Dental erosion in French adolescents

Dental erosion (DE) is a non-carious lesion consisting of progressive and irreversible loss of dental hard tissue due to the chemical process of acid dissolution that does not involve bacterial plaque acid [1, 2]. Its overall clinical appearance may also involve a frictional component, such as abrasion or attrition, particularly in older age groups. Since the 2000s, different epidemiological studies focusing on the prevalence or the aetiology of DE in adolescents recognised them as an at-risk population due to their eating behaviours. The studies were carried out in the Americas [3‐14], Arabian countries [15‐23], an Asian country [24, 25] and in Western Europe [2, 26‐35]. The prevalence of DE ranged from 7 to 95 % and, except in two studies, the extension of severe erosion into dentine was usually infrequent [11, 16] (Table 1). The wide variation of prevalence in teenagers is suggestive of the difficulty in finding a unanimously accepted index among researchers for measuring and detecting erosive lesions. A recent systematic review estimated an overall worldwide prevalence of tooth erosion of 30 % (95 % CI: 24–37) by mixing different clinical indices and without specifying the teeth examined. Futhermore, the review included population-based studies in the permanent teeth of children and adolescents aged 8–19 years [36].

When focusing on Europeans adolescents, the prevalence of DE has ranged from 18 to 64 % [28, 33] but no epidemiological study of DE has so far been carried out in France (Table 1). The prevalence of DE was only indirectly considered in the study of Bartlett et al. [37]; it focused on the prevalence of tooth wear in 18–35 year-old Europeans including France and six other countries. The index used to measure both severity and distribution of tooth wear was the Basic Erosive Wear Examination (BEWE), as recommended by different authors [1, 38‐41] but the protocol did not consider all surfaces, just the buccal and lingual surfaces of all teeth [37]. Nevertheless early signs of erosion are often observed on the occlusal surfaces of molars [1]. The problem of which clinical index to use and which teeth and tooth surfaces to observe arises since many different methods are available in the literature (Table 1). Finally, no studies that address the risk indicators for DE in France have been found.

The primary objective of the present study was to assess the prevalence of DE using the total BEWE score in a sample of French adolescents. The secondary objectives were to observe changes in prevalence depending on both the cutoff value of total BEWE score on different teeth/dental surfaces examined, and to identify the related risk factors.

Of the 495 subjects invited to participate, 143 did not return the parental consent, 3 were absent on the day of the visit dates and 18 were excluded. The 331 children were aged 14.4 ± 0.5 years. There were 174 girls and 157 boys included; 12.1 % (n = 40) were enrolled in PES and 5.1 % (n = 17) in rural schools.

The highest total BEWE score ≥ 3 (cumulative score of all sextants) in our study was in the range 9–13 (medium risk level) for only one adolescent. When the total BEWE cutoff score was ≥ 3, prevalence was 39 % (primary objective). When the cut off value was 1, i.e. at least one tooth with signs of DE, the prevalence depended on the dental surfaces observed. If only maxillary incisors were examined, as in the method used in some studies carried out in adolescents [7, 12, 23] (Table 1), the prevalence decreased from 39 to 3.9 %. Conversely, if first molars were examined in addition to the maxillary incisors, whatever the surfaces considered, the prevalence was about 54 %, close to 56.8 % for all the surfaces examined on all permanent teeth (Table 2). These results depend on the distribution of the DE lesions. Light extension (BEWE 3–8) was more frequent in mandibular (16.9) compared with maxillary (9.0) teeth. The BEWE score 3 was found just once on the occlusal subsurface of the second maxillary right premolar and score 2 was found on occlusal surfaces of permanent molars and second premolars. First molars, and more particularly the lower ones, were the most affected teeth (Table 3). If we consider the results for each kind of tooth, 98.0 % of the subjects with at least one second molar affected by DE presented also DE on the first molars. Second premolars were more often affected than both the first ones and the second molars.

The risk factors for DE (Total BEWE score ≥ 3) were, in decreasing order, the consumption of acidic beverages and sweets, and the low socio-economic category of participants. Area of residence, the presence of carious lesions (ICDAS 1–6 or 4–6) and prolonged retention of drinks in the mouth were not significantly associated with erosive experience in adjusted logistic regression analyses; visible dental biofilm was only associated if lesions ICDAS 4–6 were included in the multivariable logistic regression analysis (Table 4). Thus the consumption of acidic beverages (OR: 4.0; 95 % CI: 2.1–7.6) and sweets (OR: 3.2; 95 % CI: 1.2–8.0), low socio-economic category (OR: 2.4; 95 % CI: 1.1–5.0) and the presence of visible dental biofilm (OR: 2.0; 95 % CI: 1.2–3.4) had an effect on the primary outcome. When changing the dependent variable by substitution of primary outcome with the total BEWE score ≥ 1 considering all surfaces, independent variables which were entered as candidate variables into a stepwise multiple logistic regression analysis were different (Table 5). With this cutoff value, only acidic beverages (OR: 6.4; 95 % CI: 2.9–14.0) and drinking method (OR: 3.5; 95 % CI: 1.4–8.9) had an effect on the dependant variable.

The prevalence of DE using a total BEWE score ≥ 3 in a stratified sample of French adolescents was 39 %. This was within the confidence interval of the overall estimated prevalence of DE in European countries (33 %, 95 % IC 25–42) and outside the confidence interval of the overall worldwide prevalence of DE of 30 % (95 % IC: 24–37), both reported in a recent systematic review [36]. Except in the two studies carried out in the United States [3, 13, 14], prevalences in America ranged from 7.2 to 34.1 % and were lower than in France [4‐12] whereas the systematic review, which included fewer studies, did not indicate any significant difference between American and European countries [36]. Conversely, except for the two studies with equivalent rates [15, 17, 19‐21], four descriptive studies carried out in Arab countries indicated a higher prevalence, ranging from 51 to 95 % [16, 18, 22, 23]. Finally, by increasing order of prevalence in European countries, France was situated between The Netherlands [30, 33, 34] and Iceland [2, 29], with rates around 20–30 %, and United Kingdom [26‐28, 31, 32] or Greece [35] around 50–60 %.

This ranking by country must be considered with caution as the prevalence of DE in adolescents was studied using different clinical indices. As indicated in the systematic review of Salas et al. [36], the prevalences of DE assessed with O’Sullivan’s or Lussi’s modified scales were lower [2, 4, 7, 8, 11, 17, 24, 29, 30, 33, 34] than in the present study using the total BEWE score. On the contrary, the prevalences of DE were higher with the Tooth Wear Index (TWI) modified three times (Table 1). One of them [31] easily explains these observations because this was dichotomised as the presence or absence of dentinal exposure [22, 26, 27, 31]. In the present study, the erosive lesions involved mostly the enamel. Only the study of Hamasha et al. [15], that used the TWI modified by Millward, did not confirm these result due to the lower prevalence. In France, the prevalence was assessed with BEWE total score because it is now both the most recommended index and the more recently used, especially in adults [35, 39, 41, 46, 47]. In children and adolescents, this was only used in a retrospective study [40] and in a study with a population-based sample mixing adults and adolescents [48]. However, three prevalence studies focusing on adolescents [14, 25, 35] have used BEWE scores but with a cutoff value of 1 for DE diagnosis (Table 1). They reported prevalences higher than 50 %, as in our study, and an increase of the prevalence from 39 to 56.8 % by changing the cutoff value (Table 2). There is therefore a problem of both index choice and cut off value, not forgetting the type of tooth wear registered. Studies considering erosion, attrition (wear resulting from tooth to tooth grinding) and abrasion (wear resulting from tooth to other hard surfaces) showed higher prevalences [18, 22, 26, 27] compared with others (Table 1). This could be explained by an easier differential diagnosis in the young population than in the adult one [2, 24, 49]. Finally, the kind of tooth examined influenced the DE prevalence: the examination of maxillary incisors decreased significantly the DE prevalence whereas there was no significant difference between other situations (Table 2). Our results confirm those of other studies, since erosion was found to be greater in posterior than in anterior teeth and the most frequently affected teeth were the lower first molars [2, 3, 16, 17, 22, 31, 33] (Table 3). The most common clinical manifestation of DE was the appearance of cup-like lesions on the cusp tip of lower first molars. By contrast, other studies have recorded DE mainly on anterior teeth [4, 5, 9‐11, 24, 28, 29] where loss of smooth surface enamel is more difficult to see [50]. Yet our examination conditions in schools were optimal due to adequate light and drying facilities. The absence of DE on mandibular incisors in Table 2 is due to their protection from acid attack by the high flow of submandibular saliva [5]. Thus the examination of upper incisors alone and first molars appears sufficient in prevalence studies carried out in adolescents at an age to be fixed by consensus. In the present study, the age of 14 years was used for examination of all teeth due to exposition to possible intrinsinc and extrinsinc aetiological factors for some time; if examining upper incisors and first molars can be considered sufficient, adolescents could be examined at the age of 12. This age should allow both DE prevalence and dental caries to be registered in the same study. Regarding severity, the first degree involving the enamel alone was most common, as has been reported in most of the studies in adolescents [4‐7, 10‐12, 19‐21, 28, 30, 32, 34, 49]. To conclude this first part focusing on prevalence, the limitations of the present study should be considered. The study sample was not nationally representative. As the majority of prevalence studies [4‐8, 10‐12, 16‐31, 33‐35] (Table 1), it was a stratified sample in a particular area fairly representative of the target population. Thus the application of the results to the French population needs to be confirmed.

Dental erosion is considered a multifactorial condition. Because the present study was cross-sectional and not longitudinal, the design only permitted an analysis of the association between known risk factors and experience of DE in French adolescents to highlight eventual particular cultural behaviors. As in previous studies [17, 24], no significant difference in the prevalence of DE between urban and rural areas was found in adjusted logistic regression analyses. Contrary to the majority of the studies [3, 5, 8‐11, 16‐18, 25, 28, 33, 34], socio-economic status was associated with the experience of DE: the present study confirmed a significantly higher DE prevalence in the lowest social category [12, 24, 26, 32, 35, 49] more often cited than the contrary [7, 23]. The use of different indices could again explain these different results, because the significance of the association differed according the indices used in the same study [35]. Indeed socio-economic status had no effect on the dependant variable when a cutoff value of 1 was chosen (Table 5). Sex was not associated with DE prevalence, a result that is in accordance with numerous studies [4, 5, 7, 9‐12, 17, 18, 25, 34, 35]. This may be explained by a similar pattern of exposure to risk factors in both sexes. A higher prevalence in males was found more particularly in studies which considered all tooth wear [22, 26, 30] and it was explained by differences in muscular strength and biting forces [26]. However, others studies targeting only DE found significant differences between the sexes [2, 3, 24, 28, 29, 31, 33] and one study showed a higher prevalence in girls [24].

Concerning oral health, the significantly greater occurrence of DE in the presence of carious lesions ICDAS 1–6 or 4–6 was inconsistent because the relationships were not statistically significant in adjusted logistic regression analyses (Table 4). This is in agreement with different studies using the DMFT (Decayed, Missing, Filled Teeth) index as independent variable [5, 11, 20, 31, 33]. However, caries experience was greater [25, 28] or lesser in adolescents with erosive experience [22] according to the studies. These different results could be explained by consumption habits of acidic beverages, sugar-free (light) or regular soda drinks. In the present study, this tendency to proportional relationship between carious lesions and DE could be explained by a higher proportion of participants who consumed acid and sugar-containing cola beverages. The inconsistent relationship between DE and cavitated carious lesions can be explained by the inclusion of visible dental biofilm in one adjusted logistic regression analysis (Table 4). In all cases, the associations were close to statistical significance (Tables 4 and 5). Usually, dental biofilm protects enamel from erosive lesions, especially on anterior teeth. In contrast, the main consumption of both sugary and acidic beverages or sweets in the present study increased the quantity of dental plaque, which was significantly associated with higher DE prevalence. As in other studies [3, 12, 15, 16, 22, 24, 30], no statistically significant association was observed between oral behaviours (daily toothbrushing with fluoride toothpaste, dental examination during the past year) and DE. Only the study of Bardolia et al. [31] showed that a brushing twice a day increased the risk of DE.

Thus, diet plays a major role. In agreement with the majority of studies in adolescents since the 2000s, strong associations were found between DE and acidic beverages [6, 12, 15, 17, 20, 23‐25, 30, 31] or sweets [17, 18, 23] (Table 4). However, the acidic beverage was the sole risk factor to have an effect on the DE, whatever the cutoff value of total BEWE score (Tables 4 and 5). In France, this could be due to a parent education problem about oral health because drinks and food dispensers have been prohibited in schools since 2005. The method of drinking, keeping or not the beverage in the mouth, was also associated with DE [13, 15‐17, 30]. Only two studies did not show these associations [4, 11]. In the present study, the method of drinking had an effect on the DE for a cutoff value of 1. The frequent behaviour of children of retaining a drink in the mouth could be explained by a particular position of the tongue, the higher DE rates on second premolars compared with first premolars. While there are conflicting results from different studies, the present work confirms the most frequent results for sports drinks [6, 8, 9, 19, 24, 29], fresh fruits [6, 8, 9, 13, 24, 31] and daily vitamin C [9, 17] which were not associated with DE. Only one study (sports drinks; [15]) and four studies (fresh fruits; [17‐19, 22]) showed contrary results; in the case of fresh fruits, this concerned only oranges [22], lemon [17] or banana [19]. The present study confirmed that acid reflux and repeated vomiting were not associated with DE in adolescents [9, 11, 14, 24, 29]. Only two studies, both using TWI modified indices (which over assess DE), reported the contrary [15, 16]. This setting can sometimes be difficult to evaluate due to its subjectivity.

The DE prevalence in Alpes Maritimes (France) was estimated to reach 39 %. It is difficult to compare this estimate with other national prevalences due to the wide range of indices, choice of teeth and age used in different studies. Although the BEWE index has been recommanded, the cut-off value of 1 still needs to be stipulated, for comparison with recent studies. The examination of maxillary incisors and first permanent molars appeared sufficient for assessing DE prevalence. Finally, the age of examination should be discussed because using 12-year-olds would have the advantage of allowing a prevalence study of both DE and caries prevalence.