For many years, dental erosion was a condition of little interest to clinical dental practice or dental public health professionals. Dental erosion starts with a softening of the outermost surface by (extrinsic and intrinsic) acids of different origins. Once softened, this layer is highly vulnerable to abrasion and it can be very difficult for this surface to be resistant to common daily abrasive forces such as chewing food or toothbrushing. In this context it is important to stress that there is, in most cases, an obvious connection between dental erosion and abrasion. The combination of these two processes, which occur in daily life, is called erosive tooth wear. While the terms ‘dental erosion’ and ‘erosive tooth wear’ should more accurately be used to refer to the chemical and chemical–mechanical processes, respectively, they are often used interchangeably. Erosive tooth wear, including dental erosion, is not a new phenomenon. What is probably new is the increasing attention paid to it because caries, the main ‘tooth disease’, has been decreasing in many societies, although it is still a much more widespread issue in many geographies compared with tooth wear. There are, however, many reports that suggest the incidence of dental erosion is increasing globally.
In all cases, early diagnosis of dental erosion is important. Dental professionals may dismiss minor tooth surface loss as a normal and inevitable occurrence of daily living, and thus not appropriate for any specific intervention therapy. While a certain degree of erosive tooth wear – depending on the patient's age – may be considered physiological, it is nevertheless important to detect early stages of the erosive process. Only at the later stages in which dentine has become exposed and possibly sensitive, and the appearance and shape of the teeth have been altered, does the condition become evident during a routine examination.
Dental erosion is a condition in which many risk and protective factors are involved. Biological, behavioural and chemical factors interact with the tooth surface, which, over time, may either wear it away or protect it, depending upon the balance of these factors. Comprehensive knowledge of the different risk and protective factors is a prerequisite for initiating adequate preventive measures. There is increasing evidence from in vitro, in situ and in vivo studies that the excessive consumption of acidic drinks and foods poses a significant risk to dental hard tissues. However, hydrogen ion concentration (pH) alone does not explain the erosive potential of a particular food or drink: titratable acidity, calcium, phosphate, fluoride concentration and other factors must also be considered. Knowledge of the erosive potential of various drinks and foods allows the oral health professional to determine the patient's overall risk and helps bring it into perspective with regard to other factors. Other important factors include the manner in which drinks are consumed (sipping, swishing around in the mouth), how toothbrushing is undertaken and if acids from the stomach come into contact with the teeth. Saliva and pellicle both play key roles in the prevention of dental erosion. The flow of saliva is increased in response to different stimuli, and this not only enhances the buffering capacity within the localised environment, but it is also involved in clearing acids from exposed tooth surfaces during an erosive challenge. When an erosive solution comes in contact with dental hard tissue, it has to diffuse first through the acquired pellicle; only thereafter can it interact with the enamel. This natural, protective barrier prevents direct contact between an acid and the tooth surface. The interplay of all these factors is crucial and helps explain why some individuals exhibit more, or less, erosion than others, even if they are exposed to the same acid challenge in their diets.
Therefore, prevention of the process at an early stage is of paramount importance. First, a detailed patient assessment should be undertaken. A very important part of the patient assessment is case history taking. However, chair-side interviews are generally not sufficient to determine dietary habits that may lead to dental erosion because the patients may be unaware of their level of acid ingestion. It is therefore advisable to have such patients record their complete dietary intake. Evaluation of the erosive potential of the patient's total consumption of different acidic food items and drinks enables the dental professional to estimate the daily acid challenge. Based on these analyses, an appropriate preventive programme may be suggested to patients in order to: (1) reduce acid exposure by decreasing the frequency of ingestion of potentially harmful drinks and foods; and (2) minimise contact time with the teeth, by recommending either more rapid consumption of them, rather than sipping or swishing them around in the mouth. In addition, reflux/vomiting should be controlled.
In parallel with attempts to help control exposure to potentially erosive products, the patient's oral hygiene regimen should be optimised. It is advised that the patient receives oral hygiene products that are specifically designed to help strengthen the tooth surface against acidic attacks, as prevention against tooth surface softening that can lead to irreversible tooth surface loss is likely to be a more successful approach than attempts to reverse erosive tooth surface damage. While fluoride-containing products are well recognised for their ability to help strengthen tooth enamel against cariogenic acids, there is a growing body of evidence to suggest that not all fluorides are alike with respect to their ability to help protect tooth surfaces against erosive acids. Of the most commonly used oral hygiene products, stannous-containing products are becoming widely recognised for their ability to deliver enhanced protection against the processes of dental erosion. Stannous acts by depositing a protective barrier layer onto the enamel surface; it also has the potential to interact with the natural pellicle to provide enhanced resistance to the pellicle itself against erosive acid challenges. The barrier layer that forms on pellicle-coated enamel surfaces increases with continued product use and is retained on treated tooth surfaces for extended periods of time, providing teeth with an enhanced level of protection against erosive acids. After treatment with stannous-containing products, teeth become coated with an invisible, metal-rich barrier layer that is likely composed of precipitates, such as Sn3F3PO4, Ca(SnF3)2 or SnOHPO4, that help strengthen the enamel surface against subsequent acid attacks.
A comprehensive approach that includes an assessment of both risk and preventive factors, coupled with recommendations by the dental professional that include not only a reduction or modification in exposure to potentially damaging acids, but also encourage the use of oral hygiene products designed to help strengthen patients’ natural teeth and pellicle against dietary, erosive acids may lead to a reduction in the initiation and progression of dental erosion.
The papers in this special issue describe some approaches to help protect teeth against erosive acids, focusing on the influence of stannous and fluoride compounds on the prevention of dental erosion. The research presented in this issue includes both in vitro and in situ clinical studies evaluating numerous fluoride agents and formulations for their ability to deliver protective benefits against erosion. The studies include: (1) models that are designed to help understand the mechanisms through which stannous-based formulations are able to deliver an enhanced level of protection against erosive acids; (2) models that confirm the ability of the protective barrier layer to deposit onto pellicle coated surfaces and remain on those surfaces after product use; (3) performance models that compare the relative ability of stannous and non-stannous based formulations to protect the tooth surface against the initiation and progression of dental erosion; and (4) two in situ clinical studies confirming the protection against dental erosion delivered by stabilised stannous-containing formulations. In each of the papers included in this issue, stannous fluoride, whether delivered from the formulation as SnF2 or formed as SnF2 in situ, helps protect against the initiation and progression of dental erosion. Thus, a recommendation by dental professionals in favour of the use of stabilised, stannous-containing products as a means of assisting in the prevention of dental erosion is scientifically justified.