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The first and second parts of this study investigated the prevalence of dental erosion and possible relationships with socio-economic group and the influence of dietary intake. This third part concerns other extrinsic factors that may also have an impact on the prevalence of tooth wear involving dental erosion.

There have been several European investigations1,2,3,4,5 concerning toothbrushing frequency in children but the data collection and sampling methods were very different and do not allow direct comparison. However, Honkala et al.6 surveyed 11–13 and 15-year-old adolescents in 11 European countries and reported the highest brushing frequency in Sweden; 98% of these children brushed daily compared with the lowest levels in Spain, where only 68% of children brushed daily. Kuusela et al.7 described the oral hygiene habits of 11-year-old schoolchildren in 22 European countries and Canada. This was part of a WHO Collaborative Study based on data collected during 1993–1994. They observed the most favourable habits in Sweden, Denmark, Germany, Austria and Norway where between 73% and 83% of children brushed their teeth twice daily. At the other end of the spectrum 26%–33% of boys from Finland, Lithuania, Russia, Estonia and Latvia brushed twice daily or more. This extensive study concluded that there were considerable differences in toothbrushing frequency among children in European countries.

Toothbrushing frequency varies with gender and socio-economic background of children8,9,9 and also appears to be influenced by a number of lifestyle factors.10 Regis et al.11 stated that toothbrushing frequency in adolescents increases with increasing self-esteem.

Toothbrushing and oral hygiene practises are obviously to be encouraged in order to maintain oral health, but they may be a contributing factor to tooth wear involving dental erosion. Several studies 12,13,14,15,16,17 have shown that loss of tooth substance after exposure to citrus juices or acidic drinks is accelerated by toothbrushing.

Toothbrushing after every meal could theoretically play a major role in the development of tooth wear involving erosion if the food and drink consumed contained acidic substances. Recently, Jaeggi and Lussi18 investigated toothbrush abrasion on enamel previously exposed to a standardised artificial erosive agent. The enamel was exposed to citric acid solution for 3 minutes followed by toothbrushing for 0, 30 and 60 minutes. The tooth tissue loss was significantly lower following 60 minutes exposure to the oral environment than immediately after acidic exposure.

However, toothbrushing is normally carried out using toothpaste and conversely there may be advantages in the use of a toothpaste, particularly its fluoride content and potential to promote remineralisation following acidic challenge. Munoz et al.19 undertook a laboratory investigation of the effects of a conventional and a remineralizing toothpaste on the hardness of enamel following acidic soft drink exposure. They concluded that toothpaste could be effective in inhibiting damage due to soft drink consumption. Nevertheless the abrasives in toothpastes may exacerbate tooth wear after exposure of the dentine to acid and differences in abrasivity between various toothpastes products may lead to a spectrum of effects.

Therefore, oral hygiene practises, particularly the time and frequency of toothbrushing and usage of toothpaste, can influence the development of erosion following acid consumption. However, there is some conflicting evidence relating acid challenge and toothbrushing habits. Further information is consequently needed not only to describe the dental and oral hygiene practices in the child population, but also to try to quantify other possible related and causative factors.

Aims and objectives

The aims of this study were firstly to describe the dental history and oral hygiene practises in a cluster random sample of 14-year-old children in Birmingham, UK. The second aim was to determine whether their oral hygiene practises were associated with dental erosion.

Materials and methods

A cluster random sample of 14-year-olds was drawn from Birmingham UK, and a total of 418 children were examined; 209 were males and 209 were females. This involved 12 secondary schools covering a very broad range of social and ethnic mix. Details of the sample selection are given in Part I of this study.20 The numbers of children examined in each school differed according to the size of the school. They and their parents/carers gave informed consent to participate in this study and ethical approval was given by the Birmingham Research Ethics Committee.

All the children were examined clinically within their schools under standard illumination from a Daray light using number 6 plane mouth mirrors. The surfaces of all teeth present in the mouth were scored for dental erosion according to the criteria based on the Tooth Wear Index of Smith and Knight,21,22 with minor modifications. Extensive calibration and reproducibility exercises in the use of this index were undertaken.

The questionnaire was developed to cover dental history and oral hygiene practises that were used by the children. These included dental attendance (every six months, once a year and only when in pain); frequency of toothbrushing (less than once a week, less than once a day, once a day, twice a day, three times a day and more than three times a day); time of toothbrushing (always after a meal, sometimes after a meal, last thing at night, before breakfast and last thing at night and other); the techniques of brushing (from side to side, up and down, in circular movements and all of these techniques); type of toothbrush (manual, electric and both); replacement of toothbrush (every 3 months, every 6 months and more than 6 months); the use and type of toothpaste, mouthwash and any interdental cleaning.

The questionnaire was piloted in three studies carried out in the Unit of Paediatric Dentistry at the University of Birmingham Dental School and Hospital. Following modification of both questions and format, it was finally re-tested on another group of 35 teenagers.

After undertaking the clinical examination, the data were collected through a self-reported questionnaire completed by the children at the schools. As there was a wide range of educational attainment, some children required help to undertake this through a structured interview with standardised prompts.

All data were analysed using SPSS with Mann-Whitney U analyses and odds ratios and confidence intervals for the explanatory factor. Significance was accepted at the p < 0.05 level.

Results

The results showed that the majority of children (74%) visited their dentist on a regular basis every six months. Ten percent of the children visited the dentist once a year and 16% of the children attended the dentist only when they had pain (Table 1).

Table 1 Table 1
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The majority of children (92%) used a manual toothbrush, with only 5% using an electric toothbrush and 3% using both manual and electric. As far as toothbrush replacement was concerned, 56% replaced their toothbrush every 3 months, 39% every 6 months and 5% replaced their brush very infrequently. Other oral hygiene practises were also investigated: 44% of the children used a mouthwash and 40% claimed to use some form of interdental cleaning.

Ten percent of the children brushed three times daily, 60% brushed their teeth twice a day and 25% brushed once a day. Only 2% of the children stated that they brushed their teeth less than once a day (Figure 1). It was also important to investigate the time of day when toothbrushing was undertaken; 60% of children

Figure 1
figure 1

Frequency of brushing used by children.

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claimed to clean their teeth before breakfast and last thing at night, with a further 8% just at night (Figure 2). Toothbrushing techniques were variable, although 39% of these children stated that they cleaned their teeth with a circular motion (Figure 3).

Figure 2
figure 2

Time of day brushing undertaken by children

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Figure 3
figure 3

Toothbrushing technique used by children

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The children were asked about what type of toothpaste they used after listing some of the common toothpaste available in the market. It was found that 41.5% of the children were using Colgate or Colgate Total and less than 31.5% of the children were using a different type of toothpaste such as Aquafresh, Macleans, Own brands, Crest, Whitener, Sensodyne, Signal, Ultrabrite, and other. It was also found that 27% of the children were using more than one product from these types of toothpaste at the same time (Table 1).

Analysis of dental history and oral hygiene practises was also undertaken by gender and is shown in Table 2. Females were more likely to attend the dentist than males. There were highly significant differences between males and females (p < 0.0001, Mann-Whitney U test) in the frequency of toothbrushing; more females (70%) brushed their teeth twice a day compared with males (49%). However, there were no significant differences between genders in the periodicity of toothbrushing or types of toothpaste etc.

Table 2 Table 2
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The possible association between erosion and the questionnaire data was analysed by allocating the children on an individual basis into either the low erosion group or the moderate/severe erosion group. Table 3 shows the odds ratios and confidence intervals for dental history and oral hygiene practises, which were associated with dental erosion. Each of the variables showing no difference at all between low and moderate/severe erosion or with odds ratios value below 1 was eliminated from the table in order to simplify it. There was an association between increasing levels of dental erosion and children brushing their teeth last thing at night (OR = 3.17). This was the only association that was shown to be statistically significant. However no significant trends with odds ratios of more than 1.5 towards increasing erosion were shown with the type of toothbrush and brushing after meals.

Table 3 Table 3
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Discussion

The present study provides a considerable amount of information from this random sample of 14-year-olds with regard to dental history and oral hygiene practises. It also enabled these to be assessed as potential risk factors in relation to dental erosion.

Regular dental attendance has been encouraged in the United Kingdom; the current investigation showed that three-quarters of these teenagers visited the dentist regularly, whereas 16% of them only attended when in pain. This is very similar to the data presented in the Child Dental Health Survey4 which reported that 77% of 15-year-olds were regular dental attendees. Peterson23 and Evans et al.24 have shown that oral health behaviour and dental attendance are highly influenced by the educational levels of their parents and there is thus a higher attendance rate in those from higher socio-economic groups.

This is also apparent in toothbrushing habits. Many published studies have considered frequency of toothbrushing both in the UK and in other European countries.1,2,3,4,5,6,7 In the UK Child Dental Health Survey, O'Brien4 found that 13% of 15-year-olds brushed their teeth three or more times daily, 67% twice daily, 17% once daily and 3% less often than daily; these finding are somewhat higher than in the current study. The comparable figures were 12% brushing three times daily, 60% twice daily and 27% brushed once per day or less. There were highly significant gender differences with girls more likely to brush their teeth; this is in agreement with other studies (MacGregor et al.,10 Dummer et al.25). The time of brushing could also conceivably affect the development of erosion, particularly if this was undertaken immediately after meals or last thing at night following an acidic drink. The present investigation has shown that one third of children brushed their teeth after a meal, but of those children brushing twice daily, 60% brushed before breakfast and last thing at night. O'Brien4 reported that 80% of children brushed before bedtime. The majority of children used a manual toothbrush with a range of fluoride toothpastes and a circular movement. Almost half of them claimed to use a mouthwash. Some studies 9,26,27,28,29 have indicated that toothbrushing behaviour is associated with several factors such as social class, gender, and number of children in the family and these may influence the frequency of toothbrushing or oral hygiene in general. All these studies are based on reported toothbrushing behaviour rather than observed behaviour and as such may be considered higher values; however there should be comparability between the studies.

Associations were found between dental erosion and brushing last thing at night, after meals, toothbrushing technique and type of toothbrush. It should however, be noted that in the current investigation there were numerous variables and multiple tests of significance. The possibility, therefore, always exists of spurious results that may have occurred by chance. Nevertheless, these findings clearly highlight a number of interesting points in relation to dental erosion and oral hygiene practises. They also give clinical confirmation of the in vitro experiments undertaken by Jaeggi and Lussi18 and Davis and Winter.30 There appears to be some evidence from the current study relating the type of toothpaste to erosion (see odds ratios Table 3). It is possible that the abrasive content of toothpaste can be more important than fluoride levels. However, caution may be required in considering associations between type of toothpaste and erosion, since it was not possible to determine the duration of use of the reported type of toothpaste and 27% of children regularly used more than one kind of toothpaste.

Nevertheless, there are some potentially contradictory findings in the present investigation. For example, girls brushed more frequently than boys and in general had what would be accepted as better oral hygiene practises; overall, the levels of erosion were lower in girls. Toothbrushing and dental attendance were more frequent in higher socio-economic groups, but again there was less erosion in children from higher socio-economic groups. These apparent anomalies suggest that there is a very complex relationship between oral hygiene practises, other aetiological factors, and erosion; other potential causes of erosion such as diet may be of more importance.

Thus, in conclusion, this study has described some of the dental history and oral hygiene practises used by teenagers in Birmingham, UK. Some significant differences have been shown in relation to gender. In addition, oral hygiene practises were shown to be associated with the development of dental erosion. This is an area that requires further investigation as it is apparent that some practises traditionally regarded as desirable in the prevention of most oral disease may require modification in those who are shown to be susceptible to the development of dental erosion.