The quality of dental care and modern achievements in dental science depend strongly on understanding the properties of teeth and the basic principles and mechanisms involved in their interaction with surrounding media. Erosion is a disorder to which such properties as structural features of tooth, physiological properties of saliva, and extrinsic and intrinsic acidic sources and habits contribute, and all must be carefully considered. The degree of saturation in the surrounding solution, which is determined by pH and calcium and phosphate concentrations, is the driving force for dissolution of dental hard tissue. In relation to caries, with the calcium and phosphate concentrations in plaque fluid, the ‘critical pH’ below which enamel dissolves is about 5.5. For erosion, the critical pH is lower in products (e.g. yoghurt) containing more calcium and phosphate than plaque fluid and higher when the concentrations are lower. Dental erosion starts by initial softening of the enamel surface followed by loss of volume with a softened layer persisting at the surface of the remaining tissue. Dentine erosion is not clearly understood, so further in vivo studies, including histopathological aspects, are needed. Clinical reports show that exposure to acids combined with an insufficient salivary flow rate results in enhanced dissolution. The effects of these and other interactions result in a permanent ion/substance exchange and reorganisation within the tooth material or at its interface, thus altering its strength and structure. The rate and severity of erosion are determined by the susceptibility of the dental tissues towards dissolution. Because enamel contains less soluble mineral than dentine, it tends to erode more slowly. The chemical mechanisms of erosion are also summarised in this review. Special attention is given to the microscopic and macroscopic histopathology of erosion.

A new scoring system, the Basic Erosive Wear Examination (BEWE), has been designed to provide a simple tool for use in general practice and to allow comparison to other more discriminative indices. The most severely affected surface in each sextant is recorded with a four level score and the cumulative score classified and matched to risk levels which guide the management of the condition. The BEWE allows re-analysis and integration of results from existing studies and, in time, should initiate a consensus within the scientific community and so avoid continued proliferation of indices. Finally, this process should lead to the development of an internationally accepted, standardised and validated index. The BEWE further aims to increase the awareness of tooth erosion amongst clinicians and general dental practitioners and to provide a guide as to its management.

ETW is a clinical condition, which calls for the increased attention of the dental community and is a challenge for the cooperation with other medical specialities.

The aim of the present study was to evaluate the effects of fluoride on erosive mineral loss in human enamel and dentine using a cyclic de- and remineralisation model in situ. The study was a three-treatment (5 days each) crossover design involving 4 (enamel) or 6 (dentine) healthy volunteers. Samples were recessed in palatal mouth appliances and worn day and night except during meals and were demineralised extraorally with 0.05 M citric acid (pH 2.3) for 6 × 5 min daily. Fluoridation was performed with toothpaste (SnF₂/Olaflur; 0.14% F^–) for 3 × 5 min daily (toothpaste fluoridation) or with toothpaste in combination with a mouthrinse (SnF₂/Olaflur; 0.025% F^–) for 3 × 5 min daily and with a gel (NaF/Olaflur, 1.25% F^–) on days 1 and 3 instead of the toothpaste (intensive fluoridation). In the control group no fluoridation was performed. Mineral loss (µm) was determined with the use of longitudinal microradiography. In enamel, mineral loss was 40.7 ± 15.1 µm in the control group, 18.3 ± 12.4 µm after toothpaste fluoridation and 5.0 ± 12.2 µm after intensive fluoridation. The respective values for dentine were 49.0 ± 15.4, 35.0 ± 15.5 and 19.8 ± 12.0 µm. All differences were statistically significant (p ≤ 0.001). The results indicate that intensive fluoridation is effective in preventing enamel and dentine from mineral loss even under severely erosive conditions.

The aim of the present study was to evaluate the effect of fluoride on the progression of erosive demineralisation in human enamel and dentine using a cyclic de– and remineralisation model in vitro. The mineral content expressed in micrometres was determined daily by longitudinal microradiography (LMR) and presented as cumulative mineral loss over 5 days. For erosive demineralisation, all samples were immersed in 0.05 M citric acid (pH 2.3) for 6×10 min/day and stored in a remineralisation solution. Fluoridation measures were performed as follows: group 1: control, no fluoridation; group 2: toothpaste fluoridation 3×5 min/daily (NaF, 0.15% F^–); group 3: toothpaste fluoridation as group 2 and additionally application of a fluoride mouthrinse (Olaflur/SnF₂, 0.025%F^–) 3×5 min/daily and on days 1 and 3 gel fluoridation (Olaflur/NaF; 1.25% F^–) for 1×5 min. After the first experimental day, no significant differences were found between the groups. However, after 5 days the erosive mineral loss values for enamel were 147.5±18.7 µm in the control group, 128.1±15.0 µm in group 2 (p≤0.05) and 116.1±12.4 µm in group 3 (p≤0.001). In dentine, the respective values were 136.7±16.4, 111.8±26.9 (p≤0.001) and 60.3±17.8 (p≤0.001). The intensive fluoridation significantly reduced erosion progression in enamel but had a more pronounced effect on dentine. The results suggest that subjects with erosive lesions should use an intensive fluoridation measure.

The advantages, limitations and potential applications of available methods for studying erosion of enamel and dentine are reviewed. Special emphasis is placed on the influence of histological differences between the dental hard tissue and the stage of the erosive lesion. No method is suitable for all stages of the lesion. Factors determining the applicability of the methods are: surface condition of the specimen, type of the experimental model, nature of the lesion, need for longitudinal measurements and type of outcome. The most suitable and most widely used methods are: chemical analyses of mineral release and enamel surface hardness for early erosion, and surface profilometry and microradiography for advanced erosion. Morphological changes in eroded dental tissue have usually been characterised by scanning electron microscopy. Novel methods have also been used, but little is known of their potential and limitations. Therefore, there is a need for their further development, evaluation, consolidation and, in particular, validation.

The aim of the study was to evaluate the relevance of cations in different fluoride compounds for their effectiveness as anti-erosive agents. Human enamel samples underwent a de- and re-mineralisation procedure for 10 days. Erosive demineralisation was performed with 0.05 Mcitric acid (pH 2.3) 6 × 2 min daily followed by immersion in the test solution 6 × 2 min each. Test solutions were: SnCl₂ (815 ppm Sn; pH 2.6), NaF (250 ppm F; pH 3.5), SnF₂ (250 ppm F, 809 ppm Sn; pH 3.5), amine fluoride (AmF, 250 ppm F; pH 3.5), AmF/NaF (250 ppm F; pH 4.3), and AmF/SnF₂ (250 ppm F, 390 ppm Sn; pH 4.2). In the control group no fluoridation was performed. Mineral content was monitored by longitudinal microradiography. Finally, scanning electron microscopy was performed. The highest erosive mineral loss was found in the control group (48.0 ± 17.1 µm). Mineral loss was nearly completely inhibited by AmF/SnF₂ (5.7 ± 25.1 µm; p ≤ 0.001) and SnF₂ (–3.8 ± 14.4 µm; p ≤ 0.001) treatments. Groups treated with SnCl₂ (17.6 ± 19.5 µm; p ≤ 0.001) and NaF (13.2 ± 21.7 µm; p ≤ 0.001) showed a decrease in erosive mineral loss, AmF (41.6 ± 16.0 µm) and AmF/NaF (27.7 ± 28.4 µm) had no significant effect on erosion progression. The results indicate considerable differences between the fluoride compounds tested. Treatment with solutions containing SnF₂ was most effective.

This paper summarises the discussions which took place at the Workshop on Methodology in Erosion Research in Zürich, 2010, and aims, where possible, to offer guidance for the development and application of both in vitro and in situ models for erosion research. The prospects for clinical trials are also discussed. All models in erosion research require a number of choices regarding experimental conditions, study design and measurement techniques, and these general aspects are discussed first. Among in vitro models, simple (single- or multiple-exposure) models can be used for screening products regarding their erosive potential, while more elaborate pH cycling models can be used to simulate erosion in vivo. However, in vitro models provide limited information on intra-oral erosion. In situ models allow the effect of an erosive challenge to be evaluated under intra-oral conditions and are currently the method of choice for short-term testing of low-erosive products or preventive therapeutic products. In the future, clinical trials will allow longer-term testing. Possible methodologies for such trials are discussed.