Control of caries lesion development and progression

The first three chapters of this book have introduced the basics of what dental caries is and how to detect lesions. The next chapter will consider the concept of caries control and begins by explaining why throughout this book the preferred term is caries control, rather than prevention. Remember, the formation of the dental biofilm, and its metabolism is an ubiquitous natural process; it cannot be prevented. So: Question: Who is susceptible to caries lesion development? Answer: Everyone with teeth, from cradle to grave because the metabolism in the dental biofilm is an ubiquitous, natural process. Lesion development and progression, which may occur over time, are symptoms of the process. We should aim to control these processes so that the development of a clinically visible lesion is avoided. However, if clinical lesions develop and progress these symptoms can be arrested by controlling the environment. Thus, all patients with teeth should know how lesions may form and progress, and how to control this. Please note the emphasis on the patient. It is the patient who controls caries with the support and encouragement of the professional. The goals of medicine (and dentistry) are to promote and preserve health if it is impaired, to restore health, and minimize suffering and distress. These goals are embodied in the word ‘prevention’. It is agreed that, with dental caries, this is basically what the dental profession is doing—and has always been doing. In many ways this has become a mantra—the dentists rightly claim that they are conducting prevention when recommending the population to eat less sugar, use fluorides, brush teeth, and when lesions occur, drill and fill, in order to restore the dentition and reduce pain and discomfort. Unfortunately, when dentists go for restoration—without ensuring that the patient understands how to control further caries lesion development—they indirectly stimulate the repair cycle, which ultimately may lead to loss of teeth (see Chapter 5). Sometimes the filling may be described as ‘treatment’ to contrast it with ‘prevention’. The dentist is paid for fillings (treatment) and minimally rewarded for so-called prevention.

Detection, diagnosis, and recording in the clinic

In Chapter 1 it was stressed that while all dental biofilms exhibit intense metabolic activity, only biofilms where a shift in metabolic activity towards an enhanced acid production over longer periods of time, will result in a net loss of mineral from the underlying tooth surface. The reflection or symptom of this is what can be detected with the naked eye and classified as the caries lesion on the tooth surface. It was pointed out that lesions may be active (if nothing changes in the oral environment, they will progress) or arrested (if nothing changes they will stay as they are). Thus, the things it is necessary to know in order to make an appropriate treatment decision are: ◆ Is a lesion present? This is detection of the lesion. ◆ Is the lesion judged to be active or arrested? This decision, adding the aspect of activity to detection, is diagnosis. ◆ Is the surface of the lesion intact or is a cavity present? If there is a cavity, can the lesion be cleaned by the patient? Diagnosis has been called a ‘mental resting place on the way to a treatment decision’. For instance, grading a lesion as active implies that the clinician considers that, if nothing is done, the demineralization will progress. Figure 3.1 is a decision tree showing how the diagnostic decision may guide the treatment. Thus, the diagnosis detects and excludes disease, assesses prognosis (considering the entire oral condition of the mouth), and forms the basis for the treatment decision. Lesions where the tooth surface is intact can be managed by the patient’s caries control measures. However, a cavity in a tooth may prevent access for the toothbrush. In addition, it may be unsightly and the tooth may be sensitive. These lesions may require restorations as a part of caries control. It is the duty of the professional to discuss with the patient whether any action is required in order to control lesion progression. Finally, the diagnosis should allow the clinical course of the disease to be monitored at subsequent visits.

Introduction

A pain-free, functioning, and good-looking dentition for a lifetime seems a reasonable goal! Is this what dentists do? An advertisement for a North American dental practice recently suggested that dentists practising general dentistry provide amalgam and composite fillings, sealants, cosmetic dentistry, pulp and root canal treatment, crown and bridges, dentures, and dental implants. Moreover, they do minor oral surgery, gum disease treatment, and occasionally temporomandibular joint (TMJ) therapy, tobacco cessation, and nutrition counselling. The topics listed in the first sentence comprise the daily work in general dentistry, but do you realize that 85% of these are a direct consequence of dental caries? Yet dental caries is not mentioned as the main reason for most dental treatments. Restorative treatment is the focus of dentistry. The disease dental caries is the only disease which has been combatted with metals and composites for more than a century. Some 50 years ago the concept of prevention became fashionable. Now restorative treatment was described as ‘secondary prophylaxis’ because it was considered that once the inevitable dental caries had occurred, it had to be treated (i.e. restored) to prevent further break down of the teeth and the dentition. Therefore, it is not surprising that the most time in the dental curriculum is devoted to the many skilled restorative procedures. These have to be conducted in a moist, slippery, small, and moving oral cavity attached to a person who may find the procedure unpleasant! No wonder it is difficult to perform intra-oral restorative work of high quality as part of oral rehabilitation, and no wonder so much time in the curriculum is devoted to these aspects. However, supposing it was possible to prevent or control the disease so that restorations are reduced to a minimum? This control of caries is what this book is about! Seven chapters present the essentials of what is known about dental caries. The observations will be based on current scientific evidence. This is a hands-on book, which means that what is suggested and observed should have immediate implications for how patients may be treated.

Caries control in populations

Up to this point, the scientific basis for caries control and practical details for delivery of caries control to the individual have been given. We now change tack and consider caries control in populations. In order to follow the health profiles in populations there is an important tool called epidemiology. This literally means ‘the study of what is upon people’. It is derived from Greek where ‘epi’ means upon or among and ‘demos’ is people (population). In other words, epidemiology is the study of the distribution (how often) various diseases occur and why they appear in well-defined populations. It deals with groups of people, not individuals. Data thus obtained are used in public health for developing and monitoring strategies for health care in populations. Moreover, it can tell how diseases are influenced by hereditary factors, by physical and social environments, and human behaviour. All this helps health authorities to develop appropriate preventive interventions and make these as cost-effective as possible. In this chapter, having introduced the concepts of epidemiology, examples of caries control in two populations and its assessment using epidemiological measurements is given. However, the use of epidemiology has already been described in Chapter 4, where Dean’s observations on the relationship between fluoride in water supplies, the resulting dental fluorosis, and the concomitant caries reduction are described (see Chapter 4). In a recording system of any disease it is important to have clear criteria for diagnosis. The following are important: ◆ How valid are the criteria of measurement? Do they record what they are intended to measure? ◆ How reliable are the criteria? Reliability is also covered by the terms reproducibility, and consistency. These terms imply that the same or different examiners can use the criteria in the same way on different occasions and obtain the same result. ◆ The criteria should be clear, simple, and objective. In other words robust. This is particularly important if manifestations of a disease are to be grouped in different categories of severity, as with dental caries.

Communicating with the patient and trying to influence behaviour

In the previous chapters, the point has been made that dental caries is controllable by the patient regularly disturbing the biofilm, the use of fluoride, especially in toothpastes, and a sensible, but not draconian diet. The success of these strategies depends on the patient, but patients may choose not to comply with the health advice given to them. Many know they should not smoke, should lose weight, and take more exercise, but choose not to alter their behaviour. Altering a patient’s behaviour may be key to caries control, and for this reason all members of the dental team should be interested in strategies to modify behaviour. Motivation is about unlocking the desire within another to make a useful change in behaviour. Good communication is one of the foundations for motivation. Compliance is not likely where patients do not understand, or cannot remember the message. However, people do not change their behaviour just because someone tells them, however clearly, that this is a good idea. Motivation comes from within and cannot just be instilled. It should also be remembered that motivation to change is something that comes gradually, with most people feeling ambivalent about change. Someone who is ambivalent may see a reason to change, but may also see a reason not to change. When we try to persuade someone who is ambivalent to change, the danger is they will resist, giving voice to the counter-argument as to why they cannot change. Actually, the best way to achieve change is if the patient, rather than the health professional, says why and how they should change. In other words, it is their idea and we are there to support it. Despite all these difficulties, good communication can make all the difference in achieving behaviour change and, for this reason, this chapter will now take a detour to discuss aspects of communication. Communication is made up of more than just the actual words used to convey information. The tone used conveys the speaker’s emotions and attitudes, and so-called non-verbal communication or body language can be just as important as the actual words.

How does a caries lesion develop?

The oral cavity is an open sink. The mucous membranes and teeth are constantly covered with a salivary film whose proteins adhere to all surfaces in the mouth. Saliva is not just a fluid flushing through the oral cavity, but a highly complex proteinaceous liquid that contains millions of microorganisms (bacteria). Depending on their different surface properties (different species have different surface proteins comprising their cell wall, which coat the surface of each cell) they stick to the salivary proteins at the surfaces of mucous membranes and teeth. These oral microorganisms comprise the endogenous flora of the mouth. They are living in symbiosis with the cells of the human body and comprise what is today called the metagenome. There are more bacteria covering all body surfaces in each individual than there are eukaryotic cells in the whole body. Eukaryotes store their DNA in a membrane ‘sac’ called the nucleus. Plants, fungi, and animals are eukaryotes, whereas bacteria are prokaryotes with no distinct nuclear compartment in which to store their DNA. Prokaryotes live in a variety of ecological niches. An occlusal fissure is an example of such a niche and so is an approximal space between neighbouring teeth, the gingival crevice, and periodontal pockets. Bacteria are astonishingly varied in their biochemical capabilities—in fact, more so than eukaryotic cells and each ecological niche may have a particular environment (different pH, inflammatory exudate, etc.), which will influence the microbial function and composition. Until recently, traditional bacteriological methods were used to isolate and culture microorganisms in the laboratory, but it was realized that only a few could be cultivated! DNA sequencing techniques (genomics) of populations of microorganisms from a variety of natural habitats (including the oral cavity) showed that most species have not been found by these traditional culturing techniques. According to some estimates, about 99% of prokaryotic species remain to be characterized. For this reason alone, it does not make sense to think that a particular ‘caries microorganism’ exists. There are also implications for the many attempts to find salivary microbial and biochemical biomarkers that might be used clinically to assess caries risk.

Caries control for the patients with active lesions

Chapter 4 described caries control measures for everybody, a whole population approach. The emphasis was on oral hygiene, regularly disturbing the biofilm with fluoride toothpaste. The mode of action of fluoride was discussed in some detail to show that this therapeutic agent acts topically to interfere with the deand remineralizing processes and delaying lesion development. The relevance of minimizing sugar intake was discussed. The metabolism of sugar, by microorganisms in the biofilm, creates the acidic environment for demineralization. However, what more should be done for those presenting with active lesions? This chapter will consider how to find out why these patients are developing lesions. The chapter will then explore further oral hygiene measures that might be useful. It will question how fluoride might be boosted and their diet modified. Specific groups, such as babies and young children, those with erupting teeth, patients undergoing orthodontic treatment, and patients with dry mouths will be individually discussed. Finally, a section will discuss the difficulties of advising carers on helping those who can no longer care for themselves, either though illness, disability, old age, or dementia. The caries activity of any patient, child, or adult, is assessed at the first visit of the patient by noting how many lesions judged as active are present (both cavitated and non-cavitated) and where they are located (see Chapter 3). Please note, this assessment is mainly based on clinical assessment. Some companies produce a battery of chairside salivary tests, such as microbiological counts of specific microorganisms, but these are not needed. If the patient is coming for a regular check-up, a history of recent caries activity is available (number of lesions and fillings over the last 1–3 years). This information is most valuable. A yearly increment of one or more lesions detected clinically, would indicate a high rate of lesion formation and progression. Once a dentist has assessed an individual patient’s caries activity as high, an attempt should be made to identify the relevant risk factors for this patient. It is possible to interfere with and modify many of these factors, and thus arrest ongoing active lesions, or slow down the disease activity and diminish the rate of progression.

When should a dentist restore a cavity?

At the start of this book it was commented that some dentists see restorative dentistry (fillings) as the treatment of dental caries. These dentists see prevention of caries as a separate issue. The authors profoundly disagree with this. The previous chapters have shown how dental caries develops and what it is, so in this chapter it is important to ask the question ‘with this knowledge in mind, what is the role of restorations (restorative dentistry) in caries control?’ Are restorations required or can the problem be solved by sealing all surfaces in the oral cavity—or at least those parts where surface irregularities (occlusal fissures, grooves, pits, etc.) may favour biofilm stagnation? Therefore, this chapter starts with a discussion of so-called fissure sealants. On occlusal surfaces, caries lesions may form at the entrance to the fissure because this complex morphology may be difficult to clean, particularly in the erupting tooth that is below the level of the arch and tends to be missed as the toothbrush swings by. Fissure sealants cover the fissures with a flowable resin or highly viscous glass ionomer cement, so that they are easier to clean. Their effectiveness has been proved in many studies. When first introduced in developed nations, all molar surfaces were recommended for sealing to avoid caries development and the need for fillings. This ‘sealing all teeth’ policy would now be totally incorrect for two reasons: ◆ Caries can be controlled by cleaning alone. ◆ Many of these surfaces will never develop lesions, and this automatic sealing approach is over treatment and not cost-effective. The indications for fissure sealing are: ◆ Active fissure caries has been diagnosed, but attempts at caries control have not arrested lesion progression. ◆ Occlusal surfaces are often highly irregular, and filled with grooves and fissures, and the patient or parent either cannot, or will not, remove plaque effectively. This is particularly important in the erupting molar. This surface is particularly at risk of lesion development and progression because permanent teeth can take 6–12 months to erupt; indeed, third molars may take several years.