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Dental caries – definitions and clinical features

Ole Fejerskov and Bente Nyvad

• The editors’ view on dental caries and introduction to the book
• Terminology
• Examples of dental caries
• Background literature

The editors’ view on dental caries and introduction to the book

Dental caries is a result of metabolic activities in the microbial deposits (the dental biofilm) covering the tooth surface at any given site. Caries lesions emerge when there is an imbalance in the physiological equilibrium between the tooth mineral and the biofilm fluid. Hence, carious lesions represent the signs and symptoms of multiple de‐ and remineralization processes accrued over time.

Many symptoms of caries (e.g., cavities) are detected in the late stage of the caries process, where drilling and filling are needed to prevent further breakdown of the tooth. This is symptomatic treatment, referred to as tertiary prevention (Fig. 1.1). Primary prevention corresponds to activities aimed to prevent the earliest signs and symptoms of caries. Secondary prevention refers to any method applied to prevent further progression of already existing disease, such as noncavitated caries lesions. Tertiary prevention covers any attempt to restore/treat pulp involvement including, ultimately, tooth extraction. It is highly important to emphasize that if restorative care is not followed up by proper caries control measures, it merely adds to the vicious cycle of tooth repair and eventual tooth loss (Chapter 15).

It should, however, be realized that what happens in a single tooth or tooth surface cannot be understood without appreciating that it is part of a human being influenced by the environment in which she or he lives (Fig. 1.2).

Most people around the world do not see a dentist regularly and those who do mostly belong to the economic middle class or are well off and ready to pay for high‐tech oral rehabilitation – without necessarily appreciating how dental caries can be controlled by rather simple means. Therefore, the aim of this new edition of Dental Caries is to provide an updated knowledge on how to control and manage dental caries in populations and individuals with a specific focus on improved health outcomes.

We start the book by describing the magnitude of the caries problem in different populations (Chapter 3) together with a key chapter (Chapter 2) on strategic considerations for caries control in populations. These chapters are followed by an evaluation of the current caries diagnostic classifications and considerations about the importance of performing a proper caries diagnosis prior to making clinical treatment decisions (Chapters 4 and 5). The subsequent chapters illustrate how the oral environment, saliva (Chapter 8) and the oral microbiome (Chapters 6 and 7) modulate the metabolic processes involved in caries lesion development. Commensal microorganisms are constantly metabolizing in the biofilms of the mouth including dental biofilms on teeth leading to fluctuations in pH. These innumerable pH fluctuations result in demineralization and “remineralization” of the dental hard tissues (see Chapter 9). These processes are normal and should be considered physiologic for the oral environment. However, depending on the environmental conditions, they may over periods of months or years result in a net loss of minerals from the tooth, that is, caries lesion development and progression (Chapters 9 and 10).

Figure 1.1 Schematic illustration of the caries control concept. Because of continuous exposure to the metabolically active biofilm, disease control must be maintained lifelong. Both nonoperative and operative treatments are part of the caries control concept, but operative treatments should never be the only treatment provided for patients with active caries lesions. See text for a detailed explanation.

Figure 1.2 Schematic illustration of the determinants of the caries process. Those that act at the tooth surface level are found in the inner circle. In the outer ring are shown determinants that influence these processes at the individual and population levels.

Adapted from Fejerskov and Manji 1990 and reproduced with permission of the University of North Carolina School of Dentistry.

The following chapters provide basic knowledge about the oral environment and the importance of sugar and diets (Chapter 12), oral hygiene (Chapter 13), and fluorides (Chapter 14) in controlling the processes involved in the development of dental caries. These chapters enable the reader to understand, based on scientific evidence, why it is possible to allow for most people across the world to maintain a natural functional dentition from cradle to grave. However, it requires that people are informed and not least that public health and governmental authorities of a given society are prepared to integrate oral health into the preventive approaches for general health. A fundamentally important element of health promotion is the recognition that to achieve sustainable and equitable improvements in health, action is needed to create healthier living conditions for all. Hence, caries control cannot be seen out of context with the surrounding society, its culture, and traditions as a whole (see Fig. 1.2).

Dentists might argue that fluoride prevents dental caries. This belief originates from the times when it was first discovered that children living in areas with a higher level of fluoride in the water supplies experience fewer carious cavities than comparable age groups living in low fluoride areas (Chapter 14). However, as is stressed in Chapter 9, increased fluoride levels in the oral environment do not prevent the initiation of disease, but merely slow down the rate of lesion progression.

In Chapter 16, we introduce a clinical decision tree designed for control of dental caries in the individual patient, referred to as “The Dental Traffic Light.” This set of rules highlights the principle that only patients with active caries need professional intervention. The basic idea behind this philosophy is that individuals diagnosed with active disease should learn to control their disease activity. The dental personnel plays an important role in guiding the patient in achieving this goal.

In many populations, progression of a carious lesion from the noncavitated stage to the cavity stage is normally a slow process that may last for years. Chapter 18 gives a critical evaluation of the indications for various minimally invasive treatments that may be applied either prior to or after the development of a cavity. The important point is made that restorative treatment should be postponed as far as possible. Removing the signs of lesions by insertion of fillings is merely symptomatic and does not address the causes of the disease. For this reason, restorative treatments should never stand alone; restorative care without accompanying caries control just adds to the vicious circle of tooth repair and tooth loss.

This new edition of “Dental Caries” provides the basic knowledge on how the oral environment interacts with the dental hard tissues life‐long. There is a physiological balance between the host and the surrounding microbial environment under clinically healthy conditions. However, this balance may be interrupted by consumption of easily fermentable carbohydrates (Chapter 7). Therefore, a detailed understanding of the crucial importance of combatting the extensive misuse of free sugars in modern diets – provoked by commercial interests – is mandatory.

For more than a century, the dental profession has predominantly been focused on restorative care. However, the pandemic experience with the Covid‐19 virus (Chapter 20) has necessitated a thorough rethinking of how future restorative procedures can be conducted with due respect to the safety of patients and the staff in the dental office. The evidence presented in this textbook may hopefully facilitate rapid dissemination and implementation of cheap and effective protocols for caries control. By so doing classical operative procedures can be reduced to a minimum while maintaining a low caries incidence to the benefit of populations worldwide. The consequences for the structure of the dental profession in the future in terms of staffing and type of training of future cadres are apparent.

Terminology

Before we describe the clinical features of caries, it may be helpful to introduce some terms that are used in this textbook. Unless the reader is familiar with this terminology, it can be difficult to understand what is written in subsequent chapters.

Caries lesions may be classified in a number of ways. Caries lesions may start on enamel (enamel caries) or on the exposed root cementum and dentin (root caries). Caries lesions may also be classified according to their anatomical site. Remember, there is nothing chemically special about these sites. Therefore, lesions are predominantly found in so‐called stagnation areas where dental biofilm is allowed to persist for prolonged periods of time. Thus, lesions may commonly be found...