaging the interdisciplinary teamwork. On another edge of the problem, training dentists in dental schools to be more competent in using motivational interviewing tools and working with the health team, rather than focusing only on restorative aspects, should also be part of the multidimensional changes needed to alleviate the burden of caries disease worldwide.

Different studies have addressed the effects of interdisciplinary preventive programs to manage caries, focusing on the pregnant mother or children during early childhood. These programs involve different professionals, encompassing educators, gynecologists, midwives, pediatricians, dentists, nutritionists, social workers, and public health administrators [87–89], with promising results [83, 89–91]. Besides the obvious benefit of decreasing caries prevalence, an interdisciplinary approach for oral health and for caries management also allows a better reach to vulnerable populations, who otherwise have limited access to conventional dental treatment. The old paradigm that oral health is restricted to dentists and considered a separate entity, makes that oral health is usually not considered in a routine medical examination. Moreover, despite the importance of an integrated approach for overall health care, oral health is frequently excluded from the therapeutic management, probably due to the historic separation between medicine and dentistry and to a lack of knowledge on the NCD nature of dental caries. The latter may contribute to worsening systemic conditions. Given the traditional division between dental and medical care, including physical locations, communication among health care professionals must be optimized. The interdisciplinary approach for oral health requires efficient communication and bi-directional knowledge by the health care team. While dentists need to be more knowledgeable about systemic health, the health care team needs to know more about dentistry and how oral conditions can affect systemic health.

Dental caries must be considered non-communicable, associated with a dysbiosis of the dental biofilm and caused by free sugars exposure, but strongly linked to deleterious lifestyles and behaviors, mainly related to inappropriate dietary patterns. Modern management of the disease, therefore, should comprise acting at the individual and the community levels, incorporating caries among the public health policy for NCDs (Figure 1).

Although dentists are primarily responsible for caries management, the complex and multidimensional nature of this NCD requires the engagement of the interdisciplinary health teamwork to expand and enhance the health outcomes, beyond oral health. An appropriate inclusion of dentists and oral health in the interdisciplinary health team and in public health policies will allow comprehensively tackling caries and other NCDs, resulting in sustained healthy lifestyles, especially in those related to dietary habits.

Treating caries as a NCD becomes a novel paradigm for the dental profession, that will contribute to remediate the excessively high burden of dental disease, impacting overall health and improving quality of life, especially for those most vulnerable populations worldwide, at all ages.

RG: conception, design, and draft of the first manuscript. CF: revision of the first manuscript and incorporation of ideas and edition. CM-S, SL, NG-M, CE, SV, RC, and KG-T: contribution of initial ideas and manuscript revision. All authors gave their final approval and agree to be accountable for all aspects of the work.

This study was funded by two Chilean Government Grants (ANID): Fondecyt Regular 1210188 to RG and Fondecyt Iniciación 11200431 to SL.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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