Structured review of enamel erosion literature (1980-1998): a critical appraisal of experimental, clinical and review publications

Longitudinal correlation of 3D OCT to detect early stage erosion in bovine enamel

Erosive tissue-loss in dental enamel is of significant clinical concern because the net loss of enamel is irreversible, however, initial erosion is reversible. Micro-hardness testing is a standard method for measuring initial erosion, but its invasive nature has led to the investigation of alternative measurement techniques. Optical coherence tomography (OCT) is an attractive alternative because of its ability to non-invasively image three-dimensional volumes. In this study, a four-dimensional OCT system is used to longitudinally measure bovine enamel undergoing a continuous erosive challenge. A new method of analyzing 3D OCT volumes is introduced that compares intensity projections of the specimen surface by calculating the slope of a linear regression line between corresponding pixel intensities and the associated correlation coefficient. The OCT correlation measurements are compared to micro-hardness data and found to exhibit a linear relationship. The results show that this method is a sensitive technique for the investigation of the formation of early stage erosive lesions.

Tooth wear in the deciduous dentition of 5-7-year-old children: risk factors

This study was conducted to investigate the distribution and severity of tooth wear in deciduous dentition and its relationship with possible risk factors. A stratified cluster sample of 243 5-7-year-old children was examined using the tooth wear index of Smith and Knight, and their exposure to intrinsic and extrinsic risk factors was retrospectively investigated through a structured questionnaire. The severity of wear was quantitatively estimated by the number of surfaces with affected dentine and by the cumulative score of the sextants, based on the Basic Erosive Wear Examination scoring system. Only 1.6% of the children were tooth wear free, whereas 45.6% had moderate to severe wear involving dentine. Maxillary canines were the most affected teeth (83.2%), and occlusal/incisal the most affected surfaces (52.7%). The likelihood of tooth wear involving dentine was greater in boys than girls (OR = 1.72), in immigrants than in Greeks (OR = 1.93), and in 6- and 7-year olds than in 5-year olds (OR = 2.78 to 2.93). After adjustment for age, gender, and nationality, exposure to several dietary factors and especially to soft drinks was found to significantly affect the prevalence (OR = 1.27) and the severity of tooth wear. Every additional serving/week of consumption of soft drinks increases the number of surfaces with dentine affected by 0.03 per year (p < 0.05) and the cumulative score of sextants by 0.04 (p < 0.05). The cluster of children with the higher prevalence and severity of tooth wear had an average exposure to soft drinks of 10 servings/week for a duration of 4 years. The cumulative score of sextants was better predicted by the assessed risk factors, in comparison with the number of surfaces with affected dentine. Tooth wear is a common condition in children, related both to the physiological process of aging of dentition and to the erosive effect of dietary factors. Strategies to reduce the intake of soft drinks in children are expected to have multiple benefits preventing tooth wear in childhood and in later life, as well as many other general and oral health diseases.

Is diagnosing exposed dentine a suitable tool for grading erosive loss?

Quantifying tooth wear in general and erosion in particular mostly is made by distinguishing between lesions restricted to enamel and lesions reaching the underlying dentine. Various scores for grading have been used, but in all systems, higher scores are given in cases of exposed dentine, thus, indicating a more severe stage of the condition. Clinical diagnosis of exposed dentine is made by assessing changes in colour or optical properties of the hard tissues. This paper aims to review the literature and discuss critically problems arising form this approach. It appears that classifying the severity of erosion by the area or depth of exposed dentine is difficult and poorly reproducible, and taking into account the variation of enamel thickness, the amount of tissue lost often is not related simply to the area of exposed dentine. There has still been very little longitudinal investigation of the significance of exposed dentine as a prognostic indicator. Further work and discussion is needed to reevaluate the explanative power of current grading procedures.

Epidemiological studies of tooth wear and dental erosion in 14-year old children in North West England. Part 2: The association of diet and habits

OBJECTIVE

To determine the strength of association (expressed as Odds Ratios) of potential risk factors with erosion and tooth wear in 14-year-old schoolchildren.

DESIGN

A random sample of 2,385 children were selected by a stratified two-stage technique based on schools and children.

SETTING

Schools in NW England.

METHODS

Tooth wear was assessed by one examiner on three surfaces of all 12 anterior teeth (labial, incisal and palatal) and the occlusal surface of all four first molars using a four-point scale. Enamel wear was scored 0, dentine exposure <1/3 scored 1, >1/3 scored 2 and secondary dentine or pulpal exposure, scored 3. A questionnaire enquired about general health, dental health, habits and the frequency of intake of a wide range of foods and drinks.

RESULTS

The Odds Ratios for tooth wear on any surface for habits, reflux and certain foods were: bruxism, 1.10; stomach upset, 1.45; pickles 1.86; vinegar 1.36; salt and vinegar crisps 1.33; brown/other sauces 1.57. Similarly, the odds ratios for potentially erosive drinks were: fizzy drinks 1.32; sport drinks 1.58; herbal/lemon tea 3.97. The frequency of intake was bi-modal with 397 children drinking a can per day and 207 drinking two cans per day. A significant number drank acidic beverages at bedtime but this was not associated with dental erosion.

CONCLUSION

Although odds ratios greater than unity indicate an association, this was not high for carbonated beverages and many other acidic foods or drinks. Examining at fourteen years may not be ideal, as the determinants of erosion/tooth wear have not acted for long, the indices do not discriminate sufficiently and proportionately few subjects have dentine exposed on smooth surfaces.

Linear interpolation error in measured surfaces in a dental erosion study

An extensive palatal erosion study, which is currently being undertaken at the University of Dundee, aims to detect erosion through the precise mapping of replicas of children's incisors. All perceived sources of error are being scrutinised closely. The error due to the interpolation of surface positions from discrete point measurements has been investigated so that its contribution to the erosion estimates can be gauged. The calculation of the error statistics made use of covariance functions to express the undulation of the tooth surfaces. It has been found that, for the measurement point spacing of 150 microm being used in the current project, the interpolation error for an incisor is typically about 25 microm, to be compared with the root-mean-square error due to tooth impression and replication procedures, assessed as being in the order of +/- 3 microm, and replica measurement, assessed as being in the order of +/- 5 microm. The interpolation error constitutes a surprisingly large proportion of the overall system error. The same error estimation technique can be applied usefully and without difficulty to other research studies concerning erosion or wear in natural or restorative dental surfaces.

The validation of Quantitative light-induced fluorescence to quantify acid erosion of human enamel

OBJECTIVE

The purpose of this study was to validate the Quantitative light-induced fluorescence (QLF) device against transverse microradiography (TMR) with regard to the quantification of enamel erosion in vitro.

DESIGN

Longitudinal in vitro.

METHODS

Thirty previously extracted, caries free, human premolars were selected and prepared by gentle pumicing and coating in an acid-resistant nail-varnish save for an exposed window on the buccal surface. QLF baseline images were taken and the teeth then exposed to an erosive solution, 0.1% citric acid (pH 2.74). Teeth were removed at 30min intervals, air-dried and QLF images taken. At this time one tooth was randomly selected, removed from solution and sectioned through the lesion at three sites. The polished sample (100microm) was subjected to TMR and analysed for erosive mineral loss using proprietary software, with the DeltaZ values noted. QLF images were analysed by a blinded examiner with DeltaF and DeltaQ values recorded. Data were entered into SPSS and the correlation between the DeltaZ and DeltaF, and DeltaZ and DeltaQ values calculated.

RESULTS

A wide range of erosive lesions was produced, with a steady increase in both DeltaZ and DeltaF over time; DeltaZ (24.0 (S.D. 1.2)-6114.3 (S.D. 1177.57)); DeltaF (1.8-11.2), DeltaQ (2.5-202.6). The results were scatter plotted and a regression line calculated. A positive correlation between DeltaZ and DeltaF of 0.91 was found, and for DeltaZ and DeltaQ; 0.87.

CONCLUSIONS

The ability for QLF to detect and longitudinally monitor in vitro erosion has been shown. The strong positive correlation of DeltaF with DeltaZ suggests that percentage fluorescence loss as measured by QLF could be of great value in the development of a non-destructive, longitudinal tool for use in vitro, in situ and possibly in vivo.